Abhinav's work on usemem_remap.c

Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>

1 files changed, 66 insertions, 0 deletions

diff --git a/usemem_remap.c b/usemem_remap.c
new file mode 100644
index 0000000..95cb833
--- /dev/null
+++ b/usemem_remap.c
@@ -0,0 +1,66 @@
+/*
+ * Exercises functions in fremap.c
+ *
+ * Takes a file as argument along with its size and creates a non linear mapping in memory
+ *
+ * then reverses the page order in memory using remap_file_pages system call
+ */
+
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/mman.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <string.h>
+#include <errno.h>
+
+int main (int argc, char *argv[])
+{
+	int fd;
+	int pagesize = getpagesize();
+	int i;
+
+	unsigned long size;
+	int no_of_pages;
+
+	/* initialize to NULL */
+	unsigned char *start = NULL;
+	unsigned char *end;
+
+	if (argc != 3) {
+		fprintf(stdout, "Usage : %s FILE SIZE\n", argv[0]);
+		exit(1);
+	}
+
+	size = atoi(argv[2]);
+	no_of_pages = size / pagesize;
+
+	if ((fd = open(argv[1], O_RDWR | O_CREAT, 0666)) == -1) {
+		fprintf(stderr, "error opening file\n");
+		exit(1);
+	}
+
+	/* create a contiguous mapping */
+	if ((start = (unsigned char *) mmap(NULL, size, PROT_READ|PROT_WRITE,
+					   MAP_SHARED|MAP_POPULATE, fd, 0)) == MAP_FAILED) {
+		fprintf(stderr, "%s: mmap failed: %s\n",
+			argv[1], strerror(errno));
+		exit(1);
+	}
+
+	end = (unsigned char *) (start + size);
+
+	/* make mapping non-contiguous (reverse the page mapping order) */
+	for (i = 0; i < no_of_pages / 2; i++) {
+		if (remap_file_pages(end - (i * pagesize),
+				     pagesize, 0, i, MAP_SHARED|MAP_POPULATE) == -1) {
+			fprintf(stderr, "remap failed with error %s\n", strerror(errno));
+			exit(1);
+		}
+	}
+
+	close(fd);
+
+	return 0;
+}