• Dr. Tilmann Bubeck's avatar
    ext4: implementation of a new ioctl called EXT4_IOC_SWAP_BOOT · 393d1d1d
    Dr. Tilmann Bubeck authored
    Add a new ioctl, EXT4_IOC_SWAP_BOOT which swaps i_blocks and
    associated attributes (like i_blocks, i_size, i_flags, ...) from the
    specified inode with inode EXT4_BOOT_LOADER_INO (#5). This is
    typically used to store a boot loader in a secure part of the
    filesystem, where it can't be changed by a normal user by accident.
    The data blocks of the previous boot loader will be associated with
    the given inode.
    
    This usercode program is a simple example of the usage:
    
    int main(int argc, char *argv[])
    {
      int fd;
      int err;
    
      if ( argc != 2 ) {
        printf("usage: ext4-swap-boot-inode FILE-TO-SWAP\n");
        exit(1);
      }
    
      fd = open(argv[1], O_WRONLY);
      if ( fd < 0 ) {
        perror("open");
        exit(1);
      }
    
      err = ioctl(fd, EXT4_IOC_SWAP_BOOT);
      if ( err < 0 ) {
        perror("ioctl");
        exit(1);
      }
    
      close(fd);
      exit(0);
    }
    
    [ Modified by Theodore Ts'o to fix a number of bugs in the original code.]
    Signed-off-by: default avatarDr. Tilmann Bubeck <t.bubeck@reinform.de>
    Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
    393d1d1d
ext4.h 95.9 KB