libfdisk/src/utils.c

   1
   2 #include "fdiskP.h"
   3 #include "pathnames.h"
   4 #include "canonicalize.h"
   5
   6 #include <ctype.h>
   7
   8 /**
   9  * SECTION: utils
  10  * @title: Utils
  11  * @short_description: misc fdisk functions
  12  */
  13
  14 static int read_from_device(struct fdisk_context *cxt,
  15                 unsigned char *buf,
  16                 uintmax_t start, size_t size)
  17 {
  18         ssize_t r;
  19
  20         assert(cxt);
  21
  22         DBG(CXT, ul_debugobj(cxt, "reading: offset=%ju, size=%zu",
  23                                 start, size));
  24
  25         r = lseek(cxt->dev_fd, start, SEEK_SET);
  26         if (r == -1)
  27         {
  28                 DBG(CXT, ul_debugobj(cxt, "failed to seek to offset %ju: %m", start));
  29                 return -errno;
  30         }
  31
  32         r = read(cxt->dev_fd, buf, size);
  33         if (r < 0 || (size_t)r != size) {
  34                 if (!errno)
  35                         errno = EINVAL; /* probably too small file/device */
  36                 DBG(CXT, ul_debugobj(cxt, "failed to read %zu from offset %ju: %m",
  37                                 size, start));
  38                 return -errno;
  39         }
  40
  41         return 0;
  42 }
  43
  44
  45 /*
  46  * Zeros in-memory first sector buffer
  47  */
  48 int fdisk_init_firstsector_buffer(struct fdisk_context *cxt,
  49                                   unsigned int protect_off,
  50                                   unsigned int protect_size)
  51 {
  52         if (!cxt)
  53                 return -EINVAL;
  54
  55         assert(protect_off + protect_size <= cxt->sector_size);
  56
  57         if (!cxt->firstsector || cxt->firstsector_bufsz != cxt->sector_size) {
  58                 /* Let's allocate a new buffer if no allocated yet, or the
  59                  * current buffer has incorrect size */
  60                 if (!cxt->parent || cxt->parent->firstsector != cxt->firstsector)
  61                         free(cxt->firstsector);
  62
  63                 DBG(CXT, ul_debugobj(cxt, "initialize in-memory first sector "
  64                                 "buffer [sector_size=%lu]", cxt->sector_size));
  65                 cxt->firstsector = calloc(1, cxt->sector_size);
  66                 if (!cxt->firstsector)
  67                         return -ENOMEM;
  68
  69                 cxt->firstsector_bufsz = cxt->sector_size;
  70                 return 0;
  71         }
  72
  73         DBG(CXT, ul_debugobj(cxt, "zeroize in-memory first sector buffer"));
  74         memset(cxt->firstsector, 0, cxt->firstsector_bufsz);
  75
  76         if (protect_size) {
  77                 /*
  78                  * It would be possible to reuse data from cxt->firstsector
  79                  * (call memset() for non-protected area only) and avoid one
  80                  * read() from the device, but it seems like a too fragile
  81                  * solution as we have no clue about stuff in the buffer --
  82                  * maybe it was already modified. Let's re-read from the device
  83                  * to be sure.                  -- kzak 13-Apr-2015
  84                  */
  85                 DBG(CXT, ul_debugobj(cxt, "first sector protection enabled -- re-reading"));
  86                 read_from_device(cxt, cxt->firstsector, protect_off, protect_size);
  87         }
  88         return 0;
  89 }
  90
  91 int fdisk_read_firstsector(struct fdisk_context *cxt)
  92 {
  93         int rc;
  94
  95         assert(cxt);
  96         assert(cxt->sector_size);
  97
  98         rc = fdisk_init_firstsector_buffer(cxt, 0, 0);
  99         if (rc)
 100                 return rc;
 101
 102         assert(cxt->sector_size == cxt->firstsector_bufsz);
 103
 104
 105         return  read_from_device(cxt, cxt->firstsector, 0, cxt->sector_size);
 106 }
 107
 108 /**
 109  * fdisk_partname:
 110  * @dev: device name
 111  * @partno: partition name
 112  *
 113  * Return: allocated buffer with partition name, use free() to deallocate.
 114  */
 115 char *fdisk_partname(const char *dev, size_t partno)
 116 {
 117         char *res = NULL;
 118         const char *p = "";
 119         char *dev_mapped = NULL;
 120         int w = 0;
 121
 122         if (!dev || !*dev) {
 123                 if (asprintf(&res, "%zd", partno) > 0)
 124                         return res;
 125                 return NULL;
 126         }
 127
 128         /* It is impossible to predict /dev/dm-N partition names. */
 129         if (strncmp(dev, "/dev/dm-", sizeof("/dev/dm-") - 1) == 0) {
 130                 dev_mapped = canonicalize_dm_name (dev + 5);
 131                 if (dev_mapped)
 132                         dev = dev_mapped;
 133         }
 134
 135         w = strlen(dev);
 136         if (isdigit(dev[w - 1]))
 137 #ifdef __GNU__
 138                 p = "s";
 139 #else
 140                 p = "p";
 141 #endif
 142
 143         /* devfs kludge - note: fdisk partition names are not supposed
 144            to equal kernel names, so there is no reason to do this */
 145         if (strcmp(dev + w - 4, "disc") == 0) {
 146                 w -= 4;
 147                 p = "part";
 148         }
 149
 150         /* udev names partitions by appending -partN
 151            e.g. ata-SAMSUNG_SV8004H_0357J1FT712448-part1
 152            multipath-tools kpartx.rules also append -partN */
 153         if ((strncmp(dev, _PATH_DEV_BYID, sizeof(_PATH_DEV_BYID) - 1) == 0) ||
 154              strncmp(dev, _PATH_DEV_BYPATH, sizeof(_PATH_DEV_BYPATH) - 1) == 0 ||
 155              strncmp(dev, "/dev/mapper", sizeof("/dev/mapper") - 1) == 0) {
 156
 157                 /* check for <name><partno>, e.g. mpatha1 */
 158                 if (asprintf(&res, "%.*s%zu", w, dev, partno) <= 0)
 159                         res = NULL;
 160                 if (res && access(res, F_OK) == 0)
 161                         goto done;
 162
 163                 free(res);
 164
 165                 /* check for partition seperator "p" */
 166                 if (asprintf(&res, "%.*sp%zu", w, dev, partno) <= 0)
 167                         res = NULL;
 168                 if (res && access(res, F_OK) == 0)
 169                         goto done;
 170
 171                 free(res);
 172
 173                 /* otherwise, default to "-path" */
 174                 p = "-part";
 175         }
 176
 177         if (asprintf(&res, "%.*s%s%zu", w, dev, p, partno) <= 0)
 178                 res = NULL;
 179 done:
 180         free(dev_mapped);
 181         return res;
 182 }
 183
 184 #ifdef TEST_PROGRAM
 185 struct fdisk_label *fdisk_new_dos_label(struct fdisk_context *cxt) { return NULL; }
 186 struct fdisk_label *fdisk_new_bsd_label(struct fdisk_context *cxt) { return NULL; }
 187
 188 static int test_partnames(struct fdisk_test *ts, int argc, char *argv[])
 189 {
 190         size_t i;
 191         const char *disk = argv[1];
 192
 193         for (i = 0; i < 5; i++) {
 194                 char *p = fdisk_partname(disk, i + 1);
 195                 if (p)
 196                         printf("%zu: '%s'\n", i + 1, p);
 197                 free(p);
 198         }
 199
 200         return 0;
 201 }
 202
 203 int main(int argc, char *argv[])
 204 {
 205         struct fdisk_test tss[] = {
 206                 { "--partnames",  test_partnames,  "<diskname>" },
 207                 { NULL }
 208         };
 209
 210         return fdisk_run_test(tss, argc, argv);
 211 }
 212
 213 #endif