1 // SPDX-License-Identifier: GPL-2.0 2 #include <linux/btf.h> 3 #include <linux/kernel.h> 4 #include <linux/slab.h> 5 6 #include "trace_btf.h" 7 8 /* 9 * Find a function proto type by name, and return the btf_type with its btf 10 * in *@btf_p. Return NULL if not found. 11 * Note that caller has to call btf_put(*@btf_p) after using the btf_type. 12 */ 13 const struct btf_type *btf_find_func_proto(const char *func_name, struct btf **btf_p) 14 { 15 const struct btf_type *t; 16 s32 id; 17 18 id = bpf_find_btf_id(func_name, BTF_KIND_FUNC, btf_p); 19 if (id < 0) 20 return NULL; 21 22 /* Get BTF_KIND_FUNC type */ 23 t = btf_type_by_id(*btf_p, id); 24 if (!t || !btf_type_is_func(t)) 25 goto err; 26 27 /* The type of BTF_KIND_FUNC is BTF_KIND_FUNC_PROTO */ 28 t = btf_type_by_id(*btf_p, t->type); 29 if (!t || !btf_type_is_func_proto(t)) 30 goto err; 31 32 return t; 33 err: 34 btf_put(*btf_p); 35 return NULL; 36 } 37 38 /* 39 * Get function parameter with the number of parameters. 40 * This can return NULL if the function has no parameters. 41 * It can return -EINVAL if the @func_proto is not a function proto type. 42 */ 43 const struct btf_param *btf_get_func_param(const struct btf_type *func_proto, s32 *nr) 44 { 45 if (!btf_type_is_func_proto(func_proto)) 46 return ERR_PTR(-EINVAL); 47 48 *nr = btf_type_vlen(func_proto); 49 if (*nr > 0) 50 return (const struct btf_param *)(func_proto + 1); 51 else 52 return NULL; 53 } 54 55 #define BTF_ANON_STACK_MAX 16 56 57 struct btf_anon_stack { 58 u32 tid; 59 u32 offset; 60 }; 61 62 /* 63 * Find a member of data structure/union by name and return it. 64 * Return NULL if not found, or -EINVAL if parameter is invalid. 65 * If the member is an member of anonymous union/structure, the offset 66 * of that anonymous union/structure is stored into @anon_offset. Caller 67 * can calculate the correct offset from the root data structure by 68 * adding anon_offset to the member's offset. 69 */ 70 const struct btf_member *btf_find_struct_member(struct btf *btf, 71 const struct btf_type *type, 72 const char *member_name, 73 u32 *anon_offset) 74 { 75 struct btf_anon_stack *anon_stack; 76 const struct btf_member *member; 77 u32 tid, cur_offset = 0; 78 const char *name; 79 int i, top = 0; 80 81 anon_stack = kcalloc(BTF_ANON_STACK_MAX, sizeof(*anon_stack), GFP_KERNEL); 82 if (!anon_stack) 83 return ERR_PTR(-ENOMEM); 84 85 retry: 86 if (!btf_type_is_struct(type)) { 87 member = ERR_PTR(-EINVAL); 88 goto out; 89 } 90 91 for_each_member(i, type, member) { 92 if (!member->name_off) { 93 /* Anonymous union/struct: push it for later use */ 94 type = btf_type_skip_modifiers(btf, member->type, &tid); 95 if (type && top < BTF_ANON_STACK_MAX) { 96 anon_stack[top].tid = tid; 97 anon_stack[top++].offset = 98 cur_offset + member->offset; 99 } 100 } else { 101 name = btf_name_by_offset(btf, member->name_off); 102 if (name && !strcmp(member_name, name)) { 103 if (anon_offset) 104 *anon_offset = cur_offset; 105 goto out; 106 } 107 } 108 } 109 if (top > 0) { 110 /* Pop from the anonymous stack and retry */ 111 tid = anon_stack[--top].tid; 112 cur_offset = anon_stack[top].offset; 113 type = btf_type_by_id(btf, tid); 114 goto retry; 115 } 116 member = NULL; 117 118 out: 119 kfree(anon_stack); 120 return member; 121 } 122 123