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
  22 static const size_t dyld_cache_header_size = sizeof (struct copied_dyld_cache_header);
  23
  24 /*
  25  * The shared cache must both contain the magic ID and
  26  * match the uuid we discovered via dyld's information.
  27  */
  28 bool
  29 get_uuid_from_shared_cache_mapping(const void *addr, size_t size, uuid_t out)
  30 {
  31     const struct copied_dyld_cache_header *ch = addr;
  32     if (size < sizeof (*ch))
  33         return false;
  34     static const char prefix[] = "dyld_v1 ";
  35     if (strncmp(ch->magic, prefix, strlen(prefix)) != 0)
  36         return false;
  37     uuid_copy(out, ch->uuid);
  38     return true;
  39 }
  40
  41 /*
  42  * Look in the known places to see if we can find this one ..
  43  */
  44 char *
  45 shared_cache_filename(const uuid_t uu)
  46 {
  47     assert(!uuid_is_null(uu));
  48     static char *sc_argv[] = {
  49 #if defined(__i386__) || defined(__x86_64__)
  50         "/var/db/dyld",
  51 #elif defined(__arm__) || defined(__arm64__)
  52         "/System/Library/Caches/com.apple.dyld",
  53 #else
  54 #error undefined
  55 #endif
  56         NULL
  57     };
  58     char *nm = NULL;
  59     FTS *fts = fts_open(sc_argv, FTS_NOCHDIR | FTS_LOGICAL | FTS_XDEV, NULL);
  60     if (NULL != fts) {
  61         FTSENT *fe;
  62         while (NULL != (fe = fts_read(fts))) {
  63             if ((fe->fts_info & FTS_F) == 0 ||
  64                 (fe->fts_info & FTS_ERR) != 0)
  65                 continue;
  66
  67             static const char prefix[] = "dyld_shared_cache_";
  68             if (strncmp(fe->fts_name, prefix, strlen(prefix)) != 0)
  69                 continue;
  70
  71             if (fe->fts_statp->st_size < (off_t)dyld_cache_header_size)
  72                 continue;
  73
  74             int d = open(fe->fts_accpath, O_RDONLY);
  75             if (-1 == d) {
  76                 if (opt->debug)
  77                     printf("%s: cannot open - %s\n", fe->fts_accpath, strerror(errno));
  78                 continue;
  79             }
  80             void *addr = mmap(NULL, dyld_cache_header_size, PROT_READ, MAP_PRIVATE, d, 0);
  81             close(d);
  82             if ((void *)-1 == addr) {
  83                 if (opt->debug)
  84                     printf("%s: cannot mmap - %s\n", fe->fts_accpath, strerror(errno));
  85                 continue;
  86             }
  87             uuid_t scuuid;
  88             uuid_clear(scuuid);
  89             if (get_uuid_from_shared_cache_mapping(addr, dyld_cache_header_size, scuuid)) {
  90                 if (uuid_compare(uu, scuuid) == 0)
  91                     nm = strdup(fe->fts_accpath);
  92                 else if (opt->debug) {
  93                     uuid_string_t scstr;
  94                     uuid_unparse_lower(scuuid, scstr);
  95                     printf("%s: shared cache mismatch (%s)\n", fe->fts_accpath, scstr);
  96                 }
  97             }
  98             munmap(addr, dyld_cache_header_size);
  99             if (NULL != nm)
 100                 break;
 101         }
 102     }
 103     if (fts)
 104         fts_close(fts);
 105     return nm;
 106 }