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 */
13const 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(name: func_name, kind: 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: *btf_p, type_id: 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: *btf_p, type_id: t->type);
29 if (!t || !btf_type_is_func_proto(t))
30 goto err;
31
32 return t;
33err:
34 btf_put(btf: *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 */
43const struct btf_param *btf_get_func_param(const struct btf_type *func_proto, s32 *nr)
44{
45 if (!btf_type_is_func_proto(t: func_proto))
46 return ERR_PTR(error: -EINVAL);
47
48 *nr = btf_type_vlen(t: 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
57struct 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 */
70const 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, size: sizeof(*anon_stack), GFP_KERNEL);
82 if (!anon_stack)
83 return ERR_PTR(error: -ENOMEM);
84
85retry:
86 if (!btf_type_is_struct(t: type)) {
87 member = ERR_PTR(error: -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 if (btf_type_skip_modifiers(btf, id: member->type, res_id: &tid) &&
95 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, offset: 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, type_id: tid);
114 goto retry;
115 }
116 member = NULL;
117
118out:
119 kfree(objp: anon_stack);
120 return member;
121}
122
123

source code of linux/kernel/trace/trace_btf.c