diff options
Diffstat (limited to 'tools/objtool/check.c')
| -rw-r--r-- | tools/objtool/check.c | 3621 |
1 files changed, 2823 insertions, 798 deletions
diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 5fbb90a80d23..eb7e12ebc1d0 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -5,29 +5,34 @@ #include <string.h> #include <stdlib.h> - -#include "builtin.h" -#include "cfi.h" -#include "arch.h" -#include "check.h" -#include "special.h" -#include "warn.h" - +#include <inttypes.h> +#include <sys/mman.h> + +#include <objtool/builtin.h> +#include <objtool/cfi.h> +#include <objtool/arch.h> +#include <objtool/check.h> +#include <objtool/special.h> +#include <objtool/warn.h> +#include <objtool/endianness.h> + +#include <linux/objtool_types.h> #include <linux/hashtable.h> #include <linux/kernel.h> - -#define FAKE_JUMP_OFFSET -1 - -#define C_JUMP_TABLE_SECTION ".rodata..c_jump_table" +#include <linux/static_call_types.h> struct alternative { - struct list_head list; + struct alternative *next; struct instruction *insn; bool skip_orig; }; -const char *objname; -struct cfi_init_state initial_func_cfi; +static unsigned long nr_cfi, nr_cfi_reused, nr_cfi_cache; + +static struct cfi_init_state initial_func_cfi; +static struct cfi_state init_cfi; +static struct cfi_state func_cfi; +static struct cfi_state force_undefined_cfi; struct instruction *find_insn(struct objtool_file *file, struct section *sec, unsigned long offset) @@ -42,27 +47,29 @@ struct instruction *find_insn(struct objtool_file *file, return NULL; } -static struct instruction *next_insn_same_sec(struct objtool_file *file, - struct instruction *insn) +struct instruction *next_insn_same_sec(struct objtool_file *file, + struct instruction *insn) { - struct instruction *next = list_next_entry(insn, list); + if (insn->idx == INSN_CHUNK_MAX) + return find_insn(file, insn->sec, insn->offset + insn->len); - if (!next || &next->list == &file->insn_list || next->sec != insn->sec) + insn++; + if (!insn->len) return NULL; - return next; + return insn; } static struct instruction *next_insn_same_func(struct objtool_file *file, struct instruction *insn) { - struct instruction *next = list_next_entry(insn, list); - struct symbol *func = insn->func; + struct instruction *next = next_insn_same_sec(file, insn); + struct symbol *func = insn_func(insn); if (!func) return NULL; - if (&next->list != &file->insn_list && next->func == func) + if (next && insn_func(next) == func) return next; /* Check if we're already in the subfunction: */ @@ -73,17 +80,35 @@ static struct instruction *next_insn_same_func(struct objtool_file *file, return find_insn(file, func->cfunc->sec, func->cfunc->offset); } +static struct instruction *prev_insn_same_sec(struct objtool_file *file, + struct instruction *insn) +{ + if (insn->idx == 0) { + if (insn->prev_len) + return find_insn(file, insn->sec, insn->offset - insn->prev_len); + return NULL; + } + + return insn - 1; +} + static struct instruction *prev_insn_same_sym(struct objtool_file *file, - struct instruction *insn) + struct instruction *insn) { - struct instruction *prev = list_prev_entry(insn, list); + struct instruction *prev = prev_insn_same_sec(file, insn); - if (&prev->list != &file->insn_list && prev->func == insn->func) + if (prev && insn_func(prev) == insn_func(insn)) return prev; return NULL; } +#define for_each_insn(file, insn) \ + for (struct section *__sec, *__fake = (struct section *)1; \ + __fake; __fake = NULL) \ + for_each_sec(file, __sec) \ + sec_for_each_insn(file, __sec, insn) + #define func_for_each_insn(file, func, insn) \ for (insn = find_insn(file, func->sec, func->offset); \ insn; \ @@ -91,16 +116,13 @@ static struct instruction *prev_insn_same_sym(struct objtool_file *file, #define sym_for_each_insn(file, sym, insn) \ for (insn = find_insn(file, sym->sec, sym->offset); \ - insn && &insn->list != &file->insn_list && \ - insn->sec == sym->sec && \ - insn->offset < sym->offset + sym->len; \ - insn = list_next_entry(insn, list)) + insn && insn->offset < sym->offset + sym->len; \ + insn = next_insn_same_sec(file, insn)) #define sym_for_each_insn_continue_reverse(file, sym, insn) \ - for (insn = list_prev_entry(insn, list); \ - &insn->list != &file->insn_list && \ - insn->sec == sym->sec && insn->offset >= sym->offset; \ - insn = list_prev_entry(insn, list)) + for (insn = prev_insn_same_sec(file, insn); \ + insn && insn->offset >= sym->offset; \ + insn = prev_insn_same_sec(file, insn)) #define sec_for_each_insn_from(file, insn) \ for (; insn; insn = next_insn_same_sec(file, insn)) @@ -109,23 +131,49 @@ static struct instruction *prev_insn_same_sym(struct objtool_file *file, for (insn = next_insn_same_sec(file, insn); insn; \ insn = next_insn_same_sec(file, insn)) -static bool is_static_jump(struct instruction *insn) +static inline struct symbol *insn_call_dest(struct instruction *insn) { - return insn->type == INSN_JUMP_CONDITIONAL || - insn->type == INSN_JUMP_UNCONDITIONAL; + if (insn->type == INSN_JUMP_DYNAMIC || + insn->type == INSN_CALL_DYNAMIC) + return NULL; + + return insn->_call_dest; } -static bool is_sibling_call(struct instruction *insn) +static inline struct reloc *insn_jump_table(struct instruction *insn) { - /* An indirect jump is either a sibling call or a jump to a table. */ - if (insn->type == INSN_JUMP_DYNAMIC) - return list_empty(&insn->alts); + if (insn->type == INSN_JUMP_DYNAMIC || + insn->type == INSN_CALL_DYNAMIC) + return insn->_jump_table; - if (!is_static_jump(insn)) - return false; + return NULL; +} + +static bool is_jump_table_jump(struct instruction *insn) +{ + struct alt_group *alt_group = insn->alt_group; + + if (insn_jump_table(insn)) + return true; + + /* Retpoline alternative for a jump table? */ + return alt_group && alt_group->orig_group && + insn_jump_table(alt_group->orig_group->first_insn); +} + +static bool is_sibling_call(struct instruction *insn) +{ + /* + * Assume only STT_FUNC calls have jump-tables. + */ + if (insn_func(insn)) { + /* An indirect jump is either a sibling call or a jump to a table. */ + if (insn->type == INSN_JUMP_DYNAMIC) + return !is_jump_table_jump(insn); + } - /* add_jump_destinations() sets insn->call_dest for sibling calls. */ - return !!insn->call_dest; + /* add_jump_destinations() sets insn_call_dest(insn) for sibling calls. */ + return (is_static_jump(insn) && insn_call_dest(insn)); } /* @@ -144,42 +192,28 @@ static bool __dead_end_function(struct objtool_file *file, struct symbol *func, struct instruction *insn; bool empty = true; - /* - * Unfortunately these have to be hard coded because the noreturn - * attribute isn't provided in ELF data. - */ +#define NORETURN(func) __stringify(func), static const char * const global_noreturns[] = { - "__stack_chk_fail", - "panic", - "do_exit", - "do_task_dead", - "__module_put_and_exit", - "complete_and_exit", - "__reiserfs_panic", - "lbug_with_loc", - "fortify_panic", - "usercopy_abort", - "machine_real_restart", - "rewind_stack_do_exit", - "kunit_try_catch_throw", +#include "noreturns.h" }; +#undef NORETURN if (!func) return false; - if (func->bind == STB_WEAK) - return false; - - if (func->bind == STB_GLOBAL) + if (func->bind == STB_GLOBAL || func->bind == STB_WEAK) for (i = 0; i < ARRAY_SIZE(global_noreturns); i++) if (!strcmp(func->name, global_noreturns[i])) return true; + if (func->bind == STB_WEAK) + return false; + if (!func->len) return false; insn = find_insn(file, func->sec, func->offset); - if (!insn->func) + if (!insn || !insn_func(insn)) return false; func_for_each_insn(file, func, insn) { @@ -215,7 +249,7 @@ static bool __dead_end_function(struct objtool_file *file, struct symbol *func, return false; } - return __dead_end_function(file, dest->func, recursion+1); + return __dead_end_function(file, insn_func(dest), recursion+1); } } @@ -240,20 +274,93 @@ static void init_cfi_state(struct cfi_state *cfi) cfi->drap_offset = -1; } -static void init_insn_state(struct insn_state *state, struct section *sec) +static void init_insn_state(struct objtool_file *file, struct insn_state *state, + struct section *sec) { memset(state, 0, sizeof(*state)); init_cfi_state(&state->cfi); /* * We need the full vmlinux for noinstr validation, otherwise we can - * not correctly determine insn->call_dest->sec (external symbols do - * not have a section). + * not correctly determine insn_call_dest(insn)->sec (external symbols + * do not have a section). */ - if (vmlinux && sec) + if (opts.link && opts.noinstr && sec) state->noinstr = sec->noinstr; } +static struct cfi_state *cfi_alloc(void) +{ + struct cfi_state *cfi = calloc(1, sizeof(struct cfi_state)); + if (!cfi) { + WARN("calloc failed"); + exit(1); + } + nr_cfi++; + return cfi; +} + +static int cfi_bits; +static struct hlist_head *cfi_hash; + +static inline bool cficmp(struct cfi_state *cfi1, struct cfi_state *cfi2) +{ + return memcmp((void *)cfi1 + sizeof(cfi1->hash), + (void *)cfi2 + sizeof(cfi2->hash), + sizeof(struct cfi_state) - sizeof(struct hlist_node)); +} + +static inline u32 cfi_key(struct cfi_state *cfi) +{ + return jhash((void *)cfi + sizeof(cfi->hash), + sizeof(*cfi) - sizeof(cfi->hash), 0); +} + +static struct cfi_state *cfi_hash_find_or_add(struct cfi_state *cfi) +{ + struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)]; + struct cfi_state *obj; + + hlist_for_each_entry(obj, head, hash) { + if (!cficmp(cfi, obj)) { + nr_cfi_cache++; + return obj; + } + } + + obj = cfi_alloc(); + *obj = *cfi; + hlist_add_head(&obj->hash, head); + + return obj; +} + +static void cfi_hash_add(struct cfi_state *cfi) +{ + struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)]; + + hlist_add_head(&cfi->hash, head); +} + +static void *cfi_hash_alloc(unsigned long size) +{ + cfi_bits = max(10, ilog2(size)); + cfi_hash = mmap(NULL, sizeof(struct hlist_head) << cfi_bits, + PROT_READ|PROT_WRITE, + MAP_PRIVATE|MAP_ANON, -1, 0); + if (cfi_hash == (void *)-1L) { + WARN("mmap fail cfi_hash"); + cfi_hash = NULL; + } else if (opts.stats) { + printf("cfi_bits: %d\n", cfi_bits); + } + + return cfi_hash; +} + +static unsigned long nr_insns; +static unsigned long nr_insns_visited; + /* * Call the arch-specific instruction decoder for all the instructions and add * them to the global instruction list. @@ -264,10 +371,12 @@ static int decode_instructions(struct objtool_file *file) struct symbol *func; unsigned long offset; struct instruction *insn; - unsigned long nr_insns = 0; int ret; for_each_sec(file, sec) { + struct instruction *insns = NULL; + u8 prev_len = 0; + u8 idx = 0; if (!(sec->sh.sh_flags & SHF_EXECINSTR)) continue; @@ -278,38 +387,75 @@ static int decode_instructions(struct objtool_file *file) sec->text = true; if (!strcmp(sec->name, ".noinstr.text") || - !strcmp(sec->name, ".entry.text")) + !strcmp(sec->name, ".entry.text") || + !strcmp(sec->name, ".cpuidle.text") || + !strncmp(sec->name, ".text..__x86.", 13)) sec->noinstr = true; - for (offset = 0; offset < sec->len; offset += insn->len) { - insn = malloc(sizeof(*insn)); - if (!insn) { - WARN("malloc failed"); - return -1; + /* + * .init.text code is ran before userspace and thus doesn't + * strictly need retpolines, except for modules which are + * loaded late, they very much do need retpoline in their + * .init.text + */ + if (!strcmp(sec->name, ".init.text") && !opts.module) + sec->init = true; + + for (offset = 0; offset < sec->sh.sh_size; offset += insn->len) { + if (!insns || idx == INSN_CHUNK_MAX) { + insns = calloc(sizeof(*insn), INSN_CHUNK_SIZE); + if (!insns) { + WARN("malloc failed"); + return -1; + } + idx = 0; + } else { + idx++; } - memset(insn, 0, sizeof(*insn)); - INIT_LIST_HEAD(&insn->alts); - INIT_LIST_HEAD(&insn->stack_ops); - init_cfi_state(&insn->cfi); + insn = &insns[idx]; + insn->idx = idx; + INIT_LIST_HEAD(&insn->call_node); insn->sec = sec; insn->offset = offset; + insn->prev_len = prev_len; - ret = arch_decode_instruction(file->elf, sec, offset, - sec->len - offset, - &insn->len, &insn->type, - &insn->immediate, - &insn->stack_ops); + ret = arch_decode_instruction(file, sec, offset, + sec->sh.sh_size - offset, + insn); if (ret) - goto err; + return ret; + + prev_len = insn->len; + + /* + * By default, "ud2" is a dead end unless otherwise + * annotated, because GCC 7 inserts it for certain + * divide-by-zero cases. + */ + if (insn->type == INSN_BUG) + insn->dead_end = true; hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset)); - list_add_tail(&insn->list, &file->insn_list); nr_insns++; } - list_for_each_entry(func, &sec->symbol_list, list) { - if (func->type != STT_FUNC || func->alias != func) +// printf("%s: last chunk used: %d\n", sec->name, (int)idx); + + sec_for_each_sym(sec, func) { + if (func->type != STT_NOTYPE && func->type != STT_FUNC) + continue; + + if (func->offset == sec->sh.sh_size) { + /* Heuristic: likely an "end" symbol */ + if (func->type == STT_NOTYPE) + continue; + WARN("%s(): STT_FUNC at end of section", + func->name); + return -1; + } + + if (func->embedded_insn || func->alias != func) continue; if (!find_insn(file, sec, func->offset)) { @@ -318,19 +464,103 @@ static int decode_instructions(struct objtool_file *file) return -1; } - sym_for_each_insn(file, func, insn) - insn->func = func; + sym_for_each_insn(file, func, insn) { + insn->sym = func; + if (func->type == STT_FUNC && + insn->type == INSN_ENDBR && + list_empty(&insn->call_node)) { + if (insn->offset == func->offset) { + list_add_tail(&insn->call_node, &file->endbr_list); + file->nr_endbr++; + } else { + file->nr_endbr_int++; + } + } + } } } - if (stats) + if (opts.stats) printf("nr_insns: %lu\n", nr_insns); return 0; +} -err: - free(insn); - return ret; +/* + * Read the pv_ops[] .data table to find the static initialized values. + */ +static int add_pv_ops(struct objtool_file *file, const char *symname) +{ + struct symbol *sym, *func; + unsigned long off, end; + struct reloc *reloc; + int idx; + + sym = find_symbol_by_name(file->elf, symname); + if (!sym) + return 0; + + off = sym->offset; + end = off + sym->len; + for (;;) { + reloc = find_reloc_by_dest_range(file->elf, sym->sec, off, end - off); + if (!reloc) + break; + + func = reloc->sym; + if (func->type == STT_SECTION) + func = find_symbol_by_offset(reloc->sym->sec, + reloc_addend(reloc)); + + idx = (reloc_offset(reloc) - sym->offset) / sizeof(unsigned long); + + objtool_pv_add(file, idx, func); + + off = reloc_offset(reloc) + 1; + if (off > end) + break; + } + + return 0; +} + +/* + * Allocate and initialize file->pv_ops[]. + */ +static int init_pv_ops(struct objtool_file *file) +{ + static const char *pv_ops_tables[] = { + "pv_ops", + "xen_cpu_ops", + "xen_irq_ops", + "xen_mmu_ops", + NULL, + }; + const char *pv_ops; + struct symbol *sym; + int idx, nr; + + if (!opts.noinstr) + return 0; + + file->pv_ops = NULL; + + sym = find_symbol_by_name(file->elf, "pv_ops"); + if (!sym) + return 0; + + nr = sym->len / sizeof(unsigned long); + file->pv_ops = calloc(sizeof(struct pv_state), nr); + if (!file->pv_ops) + return -1; + + for (idx = 0; idx < nr; idx++) + INIT_LIST_HEAD(&file->pv_ops[idx].targets); + + for (idx = 0; (pv_ops = pv_ops_tables[idx]); idx++) + add_pv_ops(file, pv_ops); + + return 0; } static struct instruction *find_last_insn(struct objtool_file *file, @@ -338,9 +568,9 @@ static struct instruction *find_last_insn(struct objtool_file *file, { struct instruction *insn = NULL; unsigned int offset; - unsigned int end = (sec->len > 10) ? sec->len - 10 : 0; + unsigned int end = (sec->sh.sh_size > 10) ? sec->sh.sh_size - 10 : 0; - for (offset = sec->len - 1; offset >= end && !insn; offset--) + for (offset = sec->sh.sh_size - 1; offset >= end && !insn; offset--) insn = find_insn(file, sec, offset); return insn; @@ -351,43 +581,40 @@ static struct instruction *find_last_insn(struct objtool_file *file, */ static int add_dead_ends(struct objtool_file *file) { - struct section *sec; - struct rela *rela; + struct section *rsec; + struct reloc *reloc; struct instruction *insn; - - /* - * By default, "ud2" is a dead end unless otherwise annotated, because - * GCC 7 inserts it for certain divide-by-zero cases. - */ - for_each_insn(file, insn) - if (insn->type == INSN_BUG) - insn->dead_end = true; + s64 addend; /* * Check for manually annotated dead ends. */ - sec = find_section_by_name(file->elf, ".rela.discard.unreachable"); - if (!sec) + rsec = find_section_by_name(file->elf, ".rela.discard.unreachable"); + if (!rsec) goto reachable; - list_for_each_entry(rela, &sec->rela_list, list) { - if (rela->sym->type != STT_SECTION) { - WARN("unexpected relocation symbol type in %s", sec->name); + for_each_reloc(rsec, reloc) { + + if (reloc->sym->type != STT_SECTION) { + WARN("unexpected relocation symbol type in %s", rsec->name); return -1; } - insn = find_insn(file, rela->sym->sec, rela->addend); + + addend = reloc_addend(reloc); + + insn = find_insn(file, reloc->sym->sec, addend); if (insn) - insn = list_prev_entry(insn, list); - else if (rela->addend == rela->sym->sec->len) { - insn = find_last_insn(file, rela->sym->sec); + insn = prev_insn_same_sec(file, insn); + else if (addend == reloc->sym->sec->sh.sh_size) { + insn = find_last_insn(file, reloc->sym->sec); if (!insn) { - WARN("can't find unreachable insn at %s+0x%x", - rela->sym->sec->name, rela->addend); + WARN("can't find unreachable insn at %s+0x%" PRIx64, + reloc->sym->sec->name, addend); return -1; } } else { - WARN("can't find unreachable insn at %s+0x%x", - rela->sym->sec->name, rela->addend); + WARN("can't find unreachable insn at %s+0x%" PRIx64, + reloc->sym->sec->name, addend); return -1; } @@ -401,28 +628,32 @@ reachable: * GCC doesn't know the "ud2" is fatal, so it generates code as if it's * not a dead end. */ - sec = find_section_by_name(file->elf, ".rela.discard.reachable"); - if (!sec) + rsec = find_section_by_name(file->elf, ".rela.discard.reachable"); + if (!rsec) return 0; - list_for_each_entry(rela, &sec->rela_list, list) { - if (rela->sym->type != STT_SECTION) { - WARN("unexpected relocation symbol type in %s", sec->name); + for_each_reloc(rsec, reloc) { + + if (reloc->sym->type != STT_SECTION) { + WARN("unexpected relocation symbol type in %s", rsec->name); return -1; } - insn = find_insn(file, rela->sym->sec, rela->addend); + + addend = reloc_addend(reloc); + + insn = find_insn(file, reloc->sym->sec, addend); if (insn) - insn = list_prev_entry(insn, list); - else if (rela->addend == rela->sym->sec->len) { - insn = find_last_insn(file, rela->sym->sec); + insn = prev_insn_same_sec(file, insn); + else if (addend == reloc->sym->sec->sh.sh_size) { + insn = find_last_insn(file, reloc->sym->sec); if (!insn) { - WARN("can't find reachable insn at %s+0x%x", - rela->sym->sec->name, rela->addend); + WARN("can't find reachable insn at %s+0x%" PRIx64, + reloc->sym->sec->name, addend); return -1; } } else { - WARN("can't find reachable insn at %s+0x%x", - rela->sym->sec->name, rela->addend); + WARN("can't find reachable insn at %s+0x%" PRIx64, + reloc->sym->sec->name, addend); return -1; } @@ -432,34 +663,387 @@ reachable: return 0; } +static int create_static_call_sections(struct objtool_file *file) +{ + struct static_call_site *site; + struct section *sec; + struct instruction *insn; + struct symbol *key_sym; + char *key_name, *tmp; + int idx; + + sec = find_section_by_name(file->elf, ".static_call_sites"); + if (sec) { + INIT_LIST_HEAD(&file->static_call_list); + WARN("file already has .static_call_sites section, skipping"); + return 0; + } + + if (list_empty(&file->static_call_list)) + return 0; + + idx = 0; + list_for_each_entry(insn, &file->static_call_list, call_node) + idx++; + + sec = elf_create_section_pair(file->elf, ".static_call_sites", + sizeof(*site), idx, idx * 2); + if (!sec) + return -1; + + /* Allow modules to modify the low bits of static_call_site::key */ + sec->sh.sh_flags |= SHF_WRITE; + + idx = 0; + list_for_each_entry(insn, &file->static_call_list, call_node) { + + /* populate reloc for 'addr' */ + if (!elf_init_reloc_text_sym(file->elf, sec, + idx * sizeof(*site), idx * 2, + insn->sec, insn->offset)) + return -1; + + /* find key symbol */ + key_name = strdup(insn_call_dest(insn)->name); + if (!key_name) { + perror("strdup"); + return -1; + } + if (strncmp(key_name, STATIC_CALL_TRAMP_PREFIX_STR, + STATIC_CALL_TRAMP_PREFIX_LEN)) { + WARN("static_call: trampoline name malformed: %s", key_name); + free(key_name); + return -1; + } + tmp = key_name + STATIC_CALL_TRAMP_PREFIX_LEN - STATIC_CALL_KEY_PREFIX_LEN; + memcpy(tmp, STATIC_CALL_KEY_PREFIX_STR, STATIC_CALL_KEY_PREFIX_LEN); + + key_sym = find_symbol_by_name(file->elf, tmp); + if (!key_sym) { + if (!opts.module) { + WARN("static_call: can't find static_call_key symbol: %s", tmp); + free(key_name); + return -1; + } + + /* + * For modules(), the key might not be exported, which + * means the module can make static calls but isn't + * allowed to change them. + * + * In that case we temporarily set the key to be the + * trampoline address. This is fixed up in + * static_call_add_module(). + */ + key_sym = insn_call_dest(insn); + } + free(key_name); + + /* populate reloc for 'key' */ + if (!elf_init_reloc_data_sym(file->elf, sec, + idx * sizeof(*site) + 4, + (idx * 2) + 1, key_sym, + is_sibling_call(insn) * STATIC_CALL_SITE_TAIL)) + return -1; + + idx++; + } + + return 0; +} + +static int create_retpoline_sites_sections(struct objtool_file *file) +{ + struct instruction *insn; + struct section *sec; + int idx; + + sec = find_section_by_name(file->elf, ".retpoline_sites"); + if (sec) { + WARN("file already has .retpoline_sites, skipping"); + return 0; + } + + idx = 0; + list_for_each_entry(insn, &file->retpoline_call_list, call_node) + idx++; + + if (!idx) + return 0; + + sec = elf_create_section_pair(file->elf, ".retpoline_sites", + sizeof(int), idx, idx); + if (!sec) + return -1; + + idx = 0; + list_for_each_entry(insn, &file->retpoline_call_list, call_node) { + + if (!elf_init_reloc_text_sym(file->elf, sec, + idx * sizeof(int), idx, + insn->sec, insn->offset)) + return -1; + + idx++; + } + + return 0; +} + +static int create_return_sites_sections(struct objtool_file *file) +{ + struct instruction *insn; + struct section *sec; + int idx; + + sec = find_section_by_name(file->elf, ".return_sites"); + if (sec) { + WARN("file already has .return_sites, skipping"); + return 0; + } + + idx = 0; + list_for_each_entry(insn, &file->return_thunk_list, call_node) + idx++; + + if (!idx) + return 0; + + sec = elf_create_section_pair(file->elf, ".return_sites", + sizeof(int), idx, idx); + if (!sec) + return -1; + + idx = 0; + list_for_each_entry(insn, &file->return_thunk_list, call_node) { + + if (!elf_init_reloc_text_sym(file->elf, sec, + idx * sizeof(int), idx, + insn->sec, insn->offset)) + return -1; + + idx++; + } + + return 0; +} + +static int create_ibt_endbr_seal_sections(struct objtool_file *file) +{ + struct instruction *insn; + struct section *sec; + int idx; + + sec = find_section_by_name(file->elf, ".ibt_endbr_seal"); + if (sec) { + WARN("file already has .ibt_endbr_seal, skipping"); + return 0; + } + + idx = 0; + list_for_each_entry(insn, &file->endbr_list, call_node) + idx++; + + if (opts.stats) { + printf("ibt: ENDBR at function start: %d\n", file->nr_endbr); + printf("ibt: ENDBR inside functions: %d\n", file->nr_endbr_int); + printf("ibt: superfluous ENDBR: %d\n", idx); + } + + if (!idx) + return 0; + + sec = elf_create_section_pair(file->elf, ".ibt_endbr_seal", + sizeof(int), idx, idx); + if (!sec) + return -1; + + idx = 0; + list_for_each_entry(insn, &file->endbr_list, call_node) { + + int *site = (int *)sec->data->d_buf + idx; + struct symbol *sym = insn->sym; + *site = 0; + + if (opts.module && sym && sym->type == STT_FUNC && + insn->offset == sym->offset && + (!strcmp(sym->name, "init_module") || + !strcmp(sym->name, "cleanup_module"))) + WARN("%s(): not an indirect call target", sym->name); + + if (!elf_init_reloc_text_sym(file->elf, sec, + idx * sizeof(int), idx, + insn->sec, insn->offset)) + return -1; + + idx++; + } + + return 0; +} + +static int create_cfi_sections(struct objtool_file *file) +{ + struct section *sec; + struct symbol *sym; + int idx; + + sec = find_section_by_name(file->elf, ".cfi_sites"); + if (sec) { + INIT_LIST_HEAD(&file->call_list); + WARN("file already has .cfi_sites section, skipping"); + return 0; + } + + idx = 0; + for_each_sym(file, sym) { + if (sym->type != STT_FUNC) + continue; + + if (strncmp(sym->name, "__cfi_", 6)) + continue; + + idx++; + } + + sec = elf_create_section_pair(file->elf, ".cfi_sites", + sizeof(unsigned int), idx, idx); + if (!sec) + return -1; + + idx = 0; + for_each_sym(file, sym) { + if (sym->type != STT_FUNC) + continue; + + if (strncmp(sym->name, "__cfi_", 6)) + continue; + + if (!elf_init_reloc_text_sym(file->elf, sec, + idx * sizeof(unsigned int), idx, + sym->sec, sym->offset)) + return -1; + + idx++; + } + + return 0; +} + +static int create_mcount_loc_sections(struct objtool_file *file) +{ + size_t addr_size = elf_addr_size(file->elf); + struct instruction *insn; + struct section *sec; + int idx; + + sec = find_section_by_name(file->elf, "__mcount_loc"); + if (sec) { + INIT_LIST_HEAD(&file->mcount_loc_list); + WARN("file already has __mcount_loc section, skipping"); + return 0; + } + + if (list_empty(&file->mcount_loc_list)) + return 0; + + idx = 0; + list_for_each_entry(insn, &file->mcount_loc_list, call_node) + idx++; + + sec = elf_create_section_pair(file->elf, "__mcount_loc", addr_size, + idx, idx); + if (!sec) + return -1; + + sec->sh.sh_addralign = addr_size; + + idx = 0; + list_for_each_entry(insn, &file->mcount_loc_list, call_node) { + + struct reloc *reloc; + + reloc = elf_init_reloc_text_sym(file->elf, sec, idx * addr_size, idx, + insn->sec, insn->offset); + if (!reloc) + return -1; + + set_reloc_type(file->elf, reloc, addr_size == 8 ? R_ABS64 : R_ABS32); + + idx++; + } + + return 0; +} + +static int create_direct_call_sections(struct objtool_file *file) +{ + struct instruction *insn; + struct section *sec; + int idx; + + sec = find_section_by_name(file->elf, ".call_sites"); + if (sec) { + INIT_LIST_HEAD(&file->call_list); + WARN("file already has .call_sites section, skipping"); + return 0; + } + + if (list_empty(&file->call_list)) + return 0; + + idx = 0; + list_for_each_entry(insn, &file->call_list, call_node) + idx++; + + sec = elf_create_section_pair(file->elf, ".call_sites", + sizeof(unsigned int), idx, idx); + if (!sec) + return -1; + + idx = 0; + list_for_each_entry(insn, &file->call_list, call_node) { + + if (!elf_init_reloc_text_sym(file->elf, sec, + idx * sizeof(unsigned int), idx, + insn->sec, insn->offset)) + return -1; + + idx++; + } + + return 0; +} + /* * Warnings shouldn't be reported for ignored functions. */ static void add_ignores(struct objtool_file *file) { struct instruction *insn; - struct section *sec; + struct section *rsec; struct symbol *func; - struct rela *rela; + struct reloc *reloc; - sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard"); - if (!sec) + rsec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard"); + if (!rsec) return; - list_for_each_entry(rela, &sec->rela_list, list) { - switch (rela->sym->type) { + for_each_reloc(rsec, reloc) { + switch (reloc->sym->type) { case STT_FUNC: - func = rela->sym; + func = reloc->sym; break; case STT_SECTION: - func = find_func_by_offset(rela->sym->sec, rela->addend); + func = find_func_by_offset(reloc->sym->sec, reloc_addend(reloc)); if (!func) continue; break; default: - WARN("unexpected relocation symbol type in %s: %d", sec->name, rela->sym->type); + WARN("unexpected relocation symbol type in %s: %d", + rsec->name, reloc->sym->type); continue; } @@ -478,7 +1062,7 @@ static void add_ignores(struct objtool_file *file) static const char *uaccess_safe_builtin[] = { /* KASAN */ "kasan_report", - "check_memory_region", + "kasan_check_range", /* KASAN out-of-line */ "__asan_loadN_noabort", "__asan_load1_noabort", @@ -492,6 +1076,8 @@ static const char *uaccess_safe_builtin[] = { "__asan_store4_noabort", "__asan_store8_noabort", "__asan_store16_noabort", + "__kasan_check_read", + "__kasan_check_write", /* KASAN in-line */ "__asan_report_load_n_noabort", "__asan_report_load1_noabort", @@ -507,6 +1093,10 @@ static const char *uaccess_safe_builtin[] = { "__asan_report_store16_noabort", /* KCSAN */ "__kcsan_check_access", + "__kcsan_mb", + "__kcsan_wmb", + "__kcsan_rmb", + "__kcsan_release", "kcsan_found_watchpoint", "kcsan_setup_watchpoint", "kcsan_check_scoped_accesses", @@ -527,6 +1117,73 @@ static const char *uaccess_safe_builtin[] = { "__tsan_write4", "__tsan_write8", "__tsan_write16", + "__tsan_read_write1", + "__tsan_read_write2", + "__tsan_read_write4", + "__tsan_read_write8", + "__tsan_read_write16", + "__tsan_volatile_read1", + "__tsan_volatile_read2", + "__tsan_volatile_read4", + "__tsan_volatile_read8", + "__tsan_volatile_read16", + "__tsan_volatile_write1", + "__tsan_volatile_write2", + "__tsan_volatile_write4", + "__tsan_volatile_write8", + "__tsan_volatile_write16", + "__tsan_atomic8_load", + "__tsan_atomic16_load", + "__tsan_atomic32_load", + "__tsan_atomic64_load", + "__tsan_atomic8_store", + "__tsan_atomic16_store", + "__tsan_atomic32_store", + "__tsan_atomic64_store", + "__tsan_atomic8_exchange", + "__tsan_atomic16_exchange", + "__tsan_atomic32_exchange", + "__tsan_atomic64_exchange", + "__tsan_atomic8_fetch_add", + "__tsan_atomic16_fetch_add", + "__tsan_atomic32_fetch_add", + "__tsan_atomic64_fetch_add", + "__tsan_atomic8_fetch_sub", + "__tsan_atomic16_fetch_sub", + "__tsan_atomic32_fetch_sub", + "__tsan_atomic64_fetch_sub", + "__tsan_atomic8_fetch_and", + "__tsan_atomic16_fetch_and", + "__tsan_atomic32_fetch_and", + "__tsan_atomic64_fetch_and", + "__tsan_atomic8_fetch_or", + "__tsan_atomic16_fetch_or", + "__tsan_atomic32_fetch_or", + "__tsan_atomic64_fetch_or", + "__tsan_atomic8_fetch_xor", + "__tsan_atomic16_fetch_xor", + "__tsan_atomic32_fetch_xor", + "__tsan_atomic64_fetch_xor", + "__tsan_atomic8_fetch_nand", + "__tsan_atomic16_fetch_nand", + "__tsan_atomic32_fetch_nand", + "__tsan_atomic64_fetch_nand", + "__tsan_atomic8_compare_exchange_strong", + "__tsan_atomic16_compare_exchange_strong", + "__tsan_atomic32_compare_exchange_strong", + "__tsan_atomic64_compare_exchange_strong", + "__tsan_atomic8_compare_exchange_weak", + "__tsan_atomic16_compare_exchange_weak", + "__tsan_atomic32_compare_exchange_weak", + "__tsan_atomic64_compare_exchange_weak", + "__tsan_atomic8_compare_exchange_val", + "__tsan_atomic16_compare_exchange_val", + "__tsan_atomic32_compare_exchange_val", + "__tsan_atomic64_compare_exchange_val", + "__tsan_atomic_thread_fence", + "__tsan_atomic_signal_fence", + "__tsan_unaligned_read16", + "__tsan_unaligned_write16", /* KCOV */ "write_comp_data", "check_kcov_mode", @@ -540,16 +1197,43 @@ static const char *uaccess_safe_builtin[] = { "__sanitizer_cov_trace_cmp4", "__sanitizer_cov_trace_cmp8", "__sanitizer_cov_trace_switch", + /* KMSAN */ + "kmsan_copy_to_user", + "kmsan_report", + "kmsan_unpoison_entry_regs", + "kmsan_unpoison_memory", + "__msan_chain_origin", + "__msan_get_context_state", + "__msan_instrument_asm_store", + "__msan_metadata_ptr_for_load_1", + "__msan_metadata_ptr_for_load_2", + "__msan_metadata_ptr_for_load_4", + "__msan_metadata_ptr_for_load_8", + "__msan_metadata_ptr_for_load_n", + "__msan_metadata_ptr_for_store_1", + "__msan_metadata_ptr_for_store_2", + "__msan_metadata_ptr_for_store_4", + "__msan_metadata_ptr_for_store_8", + "__msan_metadata_ptr_for_store_n", + "__msan_poison_alloca", + "__msan_warning", /* UBSAN */ "ubsan_type_mismatch_common", "__ubsan_handle_type_mismatch", "__ubsan_handle_type_mismatch_v1", "__ubsan_handle_shift_out_of_bounds", + "__ubsan_handle_load_invalid_value", + /* STACKLEAK */ + "stackleak_track_stack", /* misc */ "csum_partial_copy_generic", - "__memcpy_mcsafe", - "mcsafe_handle_tail", + "copy_mc_fragile", + "copy_mc_fragile_handle_tail", + "copy_mc_enhanced_fast_string", "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */ + "rep_stos_alternative", + "rep_movs_alternative", + "__copy_user_nocache", NULL }; @@ -558,7 +1242,7 @@ static void add_uaccess_safe(struct objtool_file *file) struct symbol *func; const char **name; - if (!uaccess) + if (!opts.uaccess) return; for (name = uaccess_safe_builtin; *name; name++) { @@ -578,21 +1262,21 @@ static void add_uaccess_safe(struct objtool_file *file) */ static int add_ignore_alternatives(struct objtool_file *file) { - struct section *sec; - struct rela *rela; + struct section *rsec; + struct reloc *reloc; struct instruction *insn; - sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts"); - if (!sec) + rsec = find_section_by_name(file->elf, ".rela.discard.ignore_alts"); + if (!rsec) return 0; - list_for_each_entry(rela, &sec->rela_list, list) { - if (rela->sym->type != STT_SECTION) { - WARN("unexpected relocation symbol type in %s", sec->name); + for_each_reloc(rsec, reloc) { + if (reloc->sym->type != STT_SECTION) { + WARN("unexpected relocation symbol type in %s", rsec->name); return -1; } - insn = find_insn(file, rela->sym->sec, rela->addend); + insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc)); if (!insn) { WARN("bad .discard.ignore_alts entry"); return -1; @@ -605,74 +1289,348 @@ static int add_ignore_alternatives(struct objtool_file *file) } /* + * Symbols that replace INSN_CALL_DYNAMIC, every (tail) call to such a symbol + * will be added to the .retpoline_sites section. + */ +__weak bool arch_is_retpoline(struct symbol *sym) +{ + return false; +} + +/* + * Symbols that replace INSN_RETURN, every (tail) call to such a symbol + * will be added to the .return_sites section. + */ +__weak bool arch_is_rethunk(struct symbol *sym) +{ + return false; +} + +/* + * Symbols that are embedded inside other instructions, because sometimes crazy + * code exists. These are mostly ignored for validation purposes. + */ +__weak bool arch_is_embedded_insn(struct symbol *sym) +{ + return false; +} + +static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn) +{ + struct reloc *reloc; + + if (insn->no_reloc) + return NULL; + + if (!file) + return NULL; + + reloc = find_reloc_by_dest_range(file->elf, insn->sec, + insn->offset, insn->len); + if (!reloc) { + insn->no_reloc = 1; + return NULL; + } + + return reloc; +} + +static void remove_insn_ops(struct instruction *insn) +{ + struct stack_op *op, *next; + + for (op = insn->stack_ops; op; op = next) { + next = op->next; + free(op); + } + insn->stack_ops = NULL; +} + +static void annotate_call_site(struct objtool_file *file, + struct instruction *insn, bool sibling) +{ + struct reloc *reloc = insn_reloc(file, insn); + struct symbol *sym = insn_call_dest(insn); + + if (!sym) + sym = reloc->sym; + + /* + * Alternative replacement code is just template code which is + * sometimes copied to the original instruction. For now, don't + * annotate it. (In the future we might consider annotating the + * original instruction if/when it ever makes sense to do so.) + */ + if (!strcmp(insn->sec->name, ".altinstr_replacement")) + return; + + if (sym->static_call_tramp) { + list_add_tail(&insn->call_node, &file->static_call_list); + return; + } + + if (sym->retpoline_thunk) { + list_add_tail(&insn->call_node, &file->retpoline_call_list); + return; + } + + /* + * Many compilers cannot disable KCOV or sanitizer calls with a function + * attribute so they need a little help, NOP out any such calls from + * noinstr text. + */ + if (opts.hack_noinstr && insn->sec->noinstr && sym->profiling_func) { + if (reloc) + set_reloc_type(file->elf, reloc, R_NONE); + + elf_write_insn(file->elf, insn->sec, + insn->offset, insn->len, + sibling ? arch_ret_insn(insn->len) + : arch_nop_insn(insn->len)); + + insn->type = sibling ? INSN_RETURN : INSN_NOP; + + if (sibling) { + /* + * We've replaced the tail-call JMP insn by two new + * insn: RET; INT3, except we only have a single struct + * insn here. Mark it retpoline_safe to avoid the SLS + * warning, instead of adding another insn. + */ + insn->retpoline_safe = true; + } + + return; + } + + if (opts.mcount && sym->fentry) { + if (sibling) + WARN_INSN(insn, "tail call to __fentry__ !?!?"); + if (opts.mnop) { + if (reloc) + set_reloc_type(file->elf, reloc, R_NONE); + + elf_write_insn(file->elf, insn->sec, + insn->offset, insn->len, + arch_nop_insn(insn->len)); + + insn->type = INSN_NOP; + } + + list_add_tail(&insn->call_node, &file->mcount_loc_list); + return; + } + + if (insn->type == INSN_CALL && !insn->sec->init) + list_add_tail(&insn->call_node, &file->call_list); + + if (!sibling && dead_end_function(file, sym)) + insn->dead_end = true; +} + +static void add_call_dest(struct objtool_file *file, struct instruction *insn, + struct symbol *dest, bool sibling) +{ + insn->_call_dest = dest; + if (!dest) + return; + + /* + * Whatever stack impact regular CALLs have, should be undone + * by the RETURN of the called function. + * + * Annotated intra-function calls retain the stack_ops but + * are converted to JUMP, see read_intra_function_calls(). + */ + remove_insn_ops(insn); + + annotate_call_site(file, insn, sibling); +} + +static void add_retpoline_call(struct objtool_file *file, struct instruction *insn) +{ + /* + * Retpoline calls/jumps are really dynamic calls/jumps in disguise, + * so convert them accordingly. + */ + switch (insn->type) { + case INSN_CALL: + insn->type = INSN_CALL_DYNAMIC; + break; + case INSN_JUMP_UNCONDITIONAL: + insn->type = INSN_JUMP_DYNAMIC; + break; + case INSN_JUMP_CONDITIONAL: + insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL; + break; + default: + return; + } + + insn->retpoline_safe = true; + + /* + * Whatever stack impact regular CALLs have, should be undone + * by the RETURN of the called function. + * + * Annotated intra-function calls retain the stack_ops but + * are converted to JUMP, see read_intra_function_calls(). + */ + remove_insn_ops(insn); + + annotate_call_site(file, insn, false); +} + +static void add_return_call(struct objtool_file *file, struct instruction *insn, bool add) +{ + /* + * Return thunk tail calls are really just returns in disguise, + * so convert them accordingly. + */ + insn->type = INSN_RETURN; + insn->retpoline_safe = true; + + if (add) + list_add_tail(&insn->call_node, &file->return_thunk_list); +} + +static bool is_first_func_insn(struct objtool_file *file, + struct instruction *insn, struct symbol *sym) +{ + if (insn->offset == sym->offset) + return true; + + /* Allow direct CALL/JMP past ENDBR */ + if (opts.ibt) { + struct instruction *prev = prev_insn_same_sym(file, insn); + + if (prev && prev->type == INSN_ENDBR && + insn->offset == sym->offset + prev->len) + return true; + } + + return false; +} + +/* + * A sibling call is a tail-call to another symbol -- to differentiate from a + * recursive tail-call which is to the same symbol. + */ +static bool jump_is_sibling_call(struct objtool_file *file, + struct instruction *from, struct instruction *to) +{ + struct symbol *fs = from->sym; + struct symbol *ts = to->sym; + + /* Not a sibling call if from/to a symbol hole */ + if (!fs || !ts) + return false; + + /* Not a sibling call if not targeting the start of a symbol. */ + if (!is_first_func_insn(file, to, ts)) + return false; + + /* Disallow sibling calls into STT_NOTYPE */ + if (ts->type == STT_NOTYPE) + return false; + + /* Must not be self to be a sibling */ + return fs->pfunc != ts->pfunc; +} + +/* * Find the destination instructions for all jumps. */ static int add_jump_destinations(struct objtool_file *file) { - struct instruction *insn; - struct rela *rela; + struct instruction *insn, *jump_dest; + struct reloc *reloc; struct section *dest_sec; unsigned long dest_off; for_each_insn(file, insn) { - if (!is_static_jump(insn)) + if (insn->jump_dest) { + /* + * handle_group_alt() may have previously set + * 'jump_dest' for some alternatives. + */ continue; - - if (insn->ignore || insn->offset == FAKE_JUMP_OFFSET) + } + if (!is_static_jump(insn)) continue; - rela = find_rela_by_dest_range(file->elf, insn->sec, - insn->offset, insn->len); - if (!rela) { + reloc = insn_reloc(file, insn); + if (!reloc) { dest_sec = insn->sec; dest_off = arch_jump_destination(insn); - } else if (rela->sym->type == STT_SECTION) { - dest_sec = rela->sym->sec; - dest_off = arch_dest_rela_offset(rela->addend); - } else if (rela->sym->sec->idx) { - dest_sec = rela->sym->sec; - dest_off = rela->sym->sym.st_value + - arch_dest_rela_offset(rela->addend); - } else if (strstr(rela->sym->name, "_indirect_thunk_")) { + } else if (reloc->sym->type == STT_SECTION) { + dest_sec = reloc->sym->sec; + dest_off = arch_dest_reloc_offset(reloc_addend(reloc)); + } else if (reloc->sym->retpoline_thunk) { + add_retpoline_call(file, insn); + continue; + } else if (reloc->sym->return_thunk) { + add_return_call(file, insn, true); + continue; + } else if (insn_func(insn)) { /* - * Retpoline jumps are really dynamic jumps in - * disguise, so convert them accordingly. + * External sibling call or internal sibling call with + * STT_FUNC reloc. */ - if (insn->type == INSN_JUMP_UNCONDITIONAL) - insn->type = INSN_JUMP_DYNAMIC; - else - insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL; - - insn->retpoline_safe = true; + add_call_dest(file, insn, reloc->sym, true); continue; + } else if (reloc->sym->sec->idx) { + dest_sec = reloc->sym->sec; + dest_off = reloc->sym->sym.st_value + + arch_dest_reloc_offset(reloc_addend(reloc)); } else { - /* external sibling call */ - insn->call_dest = rela->sym; + /* non-func asm code jumping to another file */ continue; } - insn->jump_dest = find_insn(file, dest_sec, dest_off); - if (!insn->jump_dest) { + jump_dest = find_insn(file, dest_sec, dest_off); + if (!jump_dest) { + struct symbol *sym = find_symbol_by_offset(dest_sec, dest_off); /* - * This is a special case where an alt instruction - * jumps past the end of the section. These are - * handled later in handle_group_alt(). + * This is a special case for retbleed_untrain_ret(). + * It jumps to __x86_return_thunk(), but objtool + * can't find the thunk's starting RET + * instruction, because the RET is also in the + * middle of another instruction. Objtool only + * knows about the outer instruction. */ - if (!strcmp(insn->sec->name, ".altinstr_replacement")) + if (sym && sym->embedded_insn) { + add_return_call(file, insn, false); continue; + } - WARN_FUNC("can't find jump dest instruction at %s+0x%lx", - insn->sec, insn->offset, dest_sec->name, - dest_off); + WARN_INSN(insn, "can't find jump dest instruction at %s+0x%lx", + dest_sec->name, dest_off); return -1; } /* + * An intra-TU jump in retpoline.o might not have a relocation + * for its jump dest, in which case the above + * add_{retpoline,return}_call() didn't happen. + */ + if (jump_dest->sym && jump_dest->offset == jump_dest->sym->offset) { + if (jump_dest->sym->retpoline_thunk) { + add_retpoline_call(file, insn); + continue; + } + if (jump_dest->sym->return_thunk) { + add_return_call(file, insn, true); + continue; + } + } + + /* * Cross-function jump. */ - if (insn->func && insn->jump_dest->func && - insn->func != insn->jump_dest->func) { + if (insn_func(insn) && insn_func(jump_dest) && + insn_func(insn) != insn_func(jump_dest)) { /* * For GCC 8+, create parent/child links for any cold @@ -689,31 +1647,37 @@ static int add_jump_destinations(struct objtool_file *file) * case where the parent function's only reference to a * subfunction is through a jump table. */ - if (!strstr(insn->func->name, ".cold.") && - strstr(insn->jump_dest->func->name, ".cold.")) { - insn->func->cfunc = insn->jump_dest->func; - insn->jump_dest->func->pfunc = insn->func; - - } else if (insn->jump_dest->func->pfunc != insn->func->pfunc && - insn->jump_dest->offset == insn->jump_dest->func->offset) { - - /* internal sibling call */ - insn->call_dest = insn->jump_dest->func; + if (!strstr(insn_func(insn)->name, ".cold") && + strstr(insn_func(jump_dest)->name, ".cold")) { + insn_func(insn)->cfunc = insn_func(jump_dest); + insn_func(jump_dest)->pfunc = insn_func(insn); } } + + if (jump_is_sibling_call(file, insn, jump_dest)) { + /* + * Internal sibling call without reloc or with + * STT_SECTION reloc. + */ + add_call_dest(file, insn, insn_func(jump_dest), true); + continue; + } + + insn->jump_dest = jump_dest; } return 0; } -static void remove_insn_ops(struct instruction *insn) +static struct symbol *find_call_destination(struct section *sec, unsigned long offset) { - struct stack_op *op, *tmp; + struct symbol *call_dest; - list_for_each_entry_safe(op, tmp, &insn->stack_ops, list) { - list_del(&op->list); - free(op); - } + call_dest = find_func_by_offset(sec, offset); + if (!call_dest) + call_dest = find_symbol_by_offset(sec, offset); + + return call_dest; } /* @@ -723,139 +1687,154 @@ static int add_call_destinations(struct objtool_file *file) { struct instruction *insn; unsigned long dest_off; - struct rela *rela; + struct symbol *dest; + struct reloc *reloc; for_each_insn(file, insn) { if (insn->type != INSN_CALL) continue; - rela = find_rela_by_dest_range(file->elf, insn->sec, - insn->offset, insn->len); - if (!rela) { + reloc = insn_reloc(file, insn); + if (!reloc) { dest_off = arch_jump_destination(insn); - insn->call_dest = find_func_by_offset(insn->sec, dest_off); - if (!insn->call_dest) - insn->call_dest = find_symbol_by_offset(insn->sec, dest_off); + dest = find_call_destination(insn->sec, dest_off); + + add_call_dest(file, insn, dest, false); if (insn->ignore) continue; - if (!insn->call_dest) { - WARN_FUNC("unannotated intra-function call", insn->sec, insn->offset); + if (!insn_call_dest(insn)) { + WARN_INSN(insn, "unannotated intra-function call"); return -1; } - if (insn->func && insn->call_dest->type != STT_FUNC) { - WARN_FUNC("unsupported call to non-function", - insn->sec, insn->offset); + if (insn_func(insn) && insn_call_dest(insn)->type != STT_FUNC) { + WARN_INSN(insn, "unsupported call to non-function"); return -1; } - } else if (rela->sym->type == STT_SECTION) { - dest_off = arch_dest_rela_offset(rela->addend); - insn->call_dest = find_func_by_offset(rela->sym->sec, - dest_off); - if (!insn->call_dest) { - WARN_FUNC("can't find call dest symbol at %s+0x%lx", - insn->sec, insn->offset, - rela->sym->sec->name, - dest_off); + } else if (reloc->sym->type == STT_SECTION) { + dest_off = arch_dest_reloc_offset(reloc_addend(reloc)); + dest = find_call_destination(reloc->sym->sec, dest_off); + if (!dest) { + WARN_INSN(insn, "can't find call dest symbol at %s+0x%lx", + reloc->sym->sec->name, dest_off); return -1; } - } else - insn->call_dest = rela->sym; - /* - * Whatever stack impact regular CALLs have, should be undone - * by the RETURN of the called function. - * - * Annotated intra-function calls retain the stack_ops but - * are converted to JUMP, see read_intra_function_calls(). - */ - remove_insn_ops(insn); + add_call_dest(file, insn, dest, false); + + } else if (reloc->sym->retpoline_thunk) { + add_retpoline_call(file, insn); + + } else + add_call_dest(file, insn, reloc->sym, false); } return 0; } /* - * The .alternatives section requires some extra special care, over and above - * what other special sections require: - * - * 1. Because alternatives are patched in-place, we need to insert a fake jump - * instruction at the end so that validate_branch() skips all the original - * replaced instructions when validating the new instruction path. - * - * 2. An added wrinkle is that the new instruction length might be zero. In - * that case the old instructions are replaced with noops. We simulate that - * by creating a fake jump as the only new instruction. - * - * 3. In some cases, the alternative section includes an instruction which - * conditionally jumps to the _end_ of the entry. We have to modify these - * jumps' destinations to point back to .text rather than the end of the - * entry in .altinstr_replacement. + * The .alternatives section requires some extra special care over and above + * other special sections because alternatives are patched in place. */ static int handle_group_alt(struct objtool_file *file, struct special_alt *special_alt, struct instruction *orig_insn, struct instruction **new_insn) { - static unsigned int alt_group_next_index = 1; - struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump = NULL; - unsigned int alt_group = alt_group_next_index++; + struct instruction *last_new_insn = NULL, *insn, *nop = NULL; + struct alt_group *orig_alt_group, *new_alt_group; unsigned long dest_off; - last_orig_insn = NULL; - insn = orig_insn; - sec_for_each_insn_from(file, insn) { - if (insn->offset >= special_alt->orig_off + special_alt->orig_len) - break; - - insn->alt_group = alt_group; - last_orig_insn = insn; - } + orig_alt_group = orig_insn->alt_group; + if (!orig_alt_group) { + struct instruction *last_orig_insn = NULL; - if (next_insn_same_sec(file, last_orig_insn)) { - fake_jump = malloc(sizeof(*fake_jump)); - if (!fake_jump) { + orig_alt_group = malloc(sizeof(*orig_alt_group)); + if (!orig_alt_group) { WARN("malloc failed"); return -1; } - memset(fake_jump, 0, sizeof(*fake_jump)); - INIT_LIST_HEAD(&fake_jump->alts); - INIT_LIST_HEAD(&fake_jump->stack_ops); - init_cfi_state(&fake_jump->cfi); + orig_alt_group->cfi = calloc(special_alt->orig_len, + sizeof(struct cfi_state *)); + if (!orig_alt_group->cfi) { + WARN("calloc failed"); + return -1; + } + + insn = orig_insn; + sec_for_each_insn_from(file, insn) { + if (insn->offset >= special_alt->orig_off + special_alt->orig_len) + break; - fake_jump->sec = special_alt->new_sec; - fake_jump->offset = FAKE_JUMP_OFFSET; - fake_jump->type = INSN_JUMP_UNCONDITIONAL; - fake_jump->jump_dest = list_next_entry(last_orig_insn, list); - fake_jump->func = orig_insn->func; + insn->alt_group = orig_alt_group; + last_orig_insn = insn; + } + orig_alt_group->orig_group = NULL; + orig_alt_group->first_insn = orig_insn; + orig_alt_group->last_insn = last_orig_insn; + orig_alt_group->nop = NULL; + } else { + if (orig_alt_group->last_insn->offset + orig_alt_group->last_insn->len - + orig_alt_group->first_insn->offset != special_alt->orig_len) { + WARN_INSN(orig_insn, "weirdly overlapping alternative! %ld != %d", + orig_alt_group->last_insn->offset + + orig_alt_group->last_insn->len - + orig_alt_group->first_insn->offset, + special_alt->orig_len); + return -1; + } } - if (!special_alt->new_len) { - if (!fake_jump) { - WARN("%s: empty alternative at end of section", - special_alt->orig_sec->name); + new_alt_group = malloc(sizeof(*new_alt_group)); + if (!new_alt_group) { + WARN("malloc failed"); + return -1; + } + + if (special_alt->new_len < special_alt->orig_len) { + /* + * Insert a fake nop at the end to make the replacement + * alt_group the same size as the original. This is needed to + * allow propagate_alt_cfi() to do its magic. When the last + * instruction affects the stack, the instruction after it (the + * nop) will propagate the new state to the shared CFI array. + */ + nop = malloc(sizeof(*nop)); + if (!nop) { + WARN("malloc failed"); return -1; } + memset(nop, 0, sizeof(*nop)); + + nop->sec = special_alt->new_sec; + nop->offset = special_alt->new_off + special_alt->new_len; + nop->len = special_alt->orig_len - special_alt->new_len; + nop->type = INSN_NOP; + nop->sym = orig_insn->sym; + nop->alt_group = new_alt_group; + nop->ignore = orig_insn->ignore_alts; + } - *new_insn = fake_jump; - return 0; + if (!special_alt->new_len) { + *new_insn = nop; + goto end; } - last_new_insn = NULL; - alt_group = alt_group_next_index++; insn = *new_insn; sec_for_each_insn_from(file, insn) { + struct reloc *alt_reloc; + if (insn->offset >= special_alt->new_off + special_alt->new_len) break; last_new_insn = insn; insn->ignore = orig_insn->ignore_alts; - insn->func = orig_insn->func; - insn->alt_group = alt_group; + insn->sym = orig_insn->sym; + insn->alt_group = new_alt_group; /* * Since alternative replacement code is copy/pasted by the @@ -864,17 +1843,12 @@ static int handle_group_alt(struct objtool_file *file, * .altinstr_replacement section, unless the arch's * alternatives code can adjust the relative offsets * accordingly. - * - * The x86 alternatives code adjusts the offsets only when it - * encounters a branch instruction at the very beginning of the - * replacement group. */ - if ((insn->offset != special_alt->new_off || - (insn->type != INSN_CALL && !is_static_jump(insn))) && - find_rela_by_dest_range(file->elf, insn->sec, insn->offset, insn->len)) { + alt_reloc = insn_reloc(file, insn); + if (alt_reloc && arch_pc_relative_reloc(alt_reloc) && + !arch_support_alt_relocation(special_alt, insn, alt_reloc)) { - WARN_FUNC("unsupported relocation in alternatives section", - insn->sec, insn->offset); + WARN_INSN(insn, "unsupported relocation in alternatives section"); return -1; } @@ -886,18 +1860,11 @@ static int handle_group_alt(struct objtool_file *file, dest_off = arch_jump_destination(insn); if (dest_off == special_alt->new_off + special_alt->new_len) { - if (!fake_jump) { - WARN("%s: alternative jump to end of section", - special_alt->orig_sec->name); + insn->jump_dest = next_insn_same_sec(file, orig_alt_group->last_insn); + if (!insn->jump_dest) { + WARN_INSN(insn, "can't find alternative jump destination"); return -1; } - insn->jump_dest = fake_jump; - } - - if (!insn->jump_dest) { - WARN_FUNC("can't find alternative jump destination", - insn->sec, insn->offset); - return -1; } } @@ -907,9 +1874,12 @@ static int handle_group_alt(struct objtool_file *file, return -1; } - if (fake_jump) - list_add(&fake_jump->list, &last_new_insn->list); - +end: + new_alt_group->orig_group = orig_alt_group; + new_alt_group->first_insn = *new_insn; + new_alt_group->last_insn = last_new_insn; + new_alt_group->nop = nop; + new_alt_group->cfi = orig_alt_group->cfi; return 0; } @@ -923,16 +1893,39 @@ static int handle_jump_alt(struct objtool_file *file, struct instruction *orig_insn, struct instruction **new_insn) { - if (orig_insn->type == INSN_NOP) - return 0; + if (orig_insn->type != INSN_JUMP_UNCONDITIONAL && + orig_insn->type != INSN_NOP) { - if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) { - WARN_FUNC("unsupported instruction at jump label", - orig_insn->sec, orig_insn->offset); + WARN_INSN(orig_insn, "unsupported instruction at jump label"); return -1; } - *new_insn = list_next_entry(orig_insn, list); + if (opts.hack_jump_label && special_alt->key_addend & 2) { + struct reloc *reloc = insn_reloc(file, orig_insn); + + if (reloc) + set_reloc_type(file->elf, reloc, R_NONE); + elf_write_insn(file->elf, orig_insn->sec, + orig_insn->offset, orig_insn->len, + arch_nop_insn(orig_insn->len)); + orig_insn->type = INSN_NOP; + } + + if (orig_insn->type == INSN_NOP) { + if (orig_insn->len == 2) + file->jl_nop_short++; + else + file->jl_nop_long++; + + return 0; + } + + if (orig_insn->len == 2) + file->jl_short++; + else + file->jl_long++; + + *new_insn = next_insn_same_sec(file, orig_insn); return 0; } @@ -980,8 +1973,7 @@ static int add_special_section_alts(struct objtool_file *file) if (special_alt->group) { if (!special_alt->orig_len) { - WARN_FUNC("empty alternative entry", - orig_insn->sec, orig_insn->offset); + WARN_INSN(orig_insn, "empty alternative entry"); continue; } @@ -1006,50 +1998,58 @@ static int add_special_section_alts(struct objtool_file *file) alt->insn = new_insn; alt->skip_orig = special_alt->skip_orig; orig_insn->ignore_alts |= special_alt->skip_alt; - list_add_tail(&alt->list, &orig_insn->alts); + alt->next = orig_insn->alts; + orig_insn->alts = alt; list_del(&special_alt->list); free(special_alt); } + if (opts.stats) { + printf("jl\\\tNOP\tJMP\n"); + printf("short:\t%ld\t%ld\n", file->jl_nop_short, file->jl_short); + printf("long:\t%ld\t%ld\n", file->jl_nop_long, file->jl_long); + } + out: return ret; } static int add_jump_table(struct objtool_file *file, struct instruction *insn, - struct rela *table) + struct reloc *next_table) { - struct rela *rela = table; + struct symbol *pfunc = insn_func(insn)->pfunc; + struct reloc *table = insn_jump_table(insn); struct instruction *dest_insn; - struct alternative *alt; - struct symbol *pfunc = insn->func->pfunc; unsigned int prev_offset = 0; + struct reloc *reloc = table; + struct alternative *alt; /* - * Each @rela is a switch table relocation which points to the target + * Each @reloc is a switch table relocation which points to the target * instruction. */ - list_for_each_entry_from(rela, &table->sec->rela_list, list) { + for_each_reloc_from(table->sec, reloc) { /* Check for the end of the table: */ - if (rela != table && rela->jump_table_start) + if (reloc != table && reloc == next_table) break; /* Make sure the table entries are consecutive: */ - if (prev_offset && rela->offset != prev_offset + 8) + if (prev_offset && reloc_offset(reloc) != prev_offset + 8) break; /* Detect function pointers from contiguous objects: */ - if (rela->sym->sec == pfunc->sec && - rela->addend == pfunc->offset) + if (reloc->sym->sec == pfunc->sec && + reloc_addend(reloc) == pfunc->offset) break; - dest_insn = find_insn(file, rela->sym->sec, rela->addend); + dest_insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc)); if (!dest_insn) break; /* Make sure the destination is in the same function: */ - if (!dest_insn->func || dest_insn->func->pfunc != pfunc) + if (!insn_func(dest_insn) || insn_func(dest_insn)->pfunc != pfunc) break; alt = malloc(sizeof(*alt)); @@ -1059,13 +2059,13 @@ static int add_jump_table(struct objtool_file *file, struct instruction *insn, } alt->insn = dest_insn; - list_add_tail(&alt->list, &insn->alts); - prev_offset = rela->offset; + alt->next = insn->alts; + insn->alts = alt; + prev_offset = reloc_offset(reloc); } if (!prev_offset) { - WARN_FUNC("can't find switch jump table", - insn->sec, insn->offset); + WARN_INSN(insn, "can't find switch jump table"); return -1; } @@ -1073,56 +2073,15 @@ static int add_jump_table(struct objtool_file *file, struct instruction *insn, } /* - * find_jump_table() - Given a dynamic jump, find the switch jump table in - * .rodata associated with it. - * - * There are 3 basic patterns: - * - * 1. jmpq *[rodata addr](,%reg,8) - * - * This is the most common case by far. It jumps to an address in a simple - * jump table which is stored in .rodata. - * - * 2. jmpq *[rodata addr](%rip) - * - * This is caused by a rare GCC quirk, currently only seen in three driver - * functions in the kernel, only with certain obscure non-distro configs. - * - * As part of an optimization, GCC makes a copy of an existing switch jump - * table, modifies it, and then hard-codes the jump (albeit with an indirect - * jump) to use a single entry in the table. The rest of the jump table and - * some of its jump targets remain as dead code. - * - * In such a case we can just crudely ignore all unreachable instruction - * warnings for the entire object file. Ideally we would just ignore them - * for the function, but that would require redesigning the code quite a - * bit. And honestly that's just not worth doing: unreachable instruction - * warnings are of questionable value anyway, and this is such a rare issue. - * - * 3. mov [rodata addr],%reg1 - * ... some instructions ... - * jmpq *(%reg1,%reg2,8) - * - * This is a fairly uncommon pattern which is new for GCC 6. As of this - * writing, there are 11 occurrences of it in the allmodconfig kernel. - * - * As of GCC 7 there are quite a few more of these and the 'in between' code - * is significant. Esp. with KASAN enabled some of the code between the mov - * and jmpq uses .rodata itself, which can confuse things. - * - * TODO: Once we have DWARF CFI and smarter instruction decoding logic, - * ensure the same register is used in the mov and jump instructions. - * - * NOTE: RETPOLINE made it harder still to decode dynamic jumps. + * find_jump_table() - Given a dynamic jump, find the switch jump table + * associated with it. */ -static struct rela *find_jump_table(struct objtool_file *file, +static struct reloc *find_jump_table(struct objtool_file *file, struct symbol *func, struct instruction *insn) { - struct rela *text_rela, *table_rela; + struct reloc *table_reloc; struct instruction *dest_insn, *orig_insn = insn; - struct section *table_sec; - unsigned long table_offset; /* * Backward search using the @first_jump_src links, these help avoid @@ -1130,7 +2089,7 @@ static struct rela *find_jump_table(struct objtool_file *file, * it. */ for (; - insn && insn->func && insn->func->pfunc == func; + insn && insn_func(insn) && insn_func(insn)->pfunc == func; insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) { if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC) @@ -1143,53 +2102,14 @@ static struct rela *find_jump_table(struct objtool_file *file, insn->jump_dest->offset > orig_insn->offset)) break; - /* look for a relocation which references .rodata */ - text_rela = find_rela_by_dest_range(file->elf, insn->sec, - insn->offset, insn->len); - if (!text_rela || text_rela->sym->type != STT_SECTION || - !text_rela->sym->sec->rodata) - continue; - - table_offset = text_rela->addend; - table_sec = text_rela->sym->sec; - - if (text_rela->type == R_X86_64_PC32) - table_offset += 4; - - /* - * Make sure the .rodata address isn't associated with a - * symbol. GCC jump tables are anonymous data. - * - * Also support C jump tables which are in the same format as - * switch jump tables. For objtool to recognize them, they - * need to be placed in the C_JUMP_TABLE_SECTION section. They - * have symbols associated with them. - */ - if (find_symbol_containing(table_sec, table_offset) && - strcmp(table_sec->name, C_JUMP_TABLE_SECTION)) - continue; - - /* - * Each table entry has a rela associated with it. The rela - * should reference text in the same function as the original - * instruction. - */ - table_rela = find_rela_by_dest(file->elf, table_sec, table_offset); - if (!table_rela) + table_reloc = arch_find_switch_table(file, insn); + if (!table_reloc) continue; - dest_insn = find_insn(file, table_rela->sym->sec, table_rela->addend); - if (!dest_insn || !dest_insn->func || dest_insn->func->pfunc != func) + dest_insn = find_insn(file, table_reloc->sym->sec, reloc_addend(table_reloc)); + if (!dest_insn || !insn_func(dest_insn) || insn_func(dest_insn)->pfunc != func) continue; - /* - * Use of RIP-relative switch jumps is quite rare, and - * indicates a rare GCC quirk/bug which can leave dead code - * behind. - */ - if (text_rela->type == R_X86_64_PC32) - file->ignore_unreachables = true; - - return table_rela; + return table_reloc; } return NULL; @@ -1203,7 +2123,7 @@ static void mark_func_jump_tables(struct objtool_file *file, struct symbol *func) { struct instruction *insn, *last = NULL; - struct rela *rela; + struct reloc *reloc; func_for_each_insn(file, func, insn) { if (!last) @@ -1226,30 +2146,40 @@ static void mark_func_jump_tables(struct objtool_file *file, if (insn->type != INSN_JUMP_DYNAMIC) continue; - rela = find_jump_table(file, func, insn); - if (rela) { - rela->jump_table_start = true; - insn->jump_table = rela; - } + reloc = find_jump_table(file, func, insn); + if (reloc) + insn->_jump_table = reloc; } } static int add_func_jump_tables(struct objtool_file *file, struct symbol *func) { - struct instruction *insn; - int ret; + struct instruction *insn, *insn_t1 = NULL, *insn_t2; + int ret = 0; func_for_each_insn(file, func, insn) { - if (!insn->jump_table) + if (!insn_jump_table(insn)) + continue; + + if (!insn_t1) { + insn_t1 = insn; continue; + } + + insn_t2 = insn; - ret = add_jump_table(file, insn, insn->jump_table); + ret = add_jump_table(file, insn_t1, insn_jump_table(insn_t2)); if (ret) return ret; + + insn_t1 = insn_t2; } - return 0; + if (insn_t1) + ret = add_jump_table(file, insn_t1, NULL); + + return ret; } /* @@ -1259,112 +2189,144 @@ static int add_func_jump_tables(struct objtool_file *file, */ static int add_jump_table_alts(struct objtool_file *file) { - struct section *sec; struct symbol *func; int ret; if (!file->rodata) return 0; - for_each_sec(file, sec) { - list_for_each_entry(func, &sec->symbol_list, list) { - if (func->type != STT_FUNC) - continue; + for_each_sym(file, func) { + if (func->type != STT_FUNC) + continue; - mark_func_jump_tables(file, func); - ret = add_func_jump_tables(file, func); - if (ret) - return ret; - } + mark_func_jump_tables(file, func); + ret = add_func_jump_tables(file, func); + if (ret) + return ret; } return 0; } +static void set_func_state(struct cfi_state *state) +{ + state->cfa = initial_func_cfi.cfa; + memcpy(&state->regs, &initial_func_cfi.regs, + CFI_NUM_REGS * sizeof(struct cfi_reg)); + state->stack_size = initial_func_cfi.cfa.offset; + state->type = UNWIND_HINT_TYPE_CALL; +} + static int read_unwind_hints(struct objtool_file *file) { - struct section *sec, *relasec; - struct rela *rela; + struct cfi_state cfi = init_cfi; + struct section *sec; struct unwind_hint *hint; struct instruction *insn; - struct cfi_reg *cfa; + struct reloc *reloc; int i; sec = find_section_by_name(file->elf, ".discard.unwind_hints"); if (!sec) return 0; - relasec = sec->rela; - if (!relasec) { + if (!sec->rsec) { WARN("missing .rela.discard.unwind_hints section"); return -1; } - if (sec->len % sizeof(struct unwind_hint)) { + if (sec->sh.sh_size % sizeof(struct unwind_hint)) { WARN("struct unwind_hint size mismatch"); return -1; } file->hints = true; - for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) { + for (i = 0; i < sec->sh.sh_size / sizeof(struct unwind_hint); i++) { hint = (struct unwind_hint *)sec->data->d_buf + i; - rela = find_rela_by_dest(file->elf, sec, i * sizeof(*hint)); - if (!rela) { - WARN("can't find rela for unwind_hints[%d]", i); + reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint)); + if (!reloc) { + WARN("can't find reloc for unwind_hints[%d]", i); return -1; } - insn = find_insn(file, rela->sym->sec, rela->addend); + insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc)); if (!insn) { WARN("can't find insn for unwind_hints[%d]", i); return -1; } - cfa = &insn->cfi.cfa; + insn->hint = true; - if (hint->type == UNWIND_HINT_TYPE_RET_OFFSET) { - insn->ret_offset = hint->sp_offset; + if (hint->type == UNWIND_HINT_TYPE_UNDEFINED) { + insn->cfi = &force_undefined_cfi; continue; } - insn->hint = true; + if (hint->type == UNWIND_HINT_TYPE_SAVE) { + insn->hint = false; + insn->save = true; + continue; + } - switch (hint->sp_reg) { - case ORC_REG_UNDEFINED: - cfa->base = CFI_UNDEFINED; - break; - case ORC_REG_SP: - cfa->base = CFI_SP; - break; - case ORC_REG_BP: - cfa->base = CFI_BP; - break; - case ORC_REG_SP_INDIRECT: - cfa->base = CFI_SP_INDIRECT; - break; - case ORC_REG_R10: - cfa->base = CFI_R10; - break; - case ORC_REG_R13: - cfa->base = CFI_R13; - break; - case ORC_REG_DI: - cfa->base = CFI_DI; - break; - case ORC_REG_DX: - cfa->base = CFI_DX; - break; - default: - WARN_FUNC("unsupported unwind_hint sp base reg %d", - insn->sec, insn->offset, hint->sp_reg); + if (hint->type == UNWIND_HINT_TYPE_RESTORE) { + insn->restore = true; + continue; + } + + if (hint->type == UNWIND_HINT_TYPE_REGS_PARTIAL) { + struct symbol *sym = find_symbol_by_offset(insn->sec, insn->offset); + + if (sym && sym->bind == STB_GLOBAL) { + if (opts.ibt && insn->type != INSN_ENDBR && !insn->noendbr) { + WARN_INSN(insn, "UNWIND_HINT_IRET_REGS without ENDBR"); + } + } + } + + if (hint->type == UNWIND_HINT_TYPE_FUNC) { + insn->cfi = &func_cfi; + continue; + } + + if (insn->cfi) + cfi = *(insn->cfi); + + if (arch_decode_hint_reg(hint->sp_reg, &cfi.cfa.base)) { + WARN_INSN(insn, "unsupported unwind_hint sp base reg %d", hint->sp_reg); + return -1; + } + + cfi.cfa.offset = bswap_if_needed(file->elf, hint->sp_offset); + cfi.type = hint->type; + cfi.signal = hint->signal; + + insn->cfi = cfi_hash_find_or_add(&cfi); + } + + return 0; +} + +static int read_noendbr_hints(struct objtool_file *file) +{ + struct instruction *insn; + struct section *rsec; + struct reloc *reloc; + + rsec = find_section_by_name(file->elf, ".rela.discard.noendbr"); + if (!rsec) + return 0; + + for_each_reloc(rsec, reloc) { + insn = find_insn(file, reloc->sym->sec, + reloc->sym->offset + reloc_addend(reloc)); + if (!insn) { + WARN("bad .discard.noendbr entry"); return -1; } - cfa->offset = hint->sp_offset; - insn->cfi.type = hint->type; - insn->cfi.end = hint->end; + insn->noendbr = 1; } return 0; @@ -1372,30 +2334,31 @@ static int read_unwind_hints(struct objtool_file *file) static int read_retpoline_hints(struct objtool_file *file) { - struct section *sec; + struct section *rsec; struct instruction *insn; - struct rela *rela; + struct reloc *reloc; - sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe"); - if (!sec) + rsec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe"); + if (!rsec) return 0; - list_for_each_entry(rela, &sec->rela_list, list) { - if (rela->sym->type != STT_SECTION) { - WARN("unexpected relocation symbol type in %s", sec->name); + for_each_reloc(rsec, reloc) { + if (reloc->sym->type != STT_SECTION) { + WARN("unexpected relocation symbol type in %s", rsec->name); return -1; } - insn = find_insn(file, rela->sym->sec, rela->addend); + insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc)); if (!insn) { WARN("bad .discard.retpoline_safe entry"); return -1; } if (insn->type != INSN_JUMP_DYNAMIC && - insn->type != INSN_CALL_DYNAMIC) { - WARN_FUNC("retpoline_safe hint not an indirect jump/call", - insn->sec, insn->offset); + insn->type != INSN_CALL_DYNAMIC && + insn->type != INSN_RETURN && + insn->type != INSN_NOP) { + WARN_INSN(insn, "retpoline_safe hint not an indirect jump/call/ret/nop"); return -1; } @@ -1407,21 +2370,21 @@ static int read_retpoline_hints(struct objtool_file *file) static int read_instr_hints(struct objtool_file *file) { - struct section *sec; + struct section *rsec; struct instruction *insn; - struct rela *rela; + struct reloc *reloc; - sec = find_section_by_name(file->elf, ".rela.discard.instr_end"); - if (!sec) + rsec = find_section_by_name(file->elf, ".rela.discard.instr_end"); + if (!rsec) return 0; - list_for_each_entry(rela, &sec->rela_list, list) { - if (rela->sym->type != STT_SECTION) { - WARN("unexpected relocation symbol type in %s", sec->name); + for_each_reloc(rsec, reloc) { + if (reloc->sym->type != STT_SECTION) { + WARN("unexpected relocation symbol type in %s", rsec->name); return -1; } - insn = find_insn(file, rela->sym->sec, rela->addend); + insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc)); if (!insn) { WARN("bad .discard.instr_end entry"); return -1; @@ -1430,17 +2393,17 @@ static int read_instr_hints(struct objtool_file *file) insn->instr--; } - sec = find_section_by_name(file->elf, ".rela.discard.instr_begin"); - if (!sec) + rsec = find_section_by_name(file->elf, ".rela.discard.instr_begin"); + if (!rsec) return 0; - list_for_each_entry(rela, &sec->rela_list, list) { - if (rela->sym->type != STT_SECTION) { - WARN("unexpected relocation symbol type in %s", sec->name); + for_each_reloc(rsec, reloc) { + if (reloc->sym->type != STT_SECTION) { + WARN("unexpected relocation symbol type in %s", rsec->name); return -1; } - insn = find_insn(file, rela->sym->sec, rela->addend); + insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc)); if (!insn) { WARN("bad .discard.instr_begin entry"); return -1; @@ -1452,34 +2415,61 @@ static int read_instr_hints(struct objtool_file *file) return 0; } +static int read_validate_unret_hints(struct objtool_file *file) +{ + struct section *rsec; + struct instruction *insn; + struct reloc *reloc; + + rsec = find_section_by_name(file->elf, ".rela.discard.validate_unret"); + if (!rsec) + return 0; + + for_each_reloc(rsec, reloc) { + if (reloc->sym->type != STT_SECTION) { + WARN("unexpected relocation symbol type in %s", rsec->name); + return -1; + } + + insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc)); + if (!insn) { + WARN("bad .discard.instr_end entry"); + return -1; + } + insn->unret = 1; + } + + return 0; +} + + static int read_intra_function_calls(struct objtool_file *file) { struct instruction *insn; - struct section *sec; - struct rela *rela; + struct section *rsec; + struct reloc *reloc; - sec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls"); - if (!sec) + rsec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls"); + if (!rsec) return 0; - list_for_each_entry(rela, &sec->rela_list, list) { + for_each_reloc(rsec, reloc) { unsigned long dest_off; - if (rela->sym->type != STT_SECTION) { + if (reloc->sym->type != STT_SECTION) { WARN("unexpected relocation symbol type in %s", - sec->name); + rsec->name); return -1; } - insn = find_insn(file, rela->sym->sec, rela->addend); + insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc)); if (!insn) { WARN("bad .discard.intra_function_call entry"); return -1; } if (insn->type != INSN_CALL) { - WARN_FUNC("intra_function_call not a direct call", - insn->sec, insn->offset); + WARN_INSN(insn, "intra_function_call not a direct call"); return -1; } @@ -1490,11 +2480,10 @@ static int read_intra_function_calls(struct objtool_file *file) */ insn->type = INSN_JUMP_UNCONDITIONAL; - dest_off = insn->offset + insn->len + insn->immediate; + dest_off = arch_jump_destination(insn); insn->jump_dest = find_insn(file, insn->sec, dest_off); if (!insn->jump_dest) { - WARN_FUNC("can't find call dest at %s+0x%lx", - insn->sec, insn->offset, + WARN_INSN(insn, "can't find call dest at %s+0x%lx", insn->sec->name, dest_off); return -1; } @@ -1503,6 +2492,62 @@ static int read_intra_function_calls(struct objtool_file *file) return 0; } +/* + * Return true if name matches an instrumentation function, where calls to that + * function from noinstr code can safely be removed, but compilers won't do so. + */ +static bool is_profiling_func(const char *name) +{ + /* + * Many compilers cannot disable KCOV with a function attribute. + */ + if (!strncmp(name, "__sanitizer_cov_", 16)) + return true; + + /* + * Some compilers currently do not remove __tsan_func_entry/exit nor + * __tsan_atomic_signal_fence (used for barrier instrumentation) with + * the __no_sanitize_thread attribute, remove them. Once the kernel's + * minimum Clang version is 14.0, this can be removed. + */ + if (!strncmp(name, "__tsan_func_", 12) || + !strcmp(name, "__tsan_atomic_signal_fence")) + return true; + + return false; +} + +static int classify_symbols(struct objtool_file *file) +{ + struct symbol *func; + + for_each_sym(file, func) { + if (func->bind != STB_GLOBAL) + continue; + + if (!strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR, + strlen(STATIC_CALL_TRAMP_PREFIX_STR))) + func->static_call_tramp = true; + + if (arch_is_retpoline(func)) + func->retpoline_thunk = true; + + if (arch_is_rethunk(func)) + func->return_thunk = true; + + if (arch_is_embedded_insn(func)) + func->embedded_insn = true; + + if (arch_ftrace_match(func->name)) + func->fentry = true; + + if (is_profiling_func(func->name)) + func->profiling_func = true; + } + + return 0; +} + static void mark_rodata(struct objtool_file *file) { struct section *sec; @@ -1535,11 +2580,18 @@ static int decode_sections(struct objtool_file *file) mark_rodata(file); - ret = decode_instructions(file); + ret = init_pv_ops(file); if (ret) return ret; - ret = add_dead_ends(file); + /* + * Must be before add_{jump_call}_destination. + */ + ret = classify_symbols(file); + if (ret) + return ret; + + ret = decode_instructions(file); if (ret) return ret; @@ -1550,14 +2602,31 @@ static int decode_sections(struct objtool_file *file) if (ret) return ret; - ret = add_jump_destinations(file); + /* + * Must be before read_unwind_hints() since that needs insn->noendbr. + */ + ret = read_noendbr_hints(file); if (ret) return ret; - ret = add_special_section_alts(file); + /* + * Must be before add_jump_destinations(), which depends on 'func' + * being set for alternatives, to enable proper sibling call detection. + */ + if (opts.stackval || opts.orc || opts.uaccess || opts.noinstr) { + ret = add_special_section_alts(file); + if (ret) + return ret; + } + + ret = add_jump_destinations(file); if (ret) return ret; + /* + * Must be before add_call_destination(); it changes INSN_CALL to + * INSN_JUMP. + */ ret = read_intra_function_calls(file); if (ret) return ret; @@ -1566,6 +2635,14 @@ static int decode_sections(struct objtool_file *file) if (ret) return ret; + /* + * Must be after add_call_destinations() such that it can override + * dead_end_function() marks. + */ + ret = add_dead_ends(file); + if (ret) + return ret; + ret = add_jump_table_alts(file); if (ret) return ret; @@ -1582,42 +2659,42 @@ static int decode_sections(struct objtool_file *file) if (ret) return ret; + ret = read_validate_unret_hints(file); + if (ret) + return ret; + return 0; } -static bool is_fentry_call(struct instruction *insn) +static bool is_special_call(struct instruction *insn) { - if (insn->type == INSN_CALL && insn->call_dest && - insn->call_dest->type == STT_NOTYPE && - !strcmp(insn->call_dest->name, "__fentry__")) - return true; + if (insn->type == INSN_CALL) { + struct symbol *dest = insn_call_dest(insn); + + if (!dest) + return false; + + if (dest->fentry || dest->embedded_insn) + return true; + } return false; } static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state) { - u8 ret_offset = insn->ret_offset; struct cfi_state *cfi = &state->cfi; int i; if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap) return true; - if (cfi->cfa.offset != initial_func_cfi.cfa.offset + ret_offset) + if (cfi->cfa.offset != initial_func_cfi.cfa.offset) return true; - if (cfi->stack_size != initial_func_cfi.cfa.offset + ret_offset) + if (cfi->stack_size != initial_func_cfi.cfa.offset) return true; - /* - * If there is a ret offset hint then don't check registers - * because a callee-saved register might have been pushed on - * the stack. - */ - if (ret_offset) - return false; - for (i = 0; i < CFI_NUM_REGS; i++) { if (cfi->regs[i].base != initial_func_cfi.regs[i].base || cfi->regs[i].offset != initial_func_cfi.regs[i].offset) @@ -1627,12 +2704,20 @@ static bool has_modified_stack_frame(struct instruction *insn, struct insn_state return false; } +static bool check_reg_frame_pos(const struct cfi_reg *reg, + int expected_offset) +{ + return reg->base == CFI_CFA && + reg->offset == expected_offset; +} + static bool has_valid_stack_frame(struct insn_state *state) { struct cfi_state *cfi = &state->cfi; - if (cfi->cfa.base == CFI_BP && cfi->regs[CFI_BP].base == CFI_CFA && - cfi->regs[CFI_BP].offset == -16) + if (cfi->cfa.base == CFI_BP && + check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) && + check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8)) return true; if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP) @@ -1734,22 +2819,28 @@ static void restore_reg(struct cfi_state *cfi, unsigned char reg) * 41 5d pop %r13 * c3 retq */ -static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi, - struct stack_op *op) +static int update_cfi_state(struct instruction *insn, + struct instruction *next_insn, + struct cfi_state *cfi, struct stack_op *op) { struct cfi_reg *cfa = &cfi->cfa; struct cfi_reg *regs = cfi->regs; + /* ignore UNWIND_HINT_UNDEFINED regions */ + if (cfi->force_undefined) + return 0; + /* stack operations don't make sense with an undefined CFA */ if (cfa->base == CFI_UNDEFINED) { - if (insn->func) { - WARN_FUNC("undefined stack state", insn->sec, insn->offset); + if (insn_func(insn)) { + WARN_INSN(insn, "undefined stack state"); return -1; } return 0; } - if (cfi->type == ORC_TYPE_REGS || cfi->type == ORC_TYPE_REGS_IRET) + if (cfi->type == UNWIND_HINT_TYPE_REGS || + cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL) return update_cfi_state_regs(insn, cfi, op); switch (op->dest.type) { @@ -1760,8 +2851,7 @@ static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi, case OP_SRC_REG: if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP && cfa->base == CFI_SP && - regs[CFI_BP].base == CFI_CFA && - regs[CFI_BP].offset == -cfa->offset) { + check_reg_frame_pos(®s[CFI_BP], -cfa->offset)) { /* mov %rsp, %rbp */ cfa->base = op->dest.reg; @@ -1794,7 +2884,7 @@ static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi, } else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP && - cfa->base == CFI_BP) { + (cfa->base == CFI_BP || cfa->base == cfi->drap_reg)) { /* * mov %rbp, %rsp @@ -1821,12 +2911,58 @@ static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi, cfa->offset = -cfi->vals[op->src.reg].offset; cfi->stack_size = cfa->offset; + } else if (cfa->base == CFI_SP && + cfi->vals[op->src.reg].base == CFI_SP_INDIRECT && + cfi->vals[op->src.reg].offset == cfa->offset) { + + /* + * Stack swizzle: + * + * 1: mov %rsp, (%[tos]) + * 2: mov %[tos], %rsp + * ... + * 3: pop %rsp + * + * Where: + * + * 1 - places a pointer to the previous + * stack at the Top-of-Stack of the + * new stack. + * + * 2 - switches to the new stack. + * + * 3 - pops the Top-of-Stack to restore + * the original stack. + * + * Note: we set base to SP_INDIRECT + * here and preserve offset. Therefore + * when the unwinder reaches ToS it + * will dereference SP and then add the + * offset to find the next frame, IOW: + * (%rsp) + offset. + */ + cfa->base = CFI_SP_INDIRECT; + } else { cfa->base = CFI_UNDEFINED; cfa->offset = 0; } } + else if (op->dest.reg == CFI_SP && + cfi->vals[op->src.reg].base == CFI_SP_INDIRECT && + cfi->vals[op->src.reg].offset == cfa->offset) { + + /* + * The same stack swizzle case 2) as above. But + * because we can't change cfa->base, case 3) + * will become a regular POP. Pretend we're a + * PUSH so things don't go unbalanced. + */ + cfi->stack_size += 8; + } + + break; case OP_SRC_ADD: @@ -1879,9 +3015,8 @@ static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi, break; } - if (op->dest.reg == cfi->cfa.base) { - WARN_FUNC("unsupported stack register modification", - insn->sec, insn->offset); + if (op->dest.reg == cfi->cfa.base && !(next_insn && next_insn->hint)) { + WARN_INSN(insn, "unsupported stack register modification"); return -1; } @@ -1891,8 +3026,7 @@ static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi, if (op->dest.reg != CFI_SP || (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) || (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) { - WARN_FUNC("unsupported stack pointer realignment", - insn->sec, insn->offset); + WARN_INSN(insn, "unsupported stack pointer realignment"); return -1; } @@ -1912,6 +3046,13 @@ static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi, case OP_SRC_POP: case OP_SRC_POPF: + if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) { + + /* pop %rsp; # restore from a stack swizzle */ + cfa->base = CFI_SP; + break; + } + if (!cfi->drap && op->dest.reg == cfa->base) { /* pop %rbp */ @@ -1927,7 +3068,7 @@ static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi, cfa->offset = 0; cfi->drap_offset = -1; - } else if (regs[op->dest.reg].offset == -cfi->stack_size) { + } else if (cfi->stack_size == -regs[op->dest.reg].offset) { /* pop %reg */ restore_reg(cfi, op->dest.reg); @@ -1940,6 +3081,14 @@ static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi, break; case OP_SRC_REG_INDIRECT: + if (!cfi->drap && op->dest.reg == cfa->base && + op->dest.reg == CFI_BP) { + + /* mov disp(%rsp), %rbp */ + cfa->base = CFI_SP; + cfa->offset = cfi->stack_size; + } + if (cfi->drap && op->src.reg == CFI_BP && op->src.offset == cfi->drap_offset) { @@ -1961,13 +3110,18 @@ static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi, /* mov disp(%rbp), %reg */ /* mov disp(%rsp), %reg */ restore_reg(cfi, op->dest.reg); + + } else if (op->src.reg == CFI_SP && + op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) { + + /* mov disp(%rsp), %reg */ + restore_reg(cfi, op->dest.reg); } break; default: - WARN_FUNC("unknown stack-related instruction", - insn->sec, insn->offset); + WARN_INSN(insn, "unknown stack-related instruction"); return -1; } @@ -1997,7 +3151,7 @@ static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi, /* drap: push %rbp */ cfi->stack_size = 0; - } else if (regs[op->src.reg].base == CFI_UNDEFINED) { + } else { /* drap: push %reg */ save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size); @@ -2010,7 +3164,7 @@ static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi, } /* detect when asm code uses rbp as a scratch register */ - if (!no_fp && insn->func && op->src.reg == CFI_BP && + if (opts.stackval && insn_func(insn) && op->src.reg == CFI_BP && cfa->base != CFI_BP) cfi->bp_scratch = true; break; @@ -2026,9 +3180,7 @@ static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi, /* save drap offset so we know when to restore it */ cfi->drap_offset = op->dest.offset; - } - - else if (regs[op->src.reg].base == CFI_UNDEFINED) { + } else { /* drap: mov reg, disp(%rbp) */ save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset); @@ -2040,34 +3192,25 @@ static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi, /* mov reg, disp(%rsp) */ save_reg(cfi, op->src.reg, CFI_CFA, op->dest.offset - cfi->cfa.offset); - } - - break; - case OP_DEST_LEAVE: - if ((!cfi->drap && cfa->base != CFI_BP) || - (cfi->drap && cfa->base != cfi->drap_reg)) { - WARN_FUNC("leave instruction with modified stack frame", - insn->sec, insn->offset); - return -1; - } + } else if (op->dest.reg == CFI_SP) { - /* leave (mov %rbp, %rsp; pop %rbp) */ + /* mov reg, disp(%rsp) */ + save_reg(cfi, op->src.reg, CFI_CFA, + op->dest.offset - cfi->stack_size); - cfi->stack_size = -cfi->regs[CFI_BP].offset - 8; - restore_reg(cfi, CFI_BP); + } else if (op->src.reg == CFI_SP && op->dest.offset == 0) { - if (!cfi->drap) { - cfa->base = CFI_SP; - cfa->offset -= 8; + /* mov %rsp, (%reg); # setup a stack swizzle. */ + cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT; + cfi->vals[op->dest.reg].offset = cfa->offset; } break; case OP_DEST_MEM: if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) { - WARN_FUNC("unknown stack-related memory operation", - insn->sec, insn->offset); + WARN_INSN(insn, "unknown stack-related memory operation"); return -1; } @@ -2079,37 +3222,73 @@ static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi, break; default: - WARN_FUNC("unknown stack-related instruction", - insn->sec, insn->offset); + WARN_INSN(insn, "unknown stack-related instruction"); return -1; } return 0; } -static int handle_insn_ops(struct instruction *insn, struct insn_state *state) +/* + * The stack layouts of alternatives instructions can sometimes diverge when + * they have stack modifications. That's fine as long as the potential stack + * layouts don't conflict at any given potential instruction boundary. + * + * Flatten the CFIs of the different alternative code streams (both original + * and replacement) into a single shared CFI array which can be used to detect + * conflicts and nicely feed a linear array of ORC entries to the unwinder. + */ +static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn) { - struct stack_op *op; + struct cfi_state **alt_cfi; + int group_off; + + if (!insn->alt_group) + return 0; - list_for_each_entry(op, &insn->stack_ops, list) { - struct cfi_state old_cfi = state->cfi; - int res; + if (!insn->cfi) { + WARN("CFI missing"); + return -1; + } - res = update_cfi_state(insn, &state->cfi, op); - if (res) - return res; + alt_cfi = insn->alt_group->cfi; + group_off = insn->offset - insn->alt_group->first_insn->offset; - if (insn->alt_group && memcmp(&state->cfi, &old_cfi, sizeof(struct cfi_state))) { - WARN_FUNC("alternative modifies stack", insn->sec, insn->offset); + if (!alt_cfi[group_off]) { + alt_cfi[group_off] = insn->cfi; + } else { + if (cficmp(alt_cfi[group_off], insn->cfi)) { + struct alt_group *orig_group = insn->alt_group->orig_group ?: insn->alt_group; + struct instruction *orig = orig_group->first_insn; + char *where = offstr(insn->sec, insn->offset); + WARN_INSN(orig, "stack layout conflict in alternatives: %s", where); + free(where); return -1; } + } + + return 0; +} + +static int handle_insn_ops(struct instruction *insn, + struct instruction *next_insn, + struct insn_state *state) +{ + struct stack_op *op; + + for (op = insn->stack_ops; op; op = op->next) { + + if (update_cfi_state(insn, next_insn, &state->cfi, op)) + return 1; + + if (!insn->alt_group) + continue; if (op->dest.type == OP_DEST_PUSHF) { if (!state->uaccess_stack) { state->uaccess_stack = 1; } else if (state->uaccess_stack >> 31) { - WARN_FUNC("PUSHF stack exhausted", - insn->sec, insn->offset); + WARN_INSN(insn, "PUSHF stack exhausted"); return 1; } state->uaccess_stack <<= 1; @@ -2131,13 +3310,17 @@ static int handle_insn_ops(struct instruction *insn, struct insn_state *state) static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2) { - struct cfi_state *cfi1 = &insn->cfi; + struct cfi_state *cfi1 = insn->cfi; int i; + if (!cfi1) { + WARN("CFI missing"); + return false; + } + if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) { - WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d", - insn->sec, insn->offset, + WARN_INSN(insn, "stack state mismatch: cfa1=%d%+d cfa2=%d%+d", cfi1->cfa.base, cfi1->cfa.offset, cfi2->cfa.base, cfi2->cfa.offset); @@ -2147,8 +3330,7 @@ static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2) sizeof(struct cfi_reg))) continue; - WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d", - insn->sec, insn->offset, + WARN_INSN(insn, "stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d", i, cfi1->regs[i].base, cfi1->regs[i].offset, i, cfi2->regs[i].base, cfi2->regs[i].offset); break; @@ -2156,15 +3338,14 @@ static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2) } else if (cfi1->type != cfi2->type) { - WARN_FUNC("stack state mismatch: type1=%d type2=%d", - insn->sec, insn->offset, cfi1->type, cfi2->type); + WARN_INSN(insn, "stack state mismatch: type1=%d type2=%d", + cfi1->type, cfi2->type); } else if (cfi1->drap != cfi2->drap || (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) || (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) { - WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)", - insn->sec, insn->offset, + WARN_INSN(insn, "stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)", cfi1->drap, cfi1->drap_reg, cfi1->drap_offset, cfi2->drap, cfi2->drap_reg, cfi2->drap_offset); @@ -2184,123 +3365,202 @@ static inline bool func_uaccess_safe(struct symbol *func) static inline const char *call_dest_name(struct instruction *insn) { - if (insn->call_dest) - return insn->call_dest->name; + static char pvname[19]; + struct reloc *reloc; + int idx; + + if (insn_call_dest(insn)) + return insn_call_dest(insn)->name; + + reloc = insn_reloc(NULL, insn); + if (reloc && !strcmp(reloc->sym->name, "pv_ops")) { + idx = (reloc_addend(reloc) / sizeof(void *)); + snprintf(pvname, sizeof(pvname), "pv_ops[%d]", idx); + return pvname; + } return "{dynamic}"; } -static int validate_call(struct instruction *insn, struct insn_state *state) +static bool pv_call_dest(struct objtool_file *file, struct instruction *insn) +{ + struct symbol *target; + struct reloc *reloc; + int idx; + + reloc = insn_reloc(file, insn); + if (!reloc || strcmp(reloc->sym->name, "pv_ops")) + return false; + + idx = (arch_dest_reloc_offset(reloc_addend(reloc)) / sizeof(void *)); + + if (file->pv_ops[idx].clean) + return true; + + file->pv_ops[idx].clean = true; + + list_for_each_entry(target, &file->pv_ops[idx].targets, pv_target) { + if (!target->sec->noinstr) { + WARN("pv_ops[%d]: %s", idx, target->name); + file->pv_ops[idx].clean = false; + } + } + + return file->pv_ops[idx].clean; +} + +static inline bool noinstr_call_dest(struct objtool_file *file, + struct instruction *insn, + struct symbol *func) +{ + /* + * We can't deal with indirect function calls at present; + * assume they're instrumented. + */ + if (!func) { + if (file->pv_ops) + return pv_call_dest(file, insn); + + return false; + } + + /* + * If the symbol is from a noinstr section; we good. + */ + if (func->sec->noinstr) + return true; + + /* + * If the symbol is a static_call trampoline, we can't tell. + */ + if (func->static_call_tramp) + return true; + + /* + * The __ubsan_handle_*() calls are like WARN(), they only happen when + * something 'BAD' happened. At the risk of taking the machine down, + * let them proceed to get the message out. + */ + if (!strncmp(func->name, "__ubsan_handle_", 15)) + return true; + + return false; +} + +static int validate_call(struct objtool_file *file, + struct instruction *insn, + struct insn_state *state) { if (state->noinstr && state->instr <= 0 && - (!insn->call_dest || !insn->call_dest->sec->noinstr)) { - WARN_FUNC("call to %s() leaves .noinstr.text section", - insn->sec, insn->offset, call_dest_name(insn)); + !noinstr_call_dest(file, insn, insn_call_dest(insn))) { + WARN_INSN(insn, "call to %s() leaves .noinstr.text section", call_dest_name(insn)); return 1; } - if (state->uaccess && !func_uaccess_safe(insn->call_dest)) { - WARN_FUNC("call to %s() with UACCESS enabled", - insn->sec, insn->offset, call_dest_name(insn)); + if (state->uaccess && !func_uaccess_safe(insn_call_dest(insn))) { + WARN_INSN(insn, "call to %s() with UACCESS enabled", call_dest_name(insn)); return 1; } if (state->df) { - WARN_FUNC("call to %s() with DF set", - insn->sec, insn->offset, call_dest_name(insn)); + WARN_INSN(insn, "call to %s() with DF set", call_dest_name(insn)); return 1; } return 0; } -static int validate_sibling_call(struct instruction *insn, struct insn_state *state) +static int validate_sibling_call(struct objtool_file *file, + struct instruction *insn, + struct insn_state *state) { - if (has_modified_stack_frame(insn, state)) { - WARN_FUNC("sibling call from callable instruction with modified stack frame", - insn->sec, insn->offset); + if (insn_func(insn) && has_modified_stack_frame(insn, state)) { + WARN_INSN(insn, "sibling call from callable instruction with modified stack frame"); return 1; } - return validate_call(insn, state); + return validate_call(file, insn, state); } static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state) { if (state->noinstr && state->instr > 0) { - WARN_FUNC("return with instrumentation enabled", - insn->sec, insn->offset); + WARN_INSN(insn, "return with instrumentation enabled"); return 1; } if (state->uaccess && !func_uaccess_safe(func)) { - WARN_FUNC("return with UACCESS enabled", - insn->sec, insn->offset); + WARN_INSN(insn, "return with UACCESS enabled"); return 1; } if (!state->uaccess && func_uaccess_safe(func)) { - WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function", - insn->sec, insn->offset); + WARN_INSN(insn, "return with UACCESS disabled from a UACCESS-safe function"); return 1; } if (state->df) { - WARN_FUNC("return with DF set", - insn->sec, insn->offset); + WARN_INSN(insn, "return with DF set"); return 1; } if (func && has_modified_stack_frame(insn, state)) { - WARN_FUNC("return with modified stack frame", - insn->sec, insn->offset); + WARN_INSN(insn, "return with modified stack frame"); return 1; } if (state->cfi.bp_scratch) { - WARN_FUNC("BP used as a scratch register", - insn->sec, insn->offset); + WARN_INSN(insn, "BP used as a scratch register"); return 1; } return 0; } -/* - * Alternatives should not contain any ORC entries, this in turn means they - * should not contain any CFI ops, which implies all instructions should have - * the same same CFI state. - * - * It is possible to constuct alternatives that have unreachable holes that go - * unreported (because they're NOPs), such holes would result in CFI_UNDEFINED - * states which then results in ORC entries, which we just said we didn't want. - * - * Avoid them by copying the CFI entry of the first instruction into the whole - * alternative. - */ -static void fill_alternative_cfi(struct objtool_file *file, struct instruction *insn) +static struct instruction *next_insn_to_validate(struct objtool_file *file, + struct instruction *insn) { - struct instruction *first_insn = insn; - int alt_group = insn->alt_group; + struct alt_group *alt_group = insn->alt_group; - sec_for_each_insn_continue(file, insn) { - if (insn->alt_group != alt_group) - break; - insn->cfi = first_insn->cfi; + /* + * Simulate the fact that alternatives are patched in-place. When the + * end of a replacement alt_group is reached, redirect objtool flow to + * the end of the original alt_group. + * + * insn->alts->insn -> alt_group->first_insn + * ... + * alt_group->last_insn + * [alt_group->nop] -> next(orig_group->last_insn) + */ + if (alt_group) { + if (alt_group->nop) { + /* ->nop implies ->orig_group */ + if (insn == alt_group->last_insn) + return alt_group->nop; + if (insn == alt_group->nop) + goto next_orig; + } + if (insn == alt_group->last_insn && alt_group->orig_group) + goto next_orig; } + + return next_insn_same_sec(file, insn); + +next_orig: + return next_insn_same_sec(file, alt_group->orig_group->last_insn); } /* * Follow the branch starting at the given instruction, and recursively follow * any other branches (jumps). Meanwhile, track the frame pointer state at * each instruction and validate all the rules described in - * tools/objtool/Documentation/stack-validation.txt. + * tools/objtool/Documentation/objtool.txt. */ static int validate_branch(struct objtool_file *file, struct symbol *func, struct instruction *insn, struct insn_state state) { struct alternative *alt; - struct instruction *next_insn; + struct instruction *next_insn, *prev_insn = NULL; struct section *sec; u8 visited; int ret; @@ -2308,62 +3568,114 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, sec = insn->sec; while (1) { - next_insn = next_insn_same_sec(file, insn); + next_insn = next_insn_to_validate(file, insn); + + if (func && insn_func(insn) && func != insn_func(insn)->pfunc) { + /* Ignore KCFI type preambles, which always fall through */ + if (!strncmp(func->name, "__cfi_", 6) || + !strncmp(func->name, "__pfx_", 6)) + return 0; - if (file->c_file && func && insn->func && func != insn->func->pfunc) { WARN("%s() falls through to next function %s()", - func->name, insn->func->name); + func->name, insn_func(insn)->name); return 1; } if (func && insn->ignore) { - WARN_FUNC("BUG: why am I validating an ignored function?", - sec, insn->offset); + WARN_INSN(insn, "BUG: why am I validating an ignored function?"); return 1; } - visited = 1 << state.uaccess; - if (insn->visited) { + visited = VISITED_BRANCH << state.uaccess; + if (insn->visited & VISITED_BRANCH_MASK) { if (!insn->hint && !insn_cfi_match(insn, &state.cfi)) return 1; if (insn->visited & visited) return 0; + } else { + nr_insns_visited++; } if (state.noinstr) state.instr += insn->instr; - if (insn->hint) - state.cfi = insn->cfi; - else - insn->cfi = state.cfi; + if (insn->hint) { + if (insn->restore) { + struct instruction *save_insn, *i; + + i = insn; + save_insn = NULL; + + sym_for_each_insn_continue_reverse(file, func, i) { + if (i->save) { + save_insn = i; + break; + } + } + + if (!save_insn) { + WARN_INSN(insn, "no corresponding CFI save for CFI restore"); + return 1; + } + + if (!save_insn->visited) { + /* + * If the restore hint insn is at the + * beginning of a basic block and was + * branched to from elsewhere, and the + * save insn hasn't been visited yet, + * defer following this branch for now. + * It will be seen later via the + * straight-line path. + */ + if (!prev_insn) + return 0; + + WARN_INSN(insn, "objtool isn't smart enough to handle this CFI save/restore combo"); + return 1; + } + + insn->cfi = save_insn->cfi; + nr_cfi_reused++; + } + + state.cfi = *insn->cfi; + } else { + /* XXX track if we actually changed state.cfi */ + + if (prev_insn && !cficmp(prev_insn->cfi, &state.cfi)) { + insn->cfi = prev_insn->cfi; + nr_cfi_reused++; + } else { + insn->cfi = cfi_hash_find_or_add(&state.cfi); + } + } insn->visited |= visited; - if (!insn->ignore_alts && !list_empty(&insn->alts)) { + if (propagate_alt_cfi(file, insn)) + return 1; + + if (!insn->ignore_alts && insn->alts) { bool skip_orig = false; - list_for_each_entry(alt, &insn->alts, list) { + for (alt = insn->alts; alt; alt = alt->next) { if (alt->skip_orig) skip_orig = true; ret = validate_branch(file, func, alt->insn, state); if (ret) { - if (backtrace) - BT_FUNC("(alt)", insn); + BT_INSN(insn, "(alt)"); return ret; } } - if (insn->alt_group) - fill_alternative_cfi(file, insn); - if (skip_orig) return 0; } - if (handle_insn_ops(insn, &state)) + if (handle_insn_ops(insn, next_insn, &state)) return 1; switch (insn->type) { @@ -2373,26 +3685,25 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, case INSN_CALL: case INSN_CALL_DYNAMIC: - ret = validate_call(insn, &state); + ret = validate_call(file, insn, &state); if (ret) return ret; - if (!no_fp && func && !is_fentry_call(insn) && + if (opts.stackval && func && !is_special_call(insn) && !has_valid_stack_frame(&state)) { - WARN_FUNC("call without frame pointer save/setup", - sec, insn->offset); + WARN_INSN(insn, "call without frame pointer save/setup"); return 1; } - if (dead_end_function(file, insn->call_dest)) + if (insn->dead_end) return 0; break; case INSN_JUMP_CONDITIONAL: case INSN_JUMP_UNCONDITIONAL: - if (func && is_sibling_call(insn)) { - ret = validate_sibling_call(insn, &state); + if (is_sibling_call(insn)) { + ret = validate_sibling_call(file, insn, &state); if (ret) return ret; @@ -2400,8 +3711,7 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, ret = validate_branch(file, func, insn->jump_dest, state); if (ret) { - if (backtrace) - BT_FUNC("(branch)", insn); + BT_INSN(insn, "(branch)"); return ret; } } @@ -2413,8 +3723,8 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, case INSN_JUMP_DYNAMIC: case INSN_JUMP_DYNAMIC_CONDITIONAL: - if (func && is_sibling_call(insn)) { - ret = validate_sibling_call(insn, &state); + if (is_sibling_call(insn)) { + ret = validate_sibling_call(file, insn, &state); if (ret) return ret; } @@ -2426,15 +3736,14 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, case INSN_CONTEXT_SWITCH: if (func && (!next_insn || !next_insn->hint)) { - WARN_FUNC("unsupported instruction in callable function", - sec, insn->offset); + WARN_INSN(insn, "unsupported instruction in callable function"); return 1; } return 0; case INSN_STAC: if (state.uaccess) { - WARN_FUNC("recursive UACCESS enable", sec, insn->offset); + WARN_INSN(insn, "recursive UACCESS enable"); return 1; } @@ -2443,12 +3752,12 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, case INSN_CLAC: if (!state.uaccess && func) { - WARN_FUNC("redundant UACCESS disable", sec, insn->offset); + WARN_INSN(insn, "redundant UACCESS disable"); return 1; } if (func_uaccess_safe(func) && !state.uaccess_stack) { - WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset); + WARN_INSN(insn, "UACCESS-safe disables UACCESS"); return 1; } @@ -2456,15 +3765,19 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, break; case INSN_STD: - if (state.df) - WARN_FUNC("recursive STD", sec, insn->offset); + if (state.df) { + WARN_INSN(insn, "recursive STD"); + return 1; + } state.df = true; break; case INSN_CLD: - if (!state.df && func) - WARN_FUNC("redundant CLD", sec, insn->offset); + if (!state.df && func) { + WARN_INSN(insn, "redundant CLD"); + return 1; + } state.df = false; break; @@ -2483,40 +3796,178 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, return 1; } + prev_insn = insn; insn = next_insn; } return 0; } +static int validate_unwind_hint(struct objtool_file *file, + struct instruction *insn, + struct insn_state *state) +{ + if (insn->hint && !insn->visited && !insn->ignore) { + int ret = validate_branch(file, insn_func(insn), insn, *state); + if (ret) + BT_INSN(insn, "<=== (hint)"); + return ret; + } + + return 0; +} + static int validate_unwind_hints(struct objtool_file *file, struct section *sec) { struct instruction *insn; struct insn_state state; - int ret, warnings = 0; + int warnings = 0; if (!file->hints) return 0; - init_insn_state(&state, sec); + init_insn_state(file, &state, sec); if (sec) { - insn = find_insn(file, sec, 0); - if (!insn) - return 0; + sec_for_each_insn(file, sec, insn) + warnings += validate_unwind_hint(file, insn, &state); } else { - insn = list_first_entry(&file->insn_list, typeof(*insn), list); + for_each_insn(file, insn) + warnings += validate_unwind_hint(file, insn, &state); } - while (&insn->list != &file->insn_list && (!sec || insn->sec == sec)) { - if (insn->hint && !insn->visited) { - ret = validate_branch(file, insn->func, insn, state); - if (ret && backtrace) - BT_FUNC("<=== (hint)", insn); - warnings += ret; + return warnings; +} + +/* + * Validate rethunk entry constraint: must untrain RET before the first RET. + * + * Follow every branch (intra-function) and ensure VALIDATE_UNRET_END comes + * before an actual RET instruction. + */ +static int validate_unret(struct objtool_file *file, struct instruction *insn) +{ + struct instruction *next, *dest; + int ret; + + for (;;) { + next = next_insn_to_validate(file, insn); + + if (insn->visited & VISITED_UNRET) + return 0; + + insn->visited |= VISITED_UNRET; + + if (!insn->ignore_alts && insn->alts) { + struct alternative *alt; + bool skip_orig = false; + + for (alt = insn->alts; alt; alt = alt->next) { + if (alt->skip_orig) + skip_orig = true; + + ret = validate_unret(file, alt->insn); + if (ret) { + BT_INSN(insn, "(alt)"); + return ret; + } + } + + if (skip_orig) + return 0; } - insn = list_next_entry(insn, list); + switch (insn->type) { + + case INSN_CALL_DYNAMIC: + case INSN_JUMP_DYNAMIC: + case INSN_JUMP_DYNAMIC_CONDITIONAL: + WARN_INSN(insn, "early indirect call"); + return 1; + + case INSN_JUMP_UNCONDITIONAL: + case INSN_JUMP_CONDITIONAL: + if (!is_sibling_call(insn)) { + if (!insn->jump_dest) { + WARN_INSN(insn, "unresolved jump target after linking?!?"); + return -1; + } + ret = validate_unret(file, insn->jump_dest); + if (ret) { + BT_INSN(insn, "(branch%s)", + insn->type == INSN_JUMP_CONDITIONAL ? "-cond" : ""); + return ret; + } + + if (insn->type == INSN_JUMP_UNCONDITIONAL) + return 0; + + break; + } + + /* fallthrough */ + case INSN_CALL: + dest = find_insn(file, insn_call_dest(insn)->sec, + insn_call_dest(insn)->offset); + if (!dest) { + WARN("Unresolved function after linking!?: %s", + insn_call_dest(insn)->name); + return -1; + } + + ret = validate_unret(file, dest); + if (ret) { + BT_INSN(insn, "(call)"); + return ret; + } + /* + * If a call returns without error, it must have seen UNTRAIN_RET. + * Therefore any non-error return is a success. + */ + return 0; + + case INSN_RETURN: + WARN_INSN(insn, "RET before UNTRAIN"); + return 1; + + case INSN_NOP: + if (insn->retpoline_safe) + return 0; + break; + + default: + break; + } + + if (!next) { + WARN_INSN(insn, "teh end!"); + return -1; + } + insn = next; + } + + return 0; +} + +/* + * Validate that all branches starting at VALIDATE_UNRET_BEGIN encounter + * VALIDATE_UNRET_END before RET. + */ +static int validate_unrets(struct objtool_file *file) +{ + struct instruction *insn; + int ret, warnings = 0; + + for_each_insn(file, insn) { + if (!insn->unret) + continue; + + ret = validate_unret(file, insn); + if (ret < 0) { + WARN_INSN(insn, "Failed UNRET validation"); + return ret; + } + warnings += ret; } return warnings; @@ -2529,24 +3980,25 @@ static int validate_retpoline(struct objtool_file *file) for_each_insn(file, insn) { if (insn->type != INSN_JUMP_DYNAMIC && - insn->type != INSN_CALL_DYNAMIC) + insn->type != INSN_CALL_DYNAMIC && + insn->type != INSN_RETURN) continue; if (insn->retpoline_safe) continue; - /* - * .init.text code is ran before userspace and thus doesn't - * strictly need retpolines, except for modules which are - * loaded late, they very much do need retpoline in their - * .init.text - */ - if (!strcmp(insn->sec->name, ".init.text") && !module) + if (insn->sec->init) continue; - WARN_FUNC("indirect %s found in RETPOLINE build", - insn->sec, insn->offset, - insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call"); + if (insn->type == INSN_RETURN) { + if (opts.rethunk) { + WARN_INSN(insn, "'naked' return found in MITIGATION_RETHUNK build"); + } else + continue; + } else { + WARN_INSN(insn, "indirect %s found in MITIGATION_RETPOLINE build", + insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call"); + } warnings++; } @@ -2557,45 +4009,91 @@ static int validate_retpoline(struct objtool_file *file) static bool is_kasan_insn(struct instruction *insn) { return (insn->type == INSN_CALL && - !strcmp(insn->call_dest->name, "__asan_handle_no_return")); + !strcmp(insn_call_dest(insn)->name, "__asan_handle_no_return")); } static bool is_ubsan_insn(struct instruction *insn) { return (insn->type == INSN_CALL && - !strcmp(insn->call_dest->name, + !strcmp(insn_call_dest(insn)->name, "__ubsan_handle_builtin_unreachable")); } -static bool ignore_unreachable_insn(struct instruction *insn) +static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn) { int i; + struct instruction *prev_insn; - if (insn->ignore || insn->type == INSN_NOP) + if (insn->ignore || insn->type == INSN_NOP || insn->type == INSN_TRAP) return true; /* - * Ignore any unused exceptions. This can happen when a whitelisted - * function has an exception table entry. - * - * Also ignore alternative replacement instructions. This can happen + * Ignore alternative replacement instructions. This can happen * when a whitelisted function uses one of the ALTERNATIVE macros. */ - if (!strcmp(insn->sec->name, ".fixup") || - !strcmp(insn->sec->name, ".altinstr_replacement") || + if (!strcmp(insn->sec->name, ".altinstr_replacement") || !strcmp(insn->sec->name, ".altinstr_aux")) return true; - if (!insn->func) + /* + * Whole archive runs might encounter dead code from weak symbols. + * This is where the linker will have dropped the weak symbol in + * favour of a regular symbol, but leaves the code in place. + * + * In this case we'll find a piece of code (whole function) that is not + * covered by a !section symbol. Ignore them. + */ + if (opts.link && !insn_func(insn)) { + int size = find_symbol_hole_containing(insn->sec, insn->offset); + unsigned long end = insn->offset + size; + + if (!size) /* not a hole */ + return false; + + if (size < 0) /* hole until the end */ + return true; + + sec_for_each_insn_continue(file, insn) { + /* + * If we reach a visited instruction at or before the + * end of the hole, ignore the unreachable. + */ + if (insn->visited) + return true; + + if (insn->offset >= end) + break; + + /* + * If this hole jumps to a .cold function, mark it ignore too. + */ + if (insn->jump_dest && insn_func(insn->jump_dest) && + strstr(insn_func(insn->jump_dest)->name, ".cold")) { + struct instruction *dest = insn->jump_dest; + func_for_each_insn(file, insn_func(dest), dest) + dest->ignore = true; + } + } + return false; + } + + if (!insn_func(insn)) + return false; + + if (insn_func(insn)->static_call_tramp) + return true; /* * CONFIG_UBSAN_TRAP inserts a UD2 when it sees * __builtin_unreachable(). The BUG() macro has an unreachable() after * the UD2, which causes GCC's undefined trap logic to emit another UD2 * (or occasionally a JMP to UD2). + * + * It may also insert a UD2 after calling a __noreturn function. */ - if (list_prev_entry(insn, list)->dead_end && + prev_insn = prev_insn_same_sec(file, insn); + if (prev_insn->dead_end && (insn->type == INSN_BUG || (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest && insn->jump_dest->type == INSN_BUG))) @@ -2614,7 +4112,7 @@ static bool ignore_unreachable_insn(struct instruction *insn) if (insn->type == INSN_JUMP_UNCONDITIONAL) { if (insn->jump_dest && - insn->jump_dest->func == insn->func) { + insn_func(insn->jump_dest) == insn_func(insn)) { insn = insn->jump_dest; continue; } @@ -2622,15 +4120,83 @@ static bool ignore_unreachable_insn(struct instruction *insn) break; } - if (insn->offset + insn->len >= insn->func->offset + insn->func->len) + if (insn->offset + insn->len >= insn_func(insn)->offset + insn_func(insn)->len) break; - insn = list_next_entry(insn, list); + insn = next_insn_same_sec(file, insn); } return false; } +static int add_prefix_symbol(struct objtool_file *file, struct symbol *func) +{ + struct instruction *insn, *prev; + struct cfi_state *cfi; + + insn = find_insn(file, func->sec, func->offset); + if (!insn) + return -1; + + for (prev = prev_insn_same_sec(file, insn); + prev; + prev = prev_insn_same_sec(file, prev)) { + u64 offset; + + if (prev->type != INSN_NOP) + return -1; + + offset = func->offset - prev->offset; + + if (offset > opts.prefix) + return -1; + + if (offset < opts.prefix) + continue; + + elf_create_prefix_symbol(file->elf, func, opts.prefix); + break; + } + + if (!prev) + return -1; + + if (!insn->cfi) { + /* + * This can happen if stack validation isn't enabled or the + * function is annotated with STACK_FRAME_NON_STANDARD. + */ + return 0; + } + + /* Propagate insn->cfi to the prefix code */ + cfi = cfi_hash_find_or_add(insn->cfi); + for (; prev != insn; prev = next_insn_same_sec(file, prev)) + prev->cfi = cfi; + + return 0; +} + +static int add_prefix_symbols(struct objtool_file *file) +{ + struct section *sec; + struct symbol *func; + + for_each_sec(file, sec) { + if (!(sec->sh.sh_flags & SHF_EXECINSTR)) + continue; + + sec_for_each_sym(sec, func) { + if (func->type != STT_FUNC) + continue; + + add_prefix_symbol(file, func); + } + } + + return 0; +} + static int validate_symbol(struct objtool_file *file, struct section *sec, struct symbol *sym, struct insn_state *state) { @@ -2651,9 +4217,9 @@ static int validate_symbol(struct objtool_file *file, struct section *sec, state->uaccess = sym->uaccess_safe; - ret = validate_branch(file, insn->func, insn, *state); - if (ret && backtrace) - BT_FUNC("<=== (sym)", insn); + ret = validate_branch(file, insn_func(insn), insn, *state); + if (ret) + BT_INSN(insn, "<=== (sym)"); return ret; } @@ -2663,15 +4229,12 @@ static int validate_section(struct objtool_file *file, struct section *sec) struct symbol *func; int warnings = 0; - list_for_each_entry(func, &sec->symbol_list, list) { + sec_for_each_sym(sec, func) { if (func->type != STT_FUNC) continue; - init_insn_state(&state, sec); - state.cfi.cfa = initial_func_cfi.cfa; - memcpy(&state.cfi.regs, &initial_func_cfi.regs, - CFI_NUM_REGS * sizeof(struct cfi_reg)); - state.cfi.stack_size = initial_func_cfi.cfa.offset; + init_insn_state(file, &state, sec); + set_func_state(&state.cfi); warnings += validate_symbol(file, sec, func, &state); } @@ -2679,7 +4242,7 @@ static int validate_section(struct objtool_file *file, struct section *sec) return warnings; } -static int validate_vmlinux_functions(struct objtool_file *file) +static int validate_noinstr_sections(struct objtool_file *file) { struct section *sec; int warnings = 0; @@ -2696,6 +4259,12 @@ static int validate_vmlinux_functions(struct objtool_file *file) warnings += validate_unwind_hints(file, sec); } + sec = find_section_by_name(file->elf, ".cpuidle.text"); + if (sec) { + warnings += validate_section(file, sec); + warnings += validate_unwind_hints(file, sec); + } + return warnings; } @@ -2714,108 +4283,564 @@ static int validate_functions(struct objtool_file *file) return warnings; } -static int validate_reachable_instructions(struct objtool_file *file) +static void mark_endbr_used(struct instruction *insn) +{ + if (!list_empty(&insn->call_node)) + list_del_init(&insn->call_node); +} + +static bool noendbr_range(struct objtool_file *file, struct instruction *insn) { + struct symbol *sym = find_symbol_containing(insn->sec, insn->offset-1); + struct instruction *first; + + if (!sym) + return false; + + first = find_insn(file, sym->sec, sym->offset); + if (!first) + return false; + + if (first->type != INSN_ENDBR && !first->noendbr) + return false; + + return insn->offset == sym->offset + sym->len; +} + +static int validate_ibt_insn(struct objtool_file *file, struct instruction *insn) +{ + struct instruction *dest; + struct reloc *reloc; + unsigned long off; + int warnings = 0; + + /* + * Looking for function pointer load relocations. Ignore + * direct/indirect branches: + */ + switch (insn->type) { + case INSN_CALL: + case INSN_CALL_DYNAMIC: + case INSN_JUMP_CONDITIONAL: + case INSN_JUMP_UNCONDITIONAL: + case INSN_JUMP_DYNAMIC: + case INSN_JUMP_DYNAMIC_CONDITIONAL: + case INSN_RETURN: + case INSN_NOP: + return 0; + default: + break; + } + + for (reloc = insn_reloc(file, insn); + reloc; + reloc = find_reloc_by_dest_range(file->elf, insn->sec, + reloc_offset(reloc) + 1, + (insn->offset + insn->len) - (reloc_offset(reloc) + 1))) { + + /* + * static_call_update() references the trampoline, which + * doesn't have (or need) ENDBR. Skip warning in that case. + */ + if (reloc->sym->static_call_tramp) + continue; + + off = reloc->sym->offset; + if (reloc_type(reloc) == R_X86_64_PC32 || + reloc_type(reloc) == R_X86_64_PLT32) + off += arch_dest_reloc_offset(reloc_addend(reloc)); + else + off += reloc_addend(reloc); + + dest = find_insn(file, reloc->sym->sec, off); + if (!dest) + continue; + + if (dest->type == INSN_ENDBR) { + mark_endbr_used(dest); + continue; + } + + if (insn_func(dest) && insn_func(insn) && + insn_func(dest)->pfunc == insn_func(insn)->pfunc) { + /* + * Anything from->to self is either _THIS_IP_ or + * IRET-to-self. + * + * There is no sane way to annotate _THIS_IP_ since the + * compiler treats the relocation as a constant and is + * happy to fold in offsets, skewing any annotation we + * do, leading to vast amounts of false-positives. + * + * There's also compiler generated _THIS_IP_ through + * KCOV and such which we have no hope of annotating. + * + * As such, blanket accept self-references without + * issue. + */ + continue; + } + + /* + * Accept anything ANNOTATE_NOENDBR. + */ + if (dest->noendbr) + continue; + + /* + * Accept if this is the instruction after a symbol + * that is (no)endbr -- typical code-range usage. + */ + if (noendbr_range(file, dest)) + continue; + + WARN_INSN(insn, "relocation to !ENDBR: %s", offstr(dest->sec, dest->offset)); + + warnings++; + } + + return warnings; +} + +static int validate_ibt_data_reloc(struct objtool_file *file, + struct reloc *reloc) +{ + struct instruction *dest; + + dest = find_insn(file, reloc->sym->sec, + reloc->sym->offset + reloc_addend(reloc)); + if (!dest) + return 0; + + if (dest->type == INSN_ENDBR) { + mark_endbr_used(dest); + return 0; + } + + if (dest->noendbr) + return 0; + + WARN_FUNC("data relocation to !ENDBR: %s", + reloc->sec->base, reloc_offset(reloc), + offstr(dest->sec, dest->offset)); + + return 1; +} + +/* + * Validate IBT rules and remove used ENDBR instructions from the seal list. + * Unused ENDBR instructions will be annotated for sealing (i.e., replaced with + * NOPs) later, in create_ibt_endbr_seal_sections(). + */ +static int validate_ibt(struct objtool_file *file) +{ + struct section *sec; + struct reloc *reloc; struct instruction *insn; + int warnings = 0; + + for_each_insn(file, insn) + warnings += validate_ibt_insn(file, insn); + + for_each_sec(file, sec) { + + /* Already done by validate_ibt_insn() */ + if (sec->sh.sh_flags & SHF_EXECINSTR) + continue; + + if (!sec->rsec) + continue; + + /* + * These sections can reference text addresses, but not with + * the intent to indirect branch to them. + */ + if ((!strncmp(sec->name, ".discard", 8) && + strcmp(sec->name, ".discard.ibt_endbr_noseal")) || + !strncmp(sec->name, ".debug", 6) || + !strcmp(sec->name, ".altinstructions") || + !strcmp(sec->name, ".ibt_endbr_seal") || + !strcmp(sec->name, ".orc_unwind_ip") || + !strcmp(sec->name, ".parainstructions") || + !strcmp(sec->name, ".retpoline_sites") || + !strcmp(sec->name, ".smp_locks") || + !strcmp(sec->name, ".static_call_sites") || + !strcmp(sec->name, "_error_injection_whitelist") || + !strcmp(sec->name, "_kprobe_blacklist") || + !strcmp(sec->name, "__bug_table") || + !strcmp(sec->name, "__ex_table") || + !strcmp(sec->name, "__jump_table") || + !strcmp(sec->name, "__mcount_loc") || + !strcmp(sec->name, ".kcfi_traps") || + strstr(sec->name, "__patchable_function_entries")) + continue; + + for_each_reloc(sec->rsec, reloc) + warnings += validate_ibt_data_reloc(file, reloc); + } + + return warnings; +} + +static int validate_sls(struct objtool_file *file) +{ + struct instruction *insn, *next_insn; + int warnings = 0; + + for_each_insn(file, insn) { + next_insn = next_insn_same_sec(file, insn); + + if (insn->retpoline_safe) + continue; + + switch (insn->type) { + case INSN_RETURN: + if (!next_insn || next_insn->type != INSN_TRAP) { + WARN_INSN(insn, "missing int3 after ret"); + warnings++; + } + + break; + case INSN_JUMP_DYNAMIC: + if (!next_insn || next_insn->type != INSN_TRAP) { + WARN_INSN(insn, "missing int3 after indirect jump"); + warnings++; + } + break; + default: + break; + } + } + + return warnings; +} + +static bool ignore_noreturn_call(struct instruction *insn) +{ + struct symbol *call_dest = insn_call_dest(insn); + + /* + * FIXME: hack, we need a real noreturn solution + * + * Problem is, exc_double_fault() may or may not return, depending on + * whether CONFIG_X86_ESPFIX64 is set. But objtool has no visibility + * to the kernel config. + * + * Other potential ways to fix it: + * + * - have compiler communicate __noreturn functions somehow + * - remove CONFIG_X86_ESPFIX64 + * - read the .config file + * - add a cmdline option + * - create a generic objtool annotation format (vs a bunch of custom + * formats) and annotate it + */ + if (!strcmp(call_dest->name, "exc_double_fault")) { + /* prevent further unreachable warnings for the caller */ + insn->sym->warned = 1; + return true; + } + + return false; +} + +static int validate_reachable_instructions(struct objtool_file *file) +{ + struct instruction *insn, *prev_insn; + struct symbol *call_dest; + int warnings = 0; if (file->ignore_unreachables) return 0; for_each_insn(file, insn) { - if (insn->visited || ignore_unreachable_insn(insn)) + if (insn->visited || ignore_unreachable_insn(file, insn)) continue; - WARN_FUNC("unreachable instruction", insn->sec, insn->offset); - return 1; + prev_insn = prev_insn_same_sec(file, insn); + if (prev_insn && prev_insn->dead_end) { + call_dest = insn_call_dest(prev_insn); + if (call_dest && !ignore_noreturn_call(prev_insn)) { + WARN_INSN(insn, "%s() is missing a __noreturn annotation", + call_dest->name); + warnings++; + continue; + } + } + + WARN_INSN(insn, "unreachable instruction"); + warnings++; + } + + return warnings; +} + +/* 'funcs' is a space-separated list of function names */ +static int disas_funcs(const char *funcs) +{ + const char *objdump_str, *cross_compile; + int size, ret; + char *cmd; + + cross_compile = getenv("CROSS_COMPILE"); + + objdump_str = "%sobjdump -wdr %s | gawk -M -v _funcs='%s' '" + "BEGIN { split(_funcs, funcs); }" + "/^$/ { func_match = 0; }" + "/<.*>:/ { " + "f = gensub(/.*<(.*)>:/, \"\\\\1\", 1);" + "for (i in funcs) {" + "if (funcs[i] == f) {" + "func_match = 1;" + "base = strtonum(\"0x\" $1);" + "break;" + "}" + "}" + "}" + "{" + "if (func_match) {" + "addr = strtonum(\"0x\" $1);" + "printf(\"%%04x \", addr - base);" + "print;" + "}" + "}' 1>&2"; + + /* fake snprintf() to calculate the size */ + size = snprintf(NULL, 0, objdump_str, cross_compile, objname, funcs) + 1; + if (size <= 0) { + WARN("objdump string size calculation failed"); + return -1; + } + + cmd = malloc(size); + + /* real snprintf() */ + snprintf(cmd, size, objdump_str, cross_compile, objname, funcs); + ret = system(cmd); + if (ret) { + WARN("disassembly failed: %d", ret); + return -1; + } + + return 0; +} + +static int disas_warned_funcs(struct objtool_file *file) +{ + struct symbol *sym; + char *funcs = NULL, *tmp; + + for_each_sym(file, sym) { + if (sym->warned) { + if (!funcs) { + funcs = malloc(strlen(sym->name) + 1); + strcpy(funcs, sym->name); + } else { + tmp = malloc(strlen(funcs) + strlen(sym->name) + 2); + sprintf(tmp, "%s %s", funcs, sym->name); + free(funcs); + funcs = tmp; + } + } } + if (funcs) + disas_funcs(funcs); + return 0; } -static struct objtool_file file; +struct insn_chunk { + void *addr; + struct insn_chunk *next; +}; -int check(const char *_objname, bool orc) +/* + * Reduce peak RSS usage by freeing insns memory before writing the ELF file, + * which can trigger more allocations for .debug_* sections whose data hasn't + * been read yet. + */ +static void free_insns(struct objtool_file *file) { - int ret, warnings = 0; + struct instruction *insn; + struct insn_chunk *chunks = NULL, *chunk; - objname = _objname; + for_each_insn(file, insn) { + if (!insn->idx) { + chunk = malloc(sizeof(*chunk)); + chunk->addr = insn; + chunk->next = chunks; + chunks = chunk; + } + } - file.elf = elf_open_read(objname, orc ? O_RDWR : O_RDONLY); - if (!file.elf) - return 1; + for (chunk = chunks; chunk; chunk = chunk->next) + free(chunk->addr); +} - INIT_LIST_HEAD(&file.insn_list); - hash_init(file.insn_hash); - file.c_file = find_section_by_name(file.elf, ".comment"); - file.ignore_unreachables = no_unreachable; - file.hints = false; +int check(struct objtool_file *file) +{ + int ret, warnings = 0; arch_initial_func_cfi_state(&initial_func_cfi); + init_cfi_state(&init_cfi); + init_cfi_state(&func_cfi); + set_func_state(&func_cfi); + init_cfi_state(&force_undefined_cfi); + force_undefined_cfi.force_undefined = true; - ret = decode_sections(&file); + if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3))) + goto out; + + cfi_hash_add(&init_cfi); + cfi_hash_add(&func_cfi); + + ret = decode_sections(file); if (ret < 0) goto out; + warnings += ret; - if (list_empty(&file.insn_list)) + if (!nr_insns) goto out; - if (vmlinux && !validate_dup) { - ret = validate_vmlinux_functions(&file); + if (opts.retpoline) { + ret = validate_retpoline(file); + if (ret < 0) + return ret; + warnings += ret; + } + + if (opts.stackval || opts.orc || opts.uaccess) { + ret = validate_functions(file); if (ret < 0) goto out; + warnings += ret; + ret = validate_unwind_hints(file, NULL); + if (ret < 0) + goto out; + warnings += ret; + + if (!warnings) { + ret = validate_reachable_instructions(file); + if (ret < 0) + goto out; + warnings += ret; + } + + } else if (opts.noinstr) { + ret = validate_noinstr_sections(file); + if (ret < 0) + goto out; warnings += ret; - goto out; } - if (retpoline) { - ret = validate_retpoline(&file); + if (opts.unret) { + /* + * Must be after validate_branch() and friends, it plays + * further games with insn->visited. + */ + ret = validate_unrets(file); if (ret < 0) return ret; warnings += ret; } - ret = validate_functions(&file); - if (ret < 0) - goto out; - warnings += ret; + if (opts.ibt) { + ret = validate_ibt(file); + if (ret < 0) + goto out; + warnings += ret; + } - ret = validate_unwind_hints(&file, NULL); - if (ret < 0) - goto out; - warnings += ret; + if (opts.sls) { + ret = validate_sls(file); + if (ret < 0) + goto out; + warnings += ret; + } + + if (opts.static_call) { + ret = create_static_call_sections(file); + if (ret < 0) + goto out; + warnings += ret; + } - if (!warnings) { - ret = validate_reachable_instructions(&file); + if (opts.retpoline) { + ret = create_retpoline_sites_sections(file); if (ret < 0) goto out; warnings += ret; } - if (orc) { - ret = create_orc(&file); + if (opts.cfi) { + ret = create_cfi_sections(file); if (ret < 0) goto out; + warnings += ret; + } - ret = create_orc_sections(&file); + if (opts.rethunk) { + ret = create_return_sites_sections(file); if (ret < 0) goto out; + warnings += ret; - ret = elf_write(file.elf); + if (opts.hack_skylake) { + ret = create_direct_call_sections(file); + if (ret < 0) + goto out; + warnings += ret; + } + } + + if (opts.mcount) { + ret = create_mcount_loc_sections(file); if (ret < 0) goto out; + warnings += ret; } -out: - if (ret < 0) { - /* - * Fatal error. The binary is corrupt or otherwise broken in - * some way, or objtool itself is broken. Fail the kernel - * build. - */ - return ret; + if (opts.prefix) { + ret = add_prefix_symbols(file); + if (ret < 0) + return ret; + warnings += ret; + } + + if (opts.ibt) { + ret = create_ibt_endbr_seal_sections(file); + if (ret < 0) + goto out; + warnings += ret; + } + + if (opts.orc && nr_insns) { + ret = orc_create(file); + if (ret < 0) + goto out; + warnings += ret; + } + + free_insns(file); + + if (opts.verbose) + disas_warned_funcs(file); + + if (opts.stats) { + printf("nr_insns_visited: %ld\n", nr_insns_visited); + printf("nr_cfi: %ld\n", nr_cfi); + printf("nr_cfi_reused: %ld\n", nr_cfi_reused); + printf("nr_cfi_cache: %ld\n", nr_cfi_cache); } +out: + /* + * For now, don't fail the kernel build on fatal warnings. These + * errors are still fairly common due to the growing matrix of + * supported toolchains and their recent pace of change. + */ return 0; } |