| #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); |
| |
| } |