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Re: [Qemu-devel] Crash due to invalid env->current_tb
From: |
Adam Lackorzynski |
Subject: |
Re: [Qemu-devel] Crash due to invalid env->current_tb |
Date: |
Tue, 29 Apr 2008 20:40:11 +0200 |
User-agent: |
Mutt/1.5.17+20080114 (2008-01-14) |
On Tue Apr 29, 2008 at 20:09:00 +0300, Blue Swirl wrote:
> On 4/29/08, Adam Lackorzynski <address@hidden> wrote:
> > Hi,
> >
> > I've been experiencing crashes of latest svn Qemu, host ia32 and target
> > arm, host gcc is 'gcc version 3.4.6 (Debian 3.4.6-7)'.
> > The segfault happens because of an invalid env->current_tb which seems
> > to be caused by generated code. The following code in cpu_exec
> >
> > tc_ptr = tb->tc_ptr;
> > env->current_tb = tb;
> > gen_func = (void *)tc_ptr;
> > T0 = gen_func();
> > env->current_tb = NULL;
> >
> > is being compiled to the following
> >
> > mov 0x14(%ecx),%eax
> > mov %ecx,0x56c(%ebp)
> > xor %edi,%edi
> > call *%eax
> > mov %edi,0x56c(%ebp)
> >
> > After the call edi isn't 0 anymore and gets the bogus value. As edi is
> > callee saved the code itself seems ok.
> > When I add a barrier before "env->current_tb = NULL" the xor is placed
> > after the call and everything works fine. So might the problem be that
> > generated code isn't preserving edi/registers?
>
> Right. How did you make the barrier? My version (attached) just
> crashes, I'm not fluent on i386 assembly. Maybe your version could
> serve as a temporary fix.
I just added an 'asm volatile("")' to stop reordering of instructions
which of course isn't enough. The following works for me:
===================================================================
--- cpu-exec.c (revision 4276)
+++ cpu-exec.c (working copy)
@@ -690,6 +691,11 @@
fp.ip = tc_ptr;
fp.gp = code_gen_buffer + 2 * (1 << 20);
(*(void (*)(void)) &fp)();
+#elif defined(__i386)
+ asm volatile ("call *%1\n"
+ : "=a" (T0)
+ : "r" (gen_func)
+ : "esi", "edi");
#else
T0 = gen_func();
#endif
Adam
--
Adam address@hidden
Lackorzynski http://os.inf.tu-dresden.de/~adam/
- [Qemu-devel] Crash due to invalid env->current_tb, Adam Lackorzynski, 2008/04/29
- Re: [Qemu-devel] Crash due to invalid env->current_tb, Blue Swirl, 2008/04/29
- Re: [Qemu-devel] Crash due to invalid env->current_tb,
Adam Lackorzynski <=
- Re: [Qemu-devel] Crash due to invalid env->current_tb, Alexander Graf, 2008/04/30
- Re: [Qemu-devel] Crash due to invalid env->current_tb, Adam Lackorzynski, 2008/04/30
- Re: [Qemu-devel] Crash due to invalid env->current_tb, Adam Lackorzynski, 2008/04/30
- Re: [Qemu-devel] Crash due to invalid env->current_tb, Blue Swirl, 2008/04/30
- Re: [Qemu-devel] Crash due to invalid env->current_tb, Alexander Graf, 2008/04/30
- Re: [Qemu-devel] Crash due to invalid env->current_tb, Blue Swirl, 2008/04/30
- Re: [Qemu-devel] Crash due to invalid env->current_tb, Laurent Vivier, 2008/04/30
- Re: [Qemu-devel] Crash due to invalid env->current_tb, Adam Lackorzynski, 2008/04/30