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-rw-r--r--scripts/Makefile.build3
-rw-r--r--tools/objtool/arch.h6
-rw-r--r--tools/objtool/arch/x86/decode.c13
-rw-r--r--tools/objtool/builtin-check.c3
-rw-r--r--tools/objtool/builtin.h2
-rw-r--r--tools/objtool/check.c197
-rw-r--r--tools/objtool/check.h3
-rw-r--r--tools/objtool/elf.h1
-rw-r--r--tools/objtool/special.c18
-rw-r--r--tools/objtool/special.h1
10 files changed, 226 insertions, 21 deletions
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 76ca30cc4791..0c5969fa795f 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -222,6 +222,9 @@ endif
ifdef CONFIG_RETPOLINE
objtool_args += --retpoline
endif
+ifdef CONFIG_X86_SMAP
+ objtool_args += --uaccess
+endif
# 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory
# 'OBJECT_FILES_NON_STANDARD_foo.o := 'y': skip objtool checking for a file
diff --git a/tools/objtool/arch.h b/tools/objtool/arch.h
index b0d7dc3d71b5..467c2fe798a9 100644
--- a/tools/objtool/arch.h
+++ b/tools/objtool/arch.h
@@ -33,7 +33,9 @@
#define INSN_STACK 8
#define INSN_BUG 9
#define INSN_NOP 10
-#define INSN_OTHER 11
+#define INSN_STAC 11
+#define INSN_CLAC 12
+#define INSN_OTHER 13
#define INSN_LAST INSN_OTHER
enum op_dest_type {
@@ -41,6 +43,7 @@ enum op_dest_type {
OP_DEST_REG_INDIRECT,
OP_DEST_MEM,
OP_DEST_PUSH,
+ OP_DEST_PUSHF,
OP_DEST_LEAVE,
};
@@ -55,6 +58,7 @@ enum op_src_type {
OP_SRC_REG_INDIRECT,
OP_SRC_CONST,
OP_SRC_POP,
+ OP_SRC_POPF,
OP_SRC_ADD,
OP_SRC_AND,
};
diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index 540a209b78ab..ab20a96fee50 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -357,19 +357,26 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
/* pushf */
*type = INSN_STACK;
op->src.type = OP_SRC_CONST;
- op->dest.type = OP_DEST_PUSH;
+ op->dest.type = OP_DEST_PUSHF;
break;
case 0x9d:
/* popf */
*type = INSN_STACK;
- op->src.type = OP_SRC_POP;
+ op->src.type = OP_SRC_POPF;
op->dest.type = OP_DEST_MEM;
break;
case 0x0f:
- if (op2 >= 0x80 && op2 <= 0x8f) {
+ if (op2 == 0x01) {
+
+ if (modrm == 0xca)
+ *type = INSN_CLAC;
+ else if (modrm == 0xcb)
+ *type = INSN_STAC;
+
+ } else if (op2 >= 0x80 && op2 <= 0x8f) {
*type = INSN_JUMP_CONDITIONAL;
diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index 99f10c585cbe..f3b378126011 100644
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -29,7 +29,7 @@
#include "builtin.h"
#include "check.h"
-bool no_fp, no_unreachable, retpoline, module, backtrace;
+bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess;
static const char * const check_usage[] = {
"objtool check [<options>] file.o",
@@ -42,6 +42,7 @@ const struct option check_options[] = {
OPT_BOOLEAN('r', "retpoline", &retpoline, "Validate retpoline assumptions"),
OPT_BOOLEAN('m', "module", &module, "Indicates the object will be part of a kernel module"),
OPT_BOOLEAN('b', "backtrace", &backtrace, "unwind on error"),
+ OPT_BOOLEAN('a', "uaccess", &uaccess, "enable uaccess checking"),
OPT_END(),
};
diff --git a/tools/objtool/builtin.h b/tools/objtool/builtin.h
index 65fd3cc3c98b..69762f9c5602 100644
--- a/tools/objtool/builtin.h
+++ b/tools/objtool/builtin.h
@@ -20,7 +20,7 @@
#include <subcmd/parse-options.h>
extern const struct option check_options[];
-extern bool no_fp, no_unreachable, retpoline, module, backtrace;
+extern bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess;
extern int cmd_check(int argc, const char **argv);
extern int cmd_orc(int argc, const char **argv);
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 8118361295dd..965e954e07f4 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -443,6 +443,82 @@ static void add_ignores(struct objtool_file *file)
}
/*
+ * This is a whitelist of functions that is allowed to be called with AC set.
+ * The list is meant to be minimal and only contains compiler instrumentation
+ * ABI and a few functions used to implement *_{to,from}_user() functions.
+ *
+ * These functions must not directly change AC, but may PUSHF/POPF.
+ */
+static const char *uaccess_safe_builtin[] = {
+ /* KASAN */
+ "kasan_report",
+ "check_memory_region",
+ /* KASAN out-of-line */
+ "__asan_loadN_noabort",
+ "__asan_load1_noabort",
+ "__asan_load2_noabort",
+ "__asan_load4_noabort",
+ "__asan_load8_noabort",
+ "__asan_load16_noabort",
+ "__asan_storeN_noabort",
+ "__asan_store1_noabort",
+ "__asan_store2_noabort",
+ "__asan_store4_noabort",
+ "__asan_store8_noabort",
+ "__asan_store16_noabort",
+ /* KASAN in-line */
+ "__asan_report_load_n_noabort",
+ "__asan_report_load1_noabort",
+ "__asan_report_load2_noabort",
+ "__asan_report_load4_noabort",
+ "__asan_report_load8_noabort",
+ "__asan_report_load16_noabort",
+ "__asan_report_store_n_noabort",
+ "__asan_report_store1_noabort",
+ "__asan_report_store2_noabort",
+ "__asan_report_store4_noabort",
+ "__asan_report_store8_noabort",
+ "__asan_report_store16_noabort",
+ /* KCOV */
+ "write_comp_data",
+ "__sanitizer_cov_trace_pc",
+ "__sanitizer_cov_trace_const_cmp1",
+ "__sanitizer_cov_trace_const_cmp2",
+ "__sanitizer_cov_trace_const_cmp4",
+ "__sanitizer_cov_trace_const_cmp8",
+ "__sanitizer_cov_trace_cmp1",
+ "__sanitizer_cov_trace_cmp2",
+ "__sanitizer_cov_trace_cmp4",
+ "__sanitizer_cov_trace_cmp8",
+ /* UBSAN */
+ "ubsan_type_mismatch_common",
+ "__ubsan_handle_type_mismatch",
+ "__ubsan_handle_type_mismatch_v1",
+ /* misc */
+ "csum_partial_copy_generic",
+ "__memcpy_mcsafe",
+ "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
+ NULL
+};
+
+static void add_uaccess_safe(struct objtool_file *file)
+{
+ struct symbol *func;
+ const char **name;
+
+ if (!uaccess)
+ return;
+
+ for (name = uaccess_safe_builtin; *name; name++) {
+ func = find_symbol_by_name(file->elf, *name);
+ if (!func)
+ continue;
+
+ func->alias->uaccess_safe = true;
+ }
+}
+
+/*
* FIXME: For now, just ignore any alternatives which add retpolines. This is
* a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
* But it at least allows objtool to understand the control flow *around* the
@@ -818,6 +894,7 @@ 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);
list_del(&special_alt->list);
@@ -1239,6 +1316,7 @@ static int decode_sections(struct objtool_file *file)
return ret;
add_ignores(file);
+ add_uaccess_safe(file);
ret = add_ignore_alternatives(file);
if (ret)
@@ -1320,11 +1398,11 @@ static int update_insn_state_regs(struct instruction *insn, struct insn_state *s
return 0;
/* push */
- if (op->dest.type == OP_DEST_PUSH)
+ if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
cfa->offset += 8;
/* pop */
- if (op->src.type == OP_SRC_POP)
+ if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
cfa->offset -= 8;
/* add immediate to sp */
@@ -1581,6 +1659,7 @@ static int update_insn_state(struct instruction *insn, struct insn_state *state)
break;
case OP_SRC_POP:
+ case OP_SRC_POPF:
if (!state->drap && op->dest.type == OP_DEST_REG &&
op->dest.reg == cfa->base) {
@@ -1645,6 +1724,7 @@ static int update_insn_state(struct instruction *insn, struct insn_state *state)
break;
case OP_DEST_PUSH:
+ case OP_DEST_PUSHF:
state->stack_size += 8;
if (cfa->base == CFI_SP)
cfa->offset += 8;
@@ -1735,7 +1815,7 @@ static int update_insn_state(struct instruction *insn, struct insn_state *state)
break;
case OP_DEST_MEM:
- if (op->src.type != OP_SRC_POP) {
+ if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
WARN_FUNC("unknown stack-related memory operation",
insn->sec, insn->offset);
return -1;
@@ -1799,6 +1879,33 @@ static bool insn_state_match(struct instruction *insn, struct insn_state *state)
return false;
}
+static inline bool func_uaccess_safe(struct symbol *func)
+{
+ if (func)
+ return func->alias->uaccess_safe;
+
+ return false;
+}
+
+static inline const char *insn_dest_name(struct instruction *insn)
+{
+ if (insn->call_dest)
+ return insn->call_dest->name;
+
+ return "{dynamic}";
+}
+
+static int validate_call(struct instruction *insn, struct insn_state *state)
+{
+ if (state->uaccess && !func_uaccess_safe(insn->call_dest)) {
+ WARN_FUNC("call to %s() with UACCESS enabled",
+ insn->sec, insn->offset, insn_dest_name(insn));
+ return 1;
+ }
+
+ return 0;
+}
+
static int validate_sibling_call(struct instruction *insn, struct insn_state *state)
{
if (has_modified_stack_frame(state)) {
@@ -1807,7 +1914,7 @@ static int validate_sibling_call(struct instruction *insn, struct insn_state *st
return 1;
}
- return 0;
+ return validate_call(insn, state);
}
/*
@@ -1855,7 +1962,9 @@ static int validate_branch(struct objtool_file *file, struct instruction *first,
if (!insn->hint && !insn_state_match(insn, &state))
return 1;
- return 0;
+ /* If we were here with AC=0, but now have AC=1, go again */
+ if (insn->state.uaccess || !state.uaccess)
+ return 0;
}
if (insn->hint) {
@@ -1925,6 +2034,16 @@ static int validate_branch(struct objtool_file *file, struct instruction *first,
switch (insn->type) {
case INSN_RETURN:
+ if (state.uaccess && !func_uaccess_safe(func)) {
+ WARN_FUNC("return with UACCESS enabled", sec, insn->offset);
+ return 1;
+ }
+
+ if (!state.uaccess && func_uaccess_safe(func)) {
+ WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function", sec, insn->offset);
+ return 1;
+ }
+
if (func && has_modified_stack_frame(&state)) {
WARN_FUNC("return with modified stack frame",
sec, insn->offset);
@@ -1940,17 +2059,22 @@ static int validate_branch(struct objtool_file *file, struct instruction *first,
return 0;
case INSN_CALL:
- if (is_fentry_call(insn))
- break;
+ case INSN_CALL_DYNAMIC:
+ ret = validate_call(insn, &state);
+ if (ret)
+ return ret;
- ret = dead_end_function(file, insn->call_dest);
- if (ret == 1)
- return 0;
- if (ret == -1)
- return 1;
+ if (insn->type == INSN_CALL) {
+ if (is_fentry_call(insn))
+ break;
+
+ ret = dead_end_function(file, insn->call_dest);
+ if (ret == 1)
+ return 0;
+ if (ret == -1)
+ return 1;
+ }
- /* fallthrough */
- case INSN_CALL_DYNAMIC:
if (!no_fp && func && !has_valid_stack_frame(&state)) {
WARN_FUNC("call without frame pointer save/setup",
sec, insn->offset);
@@ -2003,6 +2127,49 @@ static int validate_branch(struct objtool_file *file, struct instruction *first,
if (update_insn_state(insn, &state))
return 1;
+ if (insn->stack_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", sec, insn->offset);
+ return 1;
+ }
+ state.uaccess_stack <<= 1;
+ state.uaccess_stack |= state.uaccess;
+ }
+
+ if (insn->stack_op.src.type == OP_SRC_POPF) {
+ if (state.uaccess_stack) {
+ state.uaccess = state.uaccess_stack & 1;
+ state.uaccess_stack >>= 1;
+ if (state.uaccess_stack == 1)
+ state.uaccess_stack = 0;
+ }
+ }
+
+ break;
+
+ case INSN_STAC:
+ if (state.uaccess) {
+ WARN_FUNC("recursive UACCESS enable", sec, insn->offset);
+ return 1;
+ }
+
+ state.uaccess = true;
+ break;
+
+ case INSN_CLAC:
+ if (!state.uaccess && insn->func) {
+ WARN_FUNC("redundant UACCESS disable", sec, insn->offset);
+ return 1;
+ }
+
+ if (func_uaccess_safe(func) && !state.uaccess_stack) {
+ WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset);
+ return 1;
+ }
+
+ state.uaccess = false;
break;
default:
@@ -2168,6 +2335,8 @@ static int validate_functions(struct objtool_file *file)
if (!insn || insn->ignore)
continue;
+ state.uaccess = func->alias->uaccess_safe;
+
ret = validate_branch(file, insn, state);
if (ret && backtrace)
BT_FUNC("<=== (func)", insn);
diff --git a/tools/objtool/check.h b/tools/objtool/check.h
index d8896eb43521..78a95d06c165 100644
--- a/tools/objtool/check.h
+++ b/tools/objtool/check.h
@@ -31,7 +31,8 @@ struct insn_state {
int stack_size;
unsigned char type;
bool bp_scratch;
- bool drap, end;
+ bool drap, end, uaccess;
+ unsigned int uaccess_stack;
int drap_reg, drap_offset;
struct cfi_reg vals[CFI_NUM_REGS];
};
diff --git a/tools/objtool/elf.h b/tools/objtool/elf.h
index 968265b4b4cd..2cc2ed49322d 100644
--- a/tools/objtool/elf.h
+++ b/tools/objtool/elf.h
@@ -62,6 +62,7 @@ struct symbol {
unsigned long offset;
unsigned int len;
struct symbol *pfunc, *cfunc, *alias;
+ bool uaccess_safe;
};
struct rela {
diff --git a/tools/objtool/special.c b/tools/objtool/special.c
index 50af4e1274b3..4e50563d87c6 100644
--- a/tools/objtool/special.c
+++ b/tools/objtool/special.c
@@ -23,6 +23,7 @@
#include <stdlib.h>
#include <string.h>
+#include "builtin.h"
#include "special.h"
#include "warn.h"
@@ -42,6 +43,7 @@
#define ALT_NEW_LEN_OFFSET 11
#define X86_FEATURE_POPCNT (4*32+23)
+#define X86_FEATURE_SMAP (9*32+20)
struct special_entry {
const char *sec;
@@ -110,6 +112,22 @@ static int get_alt_entry(struct elf *elf, struct special_entry *entry,
*/
if (feature == X86_FEATURE_POPCNT)
alt->skip_orig = true;
+
+ /*
+ * If UACCESS validation is enabled; force that alternative;
+ * otherwise force it the other way.
+ *
+ * What we want to avoid is having both the original and the
+ * alternative code flow at the same time, in that case we can
+ * find paths that see the STAC but take the NOP instead of
+ * CLAC and the other way around.
+ */
+ if (feature == X86_FEATURE_SMAP) {
+ if (uaccess)
+ alt->skip_orig = true;
+ else
+ alt->skip_alt = true;
+ }
}
orig_rela = find_rela_by_dest(sec, offset + entry->orig);
diff --git a/tools/objtool/special.h b/tools/objtool/special.h
index fad1d092f679..d5c062e718ef 100644
--- a/tools/objtool/special.h
+++ b/tools/objtool/special.h
@@ -26,6 +26,7 @@ struct special_alt {
bool group;
bool skip_orig;
+ bool skip_alt;
bool jump_or_nop;
struct section *orig_sec;
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.