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 <l...@skynet.be>
Tested-by: Luc Verhaegen <l...@skynet.be>
---
hw/xfree86/x86emu/ops.c | 20 ++++++++++++++------
1 files changed, 14 insertions(+), 6 deletions(-)
diff --git a/hw/xfree86/x86emu/ops.c b/hw/xfree86/x86emu/ops.c
index 21a0347..c6b2f0a 100644
--- a/hw/xfree86/x86emu/ops.c
+++ b/hw/xfree86/x86emu/ops.c
@@ -9691,15 +9691,23 @@ Handles opcode 0xe9
****************************************************************************/
static void x86emuOp_jump_near_IMM(u8 X86EMU_UNUSED(op1))
{
- int ip;
+ u32 ip;
START_OF_INSTR();
DECODE_PRINTF("JMP\t");
- ip = (s16)fetch_word_imm();
- ip += (s16)M.x86.R_IP;
- DECODE_PRINTF2("%04x\n", (u16)ip);
- TRACE_AND_STEP();
- M.x86.R_IP = (u16)ip;
+ if (M.x86.mode & SYSMODE_PREFIX_DATA) {
+ ip = (u32)fetch_long_imm();
+ ip += (u32)M.x86.R_EIP;
+ DECODE_PRINTF2("%08x\n", (u32)ip);
+ TRACE_AND_STEP();
+ M.x86.R_EIP = (u32)ip;
+ } else {
+ ip = (s16)fetch_word_imm();
+ ip += (s16)M.x86.R_IP;
+ DECODE_PRINTF2("%04x\n", (u16)ip);
+ TRACE_AND_STEP();
+ M.x86.R_IP = (u16)ip;
+ }
DECODE_CLEAR_SEGOVR();
END_OF_INSTR();
}
--
1.6.0.2
_______________________________________________
xorg-devel@lists.x.org: X.Org development
Archives: http://lists.x.org/archives/xorg-devel
Info: http://lists.x.org/mailman/listinfo/xorg-devel
