Use __predict_false on some fortify methods.

Give the compiler some hints that these error conditions
are unlikely to occur in practice.

Change-Id: Ifaf7322a12120ef663c8315c1a18c2dcbe4bda23

libc/bionic/__memcpy_chk.cpp

@@ -45,7 +45,7 @@
 extern "C" void *__memcpy_chk(void *dest, const void *src,
               size_t copy_amount, size_t dest_len)
 {
-    if (__builtin_expect(copy_amount > dest_len, 0)) {
+    if (__predict_false(copy_amount > dest_len)) {
         __fortify_chk_fail("memcpy buffer overflow",
                              BIONIC_EVENT_MEMCPY_BUFFER_OVERFLOW);
     }

libc/bionic/__memmove_chk.cpp

@@ -44,7 +44,7 @@
 extern "C" void *__memmove_chk (void *dest, const void *src,
               size_t len, size_t dest_len)
 {
-    if (len > dest_len) {
+    if (__predict_false(len > dest_len)) {
         __fortify_chk_fail("memmove buffer overflow",
                              BIONIC_EVENT_MEMMOVE_BUFFER_OVERFLOW);
     }

libc/bionic/__memset_chk.cpp

@@ -42,7 +42,7 @@
  * greater than 0.
  */
 extern "C" void *__memset_chk (void *dest, int c, size_t n, size_t dest_len) {
-    if (n > dest_len) {
+    if (__predict_false(n > dest_len)) {
         __fortify_chk_fail("memset buffer overflow",
                              BIONIC_EVENT_MEMSET_BUFFER_OVERFLOW);
     }

libc/bionic/__strcpy_chk.cpp

@@ -44,7 +44,7 @@
 extern "C" char *__strcpy_chk (char *dest, const char *src, size_t dest_len) {
     // TODO: optimize so we don't scan src twice.
     size_t src_len = strlen(src) + 1;
-    if (src_len > dest_len) {
+    if (__predict_false(src_len > dest_len)) {
         __fortify_chk_fail("strcpy buffer overflow",
                              BIONIC_EVENT_STRCPY_BUFFER_OVERFLOW);
     }

libc/bionic/__strlcat_chk.cpp

@@ -45,7 +45,7 @@
 extern "C" size_t __strlcat_chk(char *dest, const char *src,
               size_t supplied_size, size_t dest_len_from_compiler)
 {
-    if (supplied_size > dest_len_from_compiler) {
+    if (__predict_false(supplied_size > dest_len_from_compiler)) {
         __fortify_chk_fail("strlcat buffer overflow", 0);
     }
 

libc/bionic/__strlcpy_chk.cpp

@@ -45,7 +45,7 @@
 extern "C" size_t __strlcpy_chk(char *dest, const char *src,
               size_t supplied_size, size_t dest_len_from_compiler)
 {
-    if (supplied_size > dest_len_from_compiler) {
+    if (__predict_false(supplied_size > dest_len_from_compiler)) {
         __fortify_chk_fail("strlcpy buffer overflow", 0);
     }
 

libc/bionic/__strlen_chk.cpp

@@ -56,7 +56,7 @@
 extern "C" size_t __strlen_chk(const char *s, size_t s_len) {
     size_t ret = strlen(s);
 
-    if (__builtin_expect(ret >= s_len, 0)) {
+    if (__predict_false(ret >= s_len)) {
         __fortify_chk_fail("strlen read overflow", 0);
     }
 

libc/bionic/__strncpy_chk.cpp

@@ -44,7 +44,7 @@
 extern "C" char *__strncpy_chk (char *dest, const char *src,
               size_t len, size_t dest_len)
 {
-    if (len > dest_len) {
+    if (__predict_false(len > dest_len)) {
         __fortify_chk_fail("strncpy buffer overflow",
                              BIONIC_EVENT_STRNCPY_BUFFER_OVERFLOW);
     }

libc/bionic/__umask_chk.cpp

@@ -42,7 +42,7 @@
  * greater than 0.
  */
 extern "C" mode_t __umask_chk(mode_t mode) {
-    if ((mode & 0777) != mode) {
+    if (__predict_false((mode & 0777) != mode)) {
         __fortify_chk_fail("umask called with invalid mask", 0);
     }
 

libc/bionic/__vsnprintf_chk.cpp

@@ -50,7 +50,7 @@ extern "C" int __vsnprintf_chk(
         const char *format,
         va_list va)
 {
-    if (supplied_size > dest_len_from_compiler) {
+    if (__predict_false(supplied_size > dest_len_from_compiler)) {
         __fortify_chk_fail("vsnprintf buffer overflow", 0);
     }
 

libc/bionic/open.c

@@ -52,7 +52,7 @@ int open(const char *pathname, int flags, ...)
 }
 
 int __open_2(const char *pathname, int flags) {
-    if (flags & O_CREAT) {
+    if (__predict_false(flags & O_CREAT)) {
         __fortify_chk_fail("open(O_CREAT) called without specifying a mode", 0);
     }