enable_asan_mode

   1 #!/bin/bash -e
   2
   3 if [ $# -ne 1 ]; then
   4     echo "Usage:" 1>&2
   5     echo "  sudo $0 enable       ... enables ASanification of system libraries on your system" 1>&2
   6     echo "  sudo $0 disable      ... reverts the changes and restores the system back to normal" 1>&2
   7     echo "  $0 status            ... prints current mode" 1>&2
   8     exit 1
   9 fi
  10
  11 LIBSYSTEM_B="/usr/lib/libSystem.B.dylib"
  12 LIBSYSTEM_B_BACKUP="${LIBSYSTEM_B}-asan-mode-backup"
  13 LIBSYSTEM_B_ASAN="/usr/lib/libSystem.B_asan.dylib"
  14
  15 # If this file is present on the system and we are using a development build
  16 # then the usual memory resource limits won't be applied.
  17 # rdar://problem/43520116
  18 DISABLE_MEM_LIMIT_COOKIE_FILE="/usr/local/share/launchd-disable-memory-limits"
  19 DISABLE_MEM_LIMIT_COOKIE_CONTENTS="kEnableAsanDisableMemLimit"
  20
  21 function is_mac_os() {
  22   if [ $(sw_vers -productName | grep -c '^Mac OS') -ne 0 ]; then
  23       # Mac OS.
  24       return 0
  25   else
  26       # Something else.
  27       return 1
  28   fi
  29 }
  30
  31 function show_have_asan_mode_on_msg() {
  32     echo "Looks like your system already has ASan mode enabled, or you have a custom ${LIBSYSTEM_B} file. Not activating." 1>&2
  33 }
  34
  35 if ! is_mac_os; then
  36     # Check assumption that ${LIBSYSTEM_B} is in the dyld shared cache.
  37     if [ "$(dyld_shared_cache_util -list | grep -c "^${LIBSYSTEM_B}$")" -eq 0 ]; then
  38         echo "Error: Non macOS platform detected but ${LIBSYSTEM_B} is not in your dyld shared cache." 1>&2
  39         exit 1
  40     fi
  41 fi
  42
  43 case "$1" in
  44   enable)
  45       if [[ $(id -u) != 0 ]]; then echo "Must be run as root." 1>&2; exit 1; fi
  46
  47       if is_mac_os; then
  48           if [ -f ${LIBSYSTEM_B_BACKUP} ]; then
  49               if [ "`md5 -q ${LIBSYSTEM_B_BACKUP}`" != "`md5 -q ${LIBSYSTEM_B}`" ]; then
  50                   show_have_asan_mode_on_msg
  51                   exit 1
  52               fi
  53           fi
  54           ditto ${LIBSYSTEM_B} ${LIBSYSTEM_B_BACKUP}
  55       else
  56           # libSystem.B.dylib does not exist on non-macos platforms because it
  57           # lives in the dyld cache so we don't have a back up file. Instead
  58           # the presence of `libSystem.B.dylib` indicates that we are using ASan mode.
  59           if [ -f ${LIBSYSTEM_B} ]; then
  60               show_have_asan_mode_on_msg
  61               exit 1
  62           fi
  63           # Disable memory limits because ASan adds memory overhead.
  64           echo "${DISABLE_MEM_LIMIT_COOKIE_CONTENTS}" > "${DISABLE_MEM_LIMIT_COOKIE_FILE}"
  65       fi
  66
  67       ditto ${LIBSYSTEM_B_ASAN} ${LIBSYSTEM_B}
  68       echo "ASan mode activated. You probably want to reboot now." 1>&2
  69       exit 0
  70   ;;
  71   disable)
  72       if [[ $(id -u) != 0 ]]; then echo "Must be run as root." 1>&2; exit 1; fi
  73       if is_mac_os; then
  74           ditto ${LIBSYSTEM_B_BACKUP} ${LIBSYSTEM_B}
  75       else
  76           if [ ! -f "${LIBSYSTEM_B}" ]; then
  77               echo "ASan mode cannot be disabled if it is not already enabled" 2>&1
  78               exit 1
  79           fi
  80           if [ "`md5 -q ${LIBSYSTEM_B_ASAN}`" != "`md5 -q ${LIBSYSTEM_B}`" ]; then
  81               echo "You appear to have a custom ${LIBSYSTEM_B} file. Not deactivating." 1>&2
  82               exit 1
  83           fi
  84           # Safe to do because we've checked this is the ASan version and the normal versions
  85           # lives in the dyld shared cache.
  86           rm -f ${LIBSYSTEM_B}
  87           if [ ! -f "${DISABLE_MEM_LIMIT_COOKIE_FILE}" ] ; then
  88               echo "Warning: Can't find \"${DISABLE_MEM_LIMIT_COOKIE_FILE}\" so skipping delete" 2>&1
  89           else
  90               # Check the contents of the cookie file and only delete if it matches.
  91               # If it doesn't match we don't delete because we assume the user wants
  92               # to keep the cookie file around.
  93               if [ "$(grep -c "^${DISABLE_MEM_LIMIT_COOKIE_CONTENTS}$" "${DISABLE_MEM_LIMIT_COOKIE_FILE}")" -eq 1 ]; then
  94                   rm -f "${DISABLE_MEM_LIMIT_COOKIE_FILE}"
  95               else
  96                   echo "Warning: Not removing \"${DISABLE_MEM_LIMIT_COOKIE_FILE}\" because it has been modified" 2>&1
  97               fi
  98           fi
  99       fi
 100       echo "ASan mode deactivated. You probably want to reboot now." 1>&2
 101       exit 0
 102   ;;
 103   status)
 104       if is_mac_os; then
 105           if [ ! -f ${LIBSYSTEM_B_BACKUP} ]; then
 106               echo "ASan mode is disabled." 1>&2
 107               exit 0
 108           fi
 109
 110           if [ "`md5 -q ${LIBSYSTEM_B_BACKUP}`" == "`md5 -q ${LIBSYSTEM_B}`" ]; then
 111               echo "ASan mode is disabled." 1>&2
 112               exit 0
 113           fi
 114       else
 115           if [ ! -f ${LIBSYSTEM_B} ]; then
 116               echo "ASan mode is disabled." 1>&2
 117               exit 0
 118           fi
 119       fi
 120
 121       if [ "`md5 -q ${LIBSYSTEM_B_ASAN}`" == "`md5 -q ${LIBSYSTEM_B}`" ]; then
 122           echo "ASan mode is enabled." 1>&2
 123           exit 0
 124       fi
 125
 126       echo "Cannot tell whether ASan mode is enabled or not. You seem to have a custom ${LIBSYSTEM_B} file." 1>&2
 127       exit 1
 128   ;;
 129   *)
 130       echo "Invalid argument. Run '$0' for usage instructions." 1>&2
 131       exit 1
 132   ;;
 133 esac