Re: [PATCH bpf-next v10 11/12] selftests/bpf: add testcases for fsession cookie

[Menglong Dong <menglong.dong@linux.dev>]

On 2026/1/22 08:07 Andrii Nakryiko <andrii.nakryiko@gmail.com> write:
> On Thu, Jan 15, 2026 at 3:24 AM Menglong Dong <menglong8.dong@gmail.com> wrote:
> >
> > Test session cookie for fsession. Multiple fsession BPF progs is attached
> > to bpf_fentry_test1() and session cookie is read and write in the
> > testcase.
> >
> > Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
> > ---
> > v3:
> > - restructure the testcase by combine the testcases for session cookie and
> >   get_func_ip into one patch
> > ---
> >  .../selftests/bpf/progs/fsession_test.c       | 53 +++++++++++++++++++
> >  1 file changed, 53 insertions(+)
> >
> > diff --git a/tools/testing/selftests/bpf/progs/fsession_test.c b/tools/testing/selftests/bpf/progs/fsession_test.c
> > index f504984d42f2..4e55ca67db46 100644
> > --- a/tools/testing/selftests/bpf/progs/fsession_test.c
> > +++ b/tools/testing/selftests/bpf/progs/fsession_test.c
> > @@ -108,3 +108,56 @@ int BPF_PROG(test6, int a)
> >                 test6_entry_result = (const void *) addr == &bpf_fentry_test1;
> >         return 0;
> >  }
> > +
> > +__u64 test7_entry_ok = 0;
> > +__u64 test7_exit_ok = 0;
> > +SEC("fsession/bpf_fentry_test1")
> > +int BPF_PROG(test7, int a)
> > +{
> > +       __u64 *cookie = bpf_session_cookie(ctx);
> > +
> > +       if (!bpf_session_is_return(ctx)) {
> > +               *cookie = 0xAAAABBBBCCCCDDDDull;
> > +               test7_entry_ok = *cookie == 0xAAAABBBBCCCCDDDDull;
> 
> you are trying to double-check that writing into *cookie preserves the
> written value, is that right? Do we need volatile read here to ensure
> that compiler doesn't optimize this?

Yeah, you are right. READ_ONCE and WRITE_ONCE should be used
here. I'll use them next version.

Thanks!
Menglong Dong

> 
> > +               return 0;
> > +       }
> > +
> > +       test7_exit_ok = *cookie == 0xAAAABBBBCCCCDDDDull;
> > +       return 0;
> > +}
> > +
> > +__u64 test8_entry_ok = 0;
> > +__u64 test8_exit_ok = 0;
> > +
> > +SEC("fsession/bpf_fentry_test1")
> > +int BPF_PROG(test8, int a)
> > +{
> > +       __u64 *cookie = bpf_session_cookie(ctx);
> > +
> > +       if (!bpf_session_is_return(ctx)) {
> > +               *cookie = 0x1111222233334444ull;
> > +               test8_entry_ok = *cookie == 0x1111222233334444ull;
> > +               return 0;
> > +       }
> > +
> > +       test8_exit_ok = *cookie == 0x1111222233334444ull;
> > +       return 0;
> > +}
> > +
> > +__u64 test9_entry_result = 0;
> > +__u64 test9_exit_result = 0;
> > +
> > +SEC("fsession/bpf_fentry_test1")
> > +int BPF_PROG(test9, int a, int ret)
> > +{
> > +       __u64 *cookie = bpf_session_cookie(ctx);
> > +
> > +       if (!bpf_session_is_return(ctx)) {
> > +               test9_entry_result = a == 1 && ret == 0;
> > +               *cookie = 0x123456ULL;
> > +               return 0;
> > +       }
> > +
> > +       test9_exit_result = a == 1 && ret == 2 && *cookie == 0x123456ULL;
> > +       return 0;
> > +}
> > --
> > 2.52.0
> >
>