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Re: Cannot unwind through MIPS signal frames with ICACHE_REFILLS_WORKARO

To: "Franck Bui-Huu" <vagabon.xyz@gmail.com>, "Ralf Baechle" <ralf@linux-mips.org>
Subject: Re: Cannot unwind through MIPS signal frames with ICACHE_REFILLS_WORKAROUND_WAR
From: "Kevin D. Kissell" <kevink@mips.com>
Date: Tue, 13 Nov 2007 15:37:39 +0100
Cc: "Andrew Haley" <aph-gcc@littlepinkcloud.com>, "David Daney" <ddaney@avtrex.com>, <linux-mips@linux-mips.org>, "Richard Sandiford" <rsandifo@nildram.co.uk>, <gcc@gcc.gnu.org>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <473957B6.3030202@avtrex.com> <18233.36645.232058.964652@zebedee.pink> <20071113121036.GA6582@linux-mips.org> <cda58cb80711130514x16356ea3x4069616c9ee3caac@mail.gmail.com>
Sender: linux-mips-bounce@linux-mips.org
Franck a dit:
> > Another reason is to get rid of the classic trampoline the kernel installs
> > on the stack.  On some multiprocessor systems it requires a cacheflush
> > operation to be performed on all processors which is expensive.  Having
> > the trampoline in a vDSO would solve that.
> >
> 
> And the stack wouldn't need to have exec permission anymore.

True, though it should perhaps be noted that currently it's only on 4KSc/Sd
systems (which I know you work on) where it's even possible for the stack
*not* to have exec permissions, since the classical MIPS MMU gives
execute permission to any page that is readable.

            Regards,

            Kevin K.

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