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  * Assumes that the dyld_cache_header grows in a binary compatible fashion.
  28  */
  29 bool
  30 get_uuid_from_shared_cache_mapping(const void *addr, size_t size, uuid_t out)
  31 {
  32     const struct copied_dyld_cache_header *ch = addr;
  33     if (size < sizeof (*ch))
  34         return false;
  35     static const char prefix[] = "dyld_v";
  36     if (strncmp(ch->magic, prefix, strlen(prefix)) != 0)
  37         return false;
  38     uuid_copy(out, ch->uuid);
  39     return true;
  40 }
  41
  42 /*
  43  * Look in the known places to see if we can find this one ..
  44  */
  45 char *
  46 shared_cache_filename(const uuid_t uu)
  47 {
  48     assert(!uuid_is_null(uu));
  49     static char *sc_argv[] = {
  50 #if defined(__i386__) || defined(__x86_64__)
  51         "/var/db/dyld",
  52 #elif defined(__arm__) || defined(__arm64__)
  53         "/System/Library/Caches/com.apple.dyld",
  54 #else
  55 #error undefined
  56 #endif
  57         NULL
  58     };
  59     char *nm = NULL;
  60     FTS *fts = fts_open(sc_argv, FTS_NOCHDIR | FTS_LOGICAL | FTS_XDEV, NULL);
  61     if (NULL != fts) {
  62         FTSENT *fe;
  63         while (NULL != (fe = fts_read(fts))) {
  64             if ((fe->fts_info & FTS_F) == 0 ||
  65                 (fe->fts_info & FTS_ERR) != 0)
  66                 continue;
  67
  68             static const char prefix[] = "dyld_shared_cache_";
  69             if (strncmp(fe->fts_name, prefix, strlen(prefix)) != 0)
  70                 continue;
  71
  72             if (fe->fts_statp->st_size < (off_t)dyld_cache_header_size)
  73                 continue;
  74
  75             int d = open(fe->fts_accpath, O_RDONLY);
  76             if (-1 == d) {
  77                 if (OPTIONS_DEBUG(opt, 1))
  78                     printf("%s: cannot open - %s\n", fe->fts_accpath, strerror(errno));
  79                 continue;
  80             }
  81             void *addr = mmap(NULL, dyld_cache_header_size, PROT_READ, MAP_PRIVATE, d, 0);
  82             close(d);
  83             if ((void *)-1 == addr) {
  84                 if (OPTIONS_DEBUG(opt, 1))
  85                     printf("%s: cannot mmap - %s\n", fe->fts_accpath, strerror(errno));
  86                 continue;
  87             }
  88             uuid_t scuuid;
  89             uuid_clear(scuuid);
  90             if (get_uuid_from_shared_cache_mapping(addr, dyld_cache_header_size, scuuid)) {
  91                 if (uuid_compare(uu, scuuid) == 0)
  92                     nm = strdup(fe->fts_accpath);
  93                 else if (OPTIONS_DEBUG(opt, 3)) {
  94                     uuid_string_t scstr;
  95                     uuid_unparse_lower(scuuid, scstr);
  96                     printf("%s: shared cache mismatch (%s)\n", fe->fts_accpath, scstr);
  97                 }
  98             }
  99             munmap(addr, dyld_cache_header_size);
 100             if (NULL != nm)
 101                 break;
 102         }
 103     }
 104     if (fts)
 105         fts_close(fts);
 106     return nm;
 107 }