Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=b4c6abfef400c0f74d9b86a149a6719706cfdbbc
Commit: b4c6abfef400c0f74d9b86a149a6719706cfdbbc
Parent: a22436b7b8ec9b14a0451d9ac0fdc9d370bd7800
Author: Laurent Vivier <[EMAIL PROTECTED]>
AuthorDate: Tue Sep 25 13:36:40 2007 +0200
Committer: Avi Kivity <[EMAIL PROTECTED]>
CommitDate: Wed Jan 30 17:52:49 2008 +0200
KVM: x86 emulator: Any legacy prefix after a REX prefix nullifies its effect
This patch modifies the management of REX prefix according behavior
I saw in Xen 3.1. In Xen, this modification has been introduced by
Jan Beulich.
http://lists.xensource.com/archives/html/xen-changelog/2007-01/msg00081.html
Signed-off-by: Laurent Vivier <[EMAIL PROTECTED]>
Signed-off-by: Avi Kivity <[EMAIL PROTECTED]>
---
drivers/kvm/x86_emulate.c | 24 +++++++++++++++---------
1 files changed, 15 insertions(+), 9 deletions(-)
diff --git a/drivers/kvm/x86_emulate.c b/drivers/kvm/x86_emulate.c
index 0afe660..e294d84 100644
--- a/drivers/kvm/x86_emulate.c
+++ b/drivers/kvm/x86_emulate.c
@@ -521,7 +521,6 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct
x86_emulate_ops *ops)
{
struct decode_cache *c = &ctxt->decode;
u8 sib, rex_prefix = 0;
- unsigned int i;
int rc = 0;
int mode = ctxt->mode;
int index_reg = 0, base_reg = 0, scale, rip_relative = 0;
@@ -551,7 +550,7 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct
x86_emulate_ops *ops)
}
/* Legacy prefixes. */
- for (i = 0; i < 8; i++) {
+ for (;;) {
switch (c->b = insn_fetch(u8, 1, c->eip)) {
case 0x66: /* operand-size override */
c->op_bytes ^= 6; /* switch between 2/4 bytes */
@@ -582,6 +581,11 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct
x86_emulate_ops *ops)
case 0x36: /* SS override */
c->override_base = &ctxt->ss_base;
break;
+ case 0x40 ... 0x4f: /* REX */
+ if (mode != X86EMUL_MODE_PROT64)
+ goto done_prefixes;
+ rex_prefix = c->b;
+ continue;
case 0xf0: /* LOCK */
c->lock_prefix = 1;
break;
@@ -592,19 +596,21 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct
x86_emulate_ops *ops)
default:
goto done_prefixes;
}
+
+ /* Any legacy prefix after a REX prefix nullifies its effect. */
+
+ rex_prefix = 0;
}
done_prefixes:
/* REX prefix. */
- if ((mode == X86EMUL_MODE_PROT64) && ((c->b & 0xf0) == 0x40)) {
- rex_prefix = c->b;
- if (c->b & 8)
+ if (rex_prefix) {
+ if (rex_prefix & 8)
c->op_bytes = 8; /* REX.W */
- c->modrm_reg = (c->b & 4) << 1; /* REX.R */
- index_reg = (c->b & 2) << 2; /* REX.X */
- c->modrm_rm = base_reg = (c->b & 1) << 3; /* REG.B */
- c->b = insn_fetch(u8, 1, c->eip);
+ c->modrm_reg = (rex_prefix & 4) << 1; /* REX.R */
+ index_reg = (rex_prefix & 2) << 2; /* REX.X */
+ c->modrm_rm = base_reg = (rex_prefix & 1) << 3; /* REG.B */
}
/* Opcode byte(s). */
-
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