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Re: [MIPS] Fix handling of trap and breakpoint instructions

To: David Daney <ddaney@avtrex.com>
Subject: Re: [MIPS] Fix handling of trap and breakpoint instructions
From: Ralf Baechle <ralf@linux-mips.org>
Date: Mon, 21 Apr 2008 17:12:21 +0100
Cc: Atsushi Nemoto <anemo@mba.ocn.ne.jp>, linux-mips@linux-mips.org
In-reply-to: <480CB728.7060402@avtrex.com>
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References: <S20041689AbYDUAiN/20080421003813Z+6727@ftp.linux-mips.org> <20080421.100721.07644724.nemoto@toshiba-tops.co.jp> <480CB728.7060402@avtrex.com>
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On Mon, Apr 21, 2008 at 08:47:52AM -0700, David Daney wrote:

> Note that there has been some confusion about break codes in gas over the 
> years.  Ancient versions (I am not sure which) generated different break 
> codes than recent versions.
>
> Before changing it make sure that you don't break existing user space code.
>
> One problem (fixed around 2.4.25 or so) was the integer division by zero in 
> user space would result in SIGTRAP instead of SIGFPE.   If you change the 
> break code handling you should verify that you don't break this.

Not quite correct.  Very old and recent binutils are bug compatible.  It's
middle age gcc which unfortunately fixed the bug creating a bug ;-)

  Ralf

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