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 */
btf_find_func_proto(const char * func_name,struct btf ** btf_p)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 */
btf_get_func_param(const struct btf_type * func_proto,s32 * nr)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 */
btf_find_struct_member(struct btf * btf,const struct btf_type * type,const char * member_name,u32 * anon_offset,const struct btf_type ** member_type)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