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Date: Tue, 23 Feb 2010 17:57:23 +0000
Message-ID: <ee2e06e91002230957y27212a5avdf3d0a834d9f63a@mail.gmail.com>
Subject: Re: [Qemu-devel] gcc 4.4 miscompiling cpu_exec() ?
From: Jay Foad <jay.foad@gmail.com>
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To: Aurelien Jarno <aurelien@aurel32.net>
Cc: qemu-devel@nongnu.org

On 23 February 2010 17:03, Aurelien Jarno <aurelien@aurel32.net> wrote:
> Jay Foad a =E9crit :
>> I'm building QEMU mipsel-linux-user with Ubuntu's GCC 4.4 on an x86
>> host. Whenever I try to run a trivial MIPS executable, QEMU segfaults
>> in cpu_loop() shortly after the call to cpu_mips_exec().
>>
>> The problem seems to be that cpu_exec() doesn't preserve ebp. It tries t=
o:
>>
>> =A0 =A0 saved_env_reg =3D (host_reg_t) env;
>>
>> where env is a global variable decorated with asm("ebp"). This saves
>> ebp to the stack, but later on, in some function inlined into
>> cpu_exec(), the value on the stack gets overwritten with something
>> else.
>>
>> Has anyone else seen this?
>>
>
> Yes, but only in qemu 0.12.0 to 0.12.1. The issue should be fixed in the
> stable branch and in head.

I'm seeing it today, with sources from git:

git://git.qemu.org/qemu.git
commit 724c689357211cb929c9b957e1556f211d2b56db

Thanks,
Jay.