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authorDr. Tilmann Bubeck <t.bubeck@reinform.de>2013-04-08 12:54:05 -0400
committerTheodore Ts'o <tytso@mit.edu>2013-04-08 12:54:05 -0400
commit393d1d1d76933886d5e1ce603214c9987589c6d5 (patch)
tree2f2368a9d787ccb8e69f61a3e5023ef9c4abfd8b /Documentation/filesystems
parentf78ee70db40040e6f38a5134527d4760254d6683 (diff)
ext4: implementation of a new ioctl called EXT4_IOC_SWAP_BOOT
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: Dr. Tilmann Bubeck <t.bubeck@reinform.de> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Diffstat (limited to 'Documentation/filesystems')
-rw-r--r--Documentation/filesystems/ext4.txt10
1 files changed, 10 insertions, 0 deletions
diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt
index 34ea4f1fa6ea..5dd957d8b25b 100644
--- a/Documentation/filesystems/ext4.txt
+++ b/Documentation/filesystems/ext4.txt
@@ -587,6 +587,16 @@ Table of Ext4 specific ioctls
bitmaps and inode table, the userspace tool thus
just passes the new number of blocks.
+EXT4_IOC_SWAP_BOOT Swap 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.
+
..............................................................................
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