failed mmap fop attempt

kernel_module/user/mmap.c

@@ -0,0 +1,35 @@
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+#define PAGE_SIZE 4096
+
+int main(int argc, char **argv)
+{
+	int fd;
+	char *address = NULL;
+
+	if (argc < 2) {
+		printf("Usage: %s <mmap_file>\n", argv[0]);
+		return EXIT_FAILURE;
+	}
+	fd = open(argv[1], O_RDWR | O_SYNC);
+	if (fd < 0) {
+		perror("open");
+		return EXIT_FAILURE;
+	}
+	printf("fd = %d\n", fd);
+	address = mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+	if (address == MAP_FAILED) {
+		perror("mmap");
+		return EXIT_FAILURE;
+	}
+	printf("%s\n", address);
+	memcpy(address + 11 , "qwer", 6);
+	printf("%s\n", address);
+	close(fd);
+	return EXIT_SUCCESS;
+}