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Re: [PATCH resend] MIPS: Allow FPU emulator to use non-stack area.
- From: Rich Felker <dalias at libc dot org>
- To: Leonid Yegoshin <Leonid dot Yegoshin at imgtec dot com>
- Cc: Andy Lutomirski <luto at amacapital dot net>, Matthew Fortune <Matthew dot Fortune at imgtec dot com>, David Daney <david dot s dot daney at gmail dot com>, David Daney <ddaney at caviumnetworks dot com>, David Daney <ddaney dot cavm at gmail dot com>, "libc-alpha at sourceware dot org" <libc-alpha at sourceware dot org>, "linux-kernel at vger dot kernel dot org" <linux-kernel at vger dot kernel dot org>, "linux-mips at linux-mips dot org" <linux-mips at linux-mips dot org>, David Daney <david dot daney at cavium dot com>
- Date: Tue, 7 Oct 2014 15:21:07 -0400
- Subject: Re: [PATCH resend] MIPS: Allow FPU emulator to use non-stack area.
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- References: <54332A64 dot 5020605 at caviumnetworks dot com> <20141007000514 dot GD23797 at brightrain dot aerifal dot cx> <543334CE dot 8060305 at caviumnetworks dot com> <20141007004915 dot GF23797 at brightrain dot aerifal dot cx> <54337127 dot 40806 at gmail dot com> <6D39441BF12EF246A7ABCE6654B0235320F1E173 at LEMAIL01 dot le dot imgtec dot org> <543431DA dot 4090809 at imgtec dot com> <CALCETrUQEbb=DotSzsneN7Hano_eC-EoTMko6uKcyZXvEcktkw at mail dot gmail dot com> <20141007190943 dot GM23797 at brightrain dot aerifal dot cx> <54343C2B dot 2080801 at imgtec dot com>
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.
Rich