linux-kernel - Re: [PATCH 0/3] add new strscpy() API for string copy

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Message-ID: <1431911611.13218.1.camel@ellerman.id.au>
Date:	Mon, 18 May 2015 11:13:31 +1000
From:	Michael Ellerman <mpe@...erman.id.au>
To:	Chris Metcalf <cmetcalf@...hip.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Fabian Frederick <fabf@...net.be>,
	Randy Dunlap <rdunlap@...radead.org>,
	Rickard Strandqvist <rickard_strandqvist@...ctrumdigital.se>,
	gregkh@...uxfoundation.org, Peter Zijlstra <peterz@...radead.org>,
	"David S. Miller" <davem@...emloft.net>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Sam Ravnborg <sam@...nborg.org>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Theodore Ts'o <tytso@....edu>,
	Grant Likely <grant.likely@...aro.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-arch@...r.kernel.org
Subject: Re: [PATCH 0/3] add new strscpy() API for string copy

On Fri, 2015-05-15 at 11:15 -0400, Chris Metcalf wrote:
> On 05/14/2015 07:10 PM, Michael Ellerman wrote:
> > On Thu, 2015-04-30 at 12:01 -0400, Chris Metcalf wrote:
> >>
> >> I tested the implementation with a simple user-space harness, so I
> >> believe it is correct for the corner cases I could think of.  In
> >> particular I pairwise-tested all the unaligned values of source and
> >> dest, and tested the restriction on src page-crossing at all
> >> unaligned offsets approaching the page boundary.
> > Can you please put that in tools/testing/selftests and merge it as part of the
> > series? That way I can run the tests and be confident it works on powerpc.
> 
> Unfortunately, the strscpy patch series only changes the one previous
> user of the API, which is a tile-architecture-only driver piece, not
> particularly useful for anyone else for testing.
> 
> The testing I did pulled strscpy() and word-at-a-time out into a
> separate, standalone userspace implementation, and tested it there,
> rather than doing tests through the syscall API like 
> tools/testing/selftests.

Not everything in selftests has to or does go through the syscall API.

We (powerpc) have tests of our memcpy/memcmp/load_unaligned_zeropad that are
built as standalone test programs.

Doing that for stuff in lib/string.c does look a bit complicated, because you'd
need to pull in a bunch of kernel headers.

Do you mind posting your test code somewhere so I can run it, and maybe I can
work out how to fold it into a selftest.

cheers


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