arch/um/drivers/cow_user.c

   1 #include <stddef.h>
   2 #include <string.h>
   3 #include <errno.h>
   4 /* _XOPEN_SOURCE is needed for pread, but we define _GNU_SOURCE, which defines
   5  * that.
   6  */
   7 #include <unistd.h>
   8 #include <byteswap.h>
   9 #include <sys/time.h>
  10 #include <sys/param.h>
  11 #include <sys/user.h>
  12 #include <netinet/in.h>
  13
  14 #include "os.h"
  15
  16 #include "cow.h"
  17 #include "cow_sys.h"
  18
  19 #define PATH_LEN_V1 256
  20
  21 struct cow_header_v1 {
  22         int magic;
  23         int version;
  24         char backing_file[PATH_LEN_V1];
  25         time_t mtime;
  26         __u64 size;
  27         int sectorsize;
  28 };
  29
  30 #define PATH_LEN_V2 MAXPATHLEN
  31
  32 struct cow_header_v2 {
  33         __u32 magic;
  34         __u32 version;
  35         char backing_file[PATH_LEN_V2];
  36         time_t mtime;
  37         __u64 size;
  38         int sectorsize;
  39 };
  40
  41 /* Define PATH_LEN_V3 as the usual value of MAXPATHLEN, just hard-code it in
  42  * case other systems have different values for MAXPATHLEN
  43  */
  44 #define PATH_LEN_V3 4096
  45
  46 /* Changes from V2 -
  47  *      PATH_LEN_V3 as described above
  48  *      Explicitly specify field bit lengths for systems with different
  49  *              lengths for the usual C types.  Not sure whether char or
  50  *              time_t should be changed, this can be changed later without
  51  *              breaking compatibility
  52  *      Add alignment field so that different alignments can be used for the
  53  *              bitmap and data
  54  *      Add cow_format field to allow for the possibility of different ways
  55  *              of specifying the COW blocks.  For now, the only value is 0,
  56  *              for the traditional COW bitmap.
  57  *      Move the backing_file field to the end of the header.  This allows
  58  *              for the possibility of expanding it into the padding required
  59  *              by the bitmap alignment.
  60  *      The bitmap and data portions of the file will be aligned as specified
  61  *              by the alignment field.  This is to allow COW files to be
  62  *              put on devices with restrictions on access alignments, such as
  63  *              /dev/raw, with a 512 byte alignment restriction.  This also
  64  *              allows the data to be more aligned more strictly than on
  65  *              sector boundaries.  This is needed for ubd-mmap, which needs
  66  *              the data to be page aligned.
  67  *      Fixed (finally!) the rounding bug
  68  */
  69
  70 struct cow_header_v3 {
  71         __u32 magic;
  72         __u32 version;
  73         __u32 mtime;
  74         __u64 size;
  75         __u32 sectorsize;
  76         __u32 alignment;
  77         __u32 cow_format;
  78         char backing_file[PATH_LEN_V3];
  79 };
  80
  81 /* COW format definitions - for now, we have only the usual COW bitmap */
  82 #define COW_BITMAP 0
  83
  84 union cow_header {
  85         struct cow_header_v1 v1;
  86         struct cow_header_v2 v2;
  87         struct cow_header_v3 v3;
  88 };
  89
  90 #define COW_MAGIC 0x4f4f4f4d  /* MOOO */
  91 #define COW_VERSION 3
  92
  93 #define DIV_ROUND(x, len) (((x) + (len) - 1) / (len))
  94 #define ROUND_UP(x, align) DIV_ROUND(x, align) * (align)
  95
  96 void cow_sizes(int version, __u64 size, int sectorsize, int align,
  97                int bitmap_offset, unsigned long *bitmap_len_out,
  98                int *data_offset_out)
  99 {
 100         if(version < 3){
 101                 *bitmap_len_out = (size + sectorsize - 1) / (8 * sectorsize);
 102
 103                 *data_offset_out = bitmap_offset + *bitmap_len_out;
 104                 *data_offset_out = (*data_offset_out + sectorsize - 1) /
 105                         sectorsize;
 106                 *data_offset_out *= sectorsize;
 107         }
 108         else {
 109                 *bitmap_len_out = DIV_ROUND(size, sectorsize);
 110                 *bitmap_len_out = DIV_ROUND(*bitmap_len_out, 8);
 111
 112                 *data_offset_out = bitmap_offset + *bitmap_len_out;
 113                 *data_offset_out = ROUND_UP(*data_offset_out, align);
 114         }
 115 }
 116
 117 static int absolutize(char *to, int size, char *from)
 118 {
 119         char save_cwd[256], *slash;
 120         int remaining;
 121
 122         if(getcwd(save_cwd, sizeof(save_cwd)) == NULL) {
 123                 cow_printf("absolutize : unable to get cwd - errno = %d\n",
 124                            errno);
 125                 return(-1);
 126         }
 127         slash = strrchr(from, '/');
 128         if(slash != NULL){
 129                 *slash = '\0';
 130                 if(chdir(from)){
 131                         *slash = '/';
 132                         cow_printf("absolutize : Can't cd to '%s' - "
 133                                    "errno = %d\n", from, errno);
 134                         return(-1);
 135                 }
 136                 *slash = '/';
 137                 if(getcwd(to, size) == NULL){
 138                         cow_printf("absolutize : unable to get cwd of '%s' - "
 139                                "errno = %d\n", from, errno);
 140                         return(-1);
 141                 }
 142                 remaining = size - strlen(to);
 143                 if(strlen(slash) + 1 > remaining){
 144                         cow_printf("absolutize : unable to fit '%s' into %d "
 145                                "chars\n", from, size);
 146                         return(-1);
 147                 }
 148                 strcat(to, slash);
 149         }
 150         else {
 151                 if(strlen(save_cwd) + 1 + strlen(from) + 1 > size){
 152                         cow_printf("absolutize : unable to fit '%s' into %d "
 153                                "chars\n", from, size);
 154                         return(-1);
 155                 }
 156                 strcpy(to, save_cwd);
 157                 strcat(to, "/");
 158                 strcat(to, from);
 159         }
 160         chdir(save_cwd);
 161         return(0);
 162 }
 163
 164 int write_cow_header(char *cow_file, int fd, char *backing_file,
 165                      int sectorsize, int alignment, unsigned long long *size)
 166 {
 167         struct cow_header_v3 *header;
 168         unsigned long modtime;
 169         int err;
 170
 171         err = cow_seek_file(fd, 0);
 172         if(err < 0){
 173                 cow_printf("write_cow_header - lseek failed, err = %d\n", -err);
 174                 goto out;
 175         }
 176
 177         err = -ENOMEM;
 178         header = cow_malloc(sizeof(*header));
 179         if(header == NULL){
 180                 cow_printf("Failed to allocate COW V3 header\n");
 181                 goto out;
 182         }
 183         header->magic = htonl(COW_MAGIC);
 184         header->version = htonl(COW_VERSION);
 185
 186         err = -EINVAL;
 187         if(strlen(backing_file) > sizeof(header->backing_file) - 1){
 188                 cow_printf("Backing file name \"%s\" is too long - names are "
 189                            "limited to %d characters\n", backing_file,
 190                            sizeof(header->backing_file) - 1);
 191                 goto out_free;
 192         }
 193
 194         if(absolutize(header->backing_file, sizeof(header->backing_file),
 195                       backing_file))
 196                 goto out_free;
 197
 198         err = os_file_modtime(header->backing_file, &modtime);
 199         if(err < 0){
 200                 cow_printf("Backing file '%s' mtime request failed, "
 201                            "err = %d\n", header->backing_file, -err);
 202                 goto out_free;
 203         }
 204
 205         err = cow_file_size(header->backing_file, size);
 206         if(err < 0){
 207                 cow_printf("Couldn't get size of backing file '%s', "
 208                            "err = %d\n", header->backing_file, -err);
 209                 goto out_free;
 210         }
 211
 212         header->mtime = htonl(modtime);
 213         header->size = htonll(*size);
 214         header->sectorsize = htonl(sectorsize);
 215         header->alignment = htonl(alignment);
 216         header->cow_format = COW_BITMAP;
 217
 218         err = os_write_file(fd, header, sizeof(*header));
 219         if(err != sizeof(*header)){
 220                 cow_printf("Write of header to new COW file '%s' failed, "
 221                            "err = %d\n", cow_file, -err);
 222                 goto out_free;
 223         }
 224         err = 0;
 225  out_free:
 226         cow_free(header);
 227  out:
 228         return(err);
 229 }
 230
 231 int file_reader(__u64 offset, char *buf, int len, void *arg)
 232 {
 233         int fd = *((int *) arg);
 234
 235         return(pread(fd, buf, len, offset));
 236 }
 237
 238 /* XXX Need to sanity-check the values read from the header */
 239
 240 int read_cow_header(int (*reader)(__u64, char *, int, void *), void *arg,
 241                     __u32 *version_out, char **backing_file_out,
 242                     time_t *mtime_out, unsigned long long *size_out,
 243                     int *sectorsize_out, __u32 *align_out,
 244                     int *bitmap_offset_out)
 245 {
 246         union cow_header *header;
 247         char *file;
 248         int err, n;
 249         unsigned long version, magic;
 250
 251         header = cow_malloc(sizeof(*header));
 252         if(header == NULL){
 253                 cow_printf("read_cow_header - Failed to allocate header\n");
 254                 return(-ENOMEM);
 255         }
 256         err = -EINVAL;
 257         n = (*reader)(0, (char *) header, sizeof(*header), arg);
 258         if(n < offsetof(typeof(header->v1), backing_file)){
 259                 cow_printf("read_cow_header - short header\n");
 260                 goto out;
 261         }
 262
 263         magic = header->v1.magic;
 264         if(magic == COW_MAGIC) {
 265                 version = header->v1.version;
 266         }
 267         else if(magic == ntohl(COW_MAGIC)){
 268                 version = ntohl(header->v1.version);
 269         }
 270         /* No error printed because the non-COW case comes through here */
 271         else goto out;
 272
 273         *version_out = version;
 274
 275         if(version == 1){
 276                 if(n < sizeof(header->v1)){
 277                         cow_printf("read_cow_header - failed to read V1 "
 278                                    "header\n");
 279                         goto out;
 280                 }
 281                 *mtime_out = header->v1.mtime;
 282                 *size_out = header->v1.size;
 283                 *sectorsize_out = header->v1.sectorsize;
 284                 *bitmap_offset_out = sizeof(header->v1);
 285                 *align_out = *sectorsize_out;
 286                 file = header->v1.backing_file;
 287         }
 288         else if(version == 2){
 289                 if(n < sizeof(header->v2)){
 290                         cow_printf("read_cow_header - failed to read V2 "
 291                                    "header\n");
 292                         goto out;
 293                 }
 294                 *mtime_out = ntohl(header->v2.mtime);
 295                 *size_out = ntohll(header->v2.size);
 296                 *sectorsize_out = ntohl(header->v2.sectorsize);
 297                 *bitmap_offset_out = sizeof(header->v2);
 298                 *align_out = *sectorsize_out;
 299                 file = header->v2.backing_file;
 300         }
 301         else if(version == 3){
 302                 if(n < sizeof(header->v3)){
 303                         cow_printf("read_cow_header - failed to read V2 "
 304                                    "header\n");
 305                         goto out;
 306                 }
 307                 *mtime_out = ntohl(header->v3.mtime);
 308                 *size_out = ntohll(header->v3.size);
 309                 *sectorsize_out = ntohl(header->v3.sectorsize);
 310                 *align_out = ntohl(header->v3.alignment);
 311                 *bitmap_offset_out = ROUND_UP(sizeof(header->v3), *align_out);
 312                 file = header->v3.backing_file;
 313         }
 314         else {
 315                 cow_printf("read_cow_header - invalid COW version\n");
 316                 goto out;
 317         }
 318         err = -ENOMEM;
 319         *backing_file_out = cow_strdup(file);
 320         if(*backing_file_out == NULL){
 321                 cow_printf("read_cow_header - failed to allocate backing "
 322                            "file\n");
 323                 goto out;
 324         }
 325         err = 0;
 326  out:
 327         cow_free(header);
 328         return(err);
 329 }
 330
 331 int init_cow_file(int fd, char *cow_file, char *backing_file, int sectorsize,
 332                   int alignment, int *bitmap_offset_out,
 333                   unsigned long *bitmap_len_out, int *data_offset_out)
 334 {
 335         unsigned long long size, offset;
 336         char zero = 0;
 337         int err;
 338
 339         err = write_cow_header(cow_file, fd, backing_file, sectorsize,
 340                                alignment, &size);
 341         if(err)
 342                 goto out;
 343
 344         *bitmap_offset_out = ROUND_UP(sizeof(struct cow_header_v3), alignment);
 345         cow_sizes(COW_VERSION, size, sectorsize, alignment, *bitmap_offset_out,
 346                   bitmap_len_out, data_offset_out);
 347
 348         offset = *data_offset_out + size - sizeof(zero);
 349         err = cow_seek_file(fd, offset);
 350         if(err < 0){
 351                 cow_printf("cow bitmap lseek failed : err = %d\n", -err);
 352                 goto out;
 353         }
 354
 355         /* does not really matter how much we write it is just to set EOF
 356          * this also sets the entire COW bitmap
 357          * to zero without having to allocate it
 358          */
 359         err = cow_write_file(fd, &zero, sizeof(zero));
 360         if(err != sizeof(zero)){
 361                 cow_printf("Write of bitmap to new COW file '%s' failed, "
 362                            "err = %d\n", cow_file, -err);
 363                 err = -EINVAL;
 364                 goto out;
 365         }
 366
 367         return(0);
 368
 369  out:
 370         return(err);
 371 }
 372
 373 /*
 374  * ---------------------------------------------------------------------------
 375  * Local variables:
 376  * c-file-style: "linux"
 377  * End:
 378  */