| /* |
| * swap-offset.c |
| * |
| * This program determines the location of the swap offset for given swap file. |
| * |
| * Copyright (C) 2006 Luca Tettamanti <kronos.it@gmail.com> |
| * |
| * This file is released under the GPLv2. |
| * |
| */ |
| |
| #include "config.h" |
| #include <stdio.h> |
| #include <string.h> |
| #include <fcntl.h> |
| #include <unistd.h> |
| #include <sys/ioctl.h> |
| #include <sys/types.h> |
| #include <sys/stat.h> |
| #include <linux/fs.h> |
| #include <errno.h> |
| |
| #define SWAP_SIG "SWAPSPACE2" |
| #define SWAP_SIG_SIZE 10 |
| |
| int main(int argc, char **argv) |
| { |
| unsigned int block, last_block, first_block, blocks_per_page; |
| unsigned int offset; |
| int size, blk_size; |
| int fd; |
| unsigned int i; |
| ssize_t ret; |
| struct stat stat; |
| unsigned char buf[SWAP_SIG_SIZE]; |
| int err = 0; |
| int const page_size = getpagesize(); |
| |
| if (argc < 2) { |
| fprintf(stderr, "Usage: swap-offset <file_name>\n"); |
| return EINVAL; |
| } |
| |
| fd = open(argv[1], O_RDONLY); |
| if (fd < 0) { |
| err = errno; |
| perror("open()"); |
| return err; |
| } |
| if (fstat(fd, &stat)) { |
| err = errno; |
| perror("fstat()"); |
| goto out; |
| } |
| if (!S_ISREG(stat.st_mode)) { |
| fprintf(stderr, "Not a regular file\n"); |
| err = EINVAL; |
| goto out; |
| } |
| |
| /* Check swap signature */ |
| if (lseek(fd, page_size - SWAP_SIG_SIZE, SEEK_SET) < 0) { |
| err = errno; |
| perror("lseek()"); |
| goto out; |
| } |
| ret = read(fd, buf, SWAP_SIG_SIZE); |
| if (ret < 0) { |
| err = errno; |
| perror("read()"); |
| goto out; |
| } else if (ret < SWAP_SIG_SIZE) { |
| fprintf(stderr, "Failed to read swap signature: file is too short.\n"); |
| err = EINVAL; |
| goto out; |
| } |
| |
| if (memcmp(buf, SWAP_SIG, SWAP_SIG_SIZE)) { |
| fprintf(stderr, "Swap signature not found.\n"); |
| err = EINVAL; |
| goto out; |
| } |
| |
| if (ioctl(fd, FIGETBSZ, &blk_size)) { |
| err = errno; |
| perror("ioctl(FIGETBSZ) failed"); |
| goto out; |
| } |
| |
| blocks_per_page = page_size / blk_size; |
| |
| /* Check that the header is contiguous */ |
| last_block = 0; |
| first_block = 0; |
| size = 0; |
| for (i = 0; i < blocks_per_page; i++) { |
| block = i; |
| |
| if (ioctl(fd, FIBMAP, &block)) { |
| err = errno; |
| perror("ioctl(FIBMAP) failed"); |
| goto out; |
| } |
| |
| if (last_block && block != last_block + 1) |
| break; |
| |
| if (!first_block) |
| first_block = block; |
| |
| size += blk_size; |
| last_block = block; |
| } |
| if (size < page_size) { |
| fprintf(stderr, "Swapfile header is not contiguous and cannot " |
| "be used for suspension.\n"); |
| err = EINVAL; |
| } else { |
| offset = (unsigned long long)first_block * blk_size / page_size; |
| printf("resume offset = %u\n", offset); |
| } |
| |
| out: |
| close(fd); |
| |
| return err; |
| } |