From fe68dbb743bce5cd2c90080a4df5c0d9a29b769c Mon Sep 17 00:00:00 2001
From: Alexis Engelke <alexis.engelke@googlemail.com>
Date: Sat, 23 Jan 2021 14:28:27 +0100
Subject: [PATCH] decode: Fix LOCK handling for MOV CR/DR

---
 decode.c            | 4 ++--
 tests/test_decode.c | 1 +
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/decode.c b/decode.c
index eac0109..3c8cc35 100644
--- a/decode.c
+++ b/decode.c
@@ -334,7 +334,7 @@ prefix_end:
         op_modrm->type = FD_OT_REG;
         op_modrm->reg = modrm | (prefix_rex & PREFIX_REXB ? 8 : 0);
         op_modrm->misc = FD_RT_GPL;
-        goto op_sizes;
+        goto skip_modrm;
     }
 
     if (UNLIKELY(DESC_HAS_IMPLICIT(desc)))
@@ -425,6 +425,7 @@ prefix_end:
             }
         }
     }
+skip_modrm:
 
     if (UNLIKELY(DESC_HAS_VEXREG(desc)))
     {
@@ -564,7 +565,6 @@ prefix_end:
         instr->flags |= FD_FLAG_LOCK;
     }
 
-op_sizes:;
     uint8_t operand_sizes[4] = {
         1 << DESC_SIZE_FIX1(desc) >> 1, 1 << DESC_SIZE_FIX2(desc), op_size, vec_size
     };
diff --git a/tests/test_decode.c b/tests/test_decode.c
index 492d959..1cb73ea 100644
--- a/tests/test_decode.c
+++ b/tests/test_decode.c
@@ -106,6 +106,7 @@ main(int argc, char** argv)
     TEST64("\x48\x0f\x20\xd0", "mov rax, cr2"); // cr2 + REX.W
     TEST64("\x44\x0f\x20\x08", "UD"); // cr9
     TEST64("\x44\x0f\x21\x00", "UD"); // dr8
+    TEST32("\xf0\x0f\x20\x00", "UD"); // LOCK
     TEST("\x8c\xc0", "mov ax, es");
     TEST64("\x44\x8c\xc0", "mov ax, es");
     TEST64("\x44\x8c\xf0", "UD"); // no segment register 6