Re: [PATCH 4/7] signal/mips: Document a conflict with SI_USER with SIGFPE

From	"Maciej W. Rozycki" <macro@imgtec.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 4/7] signal/mips: Document a conflict with SI_USER with SIGFPE
Date	2017-08-07 18:20 +0200
Message-ID	<ubSV7-2zz-87@gated-at.bofh.it> (permalink)
References	<u4BvX-3ta-9@gated-at.bofh.it> <u4BvY-3ta-25@gated-at.bofh.it>
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On Tue, 18 Jul 2017, Eric W. Biederman wrote:

> diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
> index b68b4d0726d3..6c9cca9c5341 100644
> --- a/arch/mips/kernel/traps.c
> +++ b/arch/mips/kernel/traps.c
> @@ -735,7 +735,7 @@ void force_fcr31_sig(unsigned long fcr31, void __user *fault_addr,
>  	else if (fcr31 & FPU_CSR_INE_X)
>  		si.si_code = FPE_FLTRES;
>  	else
> -		si.si_code = __SI_FAULT;
> +		si.si_code = FPE_FIXME;

 This is an "impossible" state to reach unless your hardware is on fire.  
One or more of the FCSR Cause bits will have been set (in `fcr31') or the 
FPE exception would not have happened.

 Of course there could be a simulator bug, or we could have breakage 
somewhere causing `process_fpemu_return' to be called with SIGFPE and 
inconsistent `fcr31'.  So we need to handle it somehow.

 So what would be the right value of `si_code' to use here for such an 
unexpected exception condition?  I think `BUG()' would be too big a 
hammer here.  Or wouldn't it?

  Maciej

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Re: [PATCH 4/7] signal/mips: Document a conflict with SI_USER with  SIGFPE "Maciej W. Rozycki" <macro@imgtec.com> - 2017-08-07 18:20 +0200
  Re: [PATCH 4/7] signal/mips: Document a conflict with SI_USER with SIGFPE Linus Torvalds <torvalds@linux-foundation.org> - 2017-08-07 19:50 +0200
    Re: [PATCH 4/7] signal/mips: Document a conflict with SI_USER with  SIGFPE Ralf Baechle <ralf@linux-mips.org> - 2017-08-07 22:00 +0200
  Re: [PATCH 4/7] signal/mips: Document a conflict with SI_USER with SIGFPE ebiederm@xmission.com (Eric W. Biederman) - 2017-08-08 17:40 +0200
    Re: [PATCH 4/7] signal/mips: Document a conflict with SI_USER with  SIGFPE "Maciej W. Rozycki" <macro@imgtec.com> - 2017-08-09 01:20 +0200

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