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[PATCH] selftests/bpf: trampoline_count: use dedicated bpf_testmod target

Sun Jian posted 1 patch 2 weeks, 4 days ago 
.../selftests/bpf/prog_tests/trampoline_count.c |  3 +--
.../selftests/bpf/progs/test_trampoline_count.c |  6 +++---
.../selftests/bpf/test_kmods/bpf_testmod.c      | 17 +++++++++++++++++
3 files changed, 21 insertions(+), 5 deletions(-)
[PATCH] selftests/bpf: trampoline_count: use dedicated bpf_testmod target
Posted by Sun Jian 2 weeks, 4 days ago 
trampoline_count fills all trampoline attachment slots for a single
target function and verifies that one extra attach fails with -E2BIG.

It currently targets bpf_modify_return_test, which is also used by
other selftests such as modify_return, get_func_ip_test, and
get_func_args_test. When such tests run in parallel, they can contend
for the same per-function trampoline quota and cause unexpected attach
failures. This issue is currently masked by harness serialization.

Move trampoline_count to a dedicated bpf_testmod target and register it
for fmod_ret attachment. This keeps the test semantics unchanged while
isolating it from other selftests, so it no longer needs to run in
serial mode. Remove the TODO comment as well.

Tested:
  ./test_progs -t trampoline_count -vv
  ./test_progs -t modify_return -vv
  ./test_progs -t get_func_ip_test -vv
  ./test_progs -t get_func_args_test -vv
  ./test_progs -j$(nproc) -t trampoline_count -vv
  ./test_progs -j$(nproc) -t
    trampoline_count,modify_return,get_func_ip_test,get_func_args_test,\
kprobe_multi_test -vv
  20 runs of:
    ./test_progs -j$(nproc) -t
    trampoline_count,modify_return,get_func_ip_test,get_func_args_test,\
kprobe_multi_test

Signed-off-by: Sun Jian <sun.jian.kdev@gmail.com>
---
 .../selftests/bpf/prog_tests/trampoline_count.c |  3 +--
 .../selftests/bpf/progs/test_trampoline_count.c |  6 +++---
 .../selftests/bpf/test_kmods/bpf_testmod.c      | 17 +++++++++++++++++
 3 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/trampoline_count.c b/tools/testing/selftests/bpf/prog_tests/trampoline_count.c
index 6cd7349d4a2b..b19358aed126 100644
--- a/tools/testing/selftests/bpf/prog_tests/trampoline_count.c
+++ b/tools/testing/selftests/bpf/prog_tests/trampoline_count.c
@@ -30,8 +30,7 @@ static struct bpf_program *load_prog(char *file, char *name, struct inst *inst)
 	return prog;
 }
 
-/* TODO: use different target function to run in concurrent mode */
-void serial_test_trampoline_count(void)
+void test_trampoline_count(void)
 {
 	char *file = "test_trampoline_count.bpf.o";
 	char *const progs[] = { "fentry_test", "fmod_ret_test", "fexit_test" };
diff --git a/tools/testing/selftests/bpf/progs/test_trampoline_count.c b/tools/testing/selftests/bpf/progs/test_trampoline_count.c
index 7765720da7d5..14ad2f53cf33 100644
--- a/tools/testing/selftests/bpf/progs/test_trampoline_count.c
+++ b/tools/testing/selftests/bpf/progs/test_trampoline_count.c
@@ -3,19 +3,19 @@
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_tracing.h>
 
-SEC("fentry/bpf_modify_return_test")
+SEC("fentry/bpf_testmod_trampoline_count_test")
 int BPF_PROG(fentry_test, int a, int *b)
 {
 	return 0;
 }
 
-SEC("fmod_ret/bpf_modify_return_test")
+SEC("fmod_ret/bpf_testmod_trampoline_count_test")
 int BPF_PROG(fmod_ret_test, int a, int *b, int ret)
 {
 	return 0;
 }
 
-SEC("fexit/bpf_modify_return_test")
+SEC("fexit/bpf_testmod_trampoline_count_test")
 int BPF_PROG(fexit_test, int a, int *b, int ret)
 {
 	return 0;
diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
index e62c6b78657f..6eaceb4dfbec 100644
--- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
+++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
@@ -581,6 +581,12 @@ noinline int bpf_fentry_shadow_test(int a)
 }
 EXPORT_SYMBOL_GPL(bpf_fentry_shadow_test);
 
+noinline int bpf_testmod_trampoline_count_test(int a, int *b)
+{
+	*b += 1;
+	return a + *b;
+}
+
 __bpf_hook_end();
 
 static struct bin_attribute bin_attr_bpf_testmod_file __ro_after_init = {
@@ -1843,6 +1849,16 @@ struct bpf_struct_ops testmod_multi_st_ops = {
 
 extern int bpf_fentry_test1(int a);
 
+BTF_KFUNCS_START(bpf_testmod_trampoline_count_ids)
+BTF_ID_FLAGS(func, bpf_testmod_trampoline_count_test)
+BTF_KFUNCS_END(bpf_testmod_trampoline_count_ids)
+
+static const struct
+btf_kfunc_id_set bpf_testmod_trampoline_count_fmodret_set = {
+	.owner = THIS_MODULE,
+	.set = &bpf_testmod_trampoline_count_ids,
+};
+
 static int bpf_testmod_init(void)
 {
 	const struct btf_id_dtor_kfunc bpf_testmod_dtors[] = {
@@ -1859,6 +1875,7 @@ static int bpf_testmod_init(void)
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &bpf_testmod_kfunc_set);
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SYSCALL, &bpf_testmod_kfunc_set);
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS, &bpf_testmod_kfunc_set);
+	ret = ret ?: register_btf_fmodret_id_set(&bpf_testmod_trampoline_count_fmodret_set);
 	ret = ret ?: register_bpf_struct_ops(&bpf_bpf_testmod_ops, bpf_testmod_ops);
 	ret = ret ?: register_bpf_struct_ops(&bpf_testmod_ops2, bpf_testmod_ops2);
 	ret = ret ?: register_bpf_struct_ops(&bpf_testmod_ops3, bpf_testmod_ops3);

base-commit: 8a30aeb0d1b4e4aaf7f7bae72f20f2ae75385ccb
-- 
2.43.0
Re: [PATCH] selftests/bpf: trampoline_count: use dedicated bpf_testmod target
Posted by bot+bpf-ci@kernel.org 2 weeks, 4 days ago 
> selftests/bpf: trampoline_count: use dedicated bpf_testmod target

Alexei Starovoitov asked for the subject to not use
"trampoline_count:" as a prefix, since it is not a standard
subsystem prefix. The preferred form would be "selftests/bpf:"
followed by a description of what the patch does.

https://lore.kernel.org/bpf/CAADnVQJ9HZTHKCzwmqUwhePbCQ5qPQrSd=yejUS17eHbMm0fuQ@mail.gmail.com/


---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/23278379564
Re: [PATCH] selftests/bpf: trampoline_count: use dedicated bpf_testmod target
Posted by Alexei Starovoitov 2 weeks, 4 days ago 
On Wed, Mar 18, 2026 at 8:12 PM Sun Jian <sun.jian.kdev@gmail.com> wrote:
>
> trampoline_count fills all trampoline attachment slots for a single
> target function and verifies that one extra attach fails with -E2BIG.

selftests/bpf: trampoline_count:

don't invent new subjects.
Use
selftests/bpf: ...

and explain what it does.
'trampoline_count:' is not a generic prefix.

pw-bot: cr
[PATCH v2] selftests/bpf: move trampoline_count to dedicated bpf_testmod target
Posted by Sun Jian 2 weeks, 4 days ago 
trampoline_count fills all trampoline attachment slots for a single
target function and verifies that one extra attach fails with -E2BIG.

It currently targets bpf_modify_return_test, which is also used by
other selftests such as modify_return, get_func_ip_test, and
get_func_args_test. When such tests run in parallel, they can contend
for the same per-function trampoline quota and cause unexpected attach
failures. This issue is currently masked by harness serialization.

Move trampoline_count to a dedicated bpf_testmod target and register it
for fmod_ret attachment. This keeps the test semantics unchanged while
isolating it from other selftests, so it no longer needs to run in
serial mode. Remove the TODO comment as well.

Tested:
  ./test_progs -t trampoline_count -vv
  ./test_progs -t modify_return -vv
  ./test_progs -t get_func_ip_test -vv
  ./test_progs -t get_func_args_test -vv
  ./test_progs -j$(nproc) -t trampoline_count -vv
  ./test_progs -j$(nproc) -t
    trampoline_count,modify_return,get_func_ip_test,get_func_args_test,\
kprobe_multi_test -vv
  20 runs of:
    ./test_progs -j$(nproc) -t
    trampoline_count,modify_return,get_func_ip_test,get_func_args_test,\
kprobe_multi_test

Signed-off-by: Sun Jian <sun.jian.kdev@gmail.com>
---

v2:
- rewrite the subject to describe the change
- resend with the correct patch content
- resend as a reply to v1

 .../selftests/bpf/prog_tests/trampoline_count.c |  3 +--
 .../selftests/bpf/progs/test_trampoline_count.c |  6 +++---
 .../selftests/bpf/test_kmods/bpf_testmod.c      | 17 +++++++++++++++++
 3 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/trampoline_count.c b/tools/testing/selftests/bpf/prog_tests/trampoline_count.c
index 6cd7349d4a2b..b19358aed126 100644
--- a/tools/testing/selftests/bpf/prog_tests/trampoline_count.c
+++ b/tools/testing/selftests/bpf/prog_tests/trampoline_count.c
@@ -30,8 +30,7 @@ static struct bpf_program *load_prog(char *file, char *name, struct inst *inst)
 	return prog;
 }
 
-/* TODO: use different target function to run in concurrent mode */
-void serial_test_trampoline_count(void)
+void test_trampoline_count(void)
 {
 	char *file = "test_trampoline_count.bpf.o";
 	char *const progs[] = { "fentry_test", "fmod_ret_test", "fexit_test" };
diff --git a/tools/testing/selftests/bpf/progs/test_trampoline_count.c b/tools/testing/selftests/bpf/progs/test_trampoline_count.c
index 7765720da7d5..14ad2f53cf33 100644
--- a/tools/testing/selftests/bpf/progs/test_trampoline_count.c
+++ b/tools/testing/selftests/bpf/progs/test_trampoline_count.c
@@ -3,19 +3,19 @@
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_tracing.h>
 
-SEC("fentry/bpf_modify_return_test")
+SEC("fentry/bpf_testmod_trampoline_count_test")
 int BPF_PROG(fentry_test, int a, int *b)
 {
 	return 0;
 }
 
-SEC("fmod_ret/bpf_modify_return_test")
+SEC("fmod_ret/bpf_testmod_trampoline_count_test")
 int BPF_PROG(fmod_ret_test, int a, int *b, int ret)
 {
 	return 0;
 }
 
-SEC("fexit/bpf_modify_return_test")
+SEC("fexit/bpf_testmod_trampoline_count_test")
 int BPF_PROG(fexit_test, int a, int *b, int ret)
 {
 	return 0;
diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
index e62c6b78657f..6eaceb4dfbec 100644
--- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
+++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
@@ -581,6 +581,12 @@ noinline int bpf_fentry_shadow_test(int a)
 }
 EXPORT_SYMBOL_GPL(bpf_fentry_shadow_test);
 
+noinline int bpf_testmod_trampoline_count_test(int a, int *b)
+{
+	*b += 1;
+	return a + *b;
+}
+
 __bpf_hook_end();
 
 static struct bin_attribute bin_attr_bpf_testmod_file __ro_after_init = {
@@ -1843,6 +1849,16 @@ struct bpf_struct_ops testmod_multi_st_ops = {
 
 extern int bpf_fentry_test1(int a);
 
+BTF_KFUNCS_START(bpf_testmod_trampoline_count_ids)
+BTF_ID_FLAGS(func, bpf_testmod_trampoline_count_test)
+BTF_KFUNCS_END(bpf_testmod_trampoline_count_ids)
+
+static const struct
+btf_kfunc_id_set bpf_testmod_trampoline_count_fmodret_set = {
+	.owner = THIS_MODULE,
+	.set = &bpf_testmod_trampoline_count_ids,
+};
+
 static int bpf_testmod_init(void)
 {
 	const struct btf_id_dtor_kfunc bpf_testmod_dtors[] = {
@@ -1859,6 +1875,7 @@ static int bpf_testmod_init(void)
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &bpf_testmod_kfunc_set);
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SYSCALL, &bpf_testmod_kfunc_set);
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS, &bpf_testmod_kfunc_set);
+	ret = ret ?: register_btf_fmodret_id_set(&bpf_testmod_trampoline_count_fmodret_set);
 	ret = ret ?: register_bpf_struct_ops(&bpf_bpf_testmod_ops, bpf_testmod_ops);
 	ret = ret ?: register_bpf_struct_ops(&bpf_testmod_ops2, bpf_testmod_ops2);
 	ret = ret ?: register_bpf_struct_ops(&bpf_testmod_ops3, bpf_testmod_ops3);

base-commit: 8a30aeb0d1b4e4aaf7f7bae72f20f2ae75385ccb
-- 
2.43.0
Re: [PATCH v2] selftests/bpf: move trampoline_count to dedicated bpf_testmod target
Posted by Paul Chaignon 2 weeks, 4 days ago 
On Thu, Mar 19, 2026 at 12:03:37PM +0800, Sun Jian wrote:
> trampoline_count fills all trampoline attachment slots for a single
> target function and verifies that one extra attach fails with -E2BIG.
> 
> It currently targets bpf_modify_return_test, which is also used by
> other selftests such as modify_return, get_func_ip_test, and
> get_func_args_test. When such tests run in parallel, they can contend
> for the same per-function trampoline quota and cause unexpected attach
> failures. This issue is currently masked by harness serialization.
> 
> Move trampoline_count to a dedicated bpf_testmod target and register it
> for fmod_ret attachment. This keeps the test semantics unchanged while
> isolating it from other selftests, so it no longer needs to run in
> serial mode. Remove the TODO comment as well.
> 
> Tested:
>   ./test_progs -t trampoline_count -vv
>   ./test_progs -t modify_return -vv
>   ./test_progs -t get_func_ip_test -vv
>   ./test_progs -t get_func_args_test -vv
>   ./test_progs -j$(nproc) -t trampoline_count -vv
>   ./test_progs -j$(nproc) -t
>     trampoline_count,modify_return,get_func_ip_test,get_func_args_test,\
> kprobe_multi_test -vv
>   20 runs of:
>     ./test_progs -j$(nproc) -t
>     trampoline_count,modify_return,get_func_ip_test,get_func_args_test,\
> kprobe_multi_test
> 
> Signed-off-by: Sun Jian <sun.jian.kdev@gmail.com>
> ---
> 
> v2:
> - rewrite the subject to describe the change
> - resend with the correct patch content

Please increment the version number when making these changes. Otherwise
it can be quite confusing to everyone. I believe this is the third
variant of your v2 on the mailing list.

> - resend as a reply to v1

That can also be a bit confusing as it will fold the email into existing
conversations. You can instead link to the previous version from the
changelogs.

[...]

Paul
Re: [PATCH v2] selftests/bpf: move trampoline_count to dedicated bpf_testmod target
Posted by sun jian 2 weeks, 3 days ago 
On Thu, Mar 19, 2026 at 7:04 PM Paul Chaignon <paul.chaignon@gmail.com> wrote:
>
> > v2:
> > - rewrite the subject to describe the change
> > - resend with the correct patch content
>
> Please increment the version number when making these changes. Otherwise
> it can be quite confusing to everyone. I believe this is the third
> variant of your v2 on the mailing list.
>
> > - resend as a reply to v1
>
> That can also be a bit confusing as it will fold the email into existing
> conversations. You can instead link to the previous version from the
> changelogs.

Hi Paul,
Thanks for the note.

Will bump the version for the next revision and send it as a new thread.

Regards,
Sun Jian
Re: [PATCH v2] selftests/bpf: move trampoline_count to dedicated bpf_testmod target
Posted by Jiri Olsa 2 weeks, 4 days ago 
On Thu, Mar 19, 2026 at 12:03:37PM +0800, Sun Jian wrote:
> trampoline_count fills all trampoline attachment slots for a single
> target function and verifies that one extra attach fails with -E2BIG.
> 
> It currently targets bpf_modify_return_test, which is also used by
> other selftests such as modify_return, get_func_ip_test, and
> get_func_args_test. When such tests run in parallel, they can contend
> for the same per-function trampoline quota and cause unexpected attach
> failures. This issue is currently masked by harness serialization.
> 
> Move trampoline_count to a dedicated bpf_testmod target and register it
> for fmod_ret attachment. This keeps the test semantics unchanged while
> isolating it from other selftests, so it no longer needs to run in
> serial mode. Remove the TODO comment as well.
> 
> Tested:
>   ./test_progs -t trampoline_count -vv
>   ./test_progs -t modify_return -vv
>   ./test_progs -t get_func_ip_test -vv
>   ./test_progs -t get_func_args_test -vv
>   ./test_progs -j$(nproc) -t trampoline_count -vv
>   ./test_progs -j$(nproc) -t
>     trampoline_count,modify_return,get_func_ip_test,get_func_args_test,\
> kprobe_multi_test -vv
>   20 runs of:
>     ./test_progs -j$(nproc) -t
>     trampoline_count,modify_return,get_func_ip_test,get_func_args_test,\
> kprobe_multi_test
> 
> Signed-off-by: Sun Jian <sun.jian.kdev@gmail.com>
> ---
> 
> v2:
> - rewrite the subject to describe the change
> - resend with the correct patch content
> - resend as a reply to v1
> 
>  .../selftests/bpf/prog_tests/trampoline_count.c |  3 +--
>  .../selftests/bpf/progs/test_trampoline_count.c |  6 +++---
>  .../selftests/bpf/test_kmods/bpf_testmod.c      | 17 +++++++++++++++++
>  3 files changed, 21 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/trampoline_count.c b/tools/testing/selftests/bpf/prog_tests/trampoline_count.c
> index 6cd7349d4a2b..b19358aed126 100644
> --- a/tools/testing/selftests/bpf/prog_tests/trampoline_count.c
> +++ b/tools/testing/selftests/bpf/prog_tests/trampoline_count.c
> @@ -30,8 +30,7 @@ static struct bpf_program *load_prog(char *file, char *name, struct inst *inst)
>  	return prog;
>  }
>  
> -/* TODO: use different target function to run in concurrent mode */
> -void serial_test_trampoline_count(void)
> +void test_trampoline_count(void)
>  {
>  	char *file = "test_trampoline_count.bpf.o";
>  	char *const progs[] = { "fentry_test", "fmod_ret_test", "fexit_test" };
> diff --git a/tools/testing/selftests/bpf/progs/test_trampoline_count.c b/tools/testing/selftests/bpf/progs/test_trampoline_count.c
> index 7765720da7d5..14ad2f53cf33 100644
> --- a/tools/testing/selftests/bpf/progs/test_trampoline_count.c
> +++ b/tools/testing/selftests/bpf/progs/test_trampoline_count.c
> @@ -3,19 +3,19 @@
>  #include <bpf/bpf_helpers.h>
>  #include <bpf/bpf_tracing.h>
>  
> -SEC("fentry/bpf_modify_return_test")
> +SEC("fentry/bpf_testmod_trampoline_count_test")
>  int BPF_PROG(fentry_test, int a, int *b)
>  {
>  	return 0;
>  }
>  
> -SEC("fmod_ret/bpf_modify_return_test")
> +SEC("fmod_ret/bpf_testmod_trampoline_count_test")
>  int BPF_PROG(fmod_ret_test, int a, int *b, int ret)
>  {
>  	return 0;
>  }
>  
> -SEC("fexit/bpf_modify_return_test")
> +SEC("fexit/bpf_testmod_trampoline_count_test")
>  int BPF_PROG(fexit_test, int a, int *b, int ret)

last part of the trampoline_count test executes the probe through the
kernel's test_run which executes bpf_modify_return_test

I don't think it changes much because the programs are doing nothing
I guess it's there just to make sure the link failure did not screw
up anything

we could call bpf_testmod_trampoline_count_test from
bpf_testmod_test_read and have the test to call
trigger_module_test_read

jirka


>  {
>  	return 0;
> diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
> index e62c6b78657f..6eaceb4dfbec 100644
> --- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
> +++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
> @@ -581,6 +581,12 @@ noinline int bpf_fentry_shadow_test(int a)
>  }
>  EXPORT_SYMBOL_GPL(bpf_fentry_shadow_test);
>  
> +noinline int bpf_testmod_trampoline_count_test(int a, int *b)
> +{
> +	*b += 1;
> +	return a + *b;
> +}
> +
>  __bpf_hook_end();
>  
>  static struct bin_attribute bin_attr_bpf_testmod_file __ro_after_init = {
> @@ -1843,6 +1849,16 @@ struct bpf_struct_ops testmod_multi_st_ops = {
>  
>  extern int bpf_fentry_test1(int a);
>  
> +BTF_KFUNCS_START(bpf_testmod_trampoline_count_ids)
> +BTF_ID_FLAGS(func, bpf_testmod_trampoline_count_test)
> +BTF_KFUNCS_END(bpf_testmod_trampoline_count_ids)
> +
> +static const struct
> +btf_kfunc_id_set bpf_testmod_trampoline_count_fmodret_set = {
> +	.owner = THIS_MODULE,
> +	.set = &bpf_testmod_trampoline_count_ids,
> +};
> +
>  static int bpf_testmod_init(void)
>  {
>  	const struct btf_id_dtor_kfunc bpf_testmod_dtors[] = {
> @@ -1859,6 +1875,7 @@ static int bpf_testmod_init(void)
>  	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &bpf_testmod_kfunc_set);
>  	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SYSCALL, &bpf_testmod_kfunc_set);
>  	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS, &bpf_testmod_kfunc_set);
> +	ret = ret ?: register_btf_fmodret_id_set(&bpf_testmod_trampoline_count_fmodret_set);
>  	ret = ret ?: register_bpf_struct_ops(&bpf_bpf_testmod_ops, bpf_testmod_ops);
>  	ret = ret ?: register_bpf_struct_ops(&bpf_testmod_ops2, bpf_testmod_ops2);
>  	ret = ret ?: register_bpf_struct_ops(&bpf_testmod_ops3, bpf_testmod_ops3);
> 
> base-commit: 8a30aeb0d1b4e4aaf7f7bae72f20f2ae75385ccb
> -- 
> 2.43.0
>
Re: [PATCH v2] selftests/bpf: move trampoline_count to dedicated bpf_testmod target
Posted by Alexei Starovoitov 2 weeks, 4 days ago 
On Wed, Mar 18, 2026 at 9:04 PM Sun Jian <sun.jian.kdev@gmail.com> wrote:
>
> trampoline_count fills all trampoline attachment slots for a single
> target function and verifies that one extra attach fails with -E2BIG.
>
> It currently targets bpf_modify_return_test, which is also used by
> other selftests such as modify_return, get_func_ip_test, and
> get_func_args_test. When such tests run in parallel, they can contend
> for the same per-function trampoline quota and cause unexpected attach
> failures. This issue is currently masked by harness serialization.
>
> Move trampoline_count to a dedicated bpf_testmod target and register it
> for fmod_ret attachment. This keeps the test semantics unchanged while
> isolating it from other selftests, so it no longer needs to run in
> serial mode. Remove the TODO comment as well.
>
> Tested:
>   ./test_progs -t trampoline_count -vv
>   ./test_progs -t modify_return -vv
>   ./test_progs -t get_func_ip_test -vv
>   ./test_progs -t get_func_args_test -vv
>   ./test_progs -j$(nproc) -t trampoline_count -vv
>   ./test_progs -j$(nproc) -t
>     trampoline_count,modify_return,get_func_ip_test,get_func_args_test,\
> kprobe_multi_test -vv
>   20 runs of:
>     ./test_progs -j$(nproc) -t
>     trampoline_count,modify_return,get_func_ip_test,get_func_args_test,\
> kprobe_multi_test
>
> Signed-off-by: Sun Jian <sun.jian.kdev@gmail.com>

if you want to land these patches please participate in code reviews:
https://lore.kernel.org/bpf/CAADnVQ+TKKptnNB25V3=bcdybh5G6c2DyW2sYtXvyRaVnPN8MA@mail.gmail.com/
Re: [PATCH v2] selftests/bpf: move trampoline_count to dedicated bpf_testmod target
Posted by sun jian 2 weeks, 3 days ago 
On Thu, Mar 19, 2026 at 2:14 PM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> if you want to land these patches please participate in code reviews:
> https://lore.kernel.org/bpf/CAADnVQ+TKKptnNB25V3=bcdybh5G6c2DyW2sYtXvyRaVnPN8MA@mail.gmail.com/

Understood.  Will participate in reviews as well.

Sun Jian
[PATCH v2] selftests/bpf: trampoline_count: use dedicated target function
Posted by Sun Jian 2 weeks, 4 days ago 
trampoline_count fills all trampoline attachment slots for a single
target function and verifies that one extra attach fails with -E2BIG.

It currently targets bpf_modify_return_test, which is also used by
modify_return and get_func_ip_test. When those tests run in parallel,
they can contend for the same per-function trampoline quota and
cause unexpected attach failures. This issue is currently masked by
harness serialization.

Add a dedicated bpf_trampoline_count_test target and switch
trampoline_count to use it. This keeps the test semantics unchanged
while isolating it from other modify_return-based selftests, so it no
longer needs to run in serial mode. Remove the TODO comment as
well.

Tested:
  ./test_progs -t trampoline_count -vv
  ./test_progs -t modify_return -vv
  ./test_progs -t get_func_ip_test -vv
  ./test_progs -j$(nproc) -t trampoline_count -vv
  ./test_progs -j$(nproc) -t
    trampoline_count,modify_return,get_func_ip_test -vv

Tested-by: Paul Chaignon <paul.chaignon@gmail.com>
Signed-off-by: Sun Jian <sun.jian.kdev@gmail.com>
---

v2:
- add Paul's Tested-by

 net/bpf/test_run.c                                        | 7 +++++++
 tools/testing/selftests/bpf/prog_tests/trampoline_count.c | 3 +--
 tools/testing/selftests/bpf/progs/test_trampoline_count.c | 6 +++---
 3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index 178c4738e63b..b41147a29f16 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -580,6 +580,12 @@ __bpf_kfunc int bpf_modify_return_test2(int a, int *b, short c, int d,
 	return a + *b + c + d + (long)e + f + g;
 }
 
+__bpf_kfunc int bpf_trampoline_count_test(int a, int *b)
+{
+	*b += 1;
+	return a + *b;
+}
+
 __bpf_kfunc int bpf_modify_return_test_tp(int nonce)
 {
 	trace_bpf_trigger_tp(nonce);
@@ -635,6 +641,7 @@ BTF_KFUNCS_START(bpf_test_modify_return_ids)
 BTF_ID_FLAGS(func, bpf_modify_return_test)
 BTF_ID_FLAGS(func, bpf_modify_return_test2)
 BTF_ID_FLAGS(func, bpf_modify_return_test_tp)
+BTF_ID_FLAGS(func, bpf_trampoline_count_test)
 BTF_ID_FLAGS(func, bpf_fentry_test1, KF_SLEEPABLE)
 BTF_KFUNCS_END(bpf_test_modify_return_ids)
 
diff --git a/tools/testing/selftests/bpf/prog_tests/trampoline_count.c b/tools/testing/selftests/bpf/prog_tests/trampoline_count.c
index 6cd7349d4a2b..b19358aed126 100644
--- a/tools/testing/selftests/bpf/prog_tests/trampoline_count.c
+++ b/tools/testing/selftests/bpf/prog_tests/trampoline_count.c
@@ -30,8 +30,7 @@ static struct bpf_program *load_prog(char *file, char *name, struct inst *inst)
 	return prog;
 }
 
-/* TODO: use different target function to run in concurrent mode */
-void serial_test_trampoline_count(void)
+void test_trampoline_count(void)
 {
 	char *file = "test_trampoline_count.bpf.o";
 	char *const progs[] = { "fentry_test", "fmod_ret_test", "fexit_test" };
diff --git a/tools/testing/selftests/bpf/progs/test_trampoline_count.c b/tools/testing/selftests/bpf/progs/test_trampoline_count.c
index 7765720da7d5..911d282fd423 100644
--- a/tools/testing/selftests/bpf/progs/test_trampoline_count.c
+++ b/tools/testing/selftests/bpf/progs/test_trampoline_count.c
@@ -3,19 +3,19 @@
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_tracing.h>
 
-SEC("fentry/bpf_modify_return_test")
+SEC("fentry/bpf_trampoline_count_test")
 int BPF_PROG(fentry_test, int a, int *b)
 {
 	return 0;
 }
 
-SEC("fmod_ret/bpf_modify_return_test")
+SEC("fmod_ret/bpf_trampoline_count_test")
 int BPF_PROG(fmod_ret_test, int a, int *b, int ret)
 {
 	return 0;
 }
 
-SEC("fexit/bpf_modify_return_test")
+SEC("fexit/bpf_trampoline_count_test")
 int BPF_PROG(fexit_test, int a, int *b, int ret)
 {
 	return 0;

base-commit: 267594792a71018788af69e836c52e34bb8054af
-- 
2.43.0

Patchew 2.1-devel-ea86937

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