gcore.tproj/dyld_shared_cache.c

   1 /*
   2  * Copyright (c) 2016 Apple Inc.  All rights reserved.
   3  */
   4
   5 #include "options.h"
   6 #include "dyld_shared_cache.h"
   7 #include "utils.h"
   8
   9 #include <stdio.h>
  10 #include <string.h>
  11 #include <strings.h>
  12 #include <stdlib.h>
  13 #include <stdarg.h>
  14 #include <unistd.h>
  15 #include <errno.h>
  16 #include <fts.h>
  17 #include <fcntl.h>
  18 #include <assert.h>
  19 #include <sys/mman.h>
  20 #include <sys/stat.h>
  21 #include <TargetConditionals.h>
  22
  23 static const size_t dyld_cache_header_size = sizeof (struct copied_dyld_cache_header);
  24
  25 /*
  26  * The shared cache must both contain the magic ID and
  27  * match the uuid we discovered via dyld's information.
  28  * Assumes that the dyld_cache_header grows in a binary compatible fashion.
  29  */
  30 bool
  31 get_uuid_from_shared_cache_mapping(const void *addr, size_t size, uuid_t out)
  32 {
  33     const struct copied_dyld_cache_header *ch = addr;
  34     if (size < sizeof (*ch))
  35         return false;
  36     static const char prefix[] = "dyld_v";
  37     if (strncmp(ch->magic, prefix, strlen(prefix)) != 0)
  38         return false;
  39     uuid_copy(out, ch->uuid);
  40     return true;
  41 }
  42
  43 /*
  44  * Look in the known places to see if we can find this one ..
  45  */
  46 char *
  47 shared_cache_filename(const uuid_t uu)
  48 {
  49     assert(!uuid_is_null(uu));
  50     static char *sc_argv[] = {
  51 #if TARGET_OS_OSX
  52         "/System/Library/dyld",
  53 #elif TARGET_OS_IPHONE
  54         "/System/Library/Caches/com.apple.dyld",
  55 #else
  56 #error undefined
  57 #endif
  58         NULL
  59     };
  60     char *nm = NULL;
  61     FTS *fts = fts_open(sc_argv, FTS_NOCHDIR | FTS_LOGICAL | FTS_XDEV, NULL);
  62     if (NULL != fts) {
  63         FTSENT *fe;
  64         while (NULL != (fe = fts_read(fts))) {
  65             if ((fe->fts_info & FTS_F) == 0 ||
  66                 (fe->fts_info & FTS_ERR) != 0)
  67                 continue;
  68
  69             static const char prefix[] = "dyld_shared_cache_";
  70             if (strncmp(fe->fts_name, prefix, strlen(prefix)) != 0)
  71                 continue;
  72
  73             if (fe->fts_statp->st_size < (off_t)dyld_cache_header_size)
  74                 continue;
  75
  76             int d = open(fe->fts_accpath, O_RDONLY);
  77             if (-1 == d) {
  78                 if (OPTIONS_DEBUG(opt, 1))
  79                     printf("%s: cannot open - %s\n", fe->fts_accpath, strerror(errno));
  80                 continue;
  81             }
  82             void *addr = mmap(NULL, dyld_cache_header_size, PROT_READ, MAP_PRIVATE, d, 0);
  83             close(d);
  84             if ((void *)-1 == addr) {
  85                 if (OPTIONS_DEBUG(opt, 1))
  86                     printf("%s: cannot mmap - %s\n", fe->fts_accpath, strerror(errno));
  87                 continue;
  88             }
  89             uuid_t scuuid;
  90             uuid_clear(scuuid);
  91             if (get_uuid_from_shared_cache_mapping(addr, dyld_cache_header_size, scuuid)) {
  92                 if (uuid_compare(uu, scuuid) == 0)
  93                     nm = strdup(fe->fts_accpath);
  94                 else if (OPTIONS_DEBUG(opt, 3)) {
  95                     uuid_string_t scstr;
  96                     uuid_unparse_lower(scuuid, scstr);
  97                     printf("%s: shared cache mismatch (%s)\n", fe->fts_accpath, scstr);
  98                 }
  99             }
 100             munmap(addr, dyld_cache_header_size);
 101             if (NULL != nm)
 102                 break;
 103         }
 104     }
 105     if (fts)
 106         fts_close(fts);
 107     return nm;
 108 }