linux-kernel - Re: [PATCH] selftests/lkdtm: Use "comm" instead of "diff" for dmesg

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Message-ID: <87lfk68lph.fsf@mpe.ellerman.id.au>
Date:   Mon, 29 Jun 2020 15:50:18 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Kees Cook <keescook@...omium.org>
Cc:     Shuah Khan <shuah@...nel.org>,
        Naresh Kamboju <naresh.kamboju@...aro.org>,
        Petr Mladek <pmladek@...e.com>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] selftests/lkdtm: Use "comm" instead of "diff" for dmesg

Kees Cook <keescook@...omium.org> writes:
> On Sat, Jun 27, 2020 at 09:51:31PM +1000, Michael Ellerman wrote:
>> Kees Cook <keescook@...omium.org> writes:
>> > Instead of full GNU diff (which smaller boot environments may not have),
>> > use "comm" which is more available.
>> 
>> Although using "comm" requires CONFIG_PRINTK_TIME=y doesn't it?
>
> No, it doesn't seem to. "comm" doesn't carry about the line prefixes.
> AIUI, the only reason for a mention of "sort" is because of how "comm"
> does its line pairing. i.e. as soon as it goes out of sync, it starts
> accounting for the disjunction between files. But that's exactly what we
> want it doing, and the prefix doesn't matter.

OK, if it works.

cheers