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-rw-r--r--swap_super.c81
1 files changed, 81 insertions, 0 deletions
diff --git a/swap_super.c b/swap_super.c
new file mode 100644
index 0000000..b6db574
--- /dev/null
+++ b/swap_super.c
@@ -0,0 +1,81 @@
+#include <unistd.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <sys/mount.h>
+/*
+ * This is a tiny test program to endian-swap
+ * the superblock on a given device.
+ * We simply read 4k from where the superblock should be
+ * do the swap, and write it back
+ * Don't use this on a real array, use mdadm.
+ */
+
+#define MD_RESERVED_BYTES (64 * 1024)
+#define MD_RESERVED_SECTORS (MD_RESERVED_BYTES / 512)
+
+#define MD_NEW_SIZE_SECTORS(x) ((x & ~(MD_RESERVED_SECTORS - 1)) - MD_RESERVED_SECTORS)
+
+extern long long lseek64(int, long long, int);
+
+int main(int argc, char *argv[])
+{
+ int fd, i;
+ unsigned long size;
+ unsigned long long offset;
+ char super[4096];
+ if (argc != 2) {
+ fprintf(stderr, "Usage: swap_super device\n");
+ exit(1);
+ }
+ fd = open(argv[1], O_RDWR);
+ if (fd<0) {
+ perror(argv[1]);
+ exit(1);
+ }
+ if (ioctl(fd, BLKGETSIZE, &size)) {
+ perror("BLKGETSIZE");
+ exit(1);
+ }
+ offset = MD_NEW_SIZE_SECTORS(size) * 512LL;
+ if (lseek64(fd, offset, 0) < 0LL) {
+ perror("lseek64");
+ exit(1);
+ }
+ if (read(fd, super, 4096) != 4096) {
+ perror("read");
+ exit(1);
+ }
+
+ for (i=0; i < 4096 ; i+=4) {
+ char t = super[i];
+ super[i] = super[i+3];
+ super[i+3] = t;
+ t=super[i+1];
+ super[i+1]=super[i+2];
+ super[i+2]=t;
+ }
+ /* swap the u64 events counters */
+ for (i=0; i<4; i++) {
+ /* events_hi and events_lo */
+ char t=super[32*4+7*4 +i];
+ super[32*4+7*4 +i] = super[32*4+8*4 +i];
+ super[32*4+8*4 +i] = t;
+
+ /* cp_events_hi and cp_events_lo */
+ t=super[32*4+9*4 +i];
+ super[32*4+9*4 +i] = super[32*4+10*4 +i];
+ super[32*4+10*4 +i] = t;
+ }
+
+ if (lseek64(fd, offset, 0) < 0LL) {
+ perror("lseek64");
+ exit(1);
+ }
+ if (write(fd, super, 4096) != 4096) {
+ perror("write");
+ exit(1);
+ }
+ exit(0);
+
+}