New patch to review for coreboot: aba752b x86emu: fix jump_near_IMM to handle DATA: flag correctly

[Stefan Reinauer]

Stefan Reinauer ([e-mail]) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/1365

-gerrit

commit aba752bc719378b667954175d05891c5b69e2c55
Author: Stefan Reinauer 
Date:   Thu Jul 26 15:48:17 2012 -0700

x86emu: fix jump_near_IMM to handle DATA: flag correctly

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.

Imported from:
    http://cgit.freedesktop.org/xorg/xserver/commit/hw/xfree86/x86emu?id=cc2c73d...
    Signed-off-by: Stefan Reinauer

Change-Id: Id08ead9b17468cf19ede45508e5dcc50e45b5acf
    Signed-off-by: Luc Verhaegen 
    Tested-by: Luc Verhaegen 
    Reviewed-by: Adam Jackson 
    Signed-off-by: Keith Packard 
---
 src/devices/oprom/x86emu/ops.c |   23 ++++++++++++++++-------
 1 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/src/devices/oprom/x86emu/ops.c b/src/devices/oprom/x86emu/ops.c
index 6bfc71c..e58dafb 100644
--- a/src/devices/oprom/x86emu/ops.c
+++ b/src/devices/oprom/x86emu/ops.c
@@ -4279,16 +4279,25 @@ 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", ip);
-    JMP_TRACE(M.x86.saved_cs, M.x86.saved_ip, M.x86.R_CS, ip, " NEAR ");
-    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);
+        JMP_TRACE(M.x86.saved_cs, M.x86.saved_ip, M.x86.R_CS, ip, " NEAR ");
+	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);
+        JMP_TRACE(M.x86.saved_cs, M.x86.saved_ip, M.x86.R_CS, ip, " NEAR ");
+        TRACE_AND_STEP();
+        M.x86.R_IP = (u16)ip;
+    }
     DECODE_CLEAR_SEGOVR();
     END_OF_INSTR();
 }