From: Tejun Heo <htejun@gmail.com>
To: Brian Gerst <brgerst@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/3] x86: Pass in pt_regs pointer for syscalls that need it
Date: Thu, 12 Feb 2009 00:05:16 +0900 [thread overview]
Message-ID: <4992E92C.5000000@gmail.com> (raw)
In-Reply-To: <73c1f2160902110659i776e1d89qc23d89363881572e@mail.gmail.com>
Brian Gerst wrote:
> On Wed, Feb 11, 2009 at 9:48 AM, Tejun Heo <htejun@gmail.com> wrote:
>> Tejun Heo wrote:
>>>> I checked the disassembly of these functions and didn't see this
>>>> happen on gcc 4.3.0.
>>> Well, tracking down why run_init_process() is returning 0 with
>>> -fstack-protector wasn't much of fun. These breakages are very subtle
>>> and if we're gonna pass in pointer to pt_regs anyway and thus can
>>> guarantee such breakage can't happen at no additional cost, I think we
>>> should do that even if it means slightly more argument fetching in a
>>> few places.
>> In addition, if we do that, we can remove the horrible
>> asmlinkage_protect() thing altogether.
>
> Like I said before, the tail-call optimization problem isn't limited
> to just this set of syscalls. There are only two real ways to fix it.
> 1) Set up a real stack frame for the syscalls instead of overalying
> pt_regs, or 2) patch gcc to tell it not to touch the args area of the
> stack.
Right, I forgot about the generic ones. We can pass pointer to
pt_regs to all of them like x86_64 does but yeah we're likely to lose
more than we gain by doing that. :-(
--
tejun
next prev parent reply other threads:[~2009-02-11 15:05 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-02-10 14:51 [PATCH 0/3] x86: Fix pt_regs passed by value Brian Gerst
2009-02-10 14:51 ` [PATCH 1/3] x86: Use pt_regs pointer in do_device_not_available() Brian Gerst
2009-02-11 7:43 ` Tejun Heo
2009-02-11 10:13 ` Ingo Molnar
2009-02-11 14:34 ` Brian Gerst
2009-02-11 14:42 ` Tejun Heo
2009-02-11 14:46 ` Brian Gerst
2009-02-11 14:53 ` Tejun Heo
2009-02-10 14:51 ` [PATCH 2/3] x86: Pass in pt_regs pointer for syscalls that need it Brian Gerst
2009-02-11 7:41 ` Tejun Heo
2009-02-11 10:18 ` Ingo Molnar
2009-02-11 14:14 ` Tejun Heo
2009-02-11 14:31 ` Brian Gerst
2009-02-11 14:41 ` Tejun Heo
2009-02-11 14:43 ` Tejun Heo
2009-02-11 14:48 ` Tejun Heo
2009-02-11 14:58 ` Ingo Molnar
2009-02-11 14:59 ` Brian Gerst
2009-02-11 15:05 ` Tejun Heo [this message]
2009-02-11 15:10 ` Brian Gerst
2009-02-11 15:14 ` Tejun Heo
2009-02-11 15:59 ` Ingo Molnar
2009-02-12 1:12 ` Tejun Heo
2009-02-11 15:01 ` Ingo Molnar
2009-02-11 17:52 ` H. Peter Anvin
2009-02-11 18:27 ` Brian Gerst
2009-02-11 19:50 ` H. Peter Anvin
2009-02-11 19:57 ` Brian Gerst
2009-02-11 20:00 ` H. Peter Anvin
2009-02-11 21:43 ` [PATCH] x86: pass in pt_regs pointer for syscalls that need it (take 2) Brian Gerst
2009-02-11 21:50 ` H. Peter Anvin
2009-02-11 22:06 ` H. Peter Anvin
2009-02-12 11:02 ` Ingo Molnar
2009-02-10 14:51 ` [PATCH 3/3] x86: Drop -fno-stack-protector after pt_regs fixes Brian Gerst
2009-02-11 11:42 ` [PATCH 0/3] x86: Fix pt_regs passed by value Ingo Molnar
2009-02-11 14:15 ` Tejun Heo
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