netdev - Re: [PATCH v3] tools: bpftool: fix reading from /proc/config.gz

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Date:   Fri, 9 Aug 2019 18:44:11 +0100
From:   Quentin Monnet <quentin.monnet@...ronome.com>
To:     Peter Wu <peter@...ensteyn.nl>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Cc:     netdev@...r.kernel.org, Stanislav Fomichev <sdf@...gle.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>
Subject: Re: [PATCH v3] tools: bpftool: fix reading from /proc/config.gz

2019-08-09 01:39 UTC+0100 ~ Peter Wu <peter@...ensteyn.nl>
> /proc/config has never existed as far as I can see, but /proc/config.gz
> is present on Arch Linux. Add support for decompressing config.gz using
> zlib which is a mandatory dependency of libelf. Replace existing stdio
> functions with gzFile operations since the latter transparently handles
> uncompressed and gzip-compressed files.
> 
> Cc: Quentin Monnet <quentin.monnet@...ronome.com>
> Signed-off-by: Peter Wu <peter@...ensteyn.nl>
> ---
>  v3: replace popen(gunzip) by linking directly to zlib. Reword commit
>      message, remove "Fixes" line. (this patch)
>  v2: fix style (reorder vars as reverse xmas tree, rename function,
>      braces), fallback to /proc/config.gz if uname() fails.
>      https://lkml.kernel.org/r/20190806010702.3303-1-peter@lekensteyn.nl
>  v1: https://lkml.kernel.org/r/20190805001541.8096-1-peter@lekensteyn.nl
> 
> Hi,
> 
> Thanks to Jakub for observing that zlib is already used by libelf, this
> simplifies the patch tremendously as the same API can be used for both
> compressed and uncompressed files. No special case exists anymore for
> fclose/pclose.
> 
> According to configure.ac in elfutils, zlib is mandatory, so I just
> assume it to be available. For simplicity I also silently assume lines
> to be less than 4096 characters. If that is not the case, then lines
> will appear truncated, but that should not be an issue for the
> CONFIG_xyz lines that we are scanning for.
> 
> Jakub requested the handle leak fix to be posted separately against the
> bpf tree, but since the whole code is rewritten I am not sure if it is
> worth it. It is an unusual edge case: /boot/config-$(uname -r) could be
> opened, but starts with unexpected data.
> 
> Kind regards,
> Peter

This version seems good to me, thanks!

Reviewed-by: Quentin Monnet <quentin.monnet@...ronome.com>