commit 5c53bb812152c3d7919cadfd47c210b181bf89ac
author Peter Maydell <peter.maydell@linaro.org> Fri Mar 28 15:29:48 2014 +0000
committer Richard Henderson <rth@twiddle.net> Mon May 12 10:03:04 2014 -0700
tree 1e6de84b05aa30c933b709bfb6097dc45b6044d0
parent 4387345a962284c77435a9644d528d2356adecc5

tcg: Avoid undefined behaviour patching code at unaligned addresses

To avoid C undefined behaviour when patching generated code,
provide wrappers tcg_patch8/16/32/64 which use the usual memcpy
trick, and use them in the i386 backend.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>

tcg/i386/tcg-target.c

diff --git a/tcg/i386/tcg-target.c b/tcg/i386/tcg-target.c
index 34ece1f..9a585ab 100644
--- a/tcg/i386/tcg-target.c
+++ b/tcg/i386/tcg-target.c
@@ -151,14 +151,14 @@
         if (value != (int32_t)value) {
             tcg_abort();
         }
-        *(uint32_t *)code_ptr = value;
+        tcg_patch32(code_ptr, value);
         break;
     case R_386_PC8:
         value -= (uintptr_t)code_ptr;
         if (value != (int8_t)value) {
             tcg_abort();
         }
-        *(uint8_t *)code_ptr = value;
+        tcg_patch8(code_ptr, value);
         break;
     default:
         tcg_abort();
@@ -1276,9 +1276,9 @@
     uint8_t **label_ptr = &l->label_ptr[0];
 
     /* resolve label address */
-    *(uint32_t *)label_ptr[0] = (uint32_t)(s->code_ptr - label_ptr[0] - 4);
+    tcg_patch32(label_ptr[0], s->code_ptr - label_ptr[0] - 4);
     if (TARGET_LONG_BITS > TCG_TARGET_REG_BITS) {
-        *(uint32_t *)label_ptr[1] = (uint32_t)(s->code_ptr - label_ptr[1] - 4);
+        tcg_patch32(label_ptr[1], s->code_ptr - label_ptr[1] - 4);
     }
 
     if (TCG_TARGET_REG_BITS == 32) {
@@ -1360,9 +1360,9 @@
     TCGReg retaddr;
 
     /* resolve label address */
-    *(uint32_t *)label_ptr[0] = (uint32_t)(s->code_ptr - label_ptr[0] - 4);
+    tcg_patch32(label_ptr[0], s->code_ptr - label_ptr[0] - 4);
     if (TARGET_LONG_BITS > TCG_TARGET_REG_BITS) {
-        *(uint32_t *)label_ptr[1] = (uint32_t)(s->code_ptr - label_ptr[1] - 4);
+        tcg_patch32(label_ptr[1], s->code_ptr - label_ptr[1] - 4);
     }
 
     if (TCG_TARGET_REG_BITS == 32) {