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 ERR_PTR(-EINVAL) if parameter is invalid. 65 * If the member is a member of an anonymous union/structure, the bit offset 66 * of that anonymous union/structure is stored into @anon_offset. 67 * If @member_type is non-NULL, the actual containing structure/union type 68 * of the found member is stored into @member_type. 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 const struct btf_type **member_type) 75 { 76 struct btf_anon_stack *anon_stack; 77 const struct btf_member *member; 78 const struct btf_type *mtype; 79 u32 tid, cur_offset = 0; 80 const char *name; 81 int i, top = 0; 82 83 if (!btf_type_is_struct(type)) 84 return ERR_PTR(-EINVAL); 85 86 anon_stack = kzalloc_objs(*anon_stack, BTF_ANON_STACK_MAX); 87 if (!anon_stack) 88 return ERR_PTR(-ENOMEM); 89 90 retry: 91 for_each_member(i, type, member) { 92 if (!member->name_off) { 93 /* Anonymous union/struct: push it for later use */ 94 mtype = btf_type_skip_modifiers(btf, member->type, &tid); 95 if (mtype && btf_type_is_struct(mtype) && 96 top < BTF_ANON_STACK_MAX) { 97 anon_stack[top].tid = tid; 98 anon_stack[top++].offset = cur_offset + 99 __btf_member_bit_offset(type, member); 100 } 101 } else { 102 name = btf_name_by_offset(btf, member->name_off); 103 if (name && !strcmp(member_name, name)) { 104 if (anon_offset) 105 *anon_offset = cur_offset; 106 if (member_type) 107 *member_type = type; 108 goto out; 109 } 110 } 111 } 112 if (top > 0) { 113 /* Pop from the anonymous stack and retry */ 114 tid = anon_stack[--top].tid; 115 cur_offset = anon_stack[top].offset; 116 type = btf_type_by_id(btf, tid); 117 goto retry; 118 } 119 member = NULL; 120 121 out: 122 kfree(anon_stack); 123 return member; 124 } 125 126