On Mon, Jun 10, 2024 at 6:04 AM Jiri Olsa <olsajiri@xxxxxxxxx> wrote:
>
> On Sat, Jun 08, 2024 at 03:16:02PM -0600, Daniel Xu wrote:
> > The prototype defined in bpf_kfuncs.h was not in line with how the
> > actual kfunc was defined. This causes compilation errors when kfunc
> > prototypes are generated from BTF.
> >
> > Fix by aligning with actual kfunc definition.
> >
> > Signed-off-by: Daniel Xu <dxu@xxxxxxxxx>
> > ---
> > tools/testing/selftests/bpf/bpf_kfuncs.h | 2 +-
> > tools/testing/selftests/bpf/progs/kprobe_multi_session_cookie.c | 2 +-
> > 2 files changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/tools/testing/selftests/bpf/bpf_kfuncs.h b/tools/testing/selftests/bpf/bpf_kfuncs.h
> > index be91a6919315..3b6675ab4086 100644
> > --- a/tools/testing/selftests/bpf/bpf_kfuncs.h
> > +++ b/tools/testing/selftests/bpf/bpf_kfuncs.h
> > @@ -77,5 +77,5 @@ extern int bpf_verify_pkcs7_signature(struct bpf_dynptr *data_ptr,
> > struct bpf_key *trusted_keyring) __ksym;
> >
> > extern bool bpf_session_is_return(void) __ksym __weak;
> > -extern long *bpf_session_cookie(void) __ksym __weak;
> > +extern __u64 *bpf_session_cookie(void) __ksym __weak;
>
> the original intent was to expose long instead of __u64 :-\
>
Cookies internally are always u64 (8 byte values). Marking them
internally in the kernel as long could lead to problems on 32-bit
architectures, potentially (it still needs to be 64-bit value
according to BPF contract, but we'll allocate only 4 bytes for them).
It seems better and safer to be explicit with __u64/u64 for cookies everywhere.
What am I missing?
> could we rather change the bpf_session_cookie function to return long?
> should be just return value type change
>
> thanks,
> jirka
>
>
> > #endif
> > diff --git a/tools/testing/selftests/bpf/progs/kprobe_multi_session_cookie.c b/tools/testing/selftests/bpf/progs/kprobe_multi_session_cookie.c
> > index d49070803e22..0835b5edf685 100644
> > --- a/tools/testing/selftests/bpf/progs/kprobe_multi_session_cookie.c
> > +++ b/tools/testing/selftests/bpf/progs/kprobe_multi_session_cookie.c
> > @@ -25,7 +25,7 @@ int BPF_PROG(trigger)
> >
> > static int check_cookie(__u64 val, __u64 *result)
> > {
> > - long *cookie;
> > + __u64 *cookie;
> >
> > if (bpf_get_current_pid_tgid() >> 32 != pid)
> > return 1;
> > --
> > 2.44.0
> >
