From: Andreas Schwab <schwab@linux-m68k.org>
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: linuxppc-dev@lists.ozlabs.org, Anton Blanchard <anton@samba.org>,
paulus@samba.org
Subject: Re: [PATCH] powerpc: 32 bit getcpu VDSO function uses 64 bit instructions
Date: Thu, 27 Nov 2014 19:20:53 +0100 [thread overview]
Message-ID: <87oarstshm.fsf@igel.home> (raw)
In-Reply-To: <20141127160829.GA26139@gate.crashing.org> (Segher Boessenkool's message of "Thu, 27 Nov 2014 10:08:29 -0600")
Segher Boessenkool <segher@kernel.crashing.org> writes:
> On Wed, Nov 26, 2014 at 05:50:27PM -0600, Peter Bergner wrote:
>> On Thu, 2014-11-27 at 09:38 +1100, Michael Ellerman wrote:
>> > On Thu, 2014-11-27 at 08:11 +1100, Anton Blanchard wrote:
>> > > I used some 64 bit instructions when adding the 32 bit getcpu VDSO
>> > > function. Fix it.
>> >
>> > Ouch. The symptom is a SIGILL I presume?
>>
>> Nope, you don't get a SIGILL when executing 64-bit instructions in
>> 32-bit mode, so it'll happily just execute the instruction, doing
>> a full 64-bit compare. I'm guessing that the upper 32-bits of both
>> r3 and r4 contain zeros, so we're probably just getting lucky.
>
> You will get a SIGILL if you run on 32-bit hardware.
Not on the 7447A, fwiw.
Andreas.
--
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5
"And now for something completely different."
prev parent reply other threads:[~2014-11-27 18:28 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-26 21:11 [PATCH] powerpc: 32 bit getcpu VDSO function uses 64 bit instructions Anton Blanchard
2014-11-26 22:38 ` Michael Ellerman
2014-11-26 23:23 ` Segher Boessenkool
2014-11-26 23:28 ` Segher Boessenkool
2014-11-26 23:50 ` Peter Bergner
2014-11-27 16:08 ` Segher Boessenkool
2014-11-27 17:41 ` Peter Bergner
2014-11-27 20:50 ` Segher Boessenkool
2014-11-28 2:00 ` Benjamin Herrenschmidt
2014-11-27 18:20 ` Andreas Schwab [this message]
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