// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) /* * BTF-to-C type converter. * * Copyright (c) 2019 Facebook */ #include #include #include #include #include #include #include #include #include #include #include #include "btf.h" #include "hashmap.h" #include "libbpf.h" #include "libbpf_internal.h" static const char PREFIXES[] = "\t\t\t\t\t\t\t\t\t\t\t\t\t"; static const size_t PREFIX_CNT = sizeof(PREFIXES) - 1; static const char *pfx(int lvl) { return lvl >= PREFIX_CNT ? PREFIXES : &PREFIXES[PREFIX_CNT - lvl]; } enum btf_dump_type_order_state { NOT_ORDERED, ORDERING, ORDERED, }; enum btf_dump_type_emit_state { NOT_EMITTED, EMITTING, EMITTED, }; /* per-type auxiliary state */ struct btf_dump_type_aux_state { /* topological sorting state */ enum btf_dump_type_order_state order_state: 2; /* emitting state used to determine the need for forward declaration */ enum btf_dump_type_emit_state emit_state: 2; /* whether forward declaration was already emitted */ __u8 fwd_emitted: 1; /* whether unique non-duplicate name was already assigned */ __u8 name_resolved: 1; /* whether type is referenced from any other type */ __u8 referenced: 1; }; /* indent string length; one indent string is added for each indent level */ #define BTF_DATA_INDENT_STR_LEN 32 /* * Common internal data for BTF type data dump operations. */ struct btf_dump_data { const void *data_end; /* end of valid data to show */ bool compact; bool skip_names; bool emit_zeroes; __u8 indent_lvl; /* base indent level */ char indent_str[BTF_DATA_INDENT_STR_LEN]; /* below are used during iteration */ int depth; bool is_array_member; bool is_array_terminated; bool is_array_char; }; struct btf_dump { const struct btf *btf; btf_dump_printf_fn_t printf_fn; void *cb_ctx; int ptr_sz; bool strip_mods; bool skip_anon_defs; int last_id; /* per-type auxiliary state */ struct btf_dump_type_aux_state *type_states; size_t type_states_cap; /* per-type optional cached unique name, must be freed, if present */ const char **cached_names; size_t cached_names_cap; /* topo-sorted list of dependent type definitions */ __u32 *emit_queue; int emit_queue_cap; int emit_queue_cnt; /* * stack of type declarations (e.g., chain of modifiers, arrays, * funcs, etc) */ __u32 *decl_stack; int decl_stack_cap; int decl_stack_cnt; /* maps struct/union/enum name to a number of name occurrences */ struct hashmap *type_names; /* * maps typedef identifiers and enum value names to a number of such * name occurrences */ struct hashmap *ident_names; /* * data for typed display; allocated if needed. */ struct btf_dump_data *typed_dump; }; static size_t str_hash_fn(long key, void *ctx) { return str_hash((void *)key); } static bool str_equal_fn(long a, long b, void *ctx) { return strcmp((void *)a, (void *)b) == 0; } static const char *btf_name_of(const struct btf_dump *d, __u32 name_off) { return btf__name_by_offset(d->btf, name_off); } static void btf_dump_printf(const struct btf_dump *d, const char *fmt, ...) { va_list args; va_start(args, fmt); d->printf_fn(d->cb_ctx, fmt, args); va_end(args); } static int btf_dump_mark_referenced(struct btf_dump *d); static int btf_dump_resize(struct btf_dump *d); struct btf_dump *btf_dump__new(const struct btf *btf, btf_dump_printf_fn_t printf_fn, void *ctx, const struct btf_dump_opts *opts) { struct btf_dump *d; int err; if (!OPTS_VALID(opts, btf_dump_opts)) return libbpf_err_ptr(-EINVAL); if (!printf_fn) return libbpf_err_ptr(-EINVAL); d = calloc(1, sizeof(struct btf_dump)); if (!d) return libbpf_err_ptr(-ENOMEM); d->btf = btf; d->printf_fn = printf_fn; d->cb_ctx = ctx; d->ptr_sz = btf__pointer_size(btf) ? : sizeof(void *); d->type_names = hashmap__new(str_hash_fn, str_equal_fn, NULL); if (IS_ERR(d->type_names)) { err = PTR_ERR(d->type_names); d->type_names = NULL; goto err; } d->ident_names = hashmap__new(str_hash_fn, str_equal_fn, NULL); if (IS_ERR(d->ident_names)) { err = PTR_ERR(d->ident_names); d->ident_names = NULL; goto err; } err = btf_dump_resize(d); if (err) goto err; return d; err: btf_dump__free(d); return libbpf_err_ptr(err); } static int btf_dump_resize(struct btf_dump *d) { int err, last_id = btf__type_cnt(d->btf) - 1; if (last_id <= d->last_id) return 0; if (libbpf_ensure_mem((void **)&d->type_states, &d->type_states_cap, sizeof(*d->type_states), last_id + 1)) return -ENOMEM; if (libbpf_ensure_mem((void **)&d->cached_names, &d->cached_names_cap, sizeof(*d->cached_names), last_id + 1)) return -ENOMEM; if (d->last_id == 0) { /* VOID is special */ d->type_states[0].order_state = ORDERED; d->type_states[0].emit_state = EMITTED; } /* eagerly determine referenced types for anon enums */ err = btf_dump_mark_referenced(d); if (err) return err; d->last_id = last_id; return 0; } static void btf_dump_free_names(struct hashmap *map) { size_t bkt; struct hashmap_entry *cur; hashmap__for_each_entry(map, cur, bkt) free((void *)cur->pkey); hashmap__free(map); } void btf_dump__free(struct btf_dump *d) { int i; if (IS_ERR_OR_NULL(d)) return; free(d->type_states); if (d->cached_names) { /* any set cached name is owned by us and should be freed */ for (i = 0; i <= d->last_id; i++) { if (d->cached_names[i]) free((void *)d->cached_names[i]); } } free(d->cached_names); free(d->emit_queue); free(d->decl_stack); btf_dump_free_names(d->type_names); btf_dump_free_names(d->ident_names); free(d); } static int btf_dump_order_type(struct btf_dump *d, __u32 id, bool through_ptr); static void btf_dump_emit_type(struct btf_dump *d, __u32 id, __u32 cont_id); /* * Dump BTF type in a compilable C syntax, including all the necessary * dependent types, necessary for compilation. If some of the dependent types * were already emitted as part of previous btf_dump__dump_type() invocation * for another type, they won't be emitted again. This API allows callers to * filter out BTF types according to user-defined criterias and emitted only * minimal subset of types, necessary to compile everything. Full struct/union * definitions will still be emitted, even if the only usage is through * pointer and could be satisfied with just a forward declaration. * * Dumping is done in two high-level passes: * 1. Topologically sort type definitions to satisfy C rules of compilation. * 2. Emit type definitions in C syntax. * * Returns 0 on success; <0, otherwise. */ int btf_dump__dump_type(struct btf_dump *d, __u32 id) { int err, i; if (id >= btf__type_cnt(d->btf)) return libbpf_err(-EINVAL); err = btf_dump_resize(d); if (err) return libbpf_err(err); d->emit_queue_cnt = 0; err = btf_dump_order_type(d, id, false); if (err < 0) return libbpf_err(err); for (i = 0; i < d->emit_queue_cnt; i++) btf_dump_emit_type(d, d->emit_queue[i], 0 /*top-level*/); return 0; } /* * Mark all types that are referenced from any other type. This is used to * determine top-level anonymous enums that need to be emitted as an * independent type declarations. * Anonymous enums come in two flavors: either embedded in a struct's field * definition, in which case they have to be declared inline as part of field * type declaration; or as a top-level anonymous enum, typically used for * declaring global constants. It's impossible to distinguish between two * without knowning whether given enum type was referenced from other type: * top-level anonymous enum won't be referenced by anything, while embedded * one will. */ static int btf_dump_mark_referenced(struct btf_dump *d) { int i, j, n = btf__type_cnt(d->btf); const struct btf_type *t; __u16 vlen; for (i = d->last_id + 1; i < n; i++) { t = btf__type_by_id(d->btf, i); vlen = btf_vlen(t); switch (btf_kind(t)) { case BTF_KIND_INT: case BTF_KIND_ENUM: case BTF_KIND_ENUM64: case BTF_KIND_FWD: case BTF_KIND_FLOAT: break; case BTF_KIND_VOLATILE: case BTF_KIND_CONST: case BTF_KIND_RESTRICT: case BTF_KIND_PTR: case BTF_KIND_TYPEDEF: case BTF_KIND_FUNC: case BTF_KIND_VAR: case BTF_KIND_DECL_TAG: case BTF_KIND_TYPE_TAG: d->type_states[t->type].referenced = 1; break; case BTF_KIND_ARRAY: { const struct btf_array *a = btf_array(t); d->type_states[a->index_type].referenced = 1; d->type_states[a->type].referenced = 1; break; } case BTF_KIND_STRUCT: case BTF_KIND_UNION: { const struct btf_member *m = btf_members(t); for (j = 0; j < vlen; j++, m++) d->type_states[m->type].referenced = 1; break; } case BTF_KIND_FUNC_PROTO: { const struct btf_param *p = btf_params(t); for (j = 0; j < vlen; j++, p++) d->type_states[p->type].referenced = 1; break; } case BTF_KIND_DATASEC: { const struct btf_var_secinfo *v = btf_var_secinfos(t); for (j = 0; j < vlen; j++, v++) d->type_states[v->type].referenced = 1; break; } default: return -EINVAL; } } return 0; } static int btf_dump_add_emit_queue_id(struct btf_dump *d, __u32 id) { __u32 *new_queue; size_t new_cap; if (d->emit_queue_cnt >= d->emit_queue_cap) { new_cap = max(16, d->emit_queue_cap * 3 / 2); new_queue = libbpf_reallocarray(d->emit_queue, new_cap, sizeof(new_queue[0])); if (!new_queue) return -ENOMEM; d->emit_queue = new_queue; d->emit_queue_cap = new_cap; } d->emit_queue[d->emit_queue_cnt++] = id; return 0; } /* * Determine order of emitting dependent types and specified type to satisfy * C compilation rules. This is done through topological sorting with an * additional complication which comes from C rules. The main idea for C is * that if some type is "embedded" into a struct/union, it's size needs to be * known at the time of definition of containing type. E.g., for: * * struct A {}; * struct B { struct A x; } * * struct A *HAS* to be defined before struct B, because it's "embedded", * i.e., it is part of struct B layout. But in the following case: * * struct A; * struct B { struct A *x; } * struct A {}; * * it's enough to just have a forward declaration of struct A at the time of * struct B definition, as struct B has a pointer to struct A, so the size of * field x is known without knowing struct A size: it's sizeof(void *). * * Unfortunately, there are some trickier cases we need to handle, e.g.: * * struct A {}; // if this was forward-declaration: compilation error * struct B { * struct { // anonymous struct * struct A y; * } *x; * }; * * In this case, struct B's field x is a pointer, so it's size is known * regardless of the size of (anonymous) struct it points to. But because this * struct is anonymous and thus defined inline inside struct B, *and* it * embeds struct A, compiler requires full definition of struct A to be known * before struct B can be defined. This creates a transitive dependency * between struct A and struct B. If struct A was forward-declared before * struct B definition and fully defined after struct B definition, that would * trigger compilation error. * * All this means that while we are doing topological sorting on BTF type * graph, we need to determine relationships between different types (graph * nodes): * - weak link (relationship) between X and Y, if Y *CAN* be * forward-declared at the point of X definition; * - strong link, if Y *HAS* to be fully-defined before X can be defined. * * The rule is as follows. Given a chain of BTF types from X to Y, if there is * BTF_KIND_PTR type in the chain and at least one non-anonymous type * Z (excluding X, including Y), then link is weak. Otherwise, it's strong. * Weak/strong relationship is determined recursively during DFS traversal and * is returned as a result from btf_dump_order_type(). * * btf_dump_order_type() is trying to avoid unnecessary forward declarations, * but it is not guaranteeing that no extraneous forward declarations will be * emitted. * * To avoid extra work, algorithm marks some of BTF types as ORDERED, when * it's done with them, but not for all (e.g., VOLATILE, CONST, RESTRICT, * ARRAY, FUNC_PROTO), as weak/strong semantics for those depends on the * entire graph path, so depending where from one came to that BTF type, it * might cause weak or strong ordering. For types like STRUCT/UNION/INT/ENUM, * once they are processed, there is no need to do it again, so they are * marked as ORDERED. We can mark PTR as ORDERED as well, as it semi-forces * weak link, unless subsequent referenced STRUCT/UNION/ENUM is anonymous. But * in any case, once those are processed, no need to do it again, as the * result won't change. * * Returns: * - 1, if type is part of strong link (so there is strong topological * ordering requirements); * - 0, if type is part of weak link (so can be satisfied through forward * declaration); * - <0, on error (e.g., unsatisfiable type loop detected). */ static int btf_dump_order_type(struct btf_dump *d, __u32 id, bool through_ptr) { /* * Order state is used to detect strong link cycles, but only for BTF * kinds that are or could be an independent definition (i.e., * stand-alone fwd decl, enum, typedef, struct, union). Ptrs, arrays, * func_protos, modifiers are just means to get to these definitions. * Int/void don't need definitions, they are assumed to be always * properly defined. We also ignore datasec, var, and funcs for now. * So for all non-defining kinds, we never even set ordering state, * for defining kinds we set ORDERING and subsequently ORDERED if it * forms a strong link. */ struct btf_dump_type_aux_state *tstate = &d->type_states[id]; const struct btf_type *t; __u16 vlen; int err, i; /* return true, letting typedefs know that it's ok to be emitted */ if (tstate->order_state == ORDERED) return 1; t = btf__type_by_id(d->btf, id); if (tstate->order_state == ORDERING) { /* type loop, but resolvable through fwd declaration */ if (btf_is_composite(t) && through_ptr && t->name_off != 0) return 0; pr_warn("unsatisfiable type cycle, id:[%u]\n", id); return -ELOOP; } switch (btf_kind(t)) { case BTF_KIND_INT: case BTF_KIND_FLOAT: tstate->order_state = ORDERED; return 0; case BTF_KIND_PTR: err = btf_dump_order_type(d, t->type, true); tstate->order_state = ORDERED; return err; case BTF_KIND_ARRAY: return btf_dump_order_type(d, btf_array(t)->type, false); case BTF_KIND_STRUCT: case BTF_KIND_UNION: { const struct btf_member *m = btf_members(t); /* * struct/union is part of strong link, only if it's embedded * (so no ptr in a path) or it's anonymous (so has to be * defined inline, even if declared through ptr) */ if (through_ptr && t->name_off != 0) return 0; tstate->order_state = ORDERING; vlen = btf_vlen(t); for (i = 0; i < vlen; i++, m++) { err = btf_dump_order_type(d, m->type, false); if (err < 0) return err; } if (t->name_off != 0) { err = btf_dump_add_emit_queue_id(d, id); if (err < 0) return err; } tstate->order_state = ORDERED; return 1; } case BTF_KIND_ENUM: case BTF_KIND_ENUM64: case BTF_KIND_FWD: /* * non-anonymous or non-referenced enums are top-level * declarations and should be emitted. Same logic can be * applied to FWDs, it won't hurt anyways. */ if (t->name_off != 0 || !tstate->referenced) { err = btf_dump_add_emit_queue_id(d, id); if (err) return err; } tstate->order_state = ORDERED; return 1; case BTF_KIND_TYPEDEF: { int is_strong; is_strong = btf_dump_order_type(d, t->type, through_ptr); if (is_strong < 0) return is_strong; /* typedef is similar to struct/union w.r.t. fwd-decls */ if (through_ptr && !is_strong) return 0; /* typedef is always a named definition */ err = btf_dump_add_emit_queue_id(d, id); if (err) return err; d->type_states[id].order_state = ORDERED; return 1; } case BTF_KIND_VOLATILE: case BTF_KIND_CONST: case BTF_KIND_RESTRICT: case BTF_KIND_TYPE_TAG: return btf_dump_order_type(d, t->type, through_ptr); case BTF_KIND_FUNC_PROTO: { const struct btf_param *p = btf_params(t); bool is_strong; err = btf_dump_order_type(d, t->type, through_ptr); if (err < 0) return err; is_strong = err > 0; vlen = btf_vlen(t); for (i = 0; i < vlen; i++, p++) { err = btf_dump_order_type(d, p->type, through_ptr); if (err < 0) return err; if (err > 0) is_strong = true; } return is_strong; } case BTF_KIND_FUNC: case BTF_KIND_VAR: case BTF_KIND_DATASEC: case BTF_KIND_DECL_TAG: d->type_states[id].order_state = ORDERED; return 0; default: return -EINVAL; } } static void btf_dump_emit_missing_aliases(struct btf_dump *d, __u32 id, const struct btf_type *t); static void btf_dump_emit_struct_fwd(struct btf_dump *d, __u32 id, const struct btf_type *t); static void btf_dump_emit_struct_def(struct btf_dump *d, __u32 id, const struct btf_type *t, int lvl); static void btf_dump_emit_enum_fwd(struct btf_dump *d, __u32 id, const struct btf_type *t); static void btf_dump_emit_enum_def(struct btf_dump *d, __u32 id, const struct btf_type *t, int lvl); static void btf_dump_emit_fwd_def(struct btf_dump *d, __u32 id, const struct btf_type *t); static void btf_dump_emit_typedef_def(struct btf_dump *d, __u32 id, const struct btf_type *t, int lvl); /* a local view into a shared stack */ struct id_stack { const __u32 *ids; int cnt; }; static void btf_dump_emit_type_decl(struct btf_dump *d, __u32 id, const char *fname, int lvl); static void btf_dump_emit_type_chain(struct btf_dump *d, struct id_stack *decl_stack, const char *fname, int lvl); static const char *btf_dump_type_name(struct btf_dump *d, __u32 id); static const char *btf_dump_ident_name(struct btf_dump *d, __u32 id); static size_t btf_dump_name_dups(struct btf_dump *d, struct hashmap *name_map, const char *orig_name); static bool btf_dump_is_blacklisted(struct btf_dump *d, __u32 id) { const struct btf_type *t = btf__type_by_id(d->btf, id); /* __builtin_va_list is a compiler built-in, which causes compilation * errors, when compiling w/ different compiler, then used to compile * original code (e.g., GCC to compile kernel, Clang to use generated * C header from BTF). As it is built-in, it should be already defined * properly internally in compiler. */ if (t->name_off == 0) return false; return strcmp(btf_name_of(d, t->name_off), "__builtin_va_list") == 0; } /* * Emit C-syntax definitions of types from chains of BTF types. * * High-level handling of determining necessary forward declarations are handled * by btf_dump_emit_type() itself, but all nitty-gritty details of emitting type * declarations/definitions in C syntax are handled by a combo of * btf_dump_emit_type_decl()/btf_dump_emit_type_chain() w/ delegation to * corresponding btf_dump_emit_*_{def,fwd}() functions. * * We also keep track of "containing struct/union type ID" to determine when * we reference it from inside and thus can avoid emitting unnecessary forward * declaration. * * This algorithm is designed in such a way, that even if some error occurs * (either technical, e.g., out of memory, or logical, i.e., malformed BTF * that doesn't comply to C rules completely), algorithm will try to proceed * and produce as much meaningful output as possible. */ static void btf_dump_emit_type(struct btf_dump *d, __u32 id, __u32 cont_id) { struct btf_dump_type_aux_state *tstate = &d->type_states[id]; bool top_level_def = cont_id == 0; const struct btf_type *t; __u16 kind; if (tstate->emit_state == EMITTED) return; t = btf__type_by_id(d->btf, id); kind = btf_kind(t); if (tstate->emit_state == EMITTING) { if (tstate->fwd_emitted) return; switch (kind) { case BTF_KIND_STRUCT: case BTF_KIND_UNION: /* * if we are referencing a struct/union that we are * part of - then no need for fwd declaration */ if (id == cont_id) return; if (t->name_off == 0) { pr_warn("anonymous struct/union loop, id:[%u]\n", id); return; } btf_dump_emit_struct_fwd(d, id, t); btf_dump_printf(d, ";\n\n"); tstate->fwd_emitted = 1; break; case BTF_KIND_TYPEDEF: /* * for typedef fwd_emitted means typedef definition * was emitted, but it can be used only for "weak" * references through pointer only, not for embedding */ if (!btf_dump_is_blacklisted(d, id)) { btf_dump_emit_typedef_def(d, id, t, 0); btf_dump_printf(d, ";\n\n"); } tstate->fwd_emitted = 1; break; default: break; } return; } switch (kind) { case BTF_KIND_INT: /* Emit type alias definitions if necessary */ btf_dump_emit_missing_aliases(d, id, t); tstate->emit_state = EMITTED; break; case BTF_KIND_ENUM: case BTF_KIND_ENUM64: if (top_level_def) { btf_dump_emit_enum_def(d, id, t, 0); btf_dump_printf(d, ";\n\n"); } tstate->emit_state = EMITTED; break; case BTF_KIND_PTR: case BTF_KIND_VOLATILE: case BTF_KIND_CONST: case BTF_KIND_RESTRICT: case BTF_KIND_TYPE_TAG: btf_dump_emit_type(d, t->type, cont_id); break; case BTF_KIND_ARRAY: btf_dump_emit_type(d, btf_array(t)->type, cont_id); break; case BTF_KIND_FWD: btf_dump_emit_fwd_def(d, id, t); btf_dump_printf(d, ";\n\n"); tstate->emit_state = EMITTED; break; case BTF_KIND_TYPEDEF: tstate->emit_state = EMITTING; btf_dump_emit_type(d, t->type, id); /* * typedef can server as both definition and forward * declaration; at this stage someone depends on * typedef as a forward declaration (refers to it * through pointer), so unless we already did it, * emit typedef as a forward declaration */ if (!tstate->fwd_emitted && !btf_dump_is_blacklisted(d, id)) { btf_dump_emit_typedef_def(d, id, t, 0); btf_dump_printf(d, ";\n\n"); } tstate->emit_state = EMITTED; break; case BTF_KIND_STRUCT: case BTF_KIND_UNION: tstate->emit_state = EMITTING; /* if it's a top-level struct/union definition or struct/union * is anonymous, then in C we'll be emitting all fields and * their types (as opposed to just `struct X`), so we need to * make sure that all types, referenced from struct/union * members have necessary forward-declarations, where * applicable */ if (top_level_def || t->name_off == 0) { const struct btf_member *m = btf_members(t); __u16 vlen = btf_vlen(t); int i, new_cont_id; new_cont_id = t->name_off == 0 ? cont_id : id; for (i = 0; i < vlen; i++, m++) btf_dump_emit_type(d, m->type, new_cont_id); } else if (!tstate->fwd_emitted && id != cont_id) { btf_dump_emit_struct_fwd(d, id, t); btf_dump_printf(d, ";\n\n"); tstate->fwd_emitted = 1; } if (top_level_def) { btf_dump_emit_struct_def(d, id, t, 0); btf_dump_printf(d, ";\n\n"); tstate->emit_state = EMITTED; } else { tstate->emit_state = NOT_EMITTED; } break; case BTF_KIND_FUNC_PROTO: { const struct btf_param *p = btf_params(t); __u16 n = btf_vlen(t); int i; btf_dump_emit_type(d, t->type, cont_id); for (i = 0; i < n; i++, p++) btf_dump_emit_type(d, p->type, cont_id); break; } default: break; } } static bool btf_is_struct_packed(const struct btf *btf, __u32 id, const struct btf_type *t) { const struct btf_member *m; int max_align = 1, align, i, bit_sz; __u16 vlen; m = btf_members(t); vlen = btf_vlen(t); /* all non-bitfield fields have to be naturally aligned */ for (i = 0; i < vlen; i++, m++) { align = btf__align_of(btf, m->type); bit_sz = btf_member_bitfield_size(t, i); if (align && bit_sz == 0 && m->offset % (8 * align) != 0) return true; max_align = max(align, max_align); } /* size of a non-packed struct has to be a multiple of its alignment */ if (t->size % max_align != 0) return true; /* * if original struct was marked as packed, but its layout is * naturally aligned, we'll detect that it's not packed */ return false; } static void btf_dump_emit_bit_padding(const struct btf_dump *d, int cur_off, int next_off, int next_align, bool in_bitfield, int lvl) { const struct { const char *name; int bits; } pads[] = { {"long", d->ptr_sz * 8}, {"int", 32}, {"short", 16}, {"char", 8} }; int new_off, pad_bits, bits, i; const char *pad_type; if (cur_off >= next_off) return; /* no gap */ /* For filling out padding we want to take advantage of * natural alignment rules to minimize unnecessary explicit * padding. First, we find the largest type (among long, int, * short, or char) that can be used to force naturally aligned * boundary. Once determined, we'll use such type to fill in * the remaining padding gap. In some cases we can rely on * compiler filling some gaps, but sometimes we need to force * alignment to close natural alignment with markers like * `long: 0` (this is always the case for bitfields). Note * that even if struct itself has, let's say 4-byte alignment * (i.e., it only uses up to int-aligned types), using `long: * X;` explicit padding doesn't actually change struct's * overall alignment requirements, but compiler does take into * account that type's (long, in this example) natural * alignment requirements when adding implicit padding. We use * this fact heavily and don't worry about ruining correct * struct alignment requirement. */ for (i = 0; i < ARRAY_SIZE(pads); i++) { pad_bits = pads[i].bits; pad_type = pads[i].name; new_off = roundup(cur_off, pad_bits); if (new_off <= next_off) break; } if (new_off > cur_off && new_off <= next_off) { /* We need explicit `: 0` aligning mark if next * field is right on alignment offset and its * alignment requirement is less strict than 's * alignment (so compiler won't naturally align to the * offset we expect), or if subsequent `: X`, * will actually completely fit in the remaining hole, * making compiler basically ignore `: X` * completely. */ if (in_bitfield || (new_off == next_off && roundup(cur_off, next_align * 8) != new_off) || (new_off != next_off && next_off - new_off <= new_off - cur_off)) /* but for bitfields we'll emit explicit bit count */ btf_dump_printf(d, "\n%s%s: %d;", pfx(lvl), pad_type, in_bitfield ? new_off - cur_off : 0); cur_off = new_off; } /* Now we know we start at naturally aligned offset for a chosen * padding type (long, int, short, or char), and so the rest is just * a straightforward filling of remaining padding gap with full * `: sizeof();` markers, except for the last one, which * might need smaller than sizeof() padding. */ while (cur_off != next_off) { bits = min(next_off - cur_off, pad_bits); if (bits == pad_bits) { btf_dump_printf(d, "\n%s%s: %d;", pfx(lvl), pad_type, pad_bits); cur_off += bits; continue; } /* For the remainder padding that doesn't cover entire * pad_type bit length, we pick the smallest necessary type. * This is pure aesthetics, we could have just used `long`, * but having smallest necessary one communicates better the * scale of the padding gap. */ for (i = ARRAY_SIZE(pads) - 1; i >= 0; i--) { pad_type = pads[i].name; pad_bits = pads[i].bits; if (pad_bits < bits) continue; btf_dump_printf(d, "\n%s%s: %d;", pfx(lvl), pad_type, bits); cur_off += bits; break; } } } static void btf_dump_emit_struct_fwd(struct btf_dump *d, __u32 id, const struct btf_type *t) { btf_dump_printf(d, "%s%s%s", btf_is_struct(t) ? "struct" : "union", t->name_off ? " " : "", btf_dump_type_name(d, id)); } static void btf_dump_emit_struct_def(struct btf_dump *d, __u32 id, const struct btf_type *t, int lvl) { const struct btf_member *m = btf_members(t); bool is_struct = btf_is_struct(t); bool packed, prev_bitfield = false; int align, i, off = 0; __u16 vlen = btf_vlen(t); align = btf__align_of(d->btf, id); packed = is_struct ? btf_is_struct_packed(d->btf, id, t) : 0; btf_dump_printf(d, "%s%s%s {", is_struct ? "struct" : "union", t->name_off ? " " : "", btf_dump_type_name(d, id)); for (i = 0; i < vlen; i++, m++) { const char *fname; int m_off, m_sz, m_align; bool in_bitfield; fname = btf_name_of(d, m->name_off); m_sz = btf_member_bitfield_size(t, i); m_off = btf_member_bit_offset(t, i); m_align = packed ? 1 : btf__align_of(d->btf, m->type); in_bitfield = prev_bitfield && m_sz != 0; btf_dump_emit_bit_padding(d, off, m_off, m_align, in_bitfield, lvl + 1); btf_dump_printf(d, "\n%s", pfx(lvl + 1)); btf_dump_emit_type_decl(d, m->type, fname, lvl + 1); if (m_sz) { btf_dump_printf(d, ": %d", m_sz); off = m_off + m_sz; prev_bitfield = true; } else { m_sz = max((__s64)0, btf__resolve_size(d->btf, m->type)); off = m_off + m_sz * 8; prev_bitfield = false; } btf_dump_printf(d, ";"); } /* pad at the end, if necessary */ if (is_struct) btf_dump_emit_bit_padding(d, off, t->size * 8, align, false, lvl + 1); /* * Keep `struct empty {}` on a single line, * only print newline when there are regular or padding fields. */ if (vlen || t->size) { btf_dump_printf(d, "\n"); btf_dump_printf(d, "%s}", pfx(lvl)); } else { btf_dump_printf(d, "}"); } if (packed) btf_dump_printf(d, " __attribute__((packed))"); } static const char *missing_base_types[][2] = { /* * GCC emits typedefs to its internal __PolyX_t types when compiling Arm * SIMD intrinsics. Alias them to standard base types. */ { "__Poly8_t", "unsigned char" }, { "__Poly16_t", "unsigned short" }, { "__Poly64_t", "unsigned long long" }, { "__Poly128_t", "unsigned __int128" }, }; static void btf_dump_emit_missing_aliases(struct btf_dump *d, __u32 id, const struct btf_type *t) { const char *name = btf_dump_type_name(d, id); int i; for (i = 0; i < ARRAY_SIZE(missing_base_types); i++) { if (strcmp(name, missing_base_types[i][0]) == 0) { btf_dump_printf(d, "typedef %s %s;\n\n", missing_base_types[i][1], name); break; } } } static void btf_dump_emit_enum_fwd(struct btf_dump *d, __u32 id, const struct btf_type *t) { btf_dump_printf(d, "enum %s", btf_dump_type_name(d, id)); } static void btf_dump_emit_enum32_val(struct btf_dump *d, const struct btf_type *t, int lvl, __u16 vlen) { const struct btf_enum *v = btf_enum(t); bool is_signed = btf_kflag(t); const char *fmt_str; const char *name; size_t dup_cnt; int i; for (i = 0; i < vlen; i++, v++) { name = btf_name_of(d, v->name_off); /* enumerators share namespace with typedef idents */ dup_cnt = btf_dump_name_dups(d, d->ident_names, name); if (dup_cnt > 1) { fmt_str = is_signed ? "\n%s%s___%zd = %d," : "\n%s%s___%zd = %u,"; btf_dump_printf(d, fmt_str, pfx(lvl + 1), name, dup_cnt, v->val); } else { fmt_str = is_signed ? "\n%s%s = %d," : "\n%s%s = %u,"; btf_dump_printf(d, fmt_str, pfx(lvl + 1), name, v->val); } } } static void btf_dump_emit_enum64_val(struct btf_dump *d, const struct btf_type *t, int lvl, __u16 vlen) { const struct btf_enum64 *v = btf_enum64(t); bool is_signed = btf_kflag(t); const char *fmt_str; const char *name; size_t dup_cnt; __u64 val; int i; for (i = 0; i < vlen; i++, v++) { name = btf_name_of(d, v->name_off); dup_cnt = btf_dump_name_dups(d, d->ident_names, name); val = btf_enum64_value(v); if (dup_cnt > 1) { fmt_str = is_signed ? "\n%s%s___%zd = %lldLL," : "\n%s%s___%zd = %lluULL,"; btf_dump_printf(d, fmt_str, pfx(lvl + 1), name, dup_cnt, (unsigned long long)val); } else { fmt_str = is_signed ? "\n%s%s = %lldLL," : "\n%s%s = %lluULL,"; btf_dump_printf(d, fmt_str, pfx(lvl + 1), name, (unsigned long long)val); } } } static void btf_dump_emit_enum_def(struct btf_dump *d, __u32 id, const struct btf_type *t, int lvl) { __u16 vlen = btf_vlen(t); btf_dump_printf(d, "enum%s%s", t->name_off ? " " : "", btf_dump_type_name(d, id)); if (!vlen) return; btf_dump_printf(d, " {"); if (btf_is_enum(t)) btf_dump_emit_enum32_val(d, t, lvl, vlen); else btf_dump_emit_enum64_val(d, t, lvl, vlen); btf_dump_printf(d, "\n%s}", pfx(lvl)); /* special case enums with special sizes */ if (t->size == 1) { /* one-byte enums can be forced with mode(byte) attribute */ btf_dump_printf(d, " __attribute__((mode(byte)))"); } else if (t->size == 8 && d->ptr_sz == 8) { /* enum can be 8-byte sized if one of the enumerator values * doesn't fit in 32-bit integer, or by adding mode(word) * attribute (but probably only on 64-bit architectures); do * our best here to try to satisfy the contract without adding * unnecessary attributes */ bool needs_word_mode; if (btf_is_enum(t)) { /* enum can't represent 64-bit values, so we need word mode */ needs_word_mode = true; } else { /* enum64 needs mode(word) if none of its values has * non-zero upper 32-bits (which means that all values * fit in 32-bit integers and won't cause compiler to * bump enum to be 64-bit naturally */ int i; needs_word_mode = true; for (i = 0; i < vlen; i++) { if (btf_enum64(t)[i].val_hi32 != 0) { needs_word_mode = false; break; } } } if (needs_word_mode) btf_dump_printf(d, " __attribute__((mode(word)))"); } } static void btf_dump_emit_fwd_def(struct btf_dump *d, __u32 id, const struct btf_type *t) { const char *name = btf_dump_type_name(d, id); if (btf_kflag(t)) btf_dump_printf(d, "union %s", name); else btf_dump_printf(d, "struct %s", name); } static void btf_dump_emit_typedef_def(struct btf_dump *d, __u32 id, const struct btf_type *t, int lvl) { const char *name = btf_dump_ident_name(d, id); /* * Old GCC versions are emitting invalid typedef for __gnuc_va_list * pointing to VOID. This generates warnings from btf_dump() and * results in uncompilable header file, so we are fixing it up here * with valid typedef into __builtin_va_list. */ if (t->type == 0 && strcmp(name, "__gnuc_va_list") == 0) { btf_dump_printf(d, "typedef __builtin_va_list __gnuc_va_list"); return; } btf_dump_printf(d, "typedef "); btf_dump_emit_type_decl(d, t->type, name, lvl); } static int btf_dump_push_decl_stack_id(struct btf_dump *d, __u32 id) { __u32 *new_stack; size_t new_cap; if (d->decl_stack_cnt >= d->decl_stack_cap) { new_cap = max(16, d->decl_stack_cap * 3 / 2); new_stack = libbpf_reallocarray(d->decl_stack, new_cap, sizeof(new_stack[0])); if (!new_stack) return -ENOMEM; d->decl_stack = new_stack; d->decl_stack_cap = new_cap; } d->decl_stack[d->decl_stack_cnt++] = id; return 0; } /* * Emit type declaration (e.g., field type declaration in a struct or argument * declaration in function prototype) in correct C syntax. * * For most types it's trivial, but there are few quirky type declaration * cases worth mentioning: * - function prototypes (especially nesting of function prototypes); * - arrays; * - const/volatile/restrict for pointers vs other types. * * For a good discussion of *PARSING* C syntax (as a human), see * Peter van der Linden's "Expert C Programming: Deep C Secrets", * Ch.3 "Unscrambling Declarations in C". * * It won't help with BTF to C conversion much, though, as it's an opposite * problem. So we came up with this algorithm in reverse to van der Linden's * parsing algorithm. It goes from structured BTF representation of type * declaration to a valid compilable C syntax. * * For instance, consider this C typedef: * typedef const int * const * arr[10] arr_t; * It will be represented in BTF with this chain of BTF types: * [typedef] -> [array] -> [ptr] -> [const] -> [ptr] -> [const] -> [int] * * Notice how [const] modifier always goes before type it modifies in BTF type * graph, but in C syntax, const/volatile/restrict modifiers are written to * the right of pointers, but to the left of other types. There are also other * quirks, like function pointers, arrays of them, functions returning other * functions, etc. * * We handle that by pushing all the types to a stack, until we hit "terminal" * type (int/enum/struct/union/fwd). Then depending on the kind of a type on * top of a stack, modifiers are handled differently. Array/function pointers * have also wildly different syntax and how nesting of them are done. See * code for authoritative definition. * * To avoid allocating new stack for each independent chain of BTF types, we * share one bigger stack, with each chain working only on its own local view * of a stack frame. Some care is required to "pop" stack frames after * processing type declaration chain. */ int btf_dump__emit_type_decl(struct btf_dump *d, __u32 id, const struct btf_dump_emit_type_decl_opts *opts) { const char *fname; int lvl, err; if (!OPTS_VALID(opts, btf_dump_emit_type_decl_opts)) return libbpf_err(-EINVAL); err = btf_dump_resize(d); if (err) return libbpf_err(err); fname = OPTS_GET(opts, field_name, ""); lvl = OPTS_GET(opts, indent_level, 0); d->strip_mods = OPTS_GET(opts, strip_mods, false); btf_dump_emit_type_decl(d, id, fname, lvl); d->strip_mods = false; return 0; } static void btf_dump_emit_type_decl(struct btf_dump *d, __u32 id, const char *fname, int lvl) { struct id_stack decl_stack; const struct btf_type *t; int err, stack_start; stack_start = d->decl_stack_cnt; for (;;) { t = btf__type_by_id(d->btf, id); if (d->strip_mods && btf_is_mod(t)) goto skip_mod; err = btf_dump_push_decl_stack_id(d, id); if (err < 0) { /* * if we don't have enough memory for entire type decl * chain, restore stack, emit warning, and try to * proceed nevertheless */ pr_warn("not enough memory for decl stack:%d", err); d->decl_stack_cnt = stack_start; return; } skip_mod: /* VOID */ if (id == 0) break; switch (btf_kind(t)) { case BTF_KIND_PTR: case BTF_KIND_VOLATILE: case BTF_KIND_CONST: case BTF_KIND_RESTRICT: case BTF_KIND_FUNC_PROTO: case BTF_KIND_TYPE_TAG: id = t->type; break; case BTF_KIND_ARRAY: id = btf_array(t)->type; break; case BTF_KIND_INT: case BTF_KIND_ENUM: case BTF_KIND_ENUM64: case BTF_KIND_FWD: case BTF_KIND_STRUCT: case BTF_KIND_UNION: case BTF_KIND_TYPEDEF: case BTF_KIND_FLOAT: goto done; default: pr_warn("unexpected type in decl chain, kind:%u, id:[%u]\n", btf_kind(t), id); goto done; } } done: /* * We might be inside a chain of declarations (e.g., array of function * pointers returning anonymous (so inlined) structs, having another * array field). Each of those needs its own "stack frame" to handle * emitting of declarations. Those stack frames are non-overlapping * portions of shared btf_dump->decl_stack. To make it a bit nicer to * handle this set of nested stacks, we create a view corresponding to * our own "stack frame" and work with it as an independent stack. * We'll need to clean up after emit_type_chain() returns, though. */ decl_stack.ids = d->decl_stack + stack_start; decl_stack.cnt = d->decl_stack_cnt - stack_start; btf_dump_emit_type_chain(d, &decl_stack, fname, lvl); /* * emit_type_chain() guarantees that it will pop its entire decl_stack * frame before returning. But it works with a read-only view into * decl_stack, so it doesn't actually pop anything from the * perspective of shared btf_dump->decl_stack, per se. We need to * reset decl_stack state to how it was before us to avoid it growing * all the time. */ d->decl_stack_cnt = stack_start; } static void btf_dump_emit_mods(struct btf_dump *d, struct id_stack *decl_stack) { const struct btf_type *t; __u32 id; while (decl_stack->cnt) { id = decl_stack->ids[decl_stack->cnt - 1]; t = btf__type_by_id(d->btf, id); switch (btf_kind(t)) { case BTF_KIND_VOLATILE: btf_dump_printf(d, "volatile "); break; case BTF_KIND_CONST: btf_dump_printf(d, "const "); break; case BTF_KIND_RESTRICT: btf_dump_printf(d, "restrict "); break; default: return; } decl_stack->cnt--; } } static void btf_dump_drop_mods(struct btf_dump *d, struct id_stack *decl_stack) { const struct btf_type *t; __u32 id; while (decl_stack->cnt) { id = decl_stack->ids[decl_stack->cnt - 1]; t = btf__type_by_id(d->btf, id); if (!btf_is_mod(t)) return; decl_stack->cnt--; } } static void btf_dump_emit_name(const struct btf_dump *d, const char *name, bool last_was_ptr) { bool separate = name[0] && !last_was_ptr; btf_dump_printf(d, "%s%s", separate ? " " : "", name); } static void btf_dump_emit_type_chain(struct btf_dump *d, struct id_stack *decls, const char *fname, int lvl) { /* * last_was_ptr is used to determine if we need to separate pointer * asterisk (*) from previous part of type signature with space, so * that we get `int ***`, instead of `int * * *`. We default to true * for cases where we have single pointer in a chain. E.g., in ptr -> * func_proto case. func_proto will start a new emit_type_chain call * with just ptr, which should be emitted as (*) or (*), so we * don't want to prepend space for that last pointer. */ bool last_was_ptr = true; const struct btf_type *t; const char *name; __u16 kind; __u32 id; while (decls->cnt) { id = decls->ids[--decls->cnt]; if (id == 0) { /* VOID is a special snowflake */ btf_dump_emit_mods(d, decls); btf_dump_printf(d, "void"); last_was_ptr = false; continue; } t = btf__type_by_id(d->btf, id); kind = btf_kind(t); switch (kind) { case BTF_KIND_INT: case BTF_KIND_FLOAT: btf_dump_emit_mods(d, decls); name = btf_name_of(d, t->name_off); btf_dump_printf(d, "%s", name); break; case BTF_KIND_STRUCT: case BTF_KIND_UNION: btf_dump_emit_mods(d, decls); /* inline anonymous struct/union */ if (t->name_off == 0 && !d->skip_anon_defs) btf_dump_emit_struct_def(d, id, t, lvl); else btf_dump_emit_struct_fwd(d, id, t); break; case BTF_KIND_ENUM: case BTF_KIND_ENUM64: btf_dump_emit_mods(d, decls); /* inline anonymous enum */ if (t->name_off == 0 && !d->skip_anon_defs) btf_dump_emit_enum_def(d, id, t, lvl); else btf_dump_emit_enum_fwd(d, id, t); break; case BTF_KIND_FWD: btf_dump_emit_mods(d, decls); btf_dump_emit_fwd_def(d, id, t); break; case BTF_KIND_TYPEDEF: btf_dump_emit_mods(d, decls); btf_dump_printf(d, "%s", btf_dump_ident_name(d, id)); break; case BTF_KIND_PTR: btf_dump_printf(d, "%s", last_was_ptr ? "*" : " *"); break; case BTF_KIND_VOLATILE: btf_dump_printf(d, " volatile"); break; case BTF_KIND_CONST: btf_dump_printf(d, " const"); break; case BTF_KIND_RESTRICT: btf_dump_printf(d, " restrict"); break; case BTF_KIND_TYPE_TAG: btf_dump_emit_mods(d, decls); name = btf_name_of(d, t->name_off); btf_dump_printf(d, " __attribute__((btf_type_tag(\"%s\")))", name); break; case BTF_KIND_ARRAY: { const struct btf_array *a = btf_array(t); const struct btf_type *next_t; __u32 next_id; bool multidim; /* * GCC has a bug * (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=8354) * which causes it to emit extra const/volatile * modifiers for an array, if array's element type has * const/volatile modifiers. Clang doesn't do that. * In general, it doesn't seem very meaningful to have * a const/volatile modifier for array, so we are * going to silently skip them here. */ btf_dump_drop_mods(d, decls); if (decls->cnt == 0) { btf_dump_emit_name(d, fname, last_was_ptr); btf_dump_printf(d, "[%u]", a->nelems); return; } next_id = decls->ids[decls->cnt - 1]; next_t = btf__type_by_id(d->btf, next_id); multidim = btf_is_array(next_t); /* we need space if we have named non-pointer */ if (fname[0] && !last_was_ptr) btf_dump_printf(d, " "); /* no parentheses for multi-dimensional array */ if (!multidim) btf_dump_printf(d, "("); btf_dump_emit_type_chain(d, decls, fname, lvl); if (!multidim) btf_dump_printf(d, ")"); btf_dump_printf(d, "[%u]", a->nelems); return; } case BTF_KIND_FUNC_PROTO: { const struct btf_param *p = btf_params(t); __u16 vlen = btf_vlen(t); int i; /* * GCC emits extra volatile qualifier for * __attribute__((noreturn)) function pointers. Clang * doesn't do it. It's a GCC quirk for backwards * compatibility with code written for GCC <2.5. So, * similarly to extra qualifiers for array, just drop * them, instead of handling them. */ btf_dump_drop_mods(d, decls); if (decls->cnt) { btf_dump_printf(d, " ("); btf_dump_emit_type_chain(d, decls, fname, lvl); btf_dump_printf(d, ")"); } else { btf_dump_emit_name(d, fname, last_was_ptr); } btf_dump_printf(d, "("); /* * Clang for BPF target generates func_proto with no * args as a func_proto with a single void arg (e.g., * `int (*f)(void)` vs just `int (*f)()`). We are * going to pretend there are no args for such case. */ if (vlen == 1 && p->type == 0) { btf_dump_printf(d, ")"); return; } for (i = 0; i < vlen; i++, p++) { if (i > 0) btf_dump_printf(d, ", "); /* last arg of type void is vararg */ if (i == vlen - 1 && p->type == 0) { btf_dump_printf(d, "..."); break; } name = btf_name_of(d, p->name_off); btf_dump_emit_type_decl(d, p->type, name, lvl); } btf_dump_printf(d, ")"); return; } default: pr_warn("unexpected type in decl chain, kind:%u, id:[%u]\n", kind, id); return; } last_was_ptr = kind == BTF_KIND_PTR; } btf_dump_emit_name(d, fname, last_was_ptr); } /* show type name as (type_name) */ static void btf_dump_emit_type_cast(struct btf_dump *d, __u32 id, bool top_level) { const struct btf_type *t; /* for array members, we don't bother emitting type name for each * member to avoid the redundancy of * .name = (char[4])[(char)'f',(char)'o',(char)'o',] */ if (d->typed_dump->is_array_member) return; /* avoid type name specification for variable/section; it will be done * for the associated variable value(s). */ t = btf__type_by_id(d->btf, id); if (btf_is_var(t) || btf_is_datasec(t)) return; if (top_level) btf_dump_printf(d, "("); d->skip_anon_defs = true; d->strip_mods = true; btf_dump_emit_type_decl(d, id, "", 0); d->strip_mods = false; d->skip_anon_defs = false; if (top_level) btf_dump_printf(d, ")"); } /* return number of duplicates (occurrences) of a given name */ static size_t btf_dump_name_dups(struct btf_dump *d, struct hashmap *name_map, const char *orig_name) { char *old_name, *new_name; size_t dup_cnt = 0; int err; new_name = strdup(orig_name); if (!new_name) return 1; (void)hashmap__find(name_map, orig_name, &dup_cnt); dup_cnt++; err = hashmap__set(name_map, new_name, dup_cnt, &old_name, NULL); if (err) free(new_name); free(old_name); return dup_cnt; } static const char *btf_dump_resolve_name(struct btf_dump *d, __u32 id, struct hashmap *name_map) { struct btf_dump_type_aux_state *s = &d->type_states[id]; const struct btf_type *t = btf__type_by_id(d->btf, id); const char *orig_name = btf_name_of(d, t->name_off); const char **cached_name = &d->cached_names[id]; size_t dup_cnt; if (t->name_off == 0) return ""; if (s->name_resolved) return *cached_name ? *cached_name : orig_name; if (btf_is_fwd(t) || (btf_is_enum(t) && btf_vlen(t) == 0)) { s->name_resolved = 1; return orig_name; } dup_cnt = btf_dump_name_dups(d, name_map, orig_name); if (dup_cnt > 1) { const size_t max_len = 256; char new_name[max_len]; snprintf(new_name, max_len, "%s___%zu", orig_name, dup_cnt); *cached_name = strdup(new_name); } s->name_resolved = 1; return *cached_name ? *cached_name : orig_name; } static const char *btf_dump_type_name(struct btf_dump *d, __u32 id) { return btf_dump_resolve_name(d, id, d->type_names); } static const char *btf_dump_ident_name(struct btf_dump *d, __u32 id) { return btf_dump_resolve_name(d, id, d->ident_names); } static int btf_dump_dump_type_data(struct btf_dump *d, const char *fname, const struct btf_type *t, __u32 id, const void *data, __u8 bits_offset, __u8 bit_sz); static const char *btf_dump_data_newline(struct btf_dump *d) { return d->typed_dump->compact || d->typed_dump->depth == 0 ? "" : "\n"; } static const char *btf_dump_data_delim(struct btf_dump *d) { return d->typed_dump->depth == 0 ? "" : ","; } static void btf_dump_data_pfx(struct btf_dump *d) { int i, lvl = d->typed_dump->indent_lvl + d->typed_dump->depth; if (d->typed_dump->compact) return; for (i = 0; i < lvl; i++) btf_dump_printf(d, "%s", d->typed_dump->indent_str); } /* A macro is used here as btf_type_value[s]() appends format specifiers * to the format specifier passed in; these do the work of appending * delimiters etc while the caller simply has to specify the type values * in the format specifier + value(s). */ #define btf_dump_type_values(d, fmt, ...) \ btf_dump_printf(d, fmt "%s%s", \ ##__VA_ARGS__, \ btf_dump_data_delim(d), \ btf_dump_data_newline(d)) static int btf_dump_unsupported_data(struct btf_dump *d, const struct btf_type *t, __u32 id) { btf_dump_printf(d, "", btf_kind(t)); return -ENOTSUP; } static int btf_dump_get_bitfield_value(struct btf_dump *d, const struct btf_type *t, const void *data, __u8 bits_offset, __u8 bit_sz, __u64 *value) { __u16 left_shift_bits, right_shift_bits; const __u8 *bytes = data; __u8 nr_copy_bits; __u64 num = 0; int i; /* Maximum supported bitfield size is 64 bits */ if (t->size > 8) { pr_warn("unexpected bitfield size %d\n", t->size); return -EINVAL; } /* Bitfield value retrieval is done in two steps; first relevant bytes are * stored in num, then we left/right shift num to eliminate irrelevant bits. */ #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ for (i = t->size - 1; i >= 0; i--) num = num * 256 + bytes[i]; nr_copy_bits = bit_sz + bits_offset; #elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ for (i = 0; i < t->size; i++) num = num * 256 + bytes[i]; nr_copy_bits = t->size * 8 - bits_offset; #else # error "Unrecognized __BYTE_ORDER__" #endif left_shift_bits = 64 - nr_copy_bits; right_shift_bits = 64 - bit_sz; *value = (num << left_shift_bits) >> right_shift_bits; return 0; } static int btf_dump_bitfield_check_zero(struct btf_dump *d, const struct btf_type *t, const void *data, __u8 bits_offset, __u8 bit_sz) { __u64 check_num; int err; err = btf_dump_get_bitfield_value(d, t, data, bits_offset, bit_sz, &check_num); if (err) return err; if (check_num == 0) return -ENODATA; return 0; } static int btf_dump_bitfield_data(struct btf_dump *d, const struct btf_type *t, const void *data, __u8 bits_offset, __u8 bit_sz) { __u64 print_num; int err; err = btf_dump_get_bitfield_value(d, t, data, bits_offset, bit_sz, &print_num); if (err) return err; btf_dump_type_values(d, "0x%llx", (unsigned long long)print_num); return 0; } /* ints, floats and ptrs */ static int btf_dump_base_type_check_zero(struct btf_dump *d, const struct btf_type *t, __u32 id, const void *data) { static __u8 bytecmp[16] = {}; int nr_bytes; /* For pointer types, pointer size is not defined on a per-type basis. * On dump creation however, we store the pointer size. */ if (btf_kind(t) == BTF_KIND_PTR) nr_bytes = d->ptr_sz; else nr_bytes = t->size; if (nr_bytes < 1 || nr_bytes > 16) { pr_warn("unexpected size %d for id [%u]\n", nr_bytes, id); return -EINVAL; } if (memcmp(data, bytecmp, nr_bytes) == 0) return -ENODATA; return 0; } static bool ptr_is_aligned(const struct btf *btf, __u32 type_id, const void *data) { int alignment = btf__align_of(btf, type_id); if (alignment == 0) return false; return ((uintptr_t)data) % alignment == 0; } static int btf_dump_int_data(struct btf_dump *d, const struct btf_type *t, __u32 type_id, const void *data, __u8 bits_offset) { __u8 encoding = btf_int_encoding(t); bool sign = encoding & BTF_INT_SIGNED; char buf[16] __attribute__((aligned(16))); int sz = t->size; if (sz == 0 || sz > sizeof(buf)) { pr_warn("unexpected size %d for id [%u]\n", sz, type_id); return -EINVAL; } /* handle packed int data - accesses of integers not aligned on * int boundaries can cause problems on some platforms. */ if (!ptr_is_aligned(d->btf, type_id, data)) { memcpy(buf, data, sz); data = buf; } switch (sz) { case 16: { const __u64 *ints = data; __u64 lsi, msi; /* avoid use of __int128 as some 32-bit platforms do not * support it. */ #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ lsi = ints[0]; msi = ints[1]; #elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ lsi = ints[1]; msi = ints[0]; #else # error "Unrecognized __BYTE_ORDER__" #endif if (msi == 0) btf_dump_type_values(d, "0x%llx", (unsigned long long)lsi); else btf_dump_type_values(d, "0x%llx%016llx", (unsigned long long)msi, (unsigned long long)lsi); break; } case 8: if (sign) btf_dump_type_values(d, "%lld", *(long long *)data); else btf_dump_type_values(d, "%llu", *(unsigned long long *)data); break; case 4: if (sign) btf_dump_type_values(d, "%d", *(__s32 *)data); else btf_dump_type_values(d, "%u", *(__u32 *)data); break; case 2: if (sign) btf_dump_type_values(d, "%d", *(__s16 *)data); else btf_dump_type_values(d, "%u", *(__u16 *)data); break; case 1: if (d->typed_dump->is_array_char) { /* check for null terminator */ if (d->typed_dump->is_array_terminated) break; if (*(char *)data == '\0') { d->typed_dump->is_array_terminated = true; break; } if (isprint(*(char *)data)) { btf_dump_type_values(d, "'%c'", *(char *)data); break; } } if (sign) btf_dump_type_values(d, "%d", *(__s8 *)data); else btf_dump_type_values(d, "%u", *(__u8 *)data); break; default: pr_warn("unexpected sz %d for id [%u]\n", sz, type_id); return -EINVAL; } return 0; } union float_data { long double ld; double d; float f; }; static int btf_dump_float_data(struct btf_dump *d, const struct btf_type *t, __u32 type_id, const void *data) { const union float_data *flp = data; union float_data fl; int sz = t->size; /* handle unaligned data; copy to local union */ if (!ptr_is_aligned(d->btf, type_id, data)) { memcpy(&fl, data, sz); flp = &fl; } switch (sz) { case 16: btf_dump_type_values(d, "%Lf", flp->ld); break; case 8: btf_dump_type_values(d, "%lf", flp->d); break; case 4: btf_dump_type_values(d, "%f", flp->f); break; default: pr_warn("unexpected size %d for id [%u]\n", sz, type_id); return -EINVAL; } return 0; } static int btf_dump_var_data(struct btf_dump *d, const struct btf_type *v, __u32 id, const void *data) { enum btf_func_linkage linkage = btf_var(v)->linkage; const struct btf_type *t; const char *l; __u32 type_id; switch (linkage) { case BTF_FUNC_STATIC: l = "static "; break; case BTF_FUNC_EXTERN: l = "extern "; break; case BTF_FUNC_GLOBAL: default: l = ""; break; } /* format of output here is [linkage] [type] [varname] = (type)value, * for example "static int cpu_profile_flip = (int)1" */ btf_dump_printf(d, "%s", l); type_id = v->type; t = btf__type_by_id(d->btf, type_id); btf_dump_emit_type_cast(d, type_id, false); btf_dump_printf(d, " %s = ", btf_name_of(d, v->name_off)); return btf_dump_dump_type_data(d, NULL, t, type_id, data, 0, 0); } static int btf_dump_array_data(struct btf_dump *d, const struct btf_type *t, __u32 id, const void *data) { const struct btf_array *array = btf_array(t); const struct btf_type *elem_type; __u32 i, elem_type_id; __s64 elem_size; bool is_array_member; elem_type_id = array->type; elem_type = skip_mods_and_typedefs(d->btf, elem_type_id, NULL); elem_size = btf__resolve_size(d->btf, elem_type_id); if (elem_size <= 0) { pr_warn("unexpected elem size %zd for array type [%u]\n", (ssize_t)elem_size, id); return -EINVAL; } if (btf_is_int(elem_type)) { /* * BTF_INT_CHAR encoding never seems to be set for * char arrays, so if size is 1 and element is * printable as a char, we'll do that. */ if (elem_size == 1) d->typed_dump->is_array_char = true; } /* note that we increment depth before calling btf_dump_print() below; * this is intentional. btf_dump_data_newline() will not print a * newline for depth 0 (since this leaves us with trailing newlines * at the end of typed display), so depth is incremented first. * For similar reasons, we decrement depth before showing the closing * parenthesis. */ d->typed_dump->depth++; btf_dump_printf(d, "[%s", btf_dump_data_newline(d)); /* may be a multidimensional array, so store current "is array member" * status so we can restore it correctly later. */ is_array_member = d->typed_dump->is_array_member; d->typed_dump->is_array_member = true; for (i = 0; i < array->nelems; i++, data += elem_size) { if (d->typed_dump->is_array_terminated) break; btf_dump_dump_type_data(d, NULL, elem_type, elem_type_id, data, 0, 0); } d->typed_dump->is_array_member = is_array_member; d->typed_dump->depth--; btf_dump_data_pfx(d); btf_dump_type_values(d, "]"); return 0; } static int btf_dump_struct_data(struct btf_dump *d, const struct btf_type *t, __u32 id, const void *data) { const struct btf_member *m = btf_members(t); __u16 n = btf_vlen(t); int i, err = 0; /* note that we increment depth before calling btf_dump_print() below; * this is intentional. btf_dump_data_newline() will not print a * newline for depth 0 (since this leaves us with trailing newlines * at the end of typed display), so depth is incremented first. * For similar reasons, we decrement depth before showing the closing * parenthesis. */ d->typed_dump->depth++; btf_dump_printf(d, "{%s", btf_dump_data_newline(d)); for (i = 0; i < n; i++, m++) { const struct btf_type *mtype; const char *mname; __u32 moffset; __u8 bit_sz; mtype = btf__type_by_id(d->btf, m->type); mname = btf_name_of(d, m->name_off); moffset = btf_member_bit_offset(t, i); bit_sz = btf_member_bitfield_size(t, i); err = btf_dump_dump_type_data(d, mname, mtype, m->type, data + moffset / 8, moffset % 8, bit_sz); if (err < 0) return err; } d->typed_dump->depth--; btf_dump_data_pfx(d); btf_dump_type_values(d, "}"); return err; } union ptr_data { unsigned int p; unsigned long long lp; }; static int btf_dump_ptr_data(struct btf_dump *d, const struct btf_type *t, __u32 id, const void *data) { if (ptr_is_aligned(d->btf, id, data) && d->ptr_sz == sizeof(void *)) { btf_dump_type_values(d, "%p", *(void **)data); } else { union ptr_data pt; memcpy(&pt, data, d->ptr_sz); if (d->ptr_sz == 4) btf_dump_type_values(d, "0x%x", pt.p); else btf_dump_type_values(d, "0x%llx", pt.lp); } return 0; } static int btf_dump_get_enum_value(struct btf_dump *d, const struct btf_type *t, const void *data, __u32 id, __s64 *value) { bool is_signed = btf_kflag(t); if (!ptr_is_aligned(d->btf, id, data)) { __u64 val; int err; err = btf_dump_get_bitfield_value(d, t, data, 0, 0, &val); if (err) return err; *value = (__s64)val; return 0; } switch (t->size) { case 8: *value = *(__s64 *)data; return 0; case 4: *value = is_signed ? (__s64)*(__s32 *)data : *(__u32 *)data; return 0; case 2: *value = is_signed ? *(__s16 *)data : *(__u16 *)data; return 0; case 1: *value = is_signed ? *(__s8 *)data : *(__u8 *)data; return 0; default: pr_warn("unexpected size %d for enum, id:[%u]\n", t->size, id); return -EINVAL; } } static int btf_dump_enum_data(struct btf_dump *d, const struct btf_type *t, __u32 id, const void *data) { bool is_signed; __s64 value; int i, err; err = btf_dump_get_enum_value(d, t, data, id, &value); if (err) return err; is_signed = btf_kflag(t); if (btf_is_enum(t)) { const struct btf_enum *e; for (i = 0, e = btf_enum(t); i < btf_vlen(t); i++, e++) { if (value != e->val) continue; btf_dump_type_values(d, "%s", btf_name_of(d, e->name_off)); return 0; } btf_dump_type_values(d, is_signed ? "%d" : "%u", value); } else { const struct btf_enum64 *e; for (i = 0, e = btf_enum64(t); i < btf_vlen(t); i++, e++) { if (value != btf_enum64_value(e)) continue; btf_dump_type_values(d, "%s", btf_name_of(d, e->name_off)); return 0; } btf_dump_type_values(d, is_signed ? "%lldLL" : "%lluULL", (unsigned long long)value); } return 0; } static int btf_dump_datasec_data(struct btf_dump *d, const struct btf_type *t, __u32 id, const void *data) { const struct btf_var_secinfo *vsi; const struct btf_type *var; __u32 i; int err; btf_dump_type_values(d, "SEC(\"%s\") ", btf_name_of(d, t->name_off)); for (i = 0, vsi = btf_var_secinfos(t); i < btf_vlen(t); i++, vsi++) { var = btf__type_by_id(d->btf, vsi->type); err = btf_dump_dump_type_data(d, NULL, var, vsi->type, data + vsi->offset, 0, 0); if (err < 0) return err; btf_dump_printf(d, ";"); } return 0; } /* return size of type, or if base type overflows, return -E2BIG. */ static int btf_dump_type_data_check_overflow(struct btf_dump *d, const struct btf_type *t, __u32 id, const void *data, __u8 bits_offset, __u8 bit_sz) { __s64 size; if (bit_sz) { /* bits_offset is at most 7. bit_sz is at most 128. */ __u8 nr_bytes = (bits_offset + bit_sz + 7) / 8; /* When bit_sz is non zero, it is called from * btf_dump_struct_data() where it only cares about * negative error value. * Return nr_bytes in success case to make it * consistent as the regular integer case below. */ return data + nr_bytes > d->typed_dump->data_end ? -E2BIG : nr_bytes; } size = btf__resolve_size(d->btf, id); if (size < 0 || size >= INT_MAX) { pr_warn("unexpected size [%zu] for id [%u]\n", (size_t)size, id); return -EINVAL; } /* Only do overflow checking for base types; we do not want to * avoid showing part of a struct, union or array, even if we * do not have enough data to show the full object. By * restricting overflow checking to base types we can ensure * that partial display succeeds, while avoiding overflowing * and using bogus data for display. */ t = skip_mods_and_typedefs(d->btf, id, NULL); if (!t) { pr_warn("unexpected error skipping mods/typedefs for id [%u]\n", id); return -EINVAL; } switch (btf_kind(t)) { case BTF_KIND_INT: case BTF_KIND_FLOAT: case BTF_KIND_PTR: case BTF_KIND_ENUM: case BTF_KIND_ENUM64: if (data + bits_offset / 8 + size > d->typed_dump->data_end) return -E2BIG; break; default: break; } return (int)size; } static int btf_dump_type_data_check_zero(struct btf_dump *d, const struct btf_type *t, __u32 id, const void *data, __u8 bits_offset, __u8 bit_sz) { __s64 value; int i, err; /* toplevel exceptions; we show zero values if * - we ask for them (emit_zeros) * - if we are at top-level so we see "struct empty { }" * - or if we are an array member and the array is non-empty and * not a char array; we don't want to be in a situation where we * have an integer array 0, 1, 0, 1 and only show non-zero values. * If the array contains zeroes only, or is a char array starting * with a '\0', the array-level check_zero() will prevent showing it; * we are concerned with determining zero value at the array member * level here. */ if (d->typed_dump->emit_zeroes || d->typed_dump->depth == 0 || (d->typed_dump->is_array_member && !d->typed_dump->is_array_char)) return 0; t = skip_mods_and_typedefs(d->btf, id, NULL); switch (btf_kind(t)) { case BTF_KIND_INT: if (bit_sz) return btf_dump_bitfield_check_zero(d, t, data, bits_offset, bit_sz); return btf_dump_base_type_check_zero(d, t, id, data); case BTF_KIND_FLOAT: case BTF_KIND_PTR: return btf_dump_base_type_check_zero(d, t, id, data); case BTF_KIND_ARRAY: { const struct btf_array *array = btf_array(t); const struct btf_type *elem_type; __u32 elem_type_id, elem_size; bool ischar; elem_type_id = array->type; elem_size = btf__resolve_size(d->btf, elem_type_id); elem_type = skip_mods_and_typedefs(d->btf, elem_type_id, NULL); ischar = btf_is_int(elem_type) && elem_size == 1; /* check all elements; if _any_ element is nonzero, all * of array is displayed. We make an exception however * for char arrays where the first element is 0; these * are considered zeroed also, even if later elements are * non-zero because the string is terminated. */ for (i = 0; i < array->nelems; i++) { if (i == 0 && ischar && *(char *)data == 0) return -ENODATA; err = btf_dump_type_data_check_zero(d, elem_type, elem_type_id, data + (i * elem_size), bits_offset, 0); if (err != -ENODATA) return err; } return -ENODATA; } case BTF_KIND_STRUCT: case BTF_KIND_UNION: { const struct btf_member *m = btf_members(t); __u16 n = btf_vlen(t); /* if any struct/union member is non-zero, the struct/union * is considered non-zero and dumped. */ for (i = 0; i < n; i++, m++) { const struct btf_type *mtype; __u32 moffset; mtype = btf__type_by_id(d->btf, m->type); moffset = btf_member_bit_offset(t, i); /* btf_int_bits() does not store member bitfield size; * bitfield size needs to be stored here so int display * of member can retrieve it. */ bit_sz = btf_member_bitfield_size(t, i); err = btf_dump_type_data_check_zero(d, mtype, m->type, data + moffset / 8, moffset % 8, bit_sz); if (err != ENODATA) return err; } return -ENODATA; } case BTF_KIND_ENUM: case BTF_KIND_ENUM64: err = btf_dump_get_enum_value(d, t, data, id, &value); if (err) return err; if (value == 0) return -ENODATA; return 0; default: return 0; } } /* returns size of data dumped, or error. */ static int btf_dump_dump_type_data(struct btf_dump *d, const char *fname, const struct btf_type *t, __u32 id, const void *data, __u8 bits_offset, __u8 bit_sz) { int size, err = 0; size = btf_dump_type_data_check_overflow(d, t, id, data, bits_offset, bit_sz); if (size < 0) return size; err = btf_dump_type_data_check_zero(d, t, id, data, bits_offset, bit_sz); if (err) { /* zeroed data is expected and not an error, so simply skip * dumping such data. Record other errors however. */ if (err == -ENODATA) return size; return err; } btf_dump_data_pfx(d); if (!d->typed_dump->skip_names) { if (fname && strlen(fname) > 0) btf_dump_printf(d, ".%s = ", fname); btf_dump_emit_type_cast(d, id, true); } t = skip_mods_and_typedefs(d->btf, id, NULL); switch (btf_kind(t)) { case BTF_KIND_UNKN: case BTF_KIND_FWD: case BTF_KIND_FUNC: case BTF_KIND_FUNC_PROTO: case BTF_KIND_DECL_TAG: err = btf_dump_unsupported_data(d, t, id); break; case BTF_KIND_INT: if (bit_sz) err = btf_dump_bitfield_data(d, t, data, bits_offset, bit_sz); else err = btf_dump_int_data(d, t, id, data, bits_offset); break; case BTF_KIND_FLOAT: err = btf_dump_float_data(d, t, id, data); break; case BTF_KIND_PTR: err = btf_dump_ptr_data(d, t, id, data); break; case BTF_KIND_ARRAY: err = btf_dump_array_data(d, t, id, data); break; case BTF_KIND_STRUCT: case BTF_KIND_UNION: err = btf_dump_struct_data(d, t, id, data); break; case BTF_KIND_ENUM: case BTF_KIND_ENUM64: /* handle bitfield and int enum values */ if (bit_sz) { __u64 print_num; __s64 enum_val; err = btf_dump_get_bitfield_value(d, t, data, bits_offset, bit_sz, &print_num); if (err) break; enum_val = (__s64)print_num; err = btf_dump_enum_data(d, t, id, &enum_val); } else err = btf_dump_enum_data(d, t, id, data); break; case BTF_KIND_VAR: err = btf_dump_var_data(d, t, id, data); break; case BTF_KIND_DATASEC: err = btf_dump_datasec_data(d, t, id, data); break; default: pr_warn("unexpected kind [%u] for id [%u]\n", BTF_INFO_KIND(t->info), id); return -EINVAL; } if (err < 0) return err; return size; } int btf_dump__dump_type_data(struct btf_dump *d, __u32 id, const void *data, size_t data_sz, const struct btf_dump_type_data_opts *opts) { struct btf_dump_data typed_dump = {}; const struct btf_type *t; int ret; if (!OPTS_VALID(opts, btf_dump_type_data_opts)) return libbpf_err(-EINVAL); t = btf__type_by_id(d->btf, id); if (!t) return libbpf_err(-ENOENT); d->typed_dump = &typed_dump; d->typed_dump->data_end = data + data_sz; d->typed_dump->indent_lvl = OPTS_GET(opts, indent_level, 0); /* default indent string is a tab */ if (!OPTS_GET(opts, indent_str, NULL)) d->typed_dump->indent_str[0] = '\t'; else libbpf_strlcpy(d->typed_dump->indent_str, opts->indent_str, sizeof(d->typed_dump->indent_str)); d->typed_dump->compact = OPTS_GET(opts, compact, false); d->typed_dump->skip_names = OPTS_GET(opts, skip_names, false); d->typed_dump->emit_zeroes = OPTS_GET(opts, emit_zeroes, false); ret = btf_dump_dump_type_data(d, NULL, t, id, data, 0, 0); d->typed_dump = NULL; return libbpf_err(ret); }