Commit d913aaa9 authored by Andrii Nakryiko's avatar Andrii Nakryiko
Browse files

Merge branch 'libbpf-support-module-function-syntax-for-tracing-programs' 

Viktor Malik says:

====================
libbpf: support "module:function" syntax for tracing programs

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 change 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.
---

Changes in v2:
- stylistic changes (suggested by Andrii)
- added Andrii's ack to the second patch
====================

Link: https://lore.kernel.org/r/cover.1714469650.git.vmalik@redhat.com


Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
parents 9a1a2cb5 96063588

tools/lib/bpf/libbpf.c

+26 −9
Original line number Diff line number Diff line
@@ -9862,9 +9862,20 @@ 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);

	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;
@@ -9872,6 +9883,7 @@ static int find_kernel_btf_id(struct bpf_object *obj, const char *attach_name, 
		}

		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;

tools/testing/selftests/bpf/prog_tests/module_attach.c

+6 −0
Original line number Diff line number Diff line
@@ -51,6 +51,10 @@ void test_module_attach(void) 
					     0, "bpf_testmod_test_read");

	ASSERT_OK(err, "set_attach_target");



	err = bpf_program__set_attach_target(skel->progs.handle_fentry_explicit_manual,

					     0, "bpf_testmod:bpf_testmod_test_read");

	ASSERT_OK(err, "set_attach_target_explicit");



	err = test_module_attach__load(skel);

	if (CHECK(err, "skel_load", "failed to load skeleton\n"))

		return;
@@ -70,6 +74,8 @@ void test_module_attach(void) 
	ASSERT_EQ(bss->tp_btf_read_sz, READ_SZ, "tp_btf");

	ASSERT_EQ(bss->fentry_read_sz, READ_SZ, "fentry");

	ASSERT_EQ(bss->fentry_manual_read_sz, READ_SZ, "fentry_manual");

	ASSERT_EQ(bss->fentry_explicit_read_sz, READ_SZ, "fentry_explicit");

	ASSERT_EQ(bss->fentry_explicit_manual_read_sz, READ_SZ, "fentry_explicit_manual");

	ASSERT_EQ(bss->fexit_read_sz, READ_SZ, "fexit");

	ASSERT_EQ(bss->fexit_ret, -EIO, "fexit_tet");

	ASSERT_EQ(bss->fmod_ret_read_sz, READ_SZ, "fmod_ret");

tools/testing/selftests/bpf/progs/test_module_attach.c

+23 −0
Original line number Diff line number Diff line
@@ -73,6 +73,29 @@ int BPF_PROG(handle_fentry_manual, 
	return 0;

}



__u32 fentry_explicit_read_sz = 0;



SEC("fentry/bpf_testmod:bpf_testmod_test_read")

int BPF_PROG(handle_fentry_explicit,

	     struct file *file, struct kobject *kobj,

	     struct bin_attribute *bin_attr, char *buf, loff_t off, size_t len)

{

	fentry_explicit_read_sz = len;

	return 0;

}





__u32 fentry_explicit_manual_read_sz = 0;



SEC("fentry")

int BPF_PROG(handle_fentry_explicit_manual,

	     struct file *file, struct kobject *kobj,

	     struct bin_attribute *bin_attr, char *buf, loff_t off, size_t len)

{

	fentry_explicit_manual_read_sz = len;

	return 0;

}



__u32 fexit_read_sz = 0;

int fexit_ret = 0;