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Re: Unexpected behaviour when catching SIGFPE on FPU-less system

To: Manuel Lauss <manuel.lauss@googlemail.com>
Subject: Re: Unexpected behaviour when catching SIGFPE on FPU-less system
From: David Daney <ddaney@caviumnetworks.com>
Date: Tue, 04 May 2010 13:01:23 -0700
Cc: Geert Uytterhoeven <geert@linux-m68k.org>, Ralf Baechle <ralf@linux-mips.org>, "Kevin D. Kissell" <kevink@paralogos.com>, Shane McDonald <mcdonald.shane@gmail.com>, linux-mips@linux-mips.org
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On 05/04/2010 12:30 PM, Manuel Lauss wrote:
On Tue, May 4, 2010 at 9:28 PM, Geert Uytterhoeven<geert@linux-m68k.org>  wrote:
On Tue, May 4, 2010 at 20:44, Ralf Baechle<ralf@linux-mips.org>  wrote:
On Tue, May 04, 2010 at 09:13:18AM -0700, Kevin D. Kissell wrote:

What we used to use was what I *thought* was an old public domain
program whose name was an English word that had something to do with
being exacting.  Googling with obvious keywords didn't turn it up.

Is it paranoia by any chance?  Paranoia is available as single files at:

  http://www.math.utah.edu/~beebe/software/ieee/paranoia.c
  http://www.math.utah.edu/~beebe/software/ieee/paranoia.h

You also need

http://www.math.utah.edu/~beebe/software/ieee/args.h

Ran fine on:
  - Toshiba RBTX4927 (with FPU :-)
  - Mikrotik RouterBOARD 150 (without FPU), using an older 2.6.x OpenWRT kernel

and runs into an endless loop around line 806 when built with
a softfloat toolchain (gcc-4.4.3).


From the point of view of this specific problem, using a softfloat toolchain isn't what you want to do.

The question is if the kernel's FP emulator is operating correctly, if you never execute any FP instructions (due to the use of a softfloat toolchain), you would not be testing the emulator.

David Daney

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