config/check_vanilla_allocations.py

   1 # vim: set ts=8 sts=4 et sw=4 tw=79:
   2 # This Source Code Form is subject to the terms of the Mozilla Public
   3 # License, v. 2.0. If a copy of the MPL was not distributed with this
   4 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
   5
   6 # ----------------------------------------------------------------------------
   7 # All heap allocations in SpiderMonkey must go through js_malloc, js_calloc,
   8 # js_realloc, and js_free.  This is so that any embedder who uses a custom
   9 # allocator (by defining JS_USE_CUSTOM_ALLOCATOR) will see all heap allocation
  10 # go through that custom allocator.
  11 #
  12 # Therefore, the presence of any calls to "vanilla" allocation/free functions
  13 # from within SpiderMonkey itself (e.g. malloc(), free()) is a bug.  Calls from
  14 # within mozglue and non-SpiderMonkey locations are fine; there is a list of
  15 # exceptions that can be added to as the need arises.
  16 #
  17 # This script checks for the presence of such disallowed vanilla
  18 # allocation/free function in SpiderMonkey when it's built as a library.  It
  19 # relies on |nm| from the GNU binutils, and so only works on Linux, but one
  20 # platform is good enough to catch almost all violations.
  21 #
  22 # This checking is only 100% reliable in a JS_USE_CUSTOM_ALLOCATOR build in
  23 # which the default definitions of js_malloc et al (in Utility.h) -- which call
  24 # malloc et al -- are replaced with empty definitions.  This is because the
  25 # presence and possible inlining of the default js_malloc et al can cause
  26 # malloc/calloc/realloc/free calls show up in unpredictable places.
  27 #
  28 # Unfortunately, that configuration cannot be tested on Mozilla's standard
  29 # testing infrastructure.  Instead, by default this script only tests that none
  30 # of the other vanilla allocation/free functions (operator new, memalign, etc)
  31 # are present.  If given the --aggressive flag, it will also check for
  32 # malloc/calloc/realloc/free.
  33 #
  34 # Note:  We don't check for |operator delete| and |operator delete[]|.  These
  35 # can be present somehow due to virtual destructors, but this is not too
  36 # because vanilla delete/delete[] calls don't make sense without corresponding
  37 # vanilla new/new[] calls, and any explicit calls will be caught by Valgrind's
  38 # mismatched alloc/free checking.
  39 # ----------------------------------------------------------------------------
  40
  41 from __future__ import absolute_import, print_function, unicode_literals
  42
  43 import argparse
  44 import re
  45 import subprocess
  46 import sys
  47 import buildconfig
  48
  49 # The obvious way to implement this script is to search for occurrences of
  50 # malloc et al, succeed if none are found, and fail is some are found.
  51 # However, "none are found" does not necessarily mean "none are present" --
  52 # this script could be buggy.  (Or the output format of |nm| might change in
  53 # the future.)
  54 #
  55 # So util/Utility.cpp deliberately contains a (never-called) function that
  56 # contains a single use of all the vanilla allocation/free functions.  And this
  57 # script fails if it (a) finds uses of those functions in files other than
  58 # util/Utility.cpp, *or* (b) fails to find them in util/Utility.cpp.
  59
  60 # Tracks overall success of the test.
  61 has_failed = False
  62
  63
  64 def fail(msg):
  65     print("TEST-UNEXPECTED-FAIL | check_vanilla_allocations.py |", msg)
  66     global has_failed
  67     has_failed = True
  68
  69
  70 def main():
  71     parser = argparse.ArgumentParser()
  72     parser.add_argument(
  73         "--aggressive",
  74         action="store_true",
  75         help="also check for malloc, calloc, realloc and free",
  76     )
  77     parser.add_argument("file", type=str, help="name of the file to check")
  78     args = parser.parse_args()
  79
  80     # Run |nm|.  Options:
  81     # -u: show only undefined symbols
  82     # -C: demangle symbol names
  83     # -A: show an object filename for each undefined symbol
  84     nm = buildconfig.substs.get("NM") or "nm"
  85     cmd = [nm, "-u", "-C", "-A", args.file]
  86     lines = subprocess.check_output(
  87         cmd, universal_newlines=True, stderr=subprocess.PIPE
  88     ).split("\n")
  89
  90     # alloc_fns contains all the vanilla allocation/free functions that we look
  91     # for. Regexp chars are escaped appropriately.
  92
  93     alloc_fns = [
  94         # Matches |operator new(unsigned T)|, where |T| is |int| or |long|.
  95         r"operator new\(unsigned",
  96         # Matches |operator new[](unsigned T)|, where |T| is |int| or |long|.
  97         r"operator new\[\]\(unsigned",
  98         r"memalign",
  99         # These three aren't available on all Linux configurations.
 100         # r'posix_memalign',
 101         # r'aligned_alloc',
 102         # r'valloc',
 103     ]
 104
 105     if args.aggressive:
 106         alloc_fns += [r"malloc", r"calloc", r"realloc", r"free", r"strdup"]
 107
 108     # This is like alloc_fns, but regexp chars are not escaped.
 109     alloc_fns_unescaped = [fn.replace("\\", "") for fn in alloc_fns]
 110
 111     # This regexp matches the relevant lines in the output of |nm|, which look
 112     # like the following.
 113     #
 114     #   js/src/libjs_static.a:Utility.o:              U malloc
 115     #
 116     alloc_fns_re = r"([^:/ ]+):\s+U (" + r"|".join(alloc_fns) + r")"
 117
 118     # This tracks which allocation/free functions have been seen in
 119     # util/Utility.cpp.
 120     util_Utility_cpp = set([])
 121
 122     # Would it be helpful to emit detailed line number information after a failure?
 123     emit_line_info = False
 124
 125     for line in lines:
 126         m = re.search(alloc_fns_re, line)
 127         if m is None:
 128             continue
 129
 130         filename = m.group(1)
 131
 132         # The stdc++compat library has an implicit call to operator new in
 133         # thread::_M_start_thread.
 134         if "stdc++compat" in filename:
 135             continue
 136
 137         # The memory allocator code contains calls to memalign. These are ok, so
 138         # we whitelist them.
 139         if "_memory_" in filename:
 140             continue
 141
 142         # Ignore the fuzzing code imported from m-c
 143         if "Fuzzer" in filename:
 144             continue
 145
 146         # Ignore the profiling pseudo-stack, since it needs to run even when
 147         # SpiderMonkey's allocator isn't initialized.
 148         if "ProfilingStack" in filename:
 149             continue
 150
 151         # Ignore implicit call to operator new in std::condition_variable_any.
 152         #
 153         # From intl/icu/source/common/umutex.h:
 154         # On Linux, the default constructor of std::condition_variable_any
 155         # produces an in-line reference to global operator new(), [...].
 156         if filename == "umutex.o":
 157             continue
 158
 159         # Ignore allocations from decimal conversion functions inside mozglue.
 160         if filename == "Decimal.o":
 161             continue
 162
 163         fn = m.group(2)
 164         if filename == "Utility.o":
 165             util_Utility_cpp.add(fn)
 166         else:
 167             # An allocation is present in a non-special file.  Fail!
 168             fail("'" + fn + "' present in " + filename)
 169             # Try to give more precise information about the offending code.
 170             emit_line_info = True
 171
 172     # Check that all functions we expect are used in util/Utility.cpp.  (This
 173     # will fail if the function-detection code breaks at any point.)
 174     for fn in alloc_fns_unescaped:
 175         if fn not in util_Utility_cpp:
 176             fail("'" + fn + "' isn't used as expected in util/Utility.cpp")
 177         else:
 178             util_Utility_cpp.remove(fn)
 179
 180     # This should never happen, but check just in case.
 181     if util_Utility_cpp:
 182         fail(
 183             "unexpected allocation fns used in util/Utility.cpp: "
 184             + ", ".join(util_Utility_cpp)
 185         )
 186
 187     # If we found any improper references to allocation functions, try to use
 188     # DWARF debug info to get more accurate line number information about the
 189     # bad calls. This is a lot slower than 'nm -A', and it is not always
 190     # precise when building with --enable-optimized.
 191     if emit_line_info:
 192         print("check_vanilla_allocations.py: Source lines with allocation calls:")
 193         print(
 194             "check_vanilla_allocations.py: Accurate in unoptimized builds; "
 195             "util/Utility.cpp expected."
 196         )
 197
 198         # Run |nm|.  Options:
 199         # -u: show only undefined symbols
 200         # -C: demangle symbol names
 201         # -l: show line number information for each undefined symbol
 202         cmd = ["nm", "-u", "-C", "-l", args.file]
 203         lines = subprocess.check_output(
 204             cmd, universal_newlines=True, stderr=subprocess.PIPE
 205         ).split("\n")
 206
 207         # This regexp matches the relevant lines in the output of |nm -l|,
 208         # which look like the following.
 209         #
 210         #       U malloc util/Utility.cpp:117
 211         #
 212         alloc_lines_re = r"U ((" + r"|".join(alloc_fns) + r").*)\s+(\S+:\d+)$"
 213
 214         for line in lines:
 215             m = re.search(alloc_lines_re, line)
 216             if m:
 217                 print(
 218                     "check_vanilla_allocations.py:", m.group(1), "called at", m.group(3)
 219                 )
 220
 221     if has_failed:
 222         sys.exit(1)
 223
 224     print("TEST-PASS | check_vanilla_allocations.py | ok")
 225     sys.exit(0)
 226
 227
 228 if __name__ == "__main__":
 229     main()