linux-kernel - Re: [PATCH resend] MIPS: Allow FPU emulator to use non-stack area.

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Message-ID: <CALCETrU8qPL1qKGk7FqM=LCnoeSfuwDV_bG_a=5zcOKtWfkdGw@mail.gmail.com>
Date:	Tue, 7 Oct 2014 12:28:18 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Rich Felker <dalias@...c.org>
Cc:	Leonid Yegoshin <Leonid.Yegoshin@...tec.com>,
	Matthew Fortune <Matthew.Fortune@...tec.com>,
	David Daney <david.s.daney@...il.com>,
	David Daney <ddaney@...iumnetworks.com>,
	David Daney <ddaney.cavm@...il.com>,
	"libc-alpha@...rceware.org" <libc-alpha@...rceware.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mips@...ux-mips.org" <linux-mips@...ux-mips.org>,
	David Daney <david.daney@...ium.com>
Subject: Re: [PATCH resend] MIPS: Allow FPU emulator to use non-stack area.

On Tue, Oct 7, 2014 at 12:21 PM, Rich Felker <dalias@...c.org> wrote:
> On Tue, Oct 07, 2014 at 12:16:59PM -0700, Leonid Yegoshin wrote:
>> On 10/07/2014 12:09 PM, Rich Felker wrote:
>> >I agree completely here. We should not break things (or, as it
>> >seems, leave them broken) for common usage cases that affect
>> >everyone just to coddle proprietary vendor-specific instructions.
>> >The latter just should not be used in delay slots unless the chip
>> >vendor also promises to provide fpu branch in hardware. Rich
>> And what do you propose - remove a current in-stack emulation and
>> you still think it doesn't break a status-quo?
>
> The in-stack trampoline support could be left but used only for
> emulating instructions the kernel doesn't know. This would make all
> normal binaries immediately usable with non-executable stack, and
> would avoid the only potential source of regressions. Ultimately I
> think the "xol" stuff should be removed, but that could be a long term
> goal.

Does anything break if the xol stuff is disabled for PT_GNU_STACK tasks?

>
> Rich



-- 
Andy Lutomirski
AMA Capital Management, LLC
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