Re: [PATCH 16/19] selftests/bpf: Add fentry multi func test

[Andrii Nakryiko <andrii.nakryiko@gmail.com>]

On Wed, Jun 9, 2021 at 7:29 AM Jiri Olsa <jolsa@redhat.com> wrote:
>
> On Tue, Jun 08, 2021 at 10:40:24PM -0700, Andrii Nakryiko wrote:
> > On Sat, Jun 5, 2021 at 4:12 AM Jiri Olsa <jolsa@kernel.org> wrote:
> > >
> > > Adding selftest for fentry multi func test that attaches
> > > to bpf_fentry_test* functions and checks argument values
> > > based on the processed function.
> > >
> > > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > > ---
> > >  tools/testing/selftests/bpf/multi_check.h     | 52 +++++++++++++++++++
> > >  .../bpf/prog_tests/fentry_multi_test.c        | 43 +++++++++++++++
> > >  .../selftests/bpf/progs/fentry_multi_test.c   | 18 +++++++
> > >  3 files changed, 113 insertions(+)
> > >  create mode 100644 tools/testing/selftests/bpf/multi_check.h
> > >  create mode 100644 tools/testing/selftests/bpf/prog_tests/fentry_multi_test.c
> > >  create mode 100644 tools/testing/selftests/bpf/progs/fentry_multi_test.c
> > >
> > > diff --git a/tools/testing/selftests/bpf/multi_check.h b/tools/testing/selftests/bpf/multi_check.h
> > > new file mode 100644
> > > index 000000000000..36c2a93f9be3
> > > --- /dev/null
> > > +++ b/tools/testing/selftests/bpf/multi_check.h
> >
> > we have a proper static linking now, we don't have to use header
> > inclusion hacks, let's do this properly?
>
> ok, will change
>
> >
> > > @@ -0,0 +1,52 @@
> > > +/* SPDX-License-Identifier: GPL-2.0 */
> > > +
> > > +#ifndef __MULTI_CHECK_H
> > > +#define __MULTI_CHECK_H
> > > +
> > > +extern unsigned long long bpf_fentry_test[8];
> > > +
> > > +static __attribute__((unused)) inline
> > > +void multi_arg_check(unsigned long ip, __u64 a, __u64 b, __u64 c, __u64 d, __u64 e, __u64 f, __u64 *test_result)
> > > +{
> > > +       if (ip == bpf_fentry_test[0]) {
> > > +               *test_result += (int) a == 1;
> > > +       } else if (ip == bpf_fentry_test[1]) {
> > > +               *test_result += (int) a == 2 && (__u64) b == 3;
> > > +       } else if (ip == bpf_fentry_test[2]) {
> > > +               *test_result += (char) a == 4 && (int) b == 5 && (__u64) c == 6;
> > > +       } else if (ip == bpf_fentry_test[3]) {
> > > +               *test_result += (void *) a == (void *) 7 && (char) b == 8 && (int) c == 9 && (__u64) d == 10;
> > > +       } else if (ip == bpf_fentry_test[4]) {
> > > +               *test_result += (__u64) a == 11 && (void *) b == (void *) 12 && (short) c == 13 && (int) d == 14 && (__u64) e == 15;
> > > +       } else if (ip == bpf_fentry_test[5]) {
> > > +               *test_result += (__u64) a == 16 && (void *) b == (void *) 17 && (short) c == 18 && (int) d == 19 && (void *) e == (void *) 20 && (__u64) f == 21;
> > > +       } else if (ip == bpf_fentry_test[6]) {
> > > +               *test_result += 1;
> > > +       } else if (ip == bpf_fentry_test[7]) {
> > > +               *test_result += 1;
> > > +       }
> >
> > why not use switch? and why the casting?
>
> hum, for switch I'd need constants right?

doh, of course :)

but! you don't need to fill out bpf_fentry_test[] array from
user-space, just use extern const void variables to get addresses of
those functions:

extern const void bpf_fentry_test1 __ksym;
extern const void bpf_fentry_test2 __ksym;
...

>
> casting is extra ;-) wanted to check the actual argument types,
> but probably makes no sense

probably doesn't given you already declared it u64 and use integer
values for comparison

>
> will check
>
> >
> > > +}
> > > +
> >
> > [...]
> >
> > > diff --git a/tools/testing/selftests/bpf/progs/fentry_multi_test.c b/tools/testing/selftests/bpf/progs/fentry_multi_test.c
> > > new file mode 100644
> > > index 000000000000..a443fc958e5a
> > > --- /dev/null
> > > +++ b/tools/testing/selftests/bpf/progs/fentry_multi_test.c
> > > @@ -0,0 +1,18 @@
> > > +// SPDX-License-Identifier: GPL-2.0
> > > +#include <linux/bpf.h>
> > > +#include <bpf/bpf_helpers.h>
> > > +#include <bpf/bpf_tracing.h>
> > > +#include "multi_check.h"
> > > +
> > > +char _license[] SEC("license") = "GPL";
> > > +
> > > +unsigned long long bpf_fentry_test[8];
> > > +
> > > +__u64 test_result = 0;
> > > +
> > > +SEC("fentry.multi/bpf_fentry_test*")
> >
> > wait, that's a regexp syntax that libc supports?.. Not .*? We should
> > definitely not provide btf__find_by_pattern_kind() API, I'd like to
> > avoid explaining what flavors of regexps libbpf supports.
>
> ok
>
> thanks,
> jirka
>