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Date: Thu, 18 Jul 2002 18:05:53 -0700
From: Jun Sun <jsun@mvista.com>
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To: "H. J. Lu" <hjl@lucon.org>
CC: linux-mips@oss.sgi.com
Subject: Re: Malta bus error
References: <3D375B4C.9000403@mvista.com> <20020718180759.A2091@lucon.org>
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H. J. Lu wrote:
> On Thu, Jul 18, 2002 at 05:20:28PM -0700, Jun Sun wrote:
> 
>>I got the following bus error on Malta.  Does anybody know what causes the 
>>fault?  Is there anyway to disable the error?  Or we should install a malta 
>>bus_error_handler() to discard this kind of error?
>>
>>Apparently the error has something to do with the code layout as it only 
>>happens when I start to modify an unrelated function( do_ri()).
>>
>>I am using the latest linux_2_4 branch from oss.sgi.com CVS tree.
>>
> 
> 
> I got zero problems with 2.4 kernel on oss as of Jul 11 08:18.
> 

Me neither, until I made the following change.  I of course use my own config 
file.

Using Malta's own BE handler to ignore bus error seems to fix the problem, 
although I am not sure if it is the right fix.

Jun

--- arch/mips/kernel/traps.c.orig       Thu Jul 18 15:39:50 2002
+++ arch/mips/kernel/traps.c    Thu Jul 18 16:49:32 2002
@@ -614,8 +614,7 @@
   */
  asmlinkage void do_ri(struct pt_regs *regs)
  {
-       if (!user_mode(regs))
-               BUG();
+       die_if_kernel("no ll/sc emulation for kernel code", regs);

  #ifndef CONFIG_CPU_HAS_LLSC

Jun