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ubase/swaplabel.c

81 lines
1.9 KiB
C

/* See LICENSE file for copyright and license details. */
#include <sys/types.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "util.h"
#define SWAP_MAGIC1 "SWAPSPACE2"
#define SWAP_MAGIC2 "SWAP-SPACE"
#define SWAP_MAGIC_LENGTH (10)
#define SWAP_MAGIC_OFFSET (sysconf(_SC_PAGESIZE) - SWAP_MAGIC_LENGTH)
#define SWAP_LABEL_LENGTH (16)
#define SWAP_LABEL_OFFSET (1024 + 4 + 4 + 4 + 16)
static void
usage(void)
{
eprintf("usage: %s [-L label] device\n", argv0);
}
int
main(int argc, char *argv[])
{
int setlabel = 0;
int fd;
char magic[SWAP_MAGIC_LENGTH];
char *label;
char *device;
int i;
ARGBEGIN {
case 'L':
setlabel = 1;
label = EARGF(usage());
break;
default:
usage();
} ARGEND;
if (argc < 1)
usage();
device = argv[0];
fd = open(device, O_RDWR);
if (fd < 0)
eprintf("open %s:", device);
if (lseek(fd, SWAP_MAGIC_OFFSET, SEEK_SET) != SWAP_MAGIC_OFFSET)
eprintf("failed seeking to magic position:");
if (read(fd, magic, SWAP_MAGIC_LENGTH) != SWAP_MAGIC_LENGTH)
eprintf("reading magic failed:");
if (memcmp(magic, SWAP_MAGIC1, 10) && memcmp(magic, SWAP_MAGIC2, 10))
eprintf("%s: is not a swap partition\n", device);
if (lseek(fd, SWAP_LABEL_OFFSET, SEEK_SET) != SWAP_LABEL_OFFSET)
eprintf("failed seeking to label position:");
if (!setlabel) {
label = emalloc(SWAP_LABEL_LENGTH);
if (read(fd, label, SWAP_LABEL_LENGTH) != SWAP_LABEL_LENGTH)
eprintf("reading label failed:");
for (i = 0; i < SWAP_LABEL_LENGTH && label[i] != '\0'; i++)
if (i == (SWAP_LABEL_LENGTH - 1) && label[i] != '\0')
eprintf("invalid label\n");
printf("label: %s\n", label);
free(label);
} else {
if (strlen(label) + 1 > SWAP_LABEL_LENGTH)
eprintf("label too long\n");
if (write(fd, label, strlen(label) + 1) != (ssize_t)strlen(label) + 1)
eprintf("writing label failed:");
}
fsync(fd);
close(fd);
return 0;
}