From: Gabe Black <gabeblack@google.com>
Date: Fri, 27 Oct 2017 20:46:58 +0000 (-0700)
Subject: x86: Fix VEX instruction decoding.
X-Git-Tag: v19.0.0.0~2590
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=1025ef1598b8b7c3d00b82d30458e375697b8eff;p=gem5.git

x86: Fix VEX instruction decoding.

When decoding VEX prefixed instructions, the x86 predecoder wasn't walking
past the opcode byte and so was also interpreting it as the modRM byte.

Reported-by: likunxi@fas.harvard.edu

Change-Id: I6d4bdabfa03411704c48d905c50c7b23072fc615
Reviewed-on: https://gem5-review.googlesource.com/5281
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>
---

diff --git a/src/arch/x86/decoder.cc b/src/arch/x86/decoder.cc
index 930c2b951..9c4997d6f 100644
--- a/src/arch/x86/decoder.cc
+++ b/src/arch/x86/decoder.cc
@@ -355,6 +355,7 @@ Decoder::doVexOpcodeState(uint8_t nextByte)
     DPRINTF(Decoder, "Found VEX opcode %#x.\n", nextByte);
 
     emi.opcode.op = nextByte;
+    consumeByte();
 
     switch (emi.opcode.type) {
       case TwoByteOpcode: