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Re: handle_sys question

from [Songmao Tian] [Permanent Link][Original]
To: David Daney <david.daney@cavium.com>
Subject: Re: handle_sys question
From: Songmao Tian <kingkongmao@gmail.com>
Date: Wed, 23 May 2012 16:17:21 +0800
Cc: linux-mips <linux-mips@linux-mips.org>
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OK, I find the usage. continue to read the code:-), thanks.

587 static int handle_signal(unsigned long sig, siginfo_t *info,
588     struct k_sigaction *ka, sigset_t *oldset, struct pt_regs *regs)
589 {              
590     int ret;
……
602     /* fallthrough */
603     case ERESTARTNOINTR:        /* Userland will reload $v0.  */
604         regs->regs[7] = regs->regs[26];
605         regs->cp0_epc -= 8;
606     }  



2012/5/23 David Daney <david.daney@cavium.com>
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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