From: Arnd Bergmann <arnd@arndb.de>

Building without CONFIG_BPF_EVENTS produces a build-time
warning:

WARN: resolve_btfids: unresolved symbol bpf_session_is_return

The function is actually defined in kernel/trace/bpf_trace.o,
which is built conditionally based on configuration.

Make the reference to this function conditional as well,
as is already done in the bpf verifier for other functions.

Fixes: 8fe4dc4f6456 ("bpf: change prototype of bpf_session_{cookie,is_return}")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 kernel/bpf/verifier.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 03f9e16c2abe..a5139f45e366 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -10882,7 +10882,11 @@ BTF_ID(func, bpf_task_work_schedule_resume)
 BTF_ID(func, bpf_arena_alloc_pages)
 BTF_ID(func, bpf_arena_free_pages)
 BTF_ID(func, bpf_arena_reserve_pages)
+#ifdef CONFIG_BPF_EVENTS
 BTF_ID(func, bpf_session_is_return)
+#else
+BTF_ID_UNUSED
+#endif
 BTF_ID(func, bpf_stream_vprintk)
 BTF_ID(func, bpf_stream_print_stack)
 
-- 
2.39.5

On 5/15/26 2:06 AM, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
>
> Building without CONFIG_BPF_EVENTS produces a build-time
> warning:
>
> WARN: resolve_btfids: unresolved symbol bpf_session_is_return
>
> The function is actually defined in kernel/trace/bpf_trace.o,
> which is built conditionally based on configuration.
>
> Make the reference to this function conditional as well,
> as is already done in the bpf verifier for other functions.
>
> Fixes: 8fe4dc4f6456 ("bpf: change prototype of bpf_session_{cookie,is_return}")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

LGTM exception in subject bpf_session_cookie() should be bpf_session_is_return().

Acked-by: Yonghong Song <yonghong.song@linux.dev>

> commit 2cc68d16a6fde2cca5c308c947ae835c366fe09c
> Author: Arnd Bergmann <arnd@arndb.de>
> Date:   Fri May 15 11:06:15 2026 +0200
>
>     bpf: make bpf_session_cookie() reference optional

The commit subject references bpf_session_cookie(), but the patch actually
makes bpf_session_is_return() conditional. Should the subject line be
updated to reflect the correct function name?

Reference: https://lore.kernel.org/bpf/20260515091607.ED08CC2BCB8@smtp.kernel.org/

>
>     Building without CONFIG_BPF_EVENTS produces a build-time
>     warning:
>
>     WARN: resolve_btfids: unresolved symbol bpf_session_is_return
>
>     The function is actually defined in kernel/trace/bpf_trace.o,
>     which is built conditionally based on configuration.
>
>     Make the reference to this function conditional as well,
>     as is already done in the bpf verifier for other functions.
>
>     Fixes: 8fe4dc4f6456 ("bpf: change prototype of bpf_session_{cookie,is_return}")
>     Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 76a07f09ab64..cec4edc86485 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -11088,7 +11088,11 @@ BTF_ID(func, bpf_task_work_schedule_resume)
>  BTF_ID(func, bpf_arena_alloc_pages)
>  BTF_ID(func, bpf_arena_free_pages)
>  BTF_ID(func, bpf_arena_reserve_pages)
> +#ifdef CONFIG_BPF_EVENTS
>  BTF_ID(func, bpf_session_is_return)
> +#else
> +BTF_ID_UNUSED
> +#endif
>  BTF_ID(func, bpf_stream_vprintk)
>  BTF_ID(func, bpf_stream_print_stack)


---
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/25910298674