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

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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: Andrii Nakryiko <andrii@kernel.org>
This commit is contained in:
Andrii Nakryiko
2024-05-01 09:53:48 -07:00
parent 9a1a2cb5a0 960635887c
commit d913aaa990
3 changed files with 55 additions and 9 deletions
Download Patch File Download Diff File Expand all files Collapse all files

35
tools/lib/bpf/libbpf.c
View File

@@ -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;

6
tools/testing/selftests/bpf/prog_tests/module_attach.c
View File

@@ -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");

23
tools/testing/selftests/bpf/progs/test_module_attach.c
View File

@@ -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;