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      1 /*
      2  * Copyright (C) 2017 The Android Open Source Project
      3  *
      4  * Permission is hereby granted, free of charge, to any person
      5  * obtaining a copy of this software and associated documentation
      6  * files (the "Software"), to deal in the Software without
      7  * restriction, including without limitation the rights to use, copy,
      8  * modify, merge, publish, distribute, sublicense, and/or sell copies
      9  * of the Software, and to permit persons to whom the Software is
     10  * furnished to do so, subject to the following conditions:
     11  *
     12  * The above copyright notice and this permission notice shall be
     13  * included in all copies or substantial portions of the Software.
     14  *
     15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
     16  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
     17  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
     18  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
     19  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
     20  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
     21  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
     22  * SOFTWARE.
     23  */
     24 
     25 #include "avb_ops_user.h"
     26 
     27 #include <errno.h>
     28 #include <fcntl.h>
     29 #include <linux/fs.h>
     30 #include <stdlib.h>
     31 #include <string.h>
     32 #include <sys/ioctl.h>
     33 #include <sys/stat.h>
     34 #include <sys/types.h>
     35 #include <unistd.h>
     36 
     37 #include <cutils/properties.h>
     38 #include <fs_mgr.h>
     39 
     40 #include <libavb_ab/libavb_ab.h>
     41 
     42 /* Open the appropriate fstab file and fallback to /fstab.device if
     43  * that's what's being used.
     44  */
     45 static struct fstab* open_fstab(void) {
     46   struct fstab* fstab = fs_mgr_read_fstab_default();
     47 
     48   if (fstab != NULL) {
     49     return fstab;
     50   }
     51 
     52   fstab = fs_mgr_read_fstab("/fstab.device");
     53   return fstab;
     54 }
     55 
     56 static int open_partition(const char* name, int flags) {
     57   char* path;
     58   int fd;
     59   struct fstab* fstab;
     60   struct fstab_rec* record;
     61 
     62   /* We can't use fs_mgr to look up |name| because fstab doesn't list
     63    * every slot partition (it uses the slotselect option to mask the
     64    * suffix) and |slot| is expected to be of that form, e.g. boot_a.
     65    *
     66    * We can however assume that there's an entry for the /misc mount
     67    * point and use that to get the device file for the misc
     68    * partition. From there we'll assume that a by-name scheme is used
     69    * so we can just replace the trailing "misc" by the given |name|,
     70    * e.g.
     71    *
     72    *   /dev/block/platform/soc.0/7824900.sdhci/by-name/misc ->
     73    *   /dev/block/platform/soc.0/7824900.sdhci/by-name/boot_a
     74    *
     75    * If needed, it's possible to relax this assumption in the future
     76    * by trawling /sys/block looking for the appropriate sibling of
     77    * misc and then finding an entry in /dev matching the sysfs entry.
     78    */
     79 
     80   fstab = open_fstab();
     81   if (fstab == NULL) {
     82     return -1;
     83   }
     84   record = fs_mgr_get_entry_for_mount_point(fstab, "/misc");
     85   if (record == NULL) {
     86     fs_mgr_free_fstab(fstab);
     87     return -1;
     88   }
     89   if (strcmp(name, "misc") == 0) {
     90     path = strdup(record->blk_device);
     91   } else {
     92     size_t trimmed_len, name_len;
     93     const char* end_slash = strrchr(record->blk_device, '/');
     94     if (end_slash == NULL) {
     95       fs_mgr_free_fstab(fstab);
     96       return -1;
     97     }
     98     trimmed_len = end_slash - record->blk_device + 1;
     99     name_len = strlen(name);
    100     path = calloc(trimmed_len + name_len + 1, 1);
    101     strncpy(path, record->blk_device, trimmed_len);
    102     strncpy(path + trimmed_len, name, name_len);
    103   }
    104   fs_mgr_free_fstab(fstab);
    105 
    106   fd = open(path, flags);
    107   free(path);
    108 
    109   return fd;
    110 }
    111 
    112 static AvbIOResult read_from_partition(AvbOps* ops,
    113                                        const char* partition,
    114                                        int64_t offset,
    115                                        size_t num_bytes,
    116                                        void* buffer,
    117                                        size_t* out_num_read) {
    118   int fd;
    119   off_t where;
    120   ssize_t num_read;
    121   AvbIOResult ret;
    122 
    123   fd = open_partition(partition, O_RDONLY);
    124   if (fd == -1) {
    125     ret = AVB_IO_RESULT_ERROR_NO_SUCH_PARTITION;
    126     goto out;
    127   }
    128 
    129   if (offset < 0) {
    130     uint64_t partition_size;
    131     if (ioctl(fd, BLKGETSIZE64, &partition_size) != 0) {
    132       avb_errorv(
    133           "Error getting size of \"", partition, "\" partition.\n", NULL);
    134       ret = AVB_IO_RESULT_ERROR_IO;
    135       goto out;
    136     }
    137     offset = partition_size - (-offset);
    138   }
    139 
    140   where = lseek(fd, offset, SEEK_SET);
    141   if (where == -1) {
    142     avb_error("Error seeking to offset.\n");
    143     ret = AVB_IO_RESULT_ERROR_IO;
    144     goto out;
    145   }
    146   if (where != offset) {
    147     avb_error("Error seeking to offset.\n");
    148     ret = AVB_IO_RESULT_ERROR_RANGE_OUTSIDE_PARTITION;
    149     goto out;
    150   }
    151 
    152   /* On Linux, we never get partial reads from block devices (except
    153    * for EOF).
    154    */
    155   num_read = read(fd, buffer, num_bytes);
    156   if (num_read == -1) {
    157     avb_error("Error reading data.\n");
    158     ret = AVB_IO_RESULT_ERROR_IO;
    159     goto out;
    160   }
    161   if (out_num_read != NULL) {
    162     *out_num_read = num_read;
    163   }
    164 
    165   ret = AVB_IO_RESULT_OK;
    166 
    167 out:
    168   if (fd != -1) {
    169     if (close(fd) != 0) {
    170       avb_error("Error closing file descriptor.\n");
    171     }
    172   }
    173   return ret;
    174 }
    175 
    176 static AvbIOResult write_to_partition(AvbOps* ops,
    177                                       const char* partition,
    178                                       int64_t offset,
    179                                       size_t num_bytes,
    180                                       const void* buffer) {
    181   int fd;
    182   off_t where;
    183   ssize_t num_written;
    184   AvbIOResult ret;
    185 
    186   fd = open_partition(partition, O_WRONLY);
    187   if (fd == -1) {
    188     avb_errorv("Error opening \"", partition, "\" partition.\n", NULL);
    189     ret = AVB_IO_RESULT_ERROR_IO;
    190     goto out;
    191   }
    192 
    193   where = lseek(fd, offset, SEEK_SET);
    194   if (where == -1) {
    195     avb_error("Error seeking to offset.\n");
    196     ret = AVB_IO_RESULT_ERROR_IO;
    197     goto out;
    198   }
    199   if (where != offset) {
    200     avb_error("Error seeking to offset.\n");
    201     ret = AVB_IO_RESULT_ERROR_RANGE_OUTSIDE_PARTITION;
    202     goto out;
    203   }
    204 
    205   /* On Linux, we never get partial writes on block devices. */
    206   num_written = write(fd, buffer, num_bytes);
    207   if (num_written == -1) {
    208     avb_error("Error writing data.\n");
    209     ret = AVB_IO_RESULT_ERROR_IO;
    210     goto out;
    211   }
    212 
    213   ret = AVB_IO_RESULT_OK;
    214 
    215 out:
    216   if (fd != -1) {
    217     if (close(fd) != 0) {
    218       avb_error("Error closing file descriptor.\n");
    219     }
    220   }
    221   return ret;
    222 }
    223 
    224 AvbOps* avb_ops_user_new(void) {
    225   AvbOps* ops;
    226 
    227   ops = calloc(1, sizeof(AvbOps));
    228   if (ops == NULL) {
    229     avb_error("Error allocating memory for AvbOps.\n");
    230     goto out;
    231   }
    232 
    233   ops->ab_ops = calloc(1, sizeof(AvbABOps));
    234   if (ops->ab_ops == NULL) {
    235     avb_error("Error allocating memory for AvbABOps.\n");
    236     free(ops);
    237     goto out;
    238   }
    239   ops->ab_ops->ops = ops;
    240 
    241   ops->read_from_partition = read_from_partition;
    242   ops->write_to_partition = write_to_partition;
    243   ops->ab_ops->read_ab_metadata = avb_ab_data_read;
    244   ops->ab_ops->write_ab_metadata = avb_ab_data_write;
    245 
    246 out:
    247   return ops;
    248 }
    249 
    250 void avb_ops_user_free(AvbOps* ops) {
    251   free(ops->ab_ops);
    252   free(ops);
    253 }
    254