[Qemu-devel] [PATCH] target/m68k: fix set_cc_op()

[Laurent Vivier]

The first call of set_cc_op() in a new translation sequence
is done with old_op set to CC_OP_DYNAMIC (-1).

This will do an out of bound access to the array cc_op_live[].

We fix that by adding an entry in cc_op_live[] for CC_OP_DYNAMIC,
and in this case we can also discard QREG_CC_OP.

Reported-by: Thomas Huth <address@hidden>
Signed-off-by: Laurent Vivier <address@hidden>
---
 target/m68k/cpu.h       | 2 +-
 target/m68k/translate.c | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/target/m68k/cpu.h b/target/m68k/cpu.h
index afae5f68ac..5d03764eab 100644
--- a/target/m68k/cpu.h
+++ b/target/m68k/cpu.h
@@ -182,7 +182,7 @@ void cpu_m68k_set_fpcr(CPUM68KState *env, uint32_t val);
  */
 typedef enum {
     /* Translator only -- use env->cc_op.  */
-    CC_OP_DYNAMIC = -1,
+    CC_OP_DYNAMIC,
 
     /* Each flag bit computed into cc_[xcnvz].  */
     CC_OP_FLAGS,
diff --git a/target/m68k/translate.c b/target/m68k/translate.c
index b60909222c..61ac1a8e83 100644
--- a/target/m68k/translate.c
+++ b/target/m68k/translate.c
@@ -207,6 +207,7 @@ typedef void (*disas_proc)(CPUM68KState *env, DisasContext 
*s, uint16_t insn);
 #endif
 
 static const uint8_t cc_op_live[CC_OP_NB] = {
+    [CC_OP_DYNAMIC] = CCF_C | CCF_V | CCF_Z | CCF_N | CCF_X,
     [CC_OP_FLAGS] = CCF_C | CCF_V | CCF_Z | CCF_N | CCF_X,
     [CC_OP_ADDB ... CC_OP_ADDL] = CCF_X | CCF_N | CCF_V,
     [CC_OP_SUBB ... CC_OP_SUBL] = CCF_X | CCF_N | CCF_V,
@@ -237,6 +238,11 @@ static void set_cc_op(DisasContext *s, CCOp op)
     if (dead & CCF_V) {
         tcg_gen_discard_i32(QREG_CC_V);
     }
+
+    /* Discard any computed CC_OP value */
+    if (old_op == CC_OP_DYNAMIC) {
+        tcg_gen_discard_i32(QREG_CC_OP);
+    }
 }
 
 /* Update the CPU env CC_OP state.  */
-- 
2.14.3