report memory access size for "monitor"

2 files changed, 6 insertions, 0 deletions

diff --git a/CHANGELOG b/CHANGELOG
index 9ae9fd9..97f5216 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -20,6 +20,7 @@
     is unchanged and uses a 16-bit form for source GPR.
 * reject 0f0d prefetch/nop with a register operand, which was incorrectly decoded before.
 * maskmovq and maskmovdqu now have their implicit memory access size reported correctly.
+* monitor now reports the memory access size of the monitored dword/qword.
 
 ## 2.0.0
 
diff --git a/src/long_mode/mod.rs b/src/long_mode/mod.rs
index 5d7180e..de9a323 100644
--- a/src/long_mode/mod.rs
+++ b/src/long_mode/mod.rs
@@ -8296,6 +8296,11 @@ fn read_operands<
                         match m {
                             0b000 => {
                                 instruction.opcode = Opcode::MONITOR;
+                                instruction.mem_size = if instruction.prefixes.address_size() {
+                                    4
+                                } else {
+                                    8
+                                };
                             }
                             0b001 => {
                                 instruction.opcode = Opcode::MWAIT;