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