From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:57644)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <sw@weilnetz.de>) id 1VSWFQ-0004Hq-Rq
	for qemu-devel@nongnu.org; Sat, 05 Oct 2013 14:06:42 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <sw@weilnetz.de>) id 1VSWFG-0003O2-KE
	for qemu-devel@nongnu.org; Sat, 05 Oct 2013 14:06:36 -0400
Received: from v220110690675601.yourvserver.net ([37.221.199.173]:44880)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <sw@weilnetz.de>) id 1VSWFG-0003Nw-DK
	for qemu-devel@nongnu.org; Sat, 05 Oct 2013 14:06:26 -0400
Message-ID: <5250551E.6020105@weilnetz.de>
Date: Sat, 05 Oct 2013 20:06:22 +0200
From: Stefan Weil <sw@weilnetz.de>
MIME-Version: 1.0
References: <20131003140937.GA59761@enceladus10.kn-bremen.de>	<CAFEAcA_vr+t0RdKhAywjJ_shAdVBF4j002hiz3oWCH=XkCiwaA@mail.gmail.com>	<524E6B19.9020805@siemens.com>
	<20131005175432.GA25070@enceladus10.kn-bremen.de>
In-Reply-To: <20131005175432.GA25070@enceladus10.kn-bremen.de>
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Subject: Re: [Qemu-devel] [PATCH] cpu-exec(): also reload CPUClass *cc after
 longjmp return
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Juergen Lock <qemu-l@jelal.kn-bremen.de>, Jan Kiszka <jan.kiszka@siemens.com>
Cc: Peter Maydell <peter.maydell@linaro.org>, Dimitry Andric <dim@freebsd.org>, QEMU Developers <qemu-devel@nongnu.org>, Andreas Faerber <afaerber@suse.de>

Am 05.10.2013 19:54, schrieb Juergen Lock:
> On Fri, Oct 04, 2013 at 09:15:37AM +0200, Jan Kiszka wrote:
>> On 2013-10-03 18:05, Peter Maydell wrote:
>>> On 3 October 2013 23:09, Juergen Lock <qemu-l@jelal.kn-bremen.de> wrote:
>>>> Local variable CPUClass *cc needs to be reloaded after return from longjmp
>>>> too.  (This fixes the mips-softmmu crash observed on FreeBSD when qemu is
>>>> built with clang.)
>>>>
>>>> Signed-off-by: Juergen Lock <nox@jelal.kn-bremen.de>
>>>> Found-by: Dimitry Andric <dim@FreeBSD.org>
>>>>
>>>> --- a/cpu-exec.c
>>>> +++ b/cpu-exec.c
>>>> @@ -681,6 +681,10 @@ int cpu_exec(CPUArchState *env)
>>>>               * local variables as longjmp is marked 'noreturn'. */
>>>>              cpu = current_cpu;
>>>>              env = cpu->env_ptr;
>>>> +#if !(defined(CONFIG_USER_ONLY) && \
>>>> +      (defined(TARGET_M68K) || defined(TARGET_PPC) || defined(TARGET_S390X)))
>>>> +            cc = CPU_GET_CLASS(cpu);
>>>> +#endif
>>> This is a c compiler or libc bug -- the C standard says that this
>>> local variable should not be trashed by the longjmp. We were
>>> actually discussing removing the current workarounds there...
>> But we didn't decide if we should stop supporting the affected compiler
>> versions.
>>
>> Does this issue also exist with the latest clang version available for
>> your platform?
>>
> It happens with up to date clang as it's in FreeBSD 10.0-current
> which is due for a release soon.  I think the clang folks are looking
> into this issue but I don't know if a fix will make it into the
> release...  (For now I've added the workaround to the FreeBSD
> qemu-devel port.)
>
>  Thanx,
> 	Juergen


Could you try whether QEMU crashes when it was configured with
TCG interpreter (--enable-tcg-interpreter)? If it does not crash, it
might be that TCG does not save / restore enough registers.

Which register is used for the local variable 'cc'?

Regards,
Stefan