Add mmap_write.

Author: danluu

Makefile

@@ -1,10 +1,13 @@
 mmap_read: mmap_read.c
 	gcc -o mmap_read mmap_read.c -I.
 
+mmap_write: mmap_write.c
+	gcc -o mmap_write mmap_write.c -I.
+
 pread: pread.c
 	gcc -o pread pread.c -I.
 
 pwrite: pwrite.c
 	gcc -o pwrite pwrite.c -I.
 
-all: pread pwrite mmap_read
+all: pread pwrite mmap_read mmap_write

main.py

@@ -174,7 +174,7 @@ def read_corruption_config():
 
 def setup_and_run_test(config, results_writer, do_corruption):
     error_block = (config['offset'], 1) #TODO(Wesley) multi-section errors
-    test_commands = ['./mmap_read', './pread', './pwrite']
+    test_commands = ['./mmap_read', './mmap_write', './pread', './pwrite']
     for command in test_commands:
         tmp_image_path = make_tmpfile(config['image'], config['md5sum'])
 

mmap_write.c

@@ -0,0 +1,47 @@
+#include <errno.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <sys/mman.h>
+#include <sys/types.h>
+#include <fcntl.h>
+
+#define SIZE 445
+
+int main(int argc, char *argv[])
+{
+  char *memblock;
+  int fd;
+
+  if (argc != 2) {
+    printf("Expected 1 argument (filename), found %d\n", argc-1);
+    return 1;
+  }
+
+  fd = open(argv[1], O_RDONLY);
+  if (fd < 0) {
+    printf("open fail %s\n", strerror(errno));
+    return fd;
+  }
+
+  memblock = mmap(NULL, SIZE, PROT_WRITE, MAP_PRIVATE, fd, 0);
+  if (memblock == MAP_FAILED) {
+    perror("mmap");
+    return 2;
+  }
+
+  memblock[0] = '\0';
+  // Without use of this call there is no guarantee that changes are
+  // written back before munmap(2) is called  
+  if (msync(memblock, 1, MS_SYNC)) {
+    perror("msync");
+    return 3;
+  }
+
+  if (munmap(memblock, SIZE)) {
+    perror("munmap");
+    return 4;
+  }
+  return 0;
+}