Re: Re: [PATCH v2 0/2] Fix failure to access u32* argument of tracked function

[Feng Zhou]

在 2023/4/7 18:49, Feng Zhou 写道:
> 在 2023/4/7 17:33, Jiri Olsa 写道:
> > On Fri, Apr 07, 2023 at 04:46:06PM +0800, Feng zhou wrote:
> > > From: Feng Zhou<zhoufeng.zf@xxxxxxxxxxxxx>
> > >
> > > When access traced function arguments with type is u32*, bpf 
> > > verifier failed.
> > > Because u32 have typedef, needs to skip modifier. Add 
> > > btf_type_is_modifier in
> > > is_int_ptr. Add a selftest to check it.
> > >
> > > Feng Zhou (2):
> > >    bpf/btf: Fix is_int_ptr()
> > >    selftests/bpf: Add test to access u32 ptr argument in tracing 
> > > program
> > hi,
> > it breaks several tests in test_progs suite:
> >
> > #11/36   bpf_iter/link-iter:FAIL
> > #11      bpf_iter:FAIL
> > test_dummy_st_ops_attach:FAIL:dummy_st_ops_load unexpected error: -13
> > #63/1    dummy_st_ops/dummy_st_ops_attach:FAIL
> > test_dummy_init_ret_value:FAIL:dummy_st_ops_load unexpected error: -13
> > #63/2    dummy_st_ops/dummy_init_ret_value:FAIL
> > test_dummy_init_ptr_arg:FAIL:dummy_st_ops_load unexpected error: -13
> > #63/3    dummy_st_ops/dummy_init_ptr_arg:FAIL
> > test_dummy_multiple_args:FAIL:dummy_st_ops_load unexpected error: -13
> > #63/4    dummy_st_ops/dummy_multiple_args:FAIL
> > test_dummy_sleepable:FAIL:dummy_st_ops_load unexpected error: -13
> > #63/5    dummy_st_ops/dummy_sleepable:FAIL
> > #63      dummy_st_ops:FAIL
> > test_fentry_fexit:FAIL:fentry_skel_load unexpected error: -13
> > #69      fentry_fexit:FAIL
> > test_fentry_test:FAIL:fentry_skel_load unexpected error: -13
> > #70      fentry_test:FAIL
> >
> > jirka
>
> I tried it, and it did cause the test to fail. Bpfverify reported an 
> error,
> 'R1 invalid mem access'scalar', let me confirm the reason.

I used btf_type_skip_modifiers，but did not delete
the previous "t = btf_type_by_id (btf, t- > type);"
resulting in some testcases failing. I will send a
v3 nextweek, thank you for your suggestion.


> > > Changelog:
> > > v1->v2: Addressed comments from Martin KaFai Lau
> > > - Add a selftest.
> > > - use btf_type_skip_modifiers.
> > > Some details in here:
> > > https://lore.kernel.org/all/20221012125815.76120-1-zhouchengming@xxxxxxxxxxxxx/ 
> > >
> > >
> > >   kernel/bpf/btf.c                                    |  5 ++---
> > >   net/bpf/test_run.c                                  |  8 +++++++-
> > >   .../testing/selftests/bpf/verifier/btf_ctx_access.c | 13 
> > > +++++++++++++
> > >   3 files changed, 22 insertions(+), 4 deletions(-)
> > >
> > > --
> > > 2.20.1