[PATCH] x86emu: fix jump_near_IMM to handle DATA: flag correctly.

Adam Jackson ajax at nwnk.net
Thu Oct 28 05:04:36 PDT 2010


On Sun, 2010-10-24 at 23:57 +0200, Luc Verhaegen wrote:
> Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=24348
> 
> Before (data flag ignored -> broken):
> 66                  DATA:
> e944f1              JMP       1ff6
> 
> After (fixed):
> 66                  DATA:
> e944f1ffff          JMP       00001ff8
> 
> This subtle difference in the length of decoded instruction meant
> that the VBE call jumped to the routine setting AX=0x14F (VBE Failed)
> instead of the routine that set AX=0x4F (VBE success).
> 
> The ability to run the same code in vm86 significantly aided the
> debugging of this issue. Those X.org developers who would like to drop
> vm86 better take special care towards _all_ vesa bugs, as those will
> expose further issues.
> 
> Patch applies easily to even xserver 1.4.2.
> 
> Signed-off-by: Luc Verhaegen <libv at skynet.be>
> Tested-by: Luc Verhaegen <libv at skynet.be>

Reviewed-by: Adam Jackson <ajax at redhat.com>

- ajax
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