netdev - Re: [PATCH bpf-next v4 00/21] bpf: implement bpf iterator for kernel data

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Message-ID: <20200510002731.ztx2inlfs65x2izc@ast-mbp>
Date:   Sat, 9 May 2020 17:27:31 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Yonghong Song <yhs@...com>
Cc:     Andrii Nakryiko <andriin@...com>, bpf@...r.kernel.org,
        Martin KaFai Lau <kafai@...com>, netdev@...r.kernel.org,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>, kernel-team@...com
Subject: Re: [PATCH bpf-next v4 00/21] bpf: implement bpf iterator for kernel
 data

On Sat, May 09, 2020 at 10:58:59AM -0700, Yonghong Song wrote:
> 
> Changelog:
>   v3 -> v4:
>     - in bpf_seq_read(), if start() failed with an error, return that
>       error to user space (Andrii)
>     - in bpf_seq_printf(), if reading kernel memory failed for
>       %s and %p{i,I}{4,6}, set buffer to empty string or address 0.
>       Documented this behavior in uapi header (Andrii)
>     - fix a few error handling issues for bpftool (Andrii)
>     - A few other minor fixes and cosmetic changes.

Looks great overall. Applied.
But few follow ups are necessary.

The main gotcha is that new tests need llvm with the fix
https://reviews.llvm.org/D78466.
I think it was applied to llvm 10 branch already,
but please add selftests/bpf/README.rst and mention
that above llvm commit is necessary to successfully pass the tests.
Also mention the verifier error that folks will see when llvm is buggy.

Few other nits I noticed in relevant patches.