From mboxrd@z Thu Jan  1 00:00:00 1970
From: arnaud.patard@rtp-net.org (Arnaud Patard (Rtp))
Date: Wed, 19 Jan 2011 23:06:30 +0100
Subject: [RFC][PATCH] ARM: ptrace: remove single-step emulation code
In-Reply-To: <000501cbb7ee$cdccc680$69665380$@deacon@arm.com> (Will Deacon's
	message of "Wed, 19 Jan 2011 15:37:38 -0000")
References: <1295449635-4292-1-git-send-email-will.deacon@arm.com>
	<20110119151915.GG31652@n2100.arm.linux.org.uk>
	<000501cbb7ee$cdccc680$69665380$@deacon@arm.com>
Message-ID: <87vd1kblax.fsf@lechat.rtp-net.org>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

"Will Deacon" <will.deacon@arm.com> writes:

> Hi Russell,

Hi,

>
>> On Wed, Jan 19, 2011 at 03:07:15PM +0000, Will Deacon wrote:
>> > I'm posting this as an RFC to see if anybody has a good reason to keep this
>> > code around. There's also a chance I've missed an opportunity to remove some
>> > related code, but I think I found everything. Tested on a Versatile Express,
>> > single-stepping in GDB worked fine.
>> 
>> Have you checked whether strace and ltrace use single stepping?
>
> strace works fine with this patch applied and, looking at the
> sources, it doesn't use the SINGLESTEP request. As for ltrace,
> it *does* use SINGLESTEP but it can use PTRACE_SYSCALL instead
> (indeed, it does this for sparc, ia64 and mips). ltrace doesn't
> have code for checking the ptrace return value so I'd say it's
> their bug.

afair, the current way to prevent SINGLESTEP usage in ltrace is to
modify some #ifdef. So, while I agree that not checking ptrace return
value is not nice, it has nothing to do with SINGLESTEP removal as this
call will not get compiled in. What matters is rather to know if things
are still working once the #ifdef are changed and if they're not,
finding if it's a bug in ltrace or kernel.

Arnaud