[PATCH v3 bpf-next 0/3] libbpf: Fix event name too long error and add tests

[PATCH v3 bpf-next 0/3] libbpf: Fix event name too long error and add tests

[Feng Yang]

From: Feng Yang <yangfeng@kylinos.cn>

Hi everyone,

This series tries to fix event name too long error and add tests.

When the binary path is excessively long, the generated probe_name in libbpf
exceeds the kernel's MAX_EVENT_NAME_LEN limit (64 bytes).
This causes legacy uprobe event attachment to fail with error code -22.

---
Changes in v3:
- add __sync_fetch_and_add(&index) and let snprintf() do the trimming. Thanks, Andrii Nakryiko!
- add selftests.
- Link to v2: https://lore.kernel.org/all/20250411080545.319865-1-yangfeng59949@163.com/

Changes in v2:
- Use basename() and %.32s to fix. Thanks, Hengqi Chen!
- Link to v1: https://lore.kernel.org/all/20250410052712.206785-1-yangfeng59949@163.com/

Feng Yang (3):
  libbpf: Fix event name too long error
  selftests/bpf: Add test for attaching uprobe with long event names
  selftests/bpf: Add test for attaching kprobe with long event names

 tools/lib/bpf/libbpf.c                        | 19 +++--
 .../selftests/bpf/prog_tests/attach_probe.c   | 84 +++++++++++++++++++
 .../selftests/bpf/test_kmods/bpf_testmod.c    |  5 ++
 .../bpf/test_kmods/bpf_testmod_kfunc.h        |  2 +
 4 files changed, 103 insertions(+), 7 deletions(-)

-- 
2.43.0

[PATCH v3 bpf-next 1/3] libbpf: Fix event name too long error

[Feng Yang]

From: Feng Yang <yangfeng@kylinos.cn>

When the binary path is excessively long, the generated probe_name in libbpf
exceeds the kernel's MAX_EVENT_NAME_LEN limit (64 bytes).
This causes legacy uprobe event attachment to fail with error code -22.

Before Fix:
	./test_progs -t attach_probe/kprobe-long_name
	......
	libbpf: failed to add legacy kprobe event for 'bpf_kfunc_looooooooooooooooooooooooooooooong_name+0x0': -EINVAL
	libbpf: prog 'handle_kprobe': failed to create kprobe 'bpf_kfunc_looooooooooooooooooooooooooooooong_name+0x0' perf event: -EINVAL
	test_attach_kprobe_long_event_name:FAIL:attach_kprobe_long_event_name unexpected error: -22
	test_attach_probe:PASS:uprobe_ref_ctr_cleanup 0 nsec
	#13/11   attach_probe/kprobe-long_name:FAIL
	#13      attach_probe:FAIL

	./test_progs -t attach_probe/uprobe-long_name
	......
	libbpf: failed to add legacy uprobe event for /root/linux-bpf/bpf-next/tools/testing/selftests/bpf/test_progs:0x13efd9: -EINVAL
	libbpf: prog 'handle_uprobe': failed to create uprobe '/root/linux-bpf/bpf-next/tools/testing/selftests/bpf/test_progs:0x13efd9' perf event: -EINVAL
	test_attach_uprobe_long_event_name:FAIL:attach_uprobe_long_event_name unexpected error: -22
	#13/10   attach_probe/uprobe-long_name:FAIL
	#13      attach_probe:FAIL
After Fix:
	./test_progs -t attach_probe/uprobe-long_name
	#13/10   attach_probe/uprobe-long_name:OK
	#13      attach_probe:OK
	Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED

	./test_progs -t attach_probe/kprobe-long_name
	#13/11   attach_probe/kprobe-long_name:OK
	#13      attach_probe:OK
	Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED

Fixes: 46ed5fc33db9 ("libbpf: Refactor and simplify legacy kprobe code")
Fixes: cc10623c6810 ("libbpf: Add legacy uprobe attaching support")
Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
Signed-off-by: Feng Yang <yangfeng@kylinos.cn>
---
 tools/lib/bpf/libbpf.c | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index b2591f5cab65..9e047641e001 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -60,6 +60,8 @@
 #define BPF_FS_MAGIC		0xcafe4a11
 #endif
 
+#define MAX_EVENT_NAME_LEN	64
+
 #define BPF_FS_DEFAULT_PATH "/sys/fs/bpf"
 
 #define BPF_INSN_SZ (sizeof(struct bpf_insn))
@@ -11142,10 +11144,10 @@ static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz,
 	static int index = 0;
 	int i;
 
-	snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx_%d", getpid(), kfunc_name, offset,
-		 __sync_fetch_and_add(&index, 1));
+	snprintf(buf, buf_sz, "libbpf_%u_%d_%s_0x%zx", getpid(),
+		 __sync_fetch_and_add(&index, 1), kfunc_name, offset);
 
-	/* sanitize binary_path in the probe name */
+	/* sanitize kfunc_name in the probe name */
 	for (i = 0; buf[i]; i++) {
 		if (!isalnum(buf[i]))
 			buf[i] = '_';
@@ -11270,7 +11272,7 @@ int probe_kern_syscall_wrapper(int token_fd)
 
 		return pfd >= 0 ? 1 : 0;
 	} else { /* legacy mode */
-		char probe_name[128];
+		char probe_name[MAX_EVENT_NAME_LEN];
 
 		gen_kprobe_legacy_event_name(probe_name, sizeof(probe_name), syscall_name, 0);
 		if (add_kprobe_event_legacy(probe_name, false, syscall_name, 0) < 0)
@@ -11328,7 +11330,7 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog,
 					    func_name, offset,
 					    -1 /* pid */, 0 /* ref_ctr_off */);
 	} else {
-		char probe_name[256];
+		char probe_name[MAX_EVENT_NAME_LEN];
 
 		gen_kprobe_legacy_event_name(probe_name, sizeof(probe_name),
 					     func_name, offset);
@@ -11878,9 +11880,12 @@ static int attach_uprobe_multi(const struct bpf_program *prog, long cookie, stru
 static void gen_uprobe_legacy_event_name(char *buf, size_t buf_sz,
 					 const char *binary_path, uint64_t offset)
 {
+	static int index = 0;
 	int i;
 
-	snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx", getpid(), binary_path, (size_t)offset);
+	snprintf(buf, buf_sz, "libbpf_%u_%d_%s_0x%zx", getpid(),
+		 __sync_fetch_and_add(&index, 1),
+		 basename((void *)binary_path), (size_t)offset);
 
 	/* sanitize binary_path in the probe name */
 	for (i = 0; buf[i]; i++) {
@@ -12312,7 +12317,7 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
 		pfd = perf_event_open_probe(true /* uprobe */, retprobe, binary_path,
 					    func_offset, pid, ref_ctr_off);
 	} else {
-		char probe_name[PATH_MAX + 64];
+		char probe_name[MAX_EVENT_NAME_LEN];
 
 		if (ref_ctr_off)
 			return libbpf_err_ptr(-EINVAL);
-- 
2.43.0

Re: [PATCH v3 bpf-next 1/3] libbpf: Fix event name too long error

[Jiri Olsa]

On Mon, Apr 14, 2025 at 05:34:00PM +0800, Feng Yang wrote:
> From: Feng Yang <yangfeng@kylinos.cn>
> 
> When the binary path is excessively long, the generated probe_name in libbpf
> exceeds the kernel's MAX_EVENT_NAME_LEN limit (64 bytes).
> This causes legacy uprobe event attachment to fail with error code -22.
> 
> Before Fix:
> 	./test_progs -t attach_probe/kprobe-long_name
> 	......
> 	libbpf: failed to add legacy kprobe event for 'bpf_kfunc_looooooooooooooooooooooooooooooong_name+0x0': -EINVAL
> 	libbpf: prog 'handle_kprobe': failed to create kprobe 'bpf_kfunc_looooooooooooooooooooooooooooooong_name+0x0' perf event: -EINVAL
> 	test_attach_kprobe_long_event_name:FAIL:attach_kprobe_long_event_name unexpected error: -22
> 	test_attach_probe:PASS:uprobe_ref_ctr_cleanup 0 nsec
> 	#13/11   attach_probe/kprobe-long_name:FAIL
> 	#13      attach_probe:FAIL
> 
> 	./test_progs -t attach_probe/uprobe-long_name
> 	......
> 	libbpf: failed to add legacy uprobe event for /root/linux-bpf/bpf-next/tools/testing/selftests/bpf/test_progs:0x13efd9: -EINVAL
> 	libbpf: prog 'handle_uprobe': failed to create uprobe '/root/linux-bpf/bpf-next/tools/testing/selftests/bpf/test_progs:0x13efd9' perf event: -EINVAL
> 	test_attach_uprobe_long_event_name:FAIL:attach_uprobe_long_event_name unexpected error: -22
> 	#13/10   attach_probe/uprobe-long_name:FAIL
> 	#13      attach_probe:FAIL
> After Fix:
> 	./test_progs -t attach_probe/uprobe-long_name
> 	#13/10   attach_probe/uprobe-long_name:OK
> 	#13      attach_probe:OK
> 	Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED
> 
> 	./test_progs -t attach_probe/kprobe-long_name
> 	#13/11   attach_probe/kprobe-long_name:OK
> 	#13      attach_probe:OK
> 	Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED
> 
> Fixes: 46ed5fc33db9 ("libbpf: Refactor and simplify legacy kprobe code")
> Fixes: cc10623c6810 ("libbpf: Add legacy uprobe attaching support")
> Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
> Signed-off-by: Feng Yang <yangfeng@kylinos.cn>
> ---
>  tools/lib/bpf/libbpf.c | 19 ++++++++++++-------
>  1 file changed, 12 insertions(+), 7 deletions(-)
> 
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index b2591f5cab65..9e047641e001 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -60,6 +60,8 @@
>  #define BPF_FS_MAGIC		0xcafe4a11
>  #endif
>  
> +#define MAX_EVENT_NAME_LEN	64
> +
>  #define BPF_FS_DEFAULT_PATH "/sys/fs/bpf"
>  
>  #define BPF_INSN_SZ (sizeof(struct bpf_insn))
> @@ -11142,10 +11144,10 @@ static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz,
>  	static int index = 0;
>  	int i;
>  
> -	snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx_%d", getpid(), kfunc_name, offset,
> -		 __sync_fetch_and_add(&index, 1));
> +	snprintf(buf, buf_sz, "libbpf_%u_%d_%s_0x%zx", getpid(),
> +		 __sync_fetch_and_add(&index, 1), kfunc_name, offset);

so the fix is to move unique id before kfunc_name to make sure it gets
to the event name right? would be great to have it in changelog

>  
> -	/* sanitize binary_path in the probe name */
> +	/* sanitize kfunc_name in the probe name */
>  	for (i = 0; buf[i]; i++) {
>  		if (!isalnum(buf[i]))
>  			buf[i] = '_';
> @@ -11270,7 +11272,7 @@ int probe_kern_syscall_wrapper(int token_fd)
>  
>  		return pfd >= 0 ? 1 : 0;
>  	} else { /* legacy mode */
> -		char probe_name[128];
> +		char probe_name[MAX_EVENT_NAME_LEN];
>  
>  		gen_kprobe_legacy_event_name(probe_name, sizeof(probe_name), syscall_name, 0);
>  		if (add_kprobe_event_legacy(probe_name, false, syscall_name, 0) < 0)
> @@ -11328,7 +11330,7 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog,
>  					    func_name, offset,
>  					    -1 /* pid */, 0 /* ref_ctr_off */);
>  	} else {
> -		char probe_name[256];
> +		char probe_name[MAX_EVENT_NAME_LEN];
>  
>  		gen_kprobe_legacy_event_name(probe_name, sizeof(probe_name),
>  					     func_name, offset);
> @@ -11878,9 +11880,12 @@ static int attach_uprobe_multi(const struct bpf_program *prog, long cookie, stru
>  static void gen_uprobe_legacy_event_name(char *buf, size_t buf_sz,
>  					 const char *binary_path, uint64_t offset)
>  {
> +	static int index = 0;
>  	int i;
>  
> -	snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx", getpid(), binary_path, (size_t)offset);
> +	snprintf(buf, buf_sz, "libbpf_%u_%d_%s_0x%zx", getpid(),
> +		 __sync_fetch_and_add(&index, 1),
> +		 basename((void *)binary_path), (size_t)offset);

gen_kprobe_legacy_event_name and gen_uprobe_legacy_event_name seem to
be identical now, maybe we can have just one ?

thanks,
jirka

>  
>  	/* sanitize binary_path in the probe name */
>  	for (i = 0; buf[i]; i++) {
> @@ -12312,7 +12317,7 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
>  		pfd = perf_event_open_probe(true /* uprobe */, retprobe, binary_path,
>  					    func_offset, pid, ref_ctr_off);
>  	} else {
> -		char probe_name[PATH_MAX + 64];
> +		char probe_name[MAX_EVENT_NAME_LEN];
>  
>  		if (ref_ctr_off)
>  			return libbpf_err_ptr(-EINVAL);
> -- 
> 2.43.0
> 

Re: [PATCH v3 bpf-next 1/3] libbpf: Fix event name too long error

[Feng Yang]

On Mon, 14 Apr 2025 13:43:38 +0200 Jiri Olsa <olsajiri@gmail.com> wrote:
> On Mon, Apr 14, 2025 at 05:34:00PM +0800, Feng Yang wrote:
> > From: Feng Yang <yangfeng@kylinos.cn>
> > 
> > When the binary path is excessively long, the generated probe_name in libbpf
> > exceeds the kernel's MAX_EVENT_NAME_LEN limit (64 bytes).
> > This causes legacy uprobe event attachment to fail with error code -22.
> > 
> > Before Fix:
> > 	./test_progs -t attach_probe/kprobe-long_name
> > 	......
> > 	libbpf: failed to add legacy kprobe event for 'bpf_kfunc_looooooooooooooooooooooooooooooong_name+0x0': -EINVAL
> > 	libbpf: prog 'handle_kprobe': failed to create kprobe 'bpf_kfunc_looooooooooooooooooooooooooooooong_name+0x0' perf event: -EINVAL
> > 	test_attach_kprobe_long_event_name:FAIL:attach_kprobe_long_event_name unexpected error: -22
> > 	test_attach_probe:PASS:uprobe_ref_ctr_cleanup 0 nsec
> > 	#13/11   attach_probe/kprobe-long_name:FAIL
> > 	#13      attach_probe:FAIL
> > 
> > 	./test_progs -t attach_probe/uprobe-long_name
> > 	......
> > 	libbpf: failed to add legacy uprobe event for /root/linux-bpf/bpf-next/tools/testing/selftests/bpf/test_progs:0x13efd9: -EINVAL
> > 	libbpf: prog 'handle_uprobe': failed to create uprobe '/root/linux-bpf/bpf-next/tools/testing/selftests/bpf/test_progs:0x13efd9' perf event: -EINVAL
> > 	test_attach_uprobe_long_event_name:FAIL:attach_uprobe_long_event_name unexpected error: -22
> > 	#13/10   attach_probe/uprobe-long_name:FAIL
> > 	#13      attach_probe:FAIL
> > After Fix:
> > 	./test_progs -t attach_probe/uprobe-long_name
> > 	#13/10   attach_probe/uprobe-long_name:OK
> > 	#13      attach_probe:OK
> > 	Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED
> > 
> > 	./test_progs -t attach_probe/kprobe-long_name
> > 	#13/11   attach_probe/kprobe-long_name:OK
> > 	#13      attach_probe:OK
> > 	Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED
> > 
> > Fixes: 46ed5fc33db9 ("libbpf: Refactor and simplify legacy kprobe code")
> > Fixes: cc10623c6810 ("libbpf: Add legacy uprobe attaching support")
> > Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
> > Signed-off-by: Feng Yang <yangfeng@kylinos.cn>
> > ---
> >  tools/lib/bpf/libbpf.c | 19 ++++++++++++-------
> >  1 file changed, 12 insertions(+), 7 deletions(-)
> > 
> > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> > index b2591f5cab65..9e047641e001 100644
> > --- a/tools/lib/bpf/libbpf.c
> > +++ b/tools/lib/bpf/libbpf.c
> > @@ -60,6 +60,8 @@
> >  #define BPF_FS_MAGIC		0xcafe4a11
> >  #endif
> >  
> > +#define MAX_EVENT_NAME_LEN	64
> > +
> >  #define BPF_FS_DEFAULT_PATH "/sys/fs/bpf"
> >  
> >  #define BPF_INSN_SZ (sizeof(struct bpf_insn))
> > @@ -11142,10 +11144,10 @@ static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz,
> >  	static int index = 0;
> >  	int i;
> >  
> > -	snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx_%d", getpid(), kfunc_name, offset,
> > -		 __sync_fetch_and_add(&index, 1));
> > +	snprintf(buf, buf_sz, "libbpf_%u_%d_%s_0x%zx", getpid(),
> > +		 __sync_fetch_and_add(&index, 1), kfunc_name, offset);
> 
> so the fix is to move unique id before kfunc_name to make sure it gets
> to the event name right? would be great to have it in changelog
> 

Yes, defining MAX_EVENT_NAME_LEN ensures event names are truncated via snprintf
to prevent exceeding the maximum length limit.
Moving the unique id before kfunc_name avoids truncating the id.
Regarding the changelog: Should this information go into the commit message of the patch, or somewhere else?

> 
> >  
> > -	/* sanitize binary_path in the probe name */
> > +	/* sanitize kfunc_name in the probe name */
> >  	for (i = 0; buf[i]; i++) {
> >  		if (!isalnum(buf[i]))
> >  			buf[i] = '_';
> > @@ -11270,7 +11272,7 @@ int probe_kern_syscall_wrapper(int token_fd)
> >  
> >  		return pfd >= 0 ? 1 : 0;
> >  	} else { /* legacy mode */
> > -		char probe_name[128];
> > +		char probe_name[MAX_EVENT_NAME_LEN];
> >  
> >  		gen_kprobe_legacy_event_name(probe_name, sizeof(probe_name), syscall_name, 0);
> >  		if (add_kprobe_event_legacy(probe_name, false, syscall_name, 0) < 0)
> > @@ -11328,7 +11330,7 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog,
> >  					    func_name, offset,
> >  					    -1 /* pid */, 0 /* ref_ctr_off */);
> >  	} else {
> > -		char probe_name[256];
> > +		char probe_name[MAX_EVENT_NAME_LEN];
> >  
> >  		gen_kprobe_legacy_event_name(probe_name, sizeof(probe_name),
> >  					     func_name, offset);
> > @@ -11878,9 +11880,12 @@ static int attach_uprobe_multi(const struct bpf_program *prog, long cookie, stru
> >  static void gen_uprobe_legacy_event_name(char *buf, size_t buf_sz,
> >  					 const char *binary_path, uint64_t offset)
> >  {
> > +	static int index = 0;
> >  	int i;
> >  
> > -	snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx", getpid(), binary_path, (size_t)offset);
> > +	snprintf(buf, buf_sz, "libbpf_%u_%d_%s_0x%zx", getpid(),
> > +		 __sync_fetch_and_add(&index, 1),
> > +		 basename((void *)binary_path), (size_t)offset);
> 
> gen_kprobe_legacy_event_name and gen_uprobe_legacy_event_name seem to
> be identical now, maybe we can have just one ?
> 
> thanks,
> jirka
> 

The gen_uprobe_legacy_event_name function includes an extra basename compared to gen_kprobe_legacy_event_name,
as the prefixes of binary_path are often too similar to distinguish easily.
When merging these two into a single function, is it acceptable to pass basename((void *)binary_path)
directly during the uprobe invocation, or should we remove the addition of basename? Thank you!

> >  
> >  	/* sanitize binary_path in the probe name */
> >  	for (i = 0; buf[i]; i++) {
> > @@ -12312,7 +12317,7 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
> >  		pfd = perf_event_open_probe(true /* uprobe */, retprobe, binary_path,
> >  					    func_offset, pid, ref_ctr_off);
> >  	} else {
> > -		char probe_name[PATH_MAX + 64];
> > +		char probe_name[MAX_EVENT_NAME_LEN];
> >  
> >  		if (ref_ctr_off)
> >  			return libbpf_err_ptr(-EINVAL);
> > -- 
> > 2.43.0
> > 

Re: [PATCH v3 bpf-next 1/3] libbpf: Fix event name too long error

[Jiri Olsa]

On Tue, Apr 15, 2025 at 10:01:15AM +0800, Feng Yang wrote:
> On Mon, 14 Apr 2025 13:43:38 +0200 Jiri Olsa <olsajiri@gmail.com> wrote:
> > On Mon, Apr 14, 2025 at 05:34:00PM +0800, Feng Yang wrote:
> > > From: Feng Yang <yangfeng@kylinos.cn>
> > > 
> > > When the binary path is excessively long, the generated probe_name in libbpf
> > > exceeds the kernel's MAX_EVENT_NAME_LEN limit (64 bytes).
> > > This causes legacy uprobe event attachment to fail with error code -22.
> > > 
> > > Before Fix:
> > > 	./test_progs -t attach_probe/kprobe-long_name
> > > 	......
> > > 	libbpf: failed to add legacy kprobe event for 'bpf_kfunc_looooooooooooooooooooooooooooooong_name+0x0': -EINVAL
> > > 	libbpf: prog 'handle_kprobe': failed to create kprobe 'bpf_kfunc_looooooooooooooooooooooooooooooong_name+0x0' perf event: -EINVAL
> > > 	test_attach_kprobe_long_event_name:FAIL:attach_kprobe_long_event_name unexpected error: -22
> > > 	test_attach_probe:PASS:uprobe_ref_ctr_cleanup 0 nsec
> > > 	#13/11   attach_probe/kprobe-long_name:FAIL
> > > 	#13      attach_probe:FAIL
> > > 
> > > 	./test_progs -t attach_probe/uprobe-long_name
> > > 	......
> > > 	libbpf: failed to add legacy uprobe event for /root/linux-bpf/bpf-next/tools/testing/selftests/bpf/test_progs:0x13efd9: -EINVAL
> > > 	libbpf: prog 'handle_uprobe': failed to create uprobe '/root/linux-bpf/bpf-next/tools/testing/selftests/bpf/test_progs:0x13efd9' perf event: -EINVAL
> > > 	test_attach_uprobe_long_event_name:FAIL:attach_uprobe_long_event_name unexpected error: -22
> > > 	#13/10   attach_probe/uprobe-long_name:FAIL
> > > 	#13      attach_probe:FAIL
> > > After Fix:
> > > 	./test_progs -t attach_probe/uprobe-long_name
> > > 	#13/10   attach_probe/uprobe-long_name:OK
> > > 	#13      attach_probe:OK
> > > 	Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED
> > > 
> > > 	./test_progs -t attach_probe/kprobe-long_name
> > > 	#13/11   attach_probe/kprobe-long_name:OK
> > > 	#13      attach_probe:OK
> > > 	Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED
> > > 
> > > Fixes: 46ed5fc33db9 ("libbpf: Refactor and simplify legacy kprobe code")
> > > Fixes: cc10623c6810 ("libbpf: Add legacy uprobe attaching support")
> > > Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
> > > Signed-off-by: Feng Yang <yangfeng@kylinos.cn>
> > > ---
> > >  tools/lib/bpf/libbpf.c | 19 ++++++++++++-------
> > >  1 file changed, 12 insertions(+), 7 deletions(-)
> > > 
> > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> > > index b2591f5cab65..9e047641e001 100644
> > > --- a/tools/lib/bpf/libbpf.c
> > > +++ b/tools/lib/bpf/libbpf.c
> > > @@ -60,6 +60,8 @@
> > >  #define BPF_FS_MAGIC		0xcafe4a11
> > >  #endif
> > >  
> > > +#define MAX_EVENT_NAME_LEN	64
> > > +
> > >  #define BPF_FS_DEFAULT_PATH "/sys/fs/bpf"
> > >  
> > >  #define BPF_INSN_SZ (sizeof(struct bpf_insn))
> > > @@ -11142,10 +11144,10 @@ static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz,
> > >  	static int index = 0;
> > >  	int i;
> > >  
> > > -	snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx_%d", getpid(), kfunc_name, offset,
> > > -		 __sync_fetch_and_add(&index, 1));
> > > +	snprintf(buf, buf_sz, "libbpf_%u_%d_%s_0x%zx", getpid(),
> > > +		 __sync_fetch_and_add(&index, 1), kfunc_name, offset);
> > 
> > so the fix is to move unique id before kfunc_name to make sure it gets
> > to the event name right? would be great to have it in changelog
> > 
> 
> Yes, defining MAX_EVENT_NAME_LEN ensures event names are truncated via snprintf
> to prevent exceeding the maximum length limit.
> Moving the unique id before kfunc_name avoids truncating the id.
> Regarding the changelog: Should this information go into the commit message of the patch, or somewhere else?

having this in changelog would help

> 
> > 
> > >  
> > > -	/* sanitize binary_path in the probe name */
> > > +	/* sanitize kfunc_name in the probe name */
> > >  	for (i = 0; buf[i]; i++) {
> > >  		if (!isalnum(buf[i]))
> > >  			buf[i] = '_';
> > > @@ -11270,7 +11272,7 @@ int probe_kern_syscall_wrapper(int token_fd)
> > >  
> > >  		return pfd >= 0 ? 1 : 0;
> > >  	} else { /* legacy mode */
> > > -		char probe_name[128];
> > > +		char probe_name[MAX_EVENT_NAME_LEN];
> > >  
> > >  		gen_kprobe_legacy_event_name(probe_name, sizeof(probe_name), syscall_name, 0);
> > >  		if (add_kprobe_event_legacy(probe_name, false, syscall_name, 0) < 0)
> > > @@ -11328,7 +11330,7 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog,
> > >  					    func_name, offset,
> > >  					    -1 /* pid */, 0 /* ref_ctr_off */);
> > >  	} else {
> > > -		char probe_name[256];
> > > +		char probe_name[MAX_EVENT_NAME_LEN];
> > >  
> > >  		gen_kprobe_legacy_event_name(probe_name, sizeof(probe_name),
> > >  					     func_name, offset);
> > > @@ -11878,9 +11880,12 @@ static int attach_uprobe_multi(const struct bpf_program *prog, long cookie, stru
> > >  static void gen_uprobe_legacy_event_name(char *buf, size_t buf_sz,
> > >  					 const char *binary_path, uint64_t offset)
> > >  {
> > > +	static int index = 0;
> > >  	int i;
> > >  
> > > -	snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx", getpid(), binary_path, (size_t)offset);
> > > +	snprintf(buf, buf_sz, "libbpf_%u_%d_%s_0x%zx", getpid(),
> > > +		 __sync_fetch_and_add(&index, 1),
> > > +		 basename((void *)binary_path), (size_t)offset);
> > 
> > gen_kprobe_legacy_event_name and gen_uprobe_legacy_event_name seem to
> > be identical now, maybe we can have just one ?
> > 
> > thanks,
> > jirka
> > 
> 
> The gen_uprobe_legacy_event_name function includes an extra basename compared to gen_kprobe_legacy_event_name,
> as the prefixes of binary_path are often too similar to distinguish easily.
> When merging these two into a single function, is it acceptable to pass basename((void *)binary_path)
> directly during the uprobe invocation, or should we remove the addition of basename? Thank you!

I think basename is fine, perhaps just pass it as argument
like below (on top of your change, untested)

jirka


---
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 9e047641e001..93e804b25da1 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -11138,14 +11138,13 @@ static const char *tracefs_available_filter_functions_addrs(void)
 			     : TRACEFS"/available_filter_functions_addrs";
 }
 
-static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz,
-					 const char *kfunc_name, size_t offset)
+static void gen_legacy_event_name(char *buf, size_t buf_sz, const char *name, size_t offset)
 {
 	static int index = 0;
 	int i;
 
 	snprintf(buf, buf_sz, "libbpf_%u_%d_%s_0x%zx", getpid(),
-		 __sync_fetch_and_add(&index, 1), kfunc_name, offset);
+		 __sync_fetch_and_add(&index, 1), name, offset);
 
 	/* sanitize kfunc_name in the probe name */
 	for (i = 0; buf[i]; i++) {
@@ -11274,7 +11273,7 @@ int probe_kern_syscall_wrapper(int token_fd)
 	} else { /* legacy mode */
 		char probe_name[MAX_EVENT_NAME_LEN];
 
-		gen_kprobe_legacy_event_name(probe_name, sizeof(probe_name), syscall_name, 0);
+		gen_legacy_event_name(probe_name, sizeof(probe_name), syscall_name, 0);
 		if (add_kprobe_event_legacy(probe_name, false, syscall_name, 0) < 0)
 			return 0;
 
@@ -11332,8 +11331,7 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog,
 	} else {
 		char probe_name[MAX_EVENT_NAME_LEN];
 
-		gen_kprobe_legacy_event_name(probe_name, sizeof(probe_name),
-					     func_name, offset);
+		gen_legacy_event_name(probe_name, sizeof(probe_name), func_name, offset);
 
 		legacy_probe = strdup(probe_name);
 		if (!legacy_probe)
@@ -11877,23 +11875,6 @@ static int attach_uprobe_multi(const struct bpf_program *prog, long cookie, stru
 	return ret;
 }
 
-static void gen_uprobe_legacy_event_name(char *buf, size_t buf_sz,
-					 const char *binary_path, uint64_t offset)
-{
-	static int index = 0;
-	int i;
-
-	snprintf(buf, buf_sz, "libbpf_%u_%d_%s_0x%zx", getpid(),
-		 __sync_fetch_and_add(&index, 1),
-		 basename((void *)binary_path), (size_t)offset);
-
-	/* sanitize binary_path in the probe name */
-	for (i = 0; buf[i]; i++) {
-		if (!isalnum(buf[i]))
-			buf[i] = '_';
-	}
-}
-
 static inline int add_uprobe_event_legacy(const char *probe_name, bool retprobe,
 					  const char *binary_path, size_t offset)
 {
@@ -12322,8 +12303,8 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
 		if (ref_ctr_off)
 			return libbpf_err_ptr(-EINVAL);
 
-		gen_uprobe_legacy_event_name(probe_name, sizeof(probe_name),
-					     binary_path, func_offset);
+		gen_legacy_event_name(probe_name, sizeof(probe_name),
+				      basename((char *) binary_path), func_offset);
 
 		legacy_probe = strdup(probe_name);
 		if (!legacy_probe)

[PATCH v3 bpf-next 2/3] selftests/bpf: Add test for attaching uprobe with long event names

[Feng Yang]

From: Feng Yang <yangfeng@kylinos.cn>

This test verifies that attaching uprobe/uretprobe with long event names
does not trigger EINVAL errors.

Signed-off-by: Feng Yang <yangfeng@kylinos.cn>
---
 .../selftests/bpf/prog_tests/attach_probe.c   | 49 +++++++++++++++++++
 1 file changed, 49 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/attach_probe.c b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
index 329c7862b52d..9b7f36f39c32 100644
--- a/tools/testing/selftests/bpf/prog_tests/attach_probe.c
+++ b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
@@ -122,6 +122,52 @@ static void test_attach_probe_manual(enum probe_attach_mode attach_mode)
 	test_attach_probe_manual__destroy(skel);
 }
 
+/* attach uprobe/uretprobe long event name testings */
+static void test_attach_uprobe_long_event_name(void)
+{
+	DECLARE_LIBBPF_OPTS(bpf_uprobe_opts, uprobe_opts);
+	struct bpf_link *uprobe_link, *uretprobe_link;
+	struct test_attach_probe_manual *skel;
+	ssize_t uprobe_offset;
+	char path[PATH_MAX] = {0};
+
+	skel = test_attach_probe_manual__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_kprobe_manual_open_and_load"))
+		return;
+
+	uprobe_offset = get_uprobe_offset(&trigger_func);
+	if (!ASSERT_GE(uprobe_offset, 0, "uprobe_offset"))
+		goto cleanup;
+
+	if (!ASSERT_GT(readlink("/proc/self/exe", path, PATH_MAX - 1), 0, "readlink"))
+		goto cleanup;
+
+	/* manual-attach uprobe/uretprobe */
+	uprobe_opts.attach_mode = PROBE_ATTACH_MODE_LEGACY;
+	uprobe_opts.ref_ctr_offset = 0;
+	uprobe_opts.retprobe = false;
+	uprobe_link = bpf_program__attach_uprobe_opts(skel->progs.handle_uprobe,
+						      0 /* self pid */,
+						      path,
+						      uprobe_offset,
+						      &uprobe_opts);
+	if (!ASSERT_OK_PTR(uprobe_link, "attach_uprobe_long_event_name"))
+		goto cleanup;
+	skel->links.handle_uprobe = uprobe_link;
+
+	uprobe_opts.retprobe = true;
+	uretprobe_link = bpf_program__attach_uprobe_opts(skel->progs.handle_uretprobe,
+							 -1 /* any pid */,
+							 path,
+							 uprobe_offset, &uprobe_opts);
+	if (!ASSERT_OK_PTR(uretprobe_link, "attach_uretprobe_long_event_name"))
+		goto cleanup;
+	skel->links.handle_uretprobe = uretprobe_link;
+
+cleanup:
+	test_attach_probe_manual__destroy(skel);
+}
+
 static void test_attach_probe_auto(struct test_attach_probe *skel)
 {
 	struct bpf_link *uprobe_err_link;
@@ -323,6 +369,9 @@ void test_attach_probe(void)
 	if (test__start_subtest("uprobe-ref_ctr"))
 		test_uprobe_ref_ctr(skel);
 
+	if (test__start_subtest("uprobe-long_name"))
+		test_attach_uprobe_long_event_name();
+
 cleanup:
 	test_attach_probe__destroy(skel);
 	ASSERT_EQ(uprobe_ref_ctr, 0, "uprobe_ref_ctr_cleanup");
-- 
2.43.0

[PATCH v3 bpf-next 3/3] selftests/bpf: Add test for attaching kprobe with long event names

[Feng Yang]

From: Feng Yang <yangfeng@kylinos.cn>

This test verifies that attaching kprobe/kretprobe with long event names
does not trigger EINVAL errors.

Signed-off-by: Feng Yang <yangfeng@kylinos.cn>
---
 .../selftests/bpf/prog_tests/attach_probe.c   | 35 +++++++++++++++++++
 .../selftests/bpf/test_kmods/bpf_testmod.c    |  5 +++
 .../bpf/test_kmods/bpf_testmod_kfunc.h        |  2 ++
 3 files changed, 42 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/attach_probe.c b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
index 9b7f36f39c32..633b5eb4379b 100644
--- a/tools/testing/selftests/bpf/prog_tests/attach_probe.c
+++ b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
@@ -168,6 +168,39 @@ static void test_attach_uprobe_long_event_name(void)
 	test_attach_probe_manual__destroy(skel);
 }
 
+/* attach kprobe/kretprobe long event name testings */
+static void test_attach_kprobe_long_event_name(void)
+{
+	DECLARE_LIBBPF_OPTS(bpf_kprobe_opts, kprobe_opts);
+	struct bpf_link *kprobe_link, *kretprobe_link;
+	struct test_attach_probe_manual *skel;
+
+	skel = test_attach_probe_manual__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_kprobe_manual_open_and_load"))
+		return;
+
+	/* manual-attach kprobe/kretprobe */
+	kprobe_opts.attach_mode = PROBE_ATTACH_MODE_LEGACY;
+	kprobe_opts.retprobe = false;
+	kprobe_link = bpf_program__attach_kprobe_opts(skel->progs.handle_kprobe,
+						      "bpf_kfunc_looooooooooooooooooooooooooooooong_name",
+						      &kprobe_opts);
+	if (!ASSERT_OK_PTR(kprobe_link, "attach_kprobe_long_event_name"))
+		goto cleanup;
+	skel->links.handle_kprobe = kprobe_link;
+
+	kprobe_opts.retprobe = true;
+	kretprobe_link = bpf_program__attach_kprobe_opts(skel->progs.handle_kretprobe,
+							 "bpf_kfunc_looooooooooooooooooooooooooooooong_name",
+							 &kprobe_opts);
+	if (!ASSERT_OK_PTR(kretprobe_link, "attach_kretprobe_long_event_name"))
+		goto cleanup;
+	skel->links.handle_kretprobe = kretprobe_link;
+
+cleanup:
+	test_attach_probe_manual__destroy(skel);
+}
+
 static void test_attach_probe_auto(struct test_attach_probe *skel)
 {
 	struct bpf_link *uprobe_err_link;
@@ -371,6 +404,8 @@ void test_attach_probe(void)
 
 	if (test__start_subtest("uprobe-long_name"))
 		test_attach_uprobe_long_event_name();
+	if (test__start_subtest("kprobe-long_name"))
+		test_attach_kprobe_long_event_name();
 
 cleanup:
 	test_attach_probe__destroy(skel);
diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
index f38eaf0d35ef..439f6c2b2456 100644
--- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
+++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
@@ -1053,6 +1053,10 @@ __bpf_kfunc int bpf_kfunc_st_ops_inc10(struct st_ops_args *args)
 	return args->a;
 }
 
+__bpf_kfunc void bpf_kfunc_looooooooooooooooooooooooooooooong_name(void)
+{
+}
+
 BTF_KFUNCS_START(bpf_testmod_check_kfunc_ids)
 BTF_ID_FLAGS(func, bpf_testmod_test_mod_kfunc)
 BTF_ID_FLAGS(func, bpf_kfunc_call_test1)
@@ -1093,6 +1097,7 @@ BTF_ID_FLAGS(func, bpf_kfunc_st_ops_test_prologue, KF_TRUSTED_ARGS | KF_SLEEPABL
 BTF_ID_FLAGS(func, bpf_kfunc_st_ops_test_epilogue, KF_TRUSTED_ARGS | KF_SLEEPABLE)
 BTF_ID_FLAGS(func, bpf_kfunc_st_ops_test_pro_epilogue, KF_TRUSTED_ARGS | KF_SLEEPABLE)
 BTF_ID_FLAGS(func, bpf_kfunc_st_ops_inc10, KF_TRUSTED_ARGS)
+BTF_ID_FLAGS(func, bpf_kfunc_looooooooooooooooooooooooooooooong_name)
 BTF_KFUNCS_END(bpf_testmod_check_kfunc_ids)
 
 static int bpf_testmod_ops_init(struct btf *btf)
diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h b/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h
index b58817938deb..e5b833140418 100644
--- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h
+++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h
@@ -159,4 +159,6 @@ void bpf_kfunc_trusted_task_test(struct task_struct *ptr) __ksym;
 void bpf_kfunc_trusted_num_test(int *ptr) __ksym;
 void bpf_kfunc_rcu_task_test(struct task_struct *ptr) __ksym;
 
+void bpf_kfunc_looooooooooooooooooooooooooooooong_name(void) __ksym;
+
 #endif /* _BPF_TESTMOD_KFUNC_H */
-- 
2.43.0

Re: [PATCH v3 bpf-next 3/3] selftests/bpf: Add test for attaching kprobe with long event names

[Jiri Olsa]

On Mon, Apr 14, 2025 at 05:34:02PM +0800, Feng Yang wrote:
> From: Feng Yang <yangfeng@kylinos.cn>
> 
> This test verifies that attaching kprobe/kretprobe with long event names
> does not trigger EINVAL errors.
> 
> Signed-off-by: Feng Yang <yangfeng@kylinos.cn>
> ---
>  .../selftests/bpf/prog_tests/attach_probe.c   | 35 +++++++++++++++++++
>  .../selftests/bpf/test_kmods/bpf_testmod.c    |  5 +++
>  .../bpf/test_kmods/bpf_testmod_kfunc.h        |  2 ++
>  3 files changed, 42 insertions(+)
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/attach_probe.c b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
> index 9b7f36f39c32..633b5eb4379b 100644
> --- a/tools/testing/selftests/bpf/prog_tests/attach_probe.c
> +++ b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
> @@ -168,6 +168,39 @@ static void test_attach_uprobe_long_event_name(void)
>  	test_attach_probe_manual__destroy(skel);
>  }
>  
> +/* attach kprobe/kretprobe long event name testings */
> +static void test_attach_kprobe_long_event_name(void)
> +{
> +	DECLARE_LIBBPF_OPTS(bpf_kprobe_opts, kprobe_opts);
> +	struct bpf_link *kprobe_link, *kretprobe_link;
> +	struct test_attach_probe_manual *skel;
> +
> +	skel = test_attach_probe_manual__open_and_load();
> +	if (!ASSERT_OK_PTR(skel, "skel_kprobe_manual_open_and_load"))
> +		return;
> +
> +	/* manual-attach kprobe/kretprobe */
> +	kprobe_opts.attach_mode = PROBE_ATTACH_MODE_LEGACY;
> +	kprobe_opts.retprobe = false;
> +	kprobe_link = bpf_program__attach_kprobe_opts(skel->progs.handle_kprobe,
> +						      "bpf_kfunc_looooooooooooooooooooooooooooooong_name",
> +						      &kprobe_opts);
> +	if (!ASSERT_OK_PTR(kprobe_link, "attach_kprobe_long_event_name"))
> +		goto cleanup;
> +	skel->links.handle_kprobe = kprobe_link;
> +
> +	kprobe_opts.retprobe = true;
> +	kretprobe_link = bpf_program__attach_kprobe_opts(skel->progs.handle_kretprobe,
> +							 "bpf_kfunc_looooooooooooooooooooooooooooooong_name",
> +							 &kprobe_opts);
> +	if (!ASSERT_OK_PTR(kretprobe_link, "attach_kretprobe_long_event_name"))
> +		goto cleanup;
> +	skel->links.handle_kretprobe = kretprobe_link;
> +
> +cleanup:
> +	test_attach_probe_manual__destroy(skel);
> +}
> +
>  static void test_attach_probe_auto(struct test_attach_probe *skel)
>  {
>  	struct bpf_link *uprobe_err_link;
> @@ -371,6 +404,8 @@ void test_attach_probe(void)
>  
>  	if (test__start_subtest("uprobe-long_name"))
>  		test_attach_uprobe_long_event_name();
> +	if (test__start_subtest("kprobe-long_name"))
> +		test_attach_kprobe_long_event_name();
>  
>  cleanup:
>  	test_attach_probe__destroy(skel);
> diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
> index f38eaf0d35ef..439f6c2b2456 100644
> --- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
> +++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
> @@ -1053,6 +1053,10 @@ __bpf_kfunc int bpf_kfunc_st_ops_inc10(struct st_ops_args *args)
>  	return args->a;
>  }
>  
> +__bpf_kfunc void bpf_kfunc_looooooooooooooooooooooooooooooong_name(void)
> +{
> +}

does it need to be a kfunc? IIUC it just needs to be a normal kernel/module function

jirka


> +
>  BTF_KFUNCS_START(bpf_testmod_check_kfunc_ids)
>  BTF_ID_FLAGS(func, bpf_testmod_test_mod_kfunc)
>  BTF_ID_FLAGS(func, bpf_kfunc_call_test1)
> @@ -1093,6 +1097,7 @@ BTF_ID_FLAGS(func, bpf_kfunc_st_ops_test_prologue, KF_TRUSTED_ARGS | KF_SLEEPABL
>  BTF_ID_FLAGS(func, bpf_kfunc_st_ops_test_epilogue, KF_TRUSTED_ARGS | KF_SLEEPABLE)
>  BTF_ID_FLAGS(func, bpf_kfunc_st_ops_test_pro_epilogue, KF_TRUSTED_ARGS | KF_SLEEPABLE)
>  BTF_ID_FLAGS(func, bpf_kfunc_st_ops_inc10, KF_TRUSTED_ARGS)
> +BTF_ID_FLAGS(func, bpf_kfunc_looooooooooooooooooooooooooooooong_name)
>  BTF_KFUNCS_END(bpf_testmod_check_kfunc_ids)
>  
>  static int bpf_testmod_ops_init(struct btf *btf)
> diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h b/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h
> index b58817938deb..e5b833140418 100644
> --- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h
> +++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h
> @@ -159,4 +159,6 @@ void bpf_kfunc_trusted_task_test(struct task_struct *ptr) __ksym;
>  void bpf_kfunc_trusted_num_test(int *ptr) __ksym;
>  void bpf_kfunc_rcu_task_test(struct task_struct *ptr) __ksym;
>  
> +void bpf_kfunc_looooooooooooooooooooooooooooooong_name(void) __ksym;
> +
>  #endif /* _BPF_TESTMOD_KFUNC_H */
> -- 
> 2.43.0
> 

Re: [PATCH v3 bpf-next 3/3] selftests/bpf: Add test for attaching kprobe with long event names

[Feng Yang]

On Mon, 14 Apr 2025 13:47:55 +0200, Jiri Olsa <olsajiri@gmail.com> wrote:

> On Mon, Apr 14, 2025 at 05:34:02PM +0800, Feng Yang wrote:
> > From: Feng Yang <yangfeng@kylinos.cn>
> > 
> > This test verifies that attaching kprobe/kretprobe with long event names
> > does not trigger EINVAL errors.
> > 
> > Signed-off-by: Feng Yang <yangfeng@kylinos.cn>
> > ---
> >  .../selftests/bpf/prog_tests/attach_probe.c   | 35 +++++++++++++++++++
> >  .../selftests/bpf/test_kmods/bpf_testmod.c    |  5 +++
> >  .../bpf/test_kmods/bpf_testmod_kfunc.h        |  2 ++
> >  3 files changed, 42 insertions(+)
> > 
> > diff --git a/tools/testing/selftests/bpf/prog_tests/attach_probe.c b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
> > index 9b7f36f39c32..633b5eb4379b 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/attach_probe.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
> > @@ -168,6 +168,39 @@ static void test_attach_uprobe_long_event_name(void)
> >  	test_attach_probe_manual__destroy(skel);
> >  }
> >  
> > +/* attach kprobe/kretprobe long event name testings */
> > +static void test_attach_kprobe_long_event_name(void)
> > +{
> > +	DECLARE_LIBBPF_OPTS(bpf_kprobe_opts, kprobe_opts);
> > +	struct bpf_link *kprobe_link, *kretprobe_link;
> > +	struct test_attach_probe_manual *skel;
> > +
> > +	skel = test_attach_probe_manual__open_and_load();
> > +	if (!ASSERT_OK_PTR(skel, "skel_kprobe_manual_open_and_load"))
> > +		return;
> > +
> > +	/* manual-attach kprobe/kretprobe */
> > +	kprobe_opts.attach_mode = PROBE_ATTACH_MODE_LEGACY;
> > +	kprobe_opts.retprobe = false;
> > +	kprobe_link = bpf_program__attach_kprobe_opts(skel->progs.handle_kprobe,
> > +						      "bpf_kfunc_looooooooooooooooooooooooooooooong_name",
> > +						      &kprobe_opts);
> > +	if (!ASSERT_OK_PTR(kprobe_link, "attach_kprobe_long_event_name"))
> > +		goto cleanup;
> > +	skel->links.handle_kprobe = kprobe_link;
> > +
> > +	kprobe_opts.retprobe = true;
> > +	kretprobe_link = bpf_program__attach_kprobe_opts(skel->progs.handle_kretprobe,
> > +							 "bpf_kfunc_looooooooooooooooooooooooooooooong_name",
> > +							 &kprobe_opts);
> > +	if (!ASSERT_OK_PTR(kretprobe_link, "attach_kretprobe_long_event_name"))
> > +		goto cleanup;
> > +	skel->links.handle_kretprobe = kretprobe_link;
> > +
> > +cleanup:
> > +	test_attach_probe_manual__destroy(skel);
> > +}
> > +
> >  static void test_attach_probe_auto(struct test_attach_probe *skel)
> >  {
> >  	struct bpf_link *uprobe_err_link;
> > @@ -371,6 +404,8 @@ void test_attach_probe(void)
> >  
> >  	if (test__start_subtest("uprobe-long_name"))
> >  		test_attach_uprobe_long_event_name();
> > +	if (test__start_subtest("kprobe-long_name"))
> > +		test_attach_kprobe_long_event_name();
> >  
> >  cleanup:
> >  	test_attach_probe__destroy(skel);
> > diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
> > index f38eaf0d35ef..439f6c2b2456 100644
> > --- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
> > +++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
> > @@ -1053,6 +1053,10 @@ __bpf_kfunc int bpf_kfunc_st_ops_inc10(struct st_ops_args *args)
> >  	return args->a;
> >  }
> >  
> > +__bpf_kfunc void bpf_kfunc_looooooooooooooooooooooooooooooong_name(void)
> > +{
> > +}
> 
> does it need to be a kfunc? IIUC it just needs to be a normal kernel/module function
> 
> jirka
> 

Indeed, so is it okay if I make the following modifications:

--- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
+++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
@@ -134,6 +134,10 @@ bpf_testmod_test_arg_ptr_to_struct(struct bpf_testmod_struct_arg_1 *a) {
 	return bpf_testmod_test_struct_arg_result;
 }
 
+noinline void bpf_testmod_looooooooooooooooooooooooooooooong_name(void)
+{
+}
+
 __bpf_kfunc void
 bpf_testmod_test_mod_kfunc(int i)

Thanks.

> > +
> >  BTF_KFUNCS_START(bpf_testmod_check_kfunc_ids)
> >  BTF_ID_FLAGS(func, bpf_testmod_test_mod_kfunc)
> >  BTF_ID_FLAGS(func, bpf_kfunc_call_test1)
> > @@ -1093,6 +1097,7 @@ BTF_ID_FLAGS(func, bpf_kfunc_st_ops_test_prologue, KF_TRUSTED_ARGS | KF_SLEEPABL
> >  BTF_ID_FLAGS(func, bpf_kfunc_st_ops_test_epilogue, KF_TRUSTED_ARGS | KF_SLEEPABLE)
> >  BTF_ID_FLAGS(func, bpf_kfunc_st_ops_test_pro_epilogue, KF_TRUSTED_ARGS | KF_SLEEPABLE)
> >  BTF_ID_FLAGS(func, bpf_kfunc_st_ops_inc10, KF_TRUSTED_ARGS)
> > +BTF_ID_FLAGS(func, bpf_kfunc_looooooooooooooooooooooooooooooong_name)
> >  BTF_KFUNCS_END(bpf_testmod_check_kfunc_ids)
> >  
> >  static int bpf_testmod_ops_init(struct btf *btf)
> > diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h b/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h
> > index b58817938deb..e5b833140418 100644
> > --- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h
> > +++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h
> > @@ -159,4 +159,6 @@ void bpf_kfunc_trusted_task_test(struct task_struct *ptr) __ksym;
> >  void bpf_kfunc_trusted_num_test(int *ptr) __ksym;
> >  void bpf_kfunc_rcu_task_test(struct task_struct *ptr) __ksym;
> >  
> > +void bpf_kfunc_looooooooooooooooooooooooooooooong_name(void) __ksym;
> > +
> >  #endif /* _BPF_TESTMOD_KFUNC_H */
> > -- 
> > 2.43.0
> >