Changed PowerPC CPU registers used by Zend VM to work around GCC bug.

Old registers (r28/r29) might be clobbered by _restgpr routine used for return from C function compiled with -Os.

Author: dstogov

NEWS

@@ -2,6 +2,11 @@ PHP                                                                        NEWS
 |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
 ?? ??? 2021, PHP 7.4.18
 
+- Core:
+  . Changed PowerPC CPU registers used by Zend VM to work around GCC bug.
+    Old registers (r28/r29) might be clobbered by _restgpr routine used for
+    return from C function compiled with -Os. (Dmitry)
+
 - DOM:
   . Fixed bug #66783 (UAF when appending DOMDocument to element). (cmb)
 

Zend/zend_execute.c

@@ -51,11 +51,11 @@
 #  define ZEND_VM_FP_GLOBAL_REG "%r14"
 #  define ZEND_VM_IP_GLOBAL_REG "%r15"
 # elif defined(__GNUC__) && ZEND_GCC_VERSION >= 4008 && defined(__powerpc64__)
-#  define ZEND_VM_FP_GLOBAL_REG "r28"
-#  define ZEND_VM_IP_GLOBAL_REG "r29"
+#  define ZEND_VM_FP_GLOBAL_REG "r14"
+#  define ZEND_VM_IP_GLOBAL_REG "r15"
 # elif defined(__IBMC__) && ZEND_GCC_VERSION >= 4002 && defined(__powerpc64__)
-#  define ZEND_VM_FP_GLOBAL_REG "r28"
-#  define ZEND_VM_IP_GLOBAL_REG "r29"
+#  define ZEND_VM_FP_GLOBAL_REG "r14"
+#  define ZEND_VM_IP_GLOBAL_REG "r15"
 # elif defined(__GNUC__) && ZEND_GCC_VERSION >= 4008 && defined(__aarch64__)
 #  define ZEND_VM_FP_GLOBAL_REG "x27"
 #  define ZEND_VM_IP_GLOBAL_REG "x28"