linux-kernel - Re: [PATCH -mm v2] coredump: extend core dump note section to contain file names of mapped files

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Message-Id: <20120918165819.583252C0A4@topped-with-meat.com>
Date:	Tue, 18 Sep 2012 09:58:19 -0700 (PDT)
From:	Roland McGrath <roland@...k.frob.com>
To:	Denys Vlasenko <vda.linux@...glemail.com>
Cc:	Oleg Nesterov <oleg@...hat.com>, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Amerigo Wang <amwang@...hat.com>,
	"Jonathan M. Foote" <jmfoote@...t.org>,
	Pedro Alves <palves@...hat.com>
Subject: Re: [PATCH -mm v2] coredump: extend core dump note section to contain file names of mapped files

The code needs to be macroized a bit so that compat_binfmt_elf.c will
produce a version that encodes 32-bit values correctly so as to be
compatible with the output of a native 32-bit kernel.

It's doubtful that rolling your own single loop actually performs better
than just calling strlen and memcpy.

Since you're just counting to estimate the size of a temporary buffer,
you could skip the initial loop and just estimate based on mm->map_count.
Then collect the count in the main loop and write the first word of the
buffer last.

Thanks,
Roland
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