From: Peter Bergner <bergner@vnet.ibm.com>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: linuxppc-dev@lists.ozlabs.org, paulus@samba.org,
Anton Blanchard <anton@samba.org>
Subject: Re: [PATCH] powerpc: 32 bit getcpu VDSO function uses 64 bit instructions
Date: Wed, 26 Nov 2014 17:50:27 -0600 [thread overview]
Message-ID: <1417045827.16862.32.camel@otta> (raw)
In-Reply-To: <1417041497.12952.2.camel@concordia>
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.
> Could we catch this by forcing -m32 in the CFLAGS for vdso32 ?
As Segher mentioned, GCC passing -many down to the assembler means
-m32 won't help. It was due to Anton disabling that gcc "feature",
that this was caught.
Peter
next prev parent reply other threads:[~2014-11-27 4:22 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 [this message]
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
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