add fortified implementations of write/pwrite{,64}

These are just based on the read/pread{,64} implementations with the
function calls and error messages adjusted as appropriate. The only
difference is that the buffer parameters are const.

Change-Id: Ida1597a903807f583f230d74bcedffdb7b24fcf6

tests/fortify_test.cpp

@@ -645,6 +645,22 @@ TEST_F(DEATHTEST, pread64_fortified) {
   close(fd);
 }
 
+TEST_F(DEATHTEST, pwrite_fortified) {
+  char buf[1] = {0};
+  size_t ct = atoi("2"); // prevent optimizations
+  int fd = open("/dev/null", O_WRONLY);
+  ASSERT_FORTIFY(pwrite(fd, buf, ct, 0));
+  close(fd);
+}
+
+TEST_F(DEATHTEST, pwrite64_fortified) {
+  char buf[1] = {0};
+  size_t ct = atoi("2"); // prevent optimizations
+  int fd = open("/dev/null", O_WRONLY);
+  ASSERT_FORTIFY(pwrite64(fd, buf, ct, 0));
+  close(fd);
+}
+
 TEST_F(DEATHTEST, read_fortified) {
   char buf[1];
   size_t ct = atoi("2"); // prevent optimizations
@@ -653,6 +669,14 @@ TEST_F(DEATHTEST, read_fortified) {
   close(fd);
 }
 
+TEST_F(DEATHTEST, write_fortified) {
+  char buf[1] = {0};
+  size_t ct = atoi("2"); // prevent optimizations
+  int fd = open("/dev/null", O_WRONLY);
+  ASSERT_EXIT(write(fd, buf, ct), testing::KilledBySignal(SIGABRT), "");
+  close(fd);
+}
+
 TEST_F(DEATHTEST, fread_fortified) {
   char buf[1];
   size_t ct = atoi("2"); // prevent optimizations