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// SPDX-License-Identifier: GPL-2.0
#include <linux/btf.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include "trace_btf.h"
/*
* Find a function proto type by name, and return the btf_type with its btf
* in *@btf_p. Return NULL if not found.
* Note that caller has to call btf_put(*@btf_p) after using the btf_type.
*/
const struct btf_type *btf_find_func_proto(const char *func_name, struct btf **btf_p)
{
const struct btf_type *t;
s32 id;
id = bpf_find_btf_id(func_name, BTF_KIND_FUNC, btf_p);
if (id < 0)
return NULL;
/* Get BTF_KIND_FUNC type */
t = btf_type_by_id(*btf_p, id);
if (!t || !btf_type_is_func(t))
goto err;
/* The type of BTF_KIND_FUNC is BTF_KIND_FUNC_PROTO */
t = btf_type_by_id(*btf_p, t->type);
if (!t || !btf_type_is_func_proto(t))
goto err;
return t;
err:
btf_put(*btf_p);
return NULL;
}
/*
* Get function parameter with the number of parameters.
* This can return NULL if the function has no parameters.
* It can return -EINVAL if the @func_proto is not a function proto type.
*/
const struct btf_param *btf_get_func_param(const struct btf_type *func_proto, s32 *nr)
{
if (!btf_type_is_func_proto(func_proto))
return ERR_PTR(-EINVAL);
*nr = btf_type_vlen(func_proto);
if (*nr > 0)
return (const struct btf_param *)(func_proto + 1);
else
return NULL;
}
#define BTF_ANON_STACK_MAX 16
struct btf_anon_stack {
u32 tid;
u32 offset;
};
/*
* Find a member of data structure/union by name and return it.
* Return NULL if not found, or -EINVAL if parameter is invalid.
* If the member is an member of anonymous union/structure, the offset
* of that anonymous union/structure is stored into @anon_offset. Caller
* can calculate the correct offset from the root data structure by
* adding anon_offset to the member's offset.
*/
const struct btf_member *btf_find_struct_member(struct btf *btf,
const struct btf_type *type,
const char *member_name,
u32 *anon_offset)
{
struct btf_anon_stack *anon_stack;
const struct btf_member *member;
u32 tid, cur_offset = 0;
const char *name;
int i, top = 0;
anon_stack = kcalloc(BTF_ANON_STACK_MAX, sizeof(*anon_stack), GFP_KERNEL);
if (!anon_stack)
return ERR_PTR(-ENOMEM);
retry:
if (!btf_type_is_struct(type)) {
member = ERR_PTR(-EINVAL);
goto out;
}
for_each_member(i, type, member) {
if (!member->name_off) {
/* Anonymous union/struct: push it for later use */
type = btf_type_skip_modifiers(btf, member->type, &tid);
if (type && top < BTF_ANON_STACK_MAX) {
anon_stack[top].tid = tid;
anon_stack[top++].offset =
cur_offset + member->offset;
}
} else {
name = btf_name_by_offset(btf, member->name_off);
if (name && !strcmp(member_name, name)) {
if (anon_offset)
*anon_offset = cur_offset;
goto out;
}
}
}
if (top > 0) {
/* Pop from the anonymous stack and retry */
tid = anon_stack[--top].tid;
cur_offset = anon_stack[top].offset;
type = btf_type_by_id(btf, tid);
goto retry;
}
member = NULL;
out:
kfree(anon_stack);
return member;
}
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