Re: [Patch] (big) real mode emulation - jmp rel

[Nitin A Kamble <nitin.a.kamble-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>]

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On Fri, 2007-08-17 at 05:24 -0700, Avi Kivity wrote:
> A file scope function would indeed be uglier.  But the macro has more
> serious problems; it's impossible to understand how variables are
> affected since nobody expects function local variables whose address
> is
> not taken to change after something that looks like a macro is called.
> 
> At the very least, it needs to be in uppercase so that people know
> something funny is going on.  But it's really better as a function.
> 
> (and yes, the rest of the file uses macros.  and yes, the rest of the
> file is an unmaintainable mess)

Hi Avi,
  I tried either ways, and to me the macro looks cleaner. Now I have
upper-cased it for your satisfaction. :)
  Also attached the "jmp rel short" emulation patch.

-- 
Thanks & Regards,
Nitin
Open Source Technology Center, Intel Corporation
-----------------------------------------------------------------
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commit 47259a989606e37e5ba24f6722a8258368e6d0a2
Author: Nitin A Kamble <nitin.a.kamble@intel.com>
Date:   Fri Aug 17 18:39:29 2007 -0700

    Implementing emulation of instruction
    	jmp rel short imm8
    	opcode: 0xeb
    Signed-off-by: Nitin A Kamble <nitin.a.kamble@intel.com>

diff --git a/drivers/kvm/x86_emulate.c b/drivers/kvm/x86_emulate.c
index 393dfb6..fed0b2a 100644
--- a/drivers/kvm/x86_emulate.c
+++ b/drivers/kvm/x86_emulate.c
@@ -148,7 +148,7 @@ static u8 opcode_table[256] = {
 	/* 0xE0 - 0xE7 */
 	0, 0, 0, 0, 0, 0, 0, 0,
 	/* 0xE8 - 0xEF */
-	0, SrcImm|ImplicitOps, 0, 0, 0, 0, 0, 0,
+	0, SrcImm|ImplicitOps, 0, SrcImmByte|ImplicitOps, 0, 0, 0, 0,
 	/* 0xF0 - 0xF7 */
 	0, 0, 0, 0,
 	ImplicitOps, 0,
@@ -1029,6 +1029,7 @@ grp2:		/* Grp2 */
 		src.val = _regs[VCPU_REGS_RCX];
 		goto grp2;
 	case 0xe9: /* jmp rel */
+	case 0xeb: /* jmp rel short */
 		JMP_REL(src.val);
 		no_wb = 1; /* Disable writeback. */
 		break;

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commit 17994104bef0da3d182d2b8736fbd1cf8d4a77f0
Author: Nitin A Kamble <nitin.a.kamble@intel.com>
Date:   Fri Aug 17 18:33:07 2007 -0700

    Implement emulation of instruction "jmp rel" opcode 0xe9
    
    Signed-off-by: Nitin A Kamble <nitin.a.kamble@intel.com>

diff --git a/drivers/kvm/x86_emulate.c b/drivers/kvm/x86_emulate.c
index b196d25..393dfb6 100644
--- a/drivers/kvm/x86_emulate.c
+++ b/drivers/kvm/x86_emulate.c
@@ -145,8 +145,10 @@ static u8 opcode_table[256] = {
 	0, 0, 0, 0,
 	/* 0xD8 - 0xDF */
 	0, 0, 0, 0, 0, 0, 0, 0,
-	/* 0xE0 - 0xEF */
-	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	/* 0xE0 - 0xE7 */
+	0, 0, 0, 0, 0, 0, 0, 0,
+	/* 0xE8 - 0xEF */
+	0, SrcImm|ImplicitOps, 0, 0, 0, 0, 0, 0,
 	/* 0xF0 - 0xF7 */
 	0, 0, 0, 0,
 	ImplicitOps, 0,
@@ -447,6 +449,12 @@ struct operand {
 			   (((reg) + _inc) & ((1UL << (ad_bytes << 3)) - 1)); \
 	} while (0)
 
+#define JMP_REL(rel) 							\
+	do {								\
+		_eip += (int)(rel);					\
+		_eip = ((op_bytes == 2) ? (uint16_t)_eip : (uint32_t)_eip); \
+	} while (0)
+
 /*
  * Given the 'reg' portion of a ModRM byte, and a register block, return a
  * pointer into the block that addresses the relevant register.
@@ -1020,6 +1028,10 @@ grp2:		/* Grp2 */
 	case 0xd2 ... 0xd3:	/* Grp2 */
 		src.val = _regs[VCPU_REGS_RCX];
 		goto grp2;
+	case 0xe9: /* jmp rel */
+		JMP_REL(src.val);
+		no_wb = 1; /* Disable writeback. */
+		break;
 	case 0xf6 ... 0xf7:	/* Grp3 */
 		switch (modrm_reg) {
 		case 0 ... 1:	/* test */

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