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Mail Archives: djgpp/2009/05/13/23:15:57

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Date: Thu, 14 May 2009 03:03:04 GMT
From: "A. Wik" <root AT dynamite DOT narpes DOT com>
Subject: Re: Please help resurrecting GDB for version 7.0 release
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On Tue, 5 May 2009, Eli Zaretskii wrote:

> > From: Rugxulo <rugxulo AT gmail DOT com>
> > Date: Mon, 4 May 2009 22:08:44 -0700 (PDT)
> > 
> > > Yes, and then test a lot on old machines which I don't even know where
> > > to find. 
> > 
> > What old machines in particular? Just cpu revisions or OSes or both??
> 
> That depends on the method you use for detecting the CPU.  If you use
> no privileged instructions, there should be no reason to test under
> different OSes, I think.  Otherwise, yes.

This may not be relevant to a specific situation, but
generally speaking, bugs can occur in any any instruction,
privileged or otherwise.  For example, the F00F and FDIV
CPU bugs[1] require no privileges[2] to trigger.  Also,
normally unprivileged instructions such as floating point
can be programmed to generate exceptions, although that is
normally only done on CPUs lacking a math co-processor or
FPU [3], such as the 486SX and most 386 (SX, DX, or null
suffix) systems.

-aw
[1]  I think I do have machines, or at least CPUs, affected
  by either of those two bugs.  If anyone has a need to
  test code under these conditions I might look into it.
[2]  LOCK is unprivileged on modern CPUs, but privileged on
  some older x86 generations; however, that's not relevant
  in the case of F00F, which occurs in the Pentium,
  P. Overdrive and P. MMX and processors.
[3]  In those cases, the exceptions allow the invocation of
  an emulator to process the missing FP instructions).
  I've had to load one for DJGPP apps on occasions.

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