[Qemu-devel] [PATCH] Fix jmp im on x86_64 when executing 32-bit code

[Qemu-devel] [PATCH] Fix jmp im on x86_64 when executing 32-bit code

[Alexander Graf]

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When running grub-install (32-bit) on an x86_64 Linux system in qemu, it
hangs on a pagefault forever, because an integer overflow occurs on the
IP on "jmp im". This patch masks overflows for 32 bit IPs on a 64 bit
system, just like it is done for 16 bit IPs already.

Using this patch, x86_64 openSUSE installation works again.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Kevin Wolf <kwolf@suse.de>



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Index: target-i386/translate.c
===================================================================
--- target-i386/translate.c	(revision 5959)
+++ target-i386/translate.c	(working copy)
@@ -6165,6 +6165,8 @@
         tval += s->pc - s->cs_base;
         if (s->dflag == 0)
             tval &= 0xffff;
+	else if(!CODE64(s))
+            tval &= 0xffffffff;
         gen_jmp(s, tval);
         break;
     case 0xea: /* ljmp im */

Re: [Qemu-devel] [PATCH] Fix jmp im on x86_64 when executing 32-bit code

[Aurelien Jarno]

On Tue, Dec 09, 2008 at 02:14:19PM +0100, Alexander Graf wrote:
> When running grub-install (32-bit) on an x86_64 Linux system in qemu, it
> hangs on a pagefault forever, because an integer overflow occurs on the
> IP on "jmp im". This patch masks overflows for 32 bit IPs on a 64 bit
> system, just like it is done for 16 bit IPs already.
> 
> Using this patch, x86_64 openSUSE installation works again.
> 
> Signed-off-by: Alexander Graf <agraf@suse.de>
> Signed-off-by: Kevin Wolf <kwolf@suse.de>
> 
> 

Thanks for your great work, it is something broken for a long time, and
it is nice to see that fixed. I have applied the patch to the SVN.

> Index: target-i386/translate.c
> ===================================================================
> --- target-i386/translate.c	(revision 5959)
> +++ target-i386/translate.c	(working copy)
> @@ -6165,6 +6165,8 @@
>          tval += s->pc - s->cs_base;
>          if (s->dflag == 0)
>              tval &= 0xffff;
> +	else if(!CODE64(s))
> +            tval &= 0xffffffff;
>          gen_jmp(s, tval);
>          break;
>      case 0xea: /* ljmp im */


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