arch/um/drivers/cow_user.c

   1 #include <stddef.h>
   2 #include <string.h>
   3 #include <errno.h>
   4 #include <unistd.h>
   5 #include <byteswap.h>
   6 #include <sys/time.h>
   7 #include <sys/param.h>
   8 #include <sys/user.h>
   9 #include <netinet/in.h>
  10
  11 #include "os.h"
  12
  13 #include "cow.h"
  14 #include "cow_sys.h"
  15
  16 #define PATH_LEN_V1 256
  17
  18 struct cow_header_v1 {
  19         int magic;
  20         int version;
  21         char backing_file[PATH_LEN_V1];
  22         time_t mtime;
  23         __u64 size;
  24         int sectorsize;
  25 };
  26
  27 #define PATH_LEN_V2 MAXPATHLEN
  28
  29 struct cow_header_v2 {
  30         __u32 magic;
  31         __u32 version;
  32         char backing_file[PATH_LEN_V2];
  33         time_t mtime;
  34         __u64 size;
  35         int sectorsize;
  36 };
  37
  38 /* Define PATH_LEN_V3 as the usual value of MAXPATHLEN, just hard-code it in
  39  * case other systems have different values for MAXPATHLEN
  40  */
  41 #define PATH_LEN_V3 4096
  42
  43 /* Changes from V2 -
  44  *      PATH_LEN_V3 as described above
  45  *      Explicitly specify field bit lengths for systems with different
  46  *              lengths for the usual C types.  Not sure whether char or
  47  *              time_t should be changed, this can be changed later without
  48  *              breaking compatibility
  49  *      Add alignment field so that different alignments can be used for the
  50  *              bitmap and data
  51  *      Add cow_format field to allow for the possibility of different ways
  52  *              of specifying the COW blocks.  For now, the only value is 0,
  53  *              for the traditional COW bitmap.
  54  *      Move the backing_file field to the end of the header.  This allows
  55  *              for the possibility of expanding it into the padding required
  56  *              by the bitmap alignment.
  57  *      The bitmap and data portions of the file will be aligned as specified
  58  *              by the alignment field.  This is to allow COW files to be
  59  *              put on devices with restrictions on access alignments, such as
  60  *              /dev/raw, with a 512 byte alignment restriction.  This also
  61  *              allows the data to be more aligned more strictly than on
  62  *              sector boundaries.  This is needed for ubd-mmap, which needs
  63  *              the data to be page aligned.
  64  *      Fixed (finally!) the rounding bug
  65  */
  66
  67 struct cow_header_v3 {
  68         __u32 magic;
  69         __u32 version;
  70         time_t mtime;
  71         __u64 size;
  72         __u32 sectorsize;
  73         __u32 alignment;
  74         __u32 cow_format;
  75         char backing_file[PATH_LEN_V3];
  76 };
  77
  78 /* COW format definitions - for now, we have only the usual COW bitmap */
  79 #define COW_BITMAP 0
  80
  81 union cow_header {
  82         struct cow_header_v1 v1;
  83         struct cow_header_v2 v2;
  84         struct cow_header_v3 v3;
  85 };
  86
  87 #define COW_MAGIC 0x4f4f4f4d  /* MOOO */
  88 #define COW_VERSION 3
  89
  90 #define DIV_ROUND(x, len) (((x) + (len) - 1) / (len))
  91 #define ROUND_UP(x, align) DIV_ROUND(x, align) * (align)
  92
  93 void cow_sizes(int version, __u64 size, int sectorsize, int align,
  94                int bitmap_offset, unsigned long *bitmap_len_out,
  95                int *data_offset_out)
  96 {
  97         if(version < 3){
  98                 *bitmap_len_out = (size + sectorsize - 1) / (8 * sectorsize);
  99
 100                 *data_offset_out = bitmap_offset + *bitmap_len_out;
 101                 *data_offset_out = (*data_offset_out + sectorsize - 1) /
 102                         sectorsize;
 103                 *data_offset_out *= sectorsize;
 104         }
 105         else {
 106                 *bitmap_len_out = DIV_ROUND(size, sectorsize);
 107                 *bitmap_len_out = DIV_ROUND(*bitmap_len_out, 8);
 108
 109                 *data_offset_out = bitmap_offset + *bitmap_len_out;
 110                 *data_offset_out = ROUND_UP(*data_offset_out, align);
 111         }
 112 }
 113
 114 static int absolutize(char *to, int size, char *from)
 115 {
 116         char save_cwd[256], *slash;
 117         int remaining;
 118
 119         if(getcwd(save_cwd, sizeof(save_cwd)) == NULL) {
 120                 cow_printf("absolutize : unable to get cwd - errno = %d\n",
 121                            errno);
 122                 return(-1);
 123         }
 124         slash = strrchr(from, '/');
 125         if(slash != NULL){
 126                 *slash = '\0';
 127                 if(chdir(from)){
 128                         *slash = '/';
 129                         cow_printf("absolutize : Can't cd to '%s' - "
 130                                    "errno = %d\n", from, errno);
 131                         return(-1);
 132                 }
 133                 *slash = '/';
 134                 if(getcwd(to, size) == NULL){
 135                         cow_printf("absolutize : unable to get cwd of '%s' - "
 136                                "errno = %d\n", from, errno);
 137                         return(-1);
 138                 }
 139                 remaining = size - strlen(to);
 140                 if(strlen(slash) + 1 > remaining){
 141                         cow_printf("absolutize : unable to fit '%s' into %d "
 142                                "chars\n", from, size);
 143                         return(-1);
 144                 }
 145                 strcat(to, slash);
 146         }
 147         else {
 148                 if(strlen(save_cwd) + 1 + strlen(from) + 1 > size){
 149                         cow_printf("absolutize : unable to fit '%s' into %d "
 150                                "chars\n", from, size);
 151                         return(-1);
 152                 }
 153                 strcpy(to, save_cwd);
 154                 strcat(to, "/");
 155                 strcat(to, from);
 156         }
 157         chdir(save_cwd);
 158         return(0);
 159 }
 160
 161 int write_cow_header(char *cow_file, int fd, char *backing_file,
 162                      int sectorsize, int alignment, long long *size)
 163 {
 164         struct cow_header_v3 *header;
 165         unsigned long modtime;
 166         int err;
 167
 168         err = cow_seek_file(fd, 0);
 169         if(err < 0){
 170                 cow_printf("write_cow_header - lseek failed, err = %d\n", -err);
 171                 goto out;
 172         }
 173
 174         err = -ENOMEM;
 175         header = cow_malloc(sizeof(*header));
 176         if(header == NULL){
 177                 cow_printf("Failed to allocate COW V3 header\n");
 178                 goto out;
 179         }
 180         header->magic = htonl(COW_MAGIC);
 181         header->version = htonl(COW_VERSION);
 182
 183         err = -EINVAL;
 184         if(strlen(backing_file) > sizeof(header->backing_file) - 1){
 185                 cow_printf("Backing file name \"%s\" is too long - names are "
 186                            "limited to %d characters\n", backing_file,
 187                            sizeof(header->backing_file) - 1);
 188                 goto out_free;
 189         }
 190
 191         if(absolutize(header->backing_file, sizeof(header->backing_file),
 192                       backing_file))
 193                 goto out_free;
 194
 195         err = os_file_modtime(header->backing_file, &modtime);
 196         if(err < 0){
 197                 cow_printf("Backing file '%s' mtime request failed, "
 198                            "err = %d\n", header->backing_file, -err);
 199                 goto out_free;
 200         }
 201
 202         err = cow_file_size(header->backing_file, size);
 203         if(err < 0){
 204                 cow_printf("Couldn't get size of backing file '%s', "
 205                            "err = %d\n", header->backing_file, -err);
 206                 goto out_free;
 207         }
 208
 209         header->mtime = htonl(modtime);
 210         header->size = htonll(*size);
 211         header->sectorsize = htonl(sectorsize);
 212         header->alignment = htonl(alignment);
 213         header->cow_format = COW_BITMAP;
 214
 215         err = os_write_file(fd, header, sizeof(*header));
 216         if(err != sizeof(*header)){
 217                 cow_printf("Write of header to new COW file '%s' failed, "
 218                            "err = %d\n", cow_file, -err);
 219                 goto out_free;
 220         }
 221         err = 0;
 222  out_free:
 223         cow_free(header);
 224  out:
 225         return(err);
 226 }
 227
 228 int file_reader(__u64 offset, char *buf, int len, void *arg)
 229 {
 230         int fd = *((int *) arg);
 231
 232         return(pread(fd, buf, len, offset));
 233 }
 234
 235 /* XXX Need to sanity-check the values read from the header */
 236
 237 int read_cow_header(int (*reader)(__u64, char *, int, void *), void *arg,
 238                     __u32 *version_out, char **backing_file_out,
 239                     time_t *mtime_out, __u64 *size_out,
 240                     int *sectorsize_out, __u32 *align_out,
 241                     int *bitmap_offset_out)
 242 {
 243         union cow_header *header;
 244         char *file;
 245         int err, n;
 246         unsigned long version, magic;
 247
 248         header = cow_malloc(sizeof(*header));
 249         if(header == NULL){
 250                 cow_printf("read_cow_header - Failed to allocate header\n");
 251                 return(-ENOMEM);
 252         }
 253         err = -EINVAL;
 254         n = (*reader)(0, (char *) header, sizeof(*header), arg);
 255         if(n < offsetof(typeof(header->v1), backing_file)){
 256                 cow_printf("read_cow_header - short header\n");
 257                 goto out;
 258         }
 259
 260         magic = header->v1.magic;
 261         if(magic == COW_MAGIC) {
 262                 version = header->v1.version;
 263         }
 264         else if(magic == ntohl(COW_MAGIC)){
 265                 version = ntohl(header->v1.version);
 266         }
 267         /* No error printed because the non-COW case comes through here */
 268         else goto out;
 269
 270         *version_out = version;
 271
 272         if(version == 1){
 273                 if(n < sizeof(header->v1)){
 274                         cow_printf("read_cow_header - failed to read V1 "
 275                                    "header\n");
 276                         goto out;
 277                 }
 278                 *mtime_out = header->v1.mtime;
 279                 *size_out = header->v1.size;
 280                 *sectorsize_out = header->v1.sectorsize;
 281                 *bitmap_offset_out = sizeof(header->v1);
 282                 *align_out = *sectorsize_out;
 283                 file = header->v1.backing_file;
 284         }
 285         else if(version == 2){
 286                 if(n < sizeof(header->v2)){
 287                         cow_printf("read_cow_header - failed to read V2 "
 288                                    "header\n");
 289                         goto out;
 290                 }
 291                 *mtime_out = ntohl(header->v2.mtime);
 292                 *size_out = ntohll(header->v2.size);
 293                 *sectorsize_out = ntohl(header->v2.sectorsize);
 294                 *bitmap_offset_out = sizeof(header->v2);
 295                 *align_out = *sectorsize_out;
 296                 file = header->v2.backing_file;
 297         }
 298         else if(version == 3){
 299                 if(n < sizeof(header->v3)){
 300                         cow_printf("read_cow_header - failed to read V2 "
 301                                    "header\n");
 302                         goto out;
 303                 }
 304                 *mtime_out = ntohl(header->v3.mtime);
 305                 *size_out = ntohll(header->v3.size);
 306                 *sectorsize_out = ntohl(header->v3.sectorsize);
 307                 *align_out = ntohl(header->v3.alignment);
 308                 *bitmap_offset_out = ROUND_UP(sizeof(header->v3), *align_out);
 309                 file = header->v3.backing_file;
 310         }
 311         else {
 312                 cow_printf("read_cow_header - invalid COW version\n");
 313                 goto out;
 314         }
 315         err = -ENOMEM;
 316         *backing_file_out = cow_strdup(file);
 317         if(*backing_file_out == NULL){
 318                 cow_printf("read_cow_header - failed to allocate backing "
 319                            "file\n");
 320                 goto out;
 321         }
 322         err = 0;
 323  out:
 324         cow_free(header);
 325         return(err);
 326 }
 327
 328 int init_cow_file(int fd, char *cow_file, char *backing_file, int sectorsize,
 329                   int alignment, int *bitmap_offset_out,
 330                   unsigned long *bitmap_len_out, int *data_offset_out)
 331 {
 332         __u64 size, offset;
 333         char zero = 0;
 334         int err;
 335
 336         err = write_cow_header(cow_file, fd, backing_file, sectorsize,
 337                                alignment, &size);
 338         if(err)
 339                 goto out;
 340
 341         *bitmap_offset_out = ROUND_UP(sizeof(struct cow_header_v3), alignment);
 342         cow_sizes(COW_VERSION, size, sectorsize, alignment, *bitmap_offset_out,
 343                   bitmap_len_out, data_offset_out);
 344
 345         offset = *data_offset_out + size - sizeof(zero);
 346         err = cow_seek_file(fd, offset);
 347         if(err < 0){
 348                 cow_printf("cow bitmap lseek failed : err = %d\n", -err);
 349                 goto out;
 350         }
 351
 352         /* does not really matter how much we write it is just to set EOF
 353          * this also sets the entire COW bitmap
 354          * to zero without having to allocate it
 355          */
 356         err = cow_write_file(fd, &zero, sizeof(zero));
 357         if(err != sizeof(zero)){
 358                 cow_printf("Write of bitmap to new COW file '%s' failed, "
 359                            "err = %d\n", cow_file, -err);
 360                 err = -EINVAL;
 361                 goto out;
 362         }
 363
 364         return(0);
 365
 366  out:
 367         return(err);
 368 }
 369
 370 /*
 371  * ---------------------------------------------------------------------------
 372  * Local variables:
 373  * c-file-style: "linux"
 374  * End:
 375  */