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ebeed8d4 MHG |
1 | // SPDX-License-Identifier: GPL-2.0 |
2 | #include <linux/btf.h> | |
3 | #include <linux/kernel.h> | |
302db0f5 | 4 | #include <linux/slab.h> |
ebeed8d4 MHG |
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 | ||
302db0f5 MHG |
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 */ | |
9704669c MHG |
94 | if (btf_type_skip_modifiers(btf, member->type, &tid) && |
95 | top < BTF_ANON_STACK_MAX) { | |
302db0f5 MHG |
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 |