swaplabel.c (1929B)
1 /* See LICENSE file for copyright and license details. */ 2 #include <sys/types.h> 3 4 #include <fcntl.h> 5 #include <stdio.h> 6 #include <stdlib.h> 7 #include <string.h> 8 #include <unistd.h> 9 10 #include "util.h" 11 12 #define SWAP_MAGIC1 "SWAPSPACE2" 13 #define SWAP_MAGIC2 "SWAP-SPACE" 14 #define SWAP_MAGIC_LENGTH (10) 15 #define SWAP_MAGIC_OFFSET (sysconf(_SC_PAGESIZE) - SWAP_MAGIC_LENGTH) 16 #define SWAP_LABEL_LENGTH (16) 17 #define SWAP_LABEL_OFFSET (1024 + 4 + 4 + 4 + 16) 18 19 static void 20 usage(void) 21 { 22 eprintf("usage: %s [-L label] device\n", argv0); 23 } 24 25 int 26 main(int argc, char *argv[]) 27 { 28 int setlabel = 0; 29 int fd; 30 char magic[SWAP_MAGIC_LENGTH]; 31 char *label; 32 char *device; 33 int i; 34 35 ARGBEGIN { 36 case 'L': 37 setlabel = 1; 38 label = EARGF(usage()); 39 break; 40 default: 41 usage(); 42 } ARGEND; 43 44 if (argc < 1) 45 usage(); 46 device = argv[0]; 47 48 fd = open(device, O_RDWR); 49 if (fd < 0) 50 eprintf("open %s:", device); 51 52 if (lseek(fd, SWAP_MAGIC_OFFSET, SEEK_SET) != SWAP_MAGIC_OFFSET) 53 eprintf("failed seeking to magic position:"); 54 if (read(fd, magic, SWAP_MAGIC_LENGTH) != SWAP_MAGIC_LENGTH) 55 eprintf("reading magic failed:"); 56 if (memcmp(magic, SWAP_MAGIC1, 10) && memcmp(magic, SWAP_MAGIC2, 10)) 57 eprintf("%s: is not a swap partition\n", device); 58 if (lseek(fd, SWAP_LABEL_OFFSET, SEEK_SET) != SWAP_LABEL_OFFSET) 59 eprintf("failed seeking to label position:"); 60 61 if (!setlabel) { 62 label = emalloc(SWAP_LABEL_LENGTH); 63 if (read(fd, label, SWAP_LABEL_LENGTH) != SWAP_LABEL_LENGTH) 64 eprintf("reading label failed:"); 65 for (i = 0; i < SWAP_LABEL_LENGTH && label[i] != '\0'; i++) 66 if (i == (SWAP_LABEL_LENGTH - 1) && label[i] != '\0') 67 eprintf("invalid label\n"); 68 printf("label: %s\n", label); 69 free(label); 70 } else { 71 if (strlen(label) + 1 > SWAP_LABEL_LENGTH) 72 eprintf("label too long\n"); 73 if (write(fd, label, strlen(label) + 1) != (ssize_t)strlen(label) + 1) 74 eprintf("writing label failed:"); 75 } 76 77 fsync(fd); 78 close(fd); 79 return 0; 80 }