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Re: handle_sys question

from [David Daney] [Permanent Link][Original]
To: Songmao Tian <kingkongmao@gmail.com>
Subject: Re: handle_sys question
From: David Daney <david.daney@cavium.com>
Date: Tue, 22 May 2012 12:46:39 -0700
Cc: linux-mips <linux-mips@linux-mips.org>
In-reply-to: <CADSewLWvfVsQob-y5Q9mc31JpecHFd6=5dRhKxdH3VvT0HXJZQ@mail.gmail.com>
References: <CADSewLWvfVsQob-y5Q9mc31JpecHFd6=5dRhKxdH3VvT0HXJZQ@mail.gmail.com>
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On 05/22/2012 02:40 AM, Songmao Tian wrote:

Hello all:
    In handle_sys there's a
50
<http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;f=arch/mips/kernel/scall32-o32.S;h=a632bc144efa1b9ca977a582864530e33ee039cb;hb=72c04af9a2d57b7945cf3de8e71461bd80695d50#l50>
         sw      a3, PT_R26(sp)          # save a3 for syscall restarting

I woner why it need to save  a3 in R26(k0) slot in the stack?
It has to go somewhere. The K0 and K1 slots aren't used to save other things. 

David Daney
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