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libbpf: support "module: Function" syntax for tracing programs

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In some situations, it is useful to explicitly specify a kernel module
to search for a tracing program target (e.g. when a function of the same
name exists in multiple modules or in vmlinux).

This patch enables that by allowing the "module:function" syntax for the
find_kernel_btf_id function. Thanks to this, the syntax can be used both
from a SEC macro (i.e. `SEC(fentry/module:function)`) and via the
bpf_program__set_attach_target API call.

Signed-off-by: Viktor Malik <vmalik@redhat.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/9085a8cb9a552de98e554deb22ff7e977d025440.1714469650.git.vmalik@redhat.com
This commit is contained in:
Viktor Malik 2024-04-30 11:38:06 +02:00 committed by Andrii Nakryiko
parent 9a1a2cb5a0
commit 8f8a024272
1 changed files with 26 additions and 9 deletions
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35
tools/lib/bpf/libbpf.c
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@ -9862,16 +9862,28 @@ static int find_kernel_btf_id(struct bpf_object *obj, const char *attach_name,
enum bpf_attach_type attach_type,
int *btf_obj_fd, int *btf_type_id)
{
int ret, i;
int ret, i, mod_len;
const char *fn_name, *mod_name = NULL;
ret = find_attach_btf_id(obj->btf_vmlinux, attach_name, attach_type);
if (ret > 0) {
*btf_obj_fd = 0; /* vmlinux BTF */
*btf_type_id = ret;
return 0;
fn_name = strchr(attach_name, ':');
if (fn_name) {
mod_name = attach_name;
mod_len = fn_name - mod_name;
fn_name++;
}
if (!mod_name || strncmp(mod_name, "vmlinux", mod_len) == 0) {
ret = find_attach_btf_id(obj->btf_vmlinux,
mod_name ? fn_name : attach_name,
attach_type);
if (ret > 0) {
*btf_obj_fd = 0; /* vmlinux BTF */
*btf_type_id = ret;
return 0;
}
if (ret != -ENOENT)
return ret;
}
if (ret != -ENOENT)
return ret;
ret = load_module_btfs(obj);
if (ret)
@ -9880,7 +9892,12 @@ static int find_kernel_btf_id(struct bpf_object *obj, const char *attach_name,
for (i = 0; i < obj->btf_module_cnt; i++) {
const struct module_btf *mod = &obj->btf_modules[i];
ret = find_attach_btf_id(mod->btf, attach_name, attach_type);
if (mod_name && strncmp(mod->name, mod_name, mod_len) != 0)
continue;
ret = find_attach_btf_id(mod->btf,
mod_name ? fn_name : attach_name,
attach_type);
if (ret > 0) {
*btf_obj_fd = mod->fd;
*btf_type_id = ret;