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(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;
33err:
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 */
43const 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
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, sizeof(*anon_stack), GFP_KERNEL);
82	if (!anon_stack)
83		return ERR_PTR(-ENOMEM);
84
85retry:
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 */
94			if (btf_type_skip_modifiers(btf, member->type, &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, 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
118out:
119	kfree(anon_stack);
120	return member;
121}
122
123