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

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Date:   Tue, 6 Oct 2020 17:43:46 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Hao Luo <haoluo@...gle.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 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>
> ---
>  tools/testing/selftests/bpf/verifier/basic.c    | 2 +-
>  tools/testing/selftests/bpf/verifier/ld_imm64.c | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/verifier/basic.c b/tools/testing/selftests/bpf/verifier/basic.c
> index b8d18642653a..de84f0d57082 100644
> --- a/tools/testing/selftests/bpf/verifier/basic.c
> +++ b/tools/testing/selftests/bpf/verifier/basic.c
> @@ -2,7 +2,7 @@
>         "empty prog",
>         .insns = {
>         },
> -       .errstr = "unknown opcode 00",
> +       .errstr = "last insn is not an exit or jmp",

in this case the new message makes more sense, so this is a good change

>         .result = REJECT,
>  },
>  {
> 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

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