From 82b8f9abcef82c3bc9cabac928253fb6bdab6d28 Mon Sep 17 00:00:00 2001
From: Derek Bruening <bruening@google.com>
Date: Mon, 7 Mar 2016 20:09:49 -0500
Subject: [PATCH] i#1899: suppress decoding warning on MPX prefixes

Until we have i#1312 and actual MPX decoding, for now we suppress the repne
prefix warning seen on Windows 10.

Fixes #1899

Review-URL: https://codereview.appspot.com/290480043
---
 core/arch/x86/decode.c         | 12 +++++++++---
 core/arch/x86/decode_private.h |  5 ++++-
 core/arch/x86/instr.c          | 10 ++++++++--
 3 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/core/arch/x86/decode.c b/core/arch/x86/decode.c
index 9b010fae0e9..46b631cd70c 100644
--- a/core/arch/x86/decode.c
+++ b/core/arch/x86/decode.c
@@ -1,5 +1,5 @@
 /* **********************************************************
- * Copyright (c) 2011-2015 Google, Inc.  All rights reserved.
+ * Copyright (c) 2011-2016 Google, Inc.  All rights reserved.
  * Copyright (c) 2000-2010 VMware, Inc.  All rights reserved.
  * **********************************************************/
 
@@ -1104,8 +1104,14 @@ read_instruction(byte *pc, byte *orig_pc,
         if (report_invalid &&
             ((di->rep_prefix &&
               /* case 6861: AMD64 opt: "rep ret" used if br tgt or after cbr */
-              (pc != di->start_pc+2 || *(di->start_pc+1) != RAW_OPCODE_ret))
-             || di->repne_prefix)) {
+              (pc != di->start_pc+2 || *(di->start_pc+1) != RAW_OPCODE_ret)) ||
+             (di->repne_prefix &&
+              /* i#1899: MPX puts repne prior to branches.  We ignore here until we have
+               * full MPX decoding support (i#1312).
+               */
+              info->type != OP_call && info->type != OP_call_ind && info->type != OP_ret &&
+              info->type != OP_jmp && info->type != OP_jmp_short &&
+              !opc_is_cbr_arch(info->type)))) {
             char bytes[17*3];
             int i;
             dcontext_t *dcontext = get_thread_private_dcontext();
diff --git a/core/arch/x86/decode_private.h b/core/arch/x86/decode_private.h
index dc79518d5c6..b41f759f48d 100644
--- a/core/arch/x86/decode_private.h
+++ b/core/arch/x86/decode_private.h
@@ -1,5 +1,5 @@
 /* **********************************************************
- * Copyright (c) 2011-2014 Google, Inc.  All rights reserved.
+ * Copyright (c) 2011-2016 Google, Inc.  All rights reserved.
  * Copyright (c) 2000-2010 VMware, Inc.  All rights reserved.
  * **********************************************************/
 
@@ -439,6 +439,9 @@ int indir_var_reg_offs_factor(int optype);
 opnd_size_t expand_subreg_size(opnd_size_t sz);
 dr_pred_type_t decode_predicate_from_instr_info(uint opcode, const instr_info_t *info);
 
+/* in instr.c, not exported to non-x86 files */
+bool opc_is_cbr_arch(int opc);
+
 /* exported tables */
 extern const instr_info_t first_byte[];
 extern const instr_info_t second_byte[];
diff --git a/core/arch/x86/instr.c b/core/arch/x86/instr.c
index 4462b8b728c..dfb5060788c 100644
--- a/core/arch/x86/instr.c
+++ b/core/arch/x86/instr.c
@@ -387,14 +387,20 @@ instr_is_return(instr_t *instr)
 /*** WARNING!  The following rely on ordering of opcodes! ***/
 
 bool
-instr_is_cbr_arch(instr_t *instr)      /* conditional branch */
+opc_is_cbr_arch(int opc)
 {
-    int opc = instr->opcode; /* caller ensures opcode is valid */
     return ((opc >= OP_jo && opc <= OP_jnle) ||
             (opc >= OP_jo_short && opc <= OP_jnle_short) ||
             (opc >= OP_loopne && opc <= OP_jecxz));
 }
 
+bool
+instr_is_cbr_arch(instr_t *instr)      /* conditional branch */
+{
+    int opc = instr->opcode; /* caller ensures opcode is valid */
+    return opc_is_cbr_arch(opc);
+}
+
 bool
 instr_is_mbr_arch(instr_t *instr)      /* multi-way branch */
 {