Re: [PATCH 1/1] target/i386: Generate an illegal opcode exception on cmp instructions with lock prefix

[Paolo Bonzini]

On 2/15/24 10:50, Ziqiao Kong wrote:

target/i386: As specified by Intel Manual Vol2 3-180, cmp instructions
are not allowed to have lock prefix and a `UD` should be raised. Without
this patch, s1->T0 will be uninitialized and used in the case OP_CMPL.

Signed-off-by: Ziqiao Kong <ziqiaok...@gmail.com>
---
  target/i386/tcg/translate.c | 11 ++++++-----
  1 file changed, 6 insertions(+), 5 deletions(-)

Queued, thanks!

Paolo

diff --git a/target/i386/tcg/translate.c b/target/i386/tcg/translate.c
index 10cba16256..07f642dc9e 100644
--- a/target/i386/tcg/translate.c
+++ b/target/i386/tcg/translate.c
@@ -1507,12 +1507,13 @@ static bool check_iopl(DisasContext *s)
  /* if d == OR_TMP0, it means memory operand (address in A0) */
  static void gen_op(DisasContext *s1, int op, MemOp ot, int d)
  {
+    /* Invalid lock prefix when destination is not memory or OP_CMPL. */
+    if ((d != OR_TMP0 || op == OP_CMPL) && s1->prefix & PREFIX_LOCK) {
+        gen_illegal_opcode(s1);
+        return;
+    }
+
      if (d != OR_TMP0) {
-        if (s1->prefix & PREFIX_LOCK) {
-            /* Lock prefix when destination is not memory.  */
-            gen_illegal_opcode(s1);
-            return;
-        }
          gen_op_mov_v_reg(s1, ot, s1->T0, d);
      } else if (!(s1->prefix & PREFIX_LOCK)) {
          gen_op_ld_v(s1, ot, s1->T0, s1->A0);