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Message-ID: <CADxym3Zu1eYTVzprqe7_8zxhzaZHKAvVKKusa-uK150Huq1mnQ@mail.gmail.com>
Date: Wed, 12 Jul 2023 11:59:49 +0800
From: Menglong Dong <menglong8.dong@...il.com>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: yhs@...a.com, daniel@...earbox.net, ast@...nel.org,
andrii@...nel.org, martin.lau@...ux.dev, song@...nel.org,
yhs@...com, john.fastabend@...il.com, kpsingh@...nel.org,
sdf@...gle.com, haoluo@...gle.com, dsahern@...nel.org,
jolsa@...nel.org, x86@...nel.org, bpf@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
Menglong Dong <imagedong@...cent.com>
Subject: Re: [PATCH RESEND bpf-next v8 3/3] selftests/bpf: add testcase for
TRACING with 6+ arguments
On Wed, Jul 12, 2023 at 7:25 AM Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
>
> On Mon, Jul 10, 2023 at 06:48:34PM +0800, menglong8.dong@...il.com wrote:
> > From: Menglong Dong <imagedong@...cent.com>
> >
> > Add fentry_many_args.c and fexit_many_args.c to test the fentry/fexit
> > with 7/11 arguments. As this feature is not supported by arm64 yet, we
> > disable these testcases for arm64 in DENYLIST.aarch64. We can combine
> > them with fentry_test.c/fexit_test.c when arm64 is supported too.
> >
> > Correspondingly, add bpf_testmod_fentry_test7() and
> > bpf_testmod_fentry_test11() to bpf_testmod.c
> >
> > Meanwhile, add bpf_modify_return_test2() to test_run.c to test the
> > MODIFY_RETURN with 7 arguments.
> >
> > Add bpf_testmod_test_struct_arg_7/bpf_testmod_test_struct_arg_7 in
> > bpf_testmod.c to test the struct in the arguments.
> >
> > And the testcases passed on x86_64:
> >
> > ./test_progs -t fexit
> > Summary: 5/14 PASSED, 0 SKIPPED, 0 FAILED
> >
> > ./test_progs -t fentry
> > Summary: 3/2 PASSED, 0 SKIPPED, 0 FAILED
> >
> > ./test_progs -t modify_return
> > Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED
> >
> > ./test_progs -t tracing_struct
> > Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED
> >
> > Signed-off-by: Menglong Dong <imagedong@...cent.com>
> > Acked-by: Yonghong Song <yhs@...com>
> > ---
> > v8:
> > - split the testcases, and add fentry_many_args/fexit_many_args to
> > DENYLIST.aarch64
> > v6:
> > - add testcases to tracing_struct.c instead of fentry_test.c and
> > fexit_test.c
> > v5:
> > - add testcases for MODIFY_RETURN
> > v4:
> > - use different type for args in bpf_testmod_fentry_test{7,12}
> > - add testcase for grabage values in ctx
> > v3:
> > - move bpf_fentry_test{7,12} to bpf_testmod.c and rename them to
> > bpf_testmod_fentry_test{7,12} meanwhile
> > - get return value by bpf_get_func_ret() in
> > "fexit/bpf_testmod_fentry_test12", as we don't change ___bpf_ctx_cast()
> > in this version
> > ---
> > net/bpf/test_run.c | 23 ++++++--
> > tools/testing/selftests/bpf/DENYLIST.aarch64 | 2 +
> > .../selftests/bpf/bpf_testmod/bpf_testmod.c | 49 ++++++++++++++++-
> > .../selftests/bpf/prog_tests/fentry_test.c | 43 +++++++++++++--
> > .../selftests/bpf/prog_tests/fexit_test.c | 43 +++++++++++++--
> > .../selftests/bpf/prog_tests/modify_return.c | 20 ++++++-
> > .../selftests/bpf/prog_tests/tracing_struct.c | 19 +++++++
> > .../selftests/bpf/progs/fentry_many_args.c | 39 ++++++++++++++
> > .../selftests/bpf/progs/fexit_many_args.c | 40 ++++++++++++++
> > .../selftests/bpf/progs/modify_return.c | 40 ++++++++++++++
> > .../selftests/bpf/progs/tracing_struct.c | 54 +++++++++++++++++++
> > 11 files changed, 358 insertions(+), 14 deletions(-)
> > create mode 100644 tools/testing/selftests/bpf/progs/fentry_many_args.c
> > create mode 100644 tools/testing/selftests/bpf/progs/fexit_many_args.c
> >
> > diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
> > index 63b11f7a5392..1c59fa60077b 100644
> > --- a/net/bpf/test_run.c
> > +++ b/net/bpf/test_run.c
> > @@ -565,6 +565,13 @@ __bpf_kfunc int bpf_modify_return_test(int a, int *b)
> > return a + *b;
> > }
> >
> > +__bpf_kfunc int bpf_modify_return_test2(int a, int *b, short c, int d,
> > + void *e, char f, int g)
> > +{
> > + *b += 1;
> > + return a + *b + c + d + (long)e + f + g;
> > +}
> > +
> > int noinline bpf_fentry_shadow_test(int a)
> > {
> > return a + 1;
> > @@ -600,9 +607,13 @@ __diag_pop();
> >
> > BTF_SET8_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_fentry_test1, KF_SLEEPABLE)
> > BTF_SET8_END(bpf_test_modify_return_ids)
> >
> > +BTF_ID_LIST(bpf_modify_return_test_id)
> > +BTF_ID(func, bpf_modify_return_test)
> > +
> > static const struct btf_kfunc_id_set bpf_test_modify_return_set = {
> > .owner = THIS_MODULE,
> > .set = &bpf_test_modify_return_ids,
> > @@ -665,9 +676,15 @@ int bpf_prog_test_run_tracing(struct bpf_prog *prog,
> > goto out;
> > break;
> > case BPF_MODIFY_RETURN:
> > - ret = bpf_modify_return_test(1, &b);
> > - if (b != 2)
> > - side_effect = 1;
> > + if (prog->aux->attach_btf_id == *bpf_modify_return_test_id) {
> > + ret = bpf_modify_return_test(1, &b);
> > + if (b != 2)
> > + side_effect = 1;
> > + } else {
> > + ret = bpf_modify_return_test2(1, &b, 3, 4, (void *)5, 6, 7);
> > + if (b != 2)
> > + side_effect = 1;
>
> Patches 1 and 2 look good, but I don't like where this check will lead us:
> attach_btf_id == *bpf_modify_return_test_id...
>
Yeah, I don't like it either, which makes the code weak.
> When Jiri did a conversion of all test func into bpf_testmod.ko I forgot
> why we couldn't move fmod_ret tests as well.
> Whatever it was the extra attach_btf_id check will make it worse.
>
I think it's because the side effect can't be verified
by the BPF program, which makes it have to be run by
bpf_prog_test_run_opts().
> For now please think of a way to test fmod_ret when bpf_prog_test_run_tracing()
> does something unconditional like:
> ret = bpf_modify_return_test(1, &b);
> if (b != 2)
> side_effect++;
> ret = bpf_modify_return_test2(1, &b, 3, 4, (void *)5, 6, 7);
Should it be like this?
ret += bpf_modify_return_test2(1, &b, 3, 4, (void *)5, 6, 7);
Or the return of bpf_modify_return_test() can't be verified.
> if (b != 2)
> side_effect++;
Thanks!
Menglong Dong
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