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(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; |
33 | err: |
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 | */ |
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(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 | |
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, size: sizeof(*anon_stack), GFP_KERNEL); |
82 | if (!anon_stack) |
83 | return ERR_PTR(error: -ENOMEM); |
84 | |
85 | retry: |
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 | |
118 | out: |
119 | kfree(objp: anon_stack); |
120 | return member; |
121 | } |
122 | |
123 | |