mount.c revision dd7bc3319deb2b77c5d07a51b7d6cd7e11b5beb0
1/* 2 * mount.c, by rmk 3 */ 4 5#include <sys/mount.h> 6#include <sys/stat.h> 7#include <fcntl.h> 8#include <errno.h> 9#include <stdio.h> 10#include <stdlib.h> 11#include <string.h> 12#include <unistd.h> 13 14#include <linux/loop.h> 15 16#define ARRAY_SIZE(x) (sizeof(x) / sizeof(x[0])) 17 18// FIXME - only one loop mount is supported at a time 19#define LOOP_DEVICE "/dev/block/loop0" 20 21struct mount_opts { 22 const char str[8]; 23 unsigned long rwmask; 24 unsigned long rwset; 25 unsigned long rwnoset; 26}; 27 28struct extra_opts { 29 char *str; 30 char *end; 31 int used_size; 32 int alloc_size; 33}; 34 35/* 36 * These options define the function of "mount(2)". 37 */ 38#define MS_TYPE (MS_REMOUNT|MS_BIND|MS_MOVE) 39 40 41static const struct mount_opts options[] = { 42 /* name mask set noset */ 43 { "async", MS_SYNCHRONOUS, 0, MS_SYNCHRONOUS }, 44 { "atime", MS_NOATIME, 0, MS_NOATIME }, 45 { "bind", MS_TYPE, MS_BIND, 0, }, 46 { "dev", MS_NODEV, 0, MS_NODEV }, 47 { "diratime", MS_NODIRATIME, 0, MS_NODIRATIME }, 48 { "dirsync", MS_DIRSYNC, MS_DIRSYNC, 0 }, 49 { "exec", MS_NOEXEC, 0, MS_NOEXEC }, 50 { "move", MS_TYPE, MS_MOVE, 0 }, 51 { "recurse", MS_REC, MS_REC, 0 }, 52 { "remount", MS_TYPE, MS_REMOUNT, 0 }, 53 { "ro", MS_RDONLY, MS_RDONLY, 0 }, 54 { "rw", MS_RDONLY, 0, MS_RDONLY }, 55 { "suid", MS_NOSUID, 0, MS_NOSUID }, 56 { "sync", MS_SYNCHRONOUS, MS_SYNCHRONOUS, 0 }, 57 { "verbose", MS_VERBOSE, MS_VERBOSE, 0 }, 58}; 59 60static void add_extra_option(struct extra_opts *extra, char *s) 61{ 62 int len = strlen(s); 63 int newlen = extra->used_size + len; 64 65 if (extra->str) 66 len++; /* +1 for ',' */ 67 68 if (newlen >= extra->alloc_size) { 69 char *new; 70 71 new = realloc(extra->str, newlen + 1); /* +1 for NUL */ 72 if (!new) 73 return; 74 75 extra->str = new; 76 extra->end = extra->str + extra->used_size; 77 extra->alloc_size = newlen; 78 } 79 80 if (extra->used_size) { 81 *extra->end = ','; 82 extra->end++; 83 } 84 strcpy(extra->end, s); 85 extra->used_size += len; 86 87} 88 89static unsigned long 90parse_mount_options(char *arg, unsigned long rwflag, struct extra_opts *extra, int* loop) 91{ 92 char *s; 93 94 *loop = 0; 95 while ((s = strsep(&arg, ",")) != NULL) { 96 char *opt = s; 97 unsigned int i; 98 int res, no = s[0] == 'n' && s[1] == 'o'; 99 100 if (no) 101 s += 2; 102 103 if (strcmp(s, "loop") == 0) { 104 *loop = 1; 105 continue; 106 } 107 for (i = 0, res = 1; i < ARRAY_SIZE(options); i++) { 108 res = strcmp(s, options[i].str); 109 110 if (res == 0) { 111 rwflag &= ~options[i].rwmask; 112 if (no) 113 rwflag |= options[i].rwnoset; 114 else 115 rwflag |= options[i].rwset; 116 } 117 if (res <= 0) 118 break; 119 } 120 121 if (res != 0 && s[0]) 122 add_extra_option(extra, opt); 123 } 124 125 return rwflag; 126} 127 128static char *progname; 129 130static struct extra_opts extra; 131static unsigned long rwflag; 132 133static int 134do_mount(char *dev, char *dir, char *type, unsigned long rwflag, void *data, int loop) 135{ 136 char *s; 137 int error = 0; 138 139 if (loop) { 140 int file_fd, device_fd; 141 142 // FIXME - only one loop mount supported at a time 143 file_fd = open(dev, O_RDWR); 144 if (file_fd < -1) { 145 perror("open backing file failed"); 146 return 1; 147 } 148 device_fd = open(LOOP_DEVICE, O_RDWR); 149 if (device_fd < -1) { 150 perror("open loop device failed"); 151 close(file_fd); 152 return 1; 153 } 154 if (ioctl(device_fd, LOOP_SET_FD, file_fd) < 0) { 155 perror("ioctl LOOP_SET_FD failed"); 156 close(file_fd); 157 close(device_fd); 158 return 1; 159 } 160 161 close(file_fd); 162 close(device_fd); 163 dev = LOOP_DEVICE; 164 } 165 166 while ((s = strsep(&type, ",")) != NULL) { 167retry: 168 if (mount(dev, dir, s, rwflag, data) == -1) { 169 error = errno; 170 /* 171 * If the filesystem is not found, or the 172 * superblock is invalid, try the next. 173 */ 174 if (error == ENODEV || error == EINVAL) 175 continue; 176 177 /* 178 * If we get EACCESS, and we're trying to 179 * mount readwrite and this isn't a remount, 180 * try read only. 181 */ 182 if (error == EACCES && 183 (rwflag & (MS_REMOUNT|MS_RDONLY)) == 0) { 184 rwflag |= MS_RDONLY; 185 goto retry; 186 } 187 break; 188 } 189 } 190 191 if (error) { 192 errno = error; 193 perror("mount"); 194 return 255; 195 } 196 197 return 0; 198} 199 200static int print_mounts() 201{ 202 FILE* f; 203 int length; 204 char buffer[100]; 205 206 f = fopen("/proc/mounts", "r"); 207 if (!f) { 208 fprintf(stdout, "could not open /proc/mounts\n"); 209 return -1; 210 } 211 212 do { 213 length = fread(buffer, 1, 100, f); 214 if (length > 0) 215 fwrite(buffer, 1, length, stdout); 216 } while (length > 0); 217 218 fclose(f); 219 return 0; 220} 221 222int mount_main(int argc, char *argv[]) 223{ 224 char *type = NULL; 225 int c; 226 int loop; 227 228 progname = argv[0]; 229 rwflag = MS_VERBOSE; 230 231 // mount with no arguments is equivalent to "cat /proc/mounts" 232 if (argc == 1) return print_mounts(); 233 234 do { 235 c = getopt(argc, argv, "o:rt:w"); 236 if (c == EOF) 237 break; 238 switch (c) { 239 case 'o': 240 rwflag = parse_mount_options(optarg, rwflag, &extra, &loop); 241 break; 242 case 'r': 243 rwflag |= MS_RDONLY; 244 break; 245 case 't': 246 type = optarg; 247 break; 248 case 'w': 249 rwflag &= ~MS_RDONLY; 250 break; 251 case '?': 252 fprintf(stderr, "%s: invalid option -%c\n", 253 progname, optopt); 254 exit(1); 255 } 256 } while (1); 257 258 /* 259 * If remount, bind or move was specified, then we don't 260 * have a "type" as such. Use the dummy "none" type. 261 */ 262 if (rwflag & MS_TYPE) 263 type = "none"; 264 265 if (optind + 2 != argc || type == NULL) { 266 fprintf(stderr, "Usage: %s [-r] [-w] [-o options] [-t type] " 267 "device directory\n", progname); 268 exit(1); 269 } 270 271 return do_mount(argv[optind], argv[optind + 1], type, rwflag, 272 extra.str, loop); 273} 274