From: ebiederm@xmission.com (Eric W. Biederman)
To: "Maciej W. Rozycki" <macro@imgtec.com>
Cc: linux-kernel@vger.kernel.org, Andy Lutomirski <luto@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Oleg Nesterov <oleg@redhat.com>,
Andrei Vagin <avagin@virtuozzo.com>,
Thomas Gleixner <tglx@linutronix.de>, Greg KH <greg@kroah.com>,
Andrey Vagin <avagin@openvz.org>, Serge Hallyn <serge@hallyn.com>,
Pavel Emelyanov <xemul@virtuozzo.com>,
Cyrill Gorcunov <gorcunov@openvz.org>,
Peter Zijlstra <peterz@infradead.org>, Willy Tarreau <w@1wt.eu>,
linux-arch@vger.kernel.org, linux-api@vger.kernel.org,
Linux Containers <containers@lists.linux-foundation.org>,
Michael Kerrisk <mtk.manpages@gmail.com>,
Ralf Baechle <ralf@linux-mips.org>
Subject: Re: [PATCH 4/7] signal/mips: Document a conflict with SI_USER with SIGFPE
Date: Tue, 08 Aug 2017 10:29:18 -0500 [thread overview]
Message-ID: <87mv7agjsh.fsf@xmission.com> (raw)
In-Reply-To: <alpine.DEB.2.00.1708071706290.17596@tp.orcam.me.uk> (Maciej W. Rozycki's message of "Mon, 7 Aug 2017 17:18:11 +0100")
"Maciej W. Rozycki" <macro@imgtec.com> writes:
> 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?
The possible solutions I can think of are:
WARN_ON_ONCE with a comment.
Add a new si_code to uapi/asm-generic/siginfo.h perhaps FPE_IMPOSSIBLE.
Like syscall numbers si_codes are cheap.
Call force_sig() instead of force_sig_info, using just a generic
si_code.
If this is truly impossible and the compiler doesn't complain just drop
the code.
Eric
next prev parent reply other threads:[~2017-08-08 15:29 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <87lgot2loq.fsf@xmission.com>
[not found] ` <87zid90vye.fsf_-_@xmission.com>
[not found] ` <20170615225426.GP31671@ZenIV.linux.org.uk>
[not found] ` <87poe4zrs1.fsf@xmission.com>
[not found] ` <CA+55aFxpv+gchzs7AYgSC8feAOV=B6mjFgBVm4Kx+83J2CNE-w@mail.gmail.com>
[not found] ` <87poe3vsa9.fsf@xmission.com>
[not found] ` <CALCETrX=SquyR8JZqHDNx=_FQKQo-0u9AxfdUwJs_hujVO2A-g@mail.gmail.com>
[not found] ` <87h8zfua59.fsf@xmission.com>
[not found] ` <CALCETrWPBn31Dye=81r2ZMainNOnDy5c_QxbU2uRjnJs0ie=Zg@mail.gmail.com>
[not found] ` <87r2yjsuwl.fsf@xmission.com>
[not found] ` <20170616191602.GA10675@1wt.eu>
2017-06-30 12:36 ` [PATCH 0/8] signal: Fix sending signals with siginfo Eric W. Biederman
2017-07-18 14:04 ` [PATCH v2 0/7] " Eric W. Biederman
2017-07-18 14:06 ` [PATCH 1/7] signal/alpha: Document a conflict with SI_USER for SIGTRAP Eric W. Biederman
[not found] ` <20170718140651.15973-1-ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2017-07-18 18:22 ` Richard Henderson
2017-07-18 14:06 ` [PATCH 4/7] signal/mips: Document a conflict with SI_USER with SIGFPE Eric W. Biederman
2017-08-07 16:18 ` Maciej W. Rozycki
2017-08-07 17:41 ` Linus Torvalds
2017-08-07 19:55 ` Ralf Baechle
2017-08-08 15:29 ` Eric W. Biederman [this message]
2017-08-08 23:19 ` Maciej W. Rozycki
[not found] ` <87o9shg7t7.fsf_-_-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2017-07-18 14:06 ` [PATCH 2/7] signal/ia64: " Eric W. Biederman
2017-07-18 14:06 ` [PATCH 3/7] signal/sparc: " Eric W. Biederman
2017-07-18 14:06 ` [PATCH 5/7] signal/testing: Don't look for __SI_FAULT in userspace Eric W. Biederman
2017-07-18 14:06 ` [PATCH 6/7] fcntl: Don't use ambiguous SIG_POLL si_codes Eric W. Biederman
[not found] ` <20170718140651.15973-6-ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2017-07-20 16:16 ` Oleg Nesterov
2017-07-21 2:33 ` Eric W. Biederman
2017-07-18 14:06 ` [PATCH 7/7] signal: Remove kernel interal si_code magic Eric W. Biederman
[not found] ` <20170718140651.15973-7-ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2017-07-18 16:57 ` Linus Torvalds
[not found] ` <CA+55aFyKsmf+BpYjcH30MGpHTDJ=zgYPx6kwyEB9CXXFxj_xsw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-07-18 17:27 ` Eric W. Biederman
[not found] ` <878tjlbqpt.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2017-07-22 20:25 ` Simplfying copy_siginfo_to_user Eric W. Biederman
[not found] ` <8760ek5ics.fsf_-_-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2017-07-24 17:43 ` Linus Torvalds
[not found] ` <CA+55aFyH5W2doo9vxXta_-pXfNXqQ19d7z48k1hmfAot+aJvMw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-07-24 19:01 ` Eric W. Biederman
2017-07-25 1:37 ` Al Viro
2017-07-31 16:37 ` Eric W. Biederman
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