linux-kernel - Re: [PATCH] bpf: Fix test_verifier after introducing resolve_pseudo

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Date:   Tue, 6 Oct 2020 17:50:52 -0700
From:   Hao Luo <haoluo@...gle.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andriin@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>
Subject: Re: [PATCH] bpf: Fix test_verifier after introducing resolve_pseudo_ldimm64

On Tue, Oct 6, 2020 at 5:43 PM Andrii Nakryiko
<andrii.nakryiko@...il.com> wrote:
>
> On Tue, Oct 6, 2020 at 4:45 PM Hao Luo <haoluo@...gle.com> wrote:
> >
> > Commit 4976b718c355 ("bpf: Introduce pseudo_btf_id") switched
> > the order of check_subprogs() and resolve_pseudo_ldimm() in
> > the verifier. Now an empty prog and the prog of a single
> > invalid ldimm expect to see the error "last insn is not an
> > exit or jmp" instead, because the check for subprogs comes
> > first. Fix the expection of the error message.
> >
> > Tested:
> >  # ./test_verifier
> >  Summary: 1130 PASSED, 538 SKIPPED, 0 FAILED
> >  and the full set of bpf selftests.
> >
> > Fixes: 4976b718c355 ("bpf: Introduce pseudo_btf_id")
> > Signed-off-by: Hao Luo <haoluo@...gle.com>
> > ---
[...]
> > diff --git a/tools/testing/selftests/bpf/verifier/ld_imm64.c b/tools/testing/selftests/bpf/verifier/ld_imm64.c
> > index 3856dba733e9..f300ba62edd0 100644
> > --- a/tools/testing/selftests/bpf/verifier/ld_imm64.c
> > +++ b/tools/testing/selftests/bpf/verifier/ld_imm64.c
> > @@ -55,7 +55,7 @@
> >         .insns = {
> >         BPF_RAW_INSN(BPF_LD | BPF_IMM | BPF_DW, 0, 0, 0, 0),
> >         },
> > -       .errstr = "invalid bpf_ld_imm64 insn",
> > +       .errstr = "last insn is not an exit or jmp",
>
> but this completely defeats the purpose of the test; better add
> BPF_EXIT_INSN() after ldimm64 instruction to actually get to
> validation of ldimm64
>

Actually there is already a test (test4) that covers this case. So it
makes sense to remove it, I think. I will resend with this change.

> >         .result = REJECT,
> >  },
> >  {
> > --
> > 2.28.0.806.g8561365e88-goog
> >