Re: [PATCH bpf-next 6/7] bpf: Add test ops for BPF_PROG_TYPE_TRACING

[KP Singh]

On 03-Mär 14:51, Andrii Nakryiko wrote:
> On Tue, Mar 3, 2020 at 6:12 AM KP Singh <kpsingh@xxxxxxxxxxxx> wrote:
> >
> > From: KP Singh <kpsingh@xxxxxxxxxx>
> >
> > The current fexit and fentry tests rely on a different program to
> > exercise the functions they attach to. Instead of doing this, implement
> > the test operations for tracing which will also be used for
> > BPF_OVERRIDE_RETURN in a subsequent patch.
> 
> typo: BPF_OVERRIDE_RETURN -> BPF_MODIFY_RETURN?

Oops :) Fixed. Thanks! Artifacts of renaming.

> 
> >
> > Also, clean up the fexit test to use the generated skeleton.
> >
> > Signed-off-by: KP Singh <kpsingh@xxxxxxxxxx>
> > ---
> 
> Nice clean up for fexit_test, thank you!

It was very satisfying :)

> 
> >  include/linux/bpf.h                           | 10 +++
> >  kernel/trace/bpf_trace.c                      |  1 +
> >  net/bpf/test_run.c                            | 38 +++++++---
> >  .../selftests/bpf/prog_tests/fentry_fexit.c   | 12 +---
> >  .../selftests/bpf/prog_tests/fentry_test.c    | 14 ++--
> >  .../selftests/bpf/prog_tests/fexit_test.c     | 69 ++++++-------------
> >  6 files changed, 68 insertions(+), 76 deletions(-)
> >
> > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > index 3cfdc216a2f4..c00919025532 100644
> > --- a/include/linux/bpf.h
> > +++ b/include/linux/bpf.h
> > @@ -1156,6 +1156,9 @@ int bpf_prog_test_run_xdp(struct bpf_prog *prog, const union bpf_attr *kattr,
> >                           union bpf_attr __user *uattr);
> >  int bpf_prog_test_run_skb(struct bpf_prog *prog, const union bpf_attr *kattr,
> >                           union bpf_attr __user *uattr);
> > +int bpf_prog_test_run_tracing(struct bpf_prog *prog,
> > +                             const union bpf_attr *kattr,
> > +                             union bpf_attr __user *uattr);
> >  int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,
> >                                      const union bpf_attr *kattr,
> >                                      union bpf_attr __user *uattr);
> > @@ -1313,6 +1316,13 @@ static inline int bpf_prog_test_run_skb(struct bpf_prog *prog,
> >         return -ENOTSUPP;
> >  }
> >
> > +static inline int bpf_prog_test_run_tracing(struct bpf_prog *prog,
> > +                                           const union bpf_attr *kattr,
> > +                                           union bpf_attr __user *uattr)
> > +{
> > +       return -ENOTSUPP;
> > +}
> > +
> >  static inline int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,
> >                                                    const union bpf_attr *kattr,
> >                                                    union bpf_attr __user *uattr)
> > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> > index 07764c761073..363e0a2c75cf 100644
> > --- a/kernel/trace/bpf_trace.c
> > +++ b/kernel/trace/bpf_trace.c
> > @@ -1266,6 +1266,7 @@ const struct bpf_verifier_ops tracing_verifier_ops = {
> >  };
> >
> >  const struct bpf_prog_ops tracing_prog_ops = {
> > +       .test_run = bpf_prog_test_run_tracing,
> >  };
> >
> >  static bool raw_tp_writable_prog_is_valid_access(int off, int size,
> > diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
> > index 562443f94133..fb54b45285b4 100644
> > --- a/net/bpf/test_run.c
> > +++ b/net/bpf/test_run.c
> > @@ -160,18 +160,38 @@ static void *bpf_test_init(const union bpf_attr *kattr, u32 size,
> >                 kfree(data);
> >                 return ERR_PTR(-EFAULT);
> >         }
> > -       if (bpf_fentry_test1(1) != 2 ||
> > -           bpf_fentry_test2(2, 3) != 5 ||
> > -           bpf_fentry_test3(4, 5, 6) != 15 ||
> > -           bpf_fentry_test4((void *)7, 8, 9, 10) != 34 ||
> > -           bpf_fentry_test5(11, (void *)12, 13, 14, 15) != 65 ||
> > -           bpf_fentry_test6(16, (void *)17, 18, 19, (void *)20, 21) != 111) {
> > -               kfree(data);
> > -               return ERR_PTR(-EFAULT);
> > -       }
> > +
> >         return data;
> >  }
> >
> > +int bpf_prog_test_run_tracing(struct bpf_prog *prog,
> > +                             const union bpf_attr *kattr,
> > +                             union bpf_attr __user *uattr)
> > +{
> > +       int err = -EFAULT;
> > +
> > +       switch (prog->expected_attach_type) {
> > +       case BPF_TRACE_FENTRY:
> > +       case BPF_TRACE_FEXIT:
> > +               if (bpf_fentry_test1(1) != 2 ||
> > +                   bpf_fentry_test2(2, 3) != 5 ||
> > +                   bpf_fentry_test3(4, 5, 6) != 15 ||
> > +                   bpf_fentry_test4((void *)7, 8, 9, 10) != 34 ||
> > +                   bpf_fentry_test5(11, (void *)12, 13, 14, 15) != 65 ||
> > +                   bpf_fentry_test6(16, (void *)17, 18, 19, (void *)20, 21) != 111)
> > +                       goto out;
> > +               break;
> > +       default:
> > +               goto out;
> > +       }
> 
> No trace_bpf_test_finish here?

Ah yes, we trace it not ony for erroneous cases. Changed it to
setting err = 0 and falling through to the trace_bpf_test_finish.

- KP

> 
> > +
> > +       return 0;
> > +
> > +out:
> > +       trace_bpf_test_finish(&err);
> > +       return err;
> > +}
> > +
> >  static void *bpf_ctx_init(const union bpf_attr *kattr, u32 max_size)
> >  {
> >         void __user *data_in = u64_to_user_ptr(kattr->test.ctx_in);
> 
> [...]