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fune/config/check_vanilla_allocations.py

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# vim: set ts=8 sts=4 et sw=4 tw=79:
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.
# ----------------------------------------------------------------------------
# All heap allocations in SpiderMonkey must go through js_malloc, js_calloc,
# js_realloc, and js_free. This is so that any embedder who uses a custom
# allocator (by defining JS_USE_CUSTOM_ALLOCATOR) will see all heap allocation
# go through that custom allocator.
#
# Therefore, the presence of any calls to "vanilla" allocation/free functions
# from within SpiderMonkey itself (e.g. malloc(), free()) is a bug. Calls from
# within mozglue and non-SpiderMonkey locations are fine; there is a list of
# exceptions that can be added to as the need arises.
#
# This script checks for the presence of such disallowed vanilla
# allocation/free function in SpiderMonkey when it's built as a library. It
# relies on |nm| from the GNU binutils, and so only works on Linux, but one
# platform is good enough to catch almost all violations.
#
# This checking is only 100% reliable in a JS_USE_CUSTOM_ALLOCATOR build in
# which the default definitions of js_malloc et al (in Utility.h) -- which call
# malloc et al -- are replaced with empty definitions. This is because the
# presence and possible inlining of the default js_malloc et al can cause
# malloc/calloc/realloc/free calls show up in unpredictable places.
#
# Unfortunately, that configuration cannot be tested on Mozilla's standard
# testing infrastructure. Instead, by default this script only tests that none
# of the other vanilla allocation/free functions (operator new, memalign, etc)
# are present. If given the --aggressive flag, it will also check for
# malloc/calloc/realloc/free.
#
# Note: We don't check for |operator delete| and |operator delete[]|. These
# can be present somehow due to virtual destructors, but this is not too
# because vanilla delete/delete[] calls don't make sense without corresponding
# vanilla new/new[] calls, and any explicit calls will be caught by Valgrind's
# mismatched alloc/free checking.
# ----------------------------------------------------------------------------
import argparse
import re
import subprocess
import sys
from collections import defaultdict
import buildconfig
# The obvious way to implement this script is to search for occurrences of
# malloc et al, succeed if none are found, and fail is some are found.
# However, "none are found" does not necessarily mean "none are present" --
# this script could be buggy. (Or the output format of |nm| might change in
# the future.)
#
# So util/Utility.cpp deliberately contains a (never-called) function that
# contains a single use of all the vanilla allocation/free functions. And this
# script fails if it (a) finds uses of those functions in files other than
# util/Utility.cpp, *or* (b) fails to find them in util/Utility.cpp.
# Tracks overall success of the test.
has_failed = False
def fail(msg):
print("TEST-UNEXPECTED-FAIL | check_vanilla_allocations.py |", msg)
global has_failed
has_failed = True
def main():
parser = argparse.ArgumentParser()
parser.add_argument(
"--aggressive",
action="store_true",
help="also check for malloc, calloc, realloc and free",
)
parser.add_argument("file", type=str, help="name of the file to check")
args = parser.parse_args()
# Run |nm|. Options:
# -C: demangle symbol names
# -A: show an object filename for each undefined symbol
nm = buildconfig.substs.get("NM") or "nm"
cmd = [nm, "-C", "-A", args.file]
lines = subprocess.check_output(
cmd, universal_newlines=True, stderr=subprocess.PIPE
).split("\n")
# alloc_fns contains all the vanilla allocation/free functions that we look
# for. Regexp chars are escaped appropriately.
operator_news = [
# Matches |operator new(unsigned T)|, where |T| is |int| or |long|.
r"operator new(unsigned",
# Matches |operator new[](unsigned T)|, where |T| is |int| or |long|.
r"operator new[](unsigned",
]
# operator new may end up inlined and replaced with moz_xmalloc.
inlined_operator_news = [
r"moz_xmalloc",
]
alloc_fns = (
operator_news
+ inlined_operator_news
+ [
r"memalign",
# These three aren't available on all Linux configurations.
# r'posix_memalign',
# r'aligned_alloc',
# r'valloc',
]
)
if args.aggressive:
alloc_fns += [r"malloc", r"calloc", r"realloc", r"free", r"strdup"]
# This is like alloc_fns, but regexp chars are not escaped.
alloc_fns_escaped = [re.escape(fn) for fn in alloc_fns]
# This regexp matches the relevant lines in the output of |nm|, which look
# like the following.
#
# js/src/libjs_static.a:Utility.o: U malloc
# js/src/libjs_static.a:Utility.o: 00000000000007e0 T js::SetSourceOptions(...)
#
# It may also, in LTO builds, look like
# js/src/libjs_static.a:Utility.o: ---------------- T js::SetSourceOptions(...)
#
nm_line_re = re.compile(r"([^:/ ]+):\s*(?:[0-9a-fA-F]*|-*)\s+([TUw]) (.*)")
alloc_fns_re = re.compile(r"|".join(alloc_fns_escaped))
# This tracks which allocation/free functions have been seen.
functions = defaultdict(set)
files = defaultdict(int)
# Files to ignore allocation/free functions from.
ignored_files = [
# Ignore implicit call to operator new in std::condition_variable_any.
#
# From intl/icu/source/common/umutex.h:
# On Linux, the default constructor of std::condition_variable_any
# produces an in-line reference to global operator new(), [...].
"umutex.o",
# Ignore allocations from decimal conversion functions inside mozglue.
"Decimal.o",
# Ignore use of std::string in regexp AST debug output.
"regexp-ast.o",
]
all_ignored_files = set((f, 1) for f in ignored_files)
# Would it be helpful to emit detailed line number information after a failure?
emit_line_info = False
prev_filename = None
for line in lines:
m = nm_line_re.search(line)
if m is None:
continue
filename, symtype, fn = m.groups()
if prev_filename != filename:
# When the same filename appears multiple times, separated by other
# file names, this denotes a different file. Thankfully, we can more
# or less safely assume that dir1/Foo.o and dir2/Foo.o are not going
# to be next to each other.
files[filename] += 1
prev_filename = filename
# The stdc++compat library has an implicit call to operator new in
# thread::_M_start_thread.
if "stdc++compat" in filename:
continue
# The memory allocator code contains calls to memalign. These are ok, so
# we whitelist them.
if "_memory_" in filename:
continue
# Ignore the fuzzing code imported from m-c
if "Fuzzer" in filename:
continue
# Ignore the profiling pseudo-stack, since it needs to run even when
# SpiderMonkey's allocator isn't initialized.
if "ProfilingStack" in filename:
continue
if symtype == "T":
# We can't match intl/components files by file name because in
# non-unified builds they overlap with files in js/src.
# So we check symbols they define, and consider files with symbols
# in the mozilla::intl namespace to be those.
if fn.startswith("mozilla::intl::"):
all_ignored_files.add((filename, files[filename]))
else:
m = alloc_fns_re.match(fn)
if m:
functions[(filename, files[filename])].add(m.group(0))
util_Utility_cpp = functions.pop(("Utility.o", 1))
if ("Utility.o", 2) in functions:
fail("There should be only one Utility.o file")
for f, n in all_ignored_files:
functions.pop((f, n), None)
if f in ignored_files and (f, 2) in functions:
fail(f"There should be only one {f} file")
for filename, n in sorted(functions):
for fn in functions[(filename, n)]:
# An allocation is present in a non-special file. Fail!
fail("'" + fn + "' present in " + filename)
# Try to give more precise information about the offending code.
emit_line_info = True
# Check that all functions we expect are used in util/Utility.cpp. (This
# will fail if the function-detection code breaks at any point.)
# operator new and its inlined equivalent are mutually exclusive.
has_operator_news = any(fn in operator_news for fn in util_Utility_cpp)
has_inlined_operator_news = any(
fn in inlined_operator_news for fn in util_Utility_cpp
)
if has_operator_news and has_inlined_operator_news:
fail(
"Both operator new and moz_xmalloc aren't expected in util/Utility.cpp at the same time"
)
for fn in alloc_fns:
if fn not in util_Utility_cpp:
if (
(fn in operator_news and not has_inlined_operator_news)
or (fn in inlined_operator_news and not has_operator_news)
or (fn not in operator_news and fn not in inlined_operator_news)
):
fail("'" + fn + "' isn't used as expected in util/Utility.cpp")
else:
util_Utility_cpp.remove(fn)
# This should never happen, but check just in case.
if util_Utility_cpp:
fail(
"unexpected allocation fns used in util/Utility.cpp: "
+ ", ".join(util_Utility_cpp)
)
# If we found any improper references to allocation functions, try to use
# DWARF debug info to get more accurate line number information about the
# bad calls. This is a lot slower than 'nm -A', and it is not always
# precise when building with --enable-optimized.
if emit_line_info:
print("check_vanilla_allocations.py: Source lines with allocation calls:")
print(
"check_vanilla_allocations.py: Accurate in unoptimized builds; "
"util/Utility.cpp expected."
)
# Run |nm|. Options:
# -u: show only undefined symbols
# -C: demangle symbol names
# -l: show line number information for each undefined symbol
cmd = ["nm", "-u", "-C", "-l", args.file]
lines = subprocess.check_output(
cmd, universal_newlines=True, stderr=subprocess.PIPE
).split("\n")
# This regexp matches the relevant lines in the output of |nm -l|,
# which look like the following.
#
# U malloc util/Utility.cpp:117
#
alloc_lines_re = (
r"[Uw] ((" + r"|".join(alloc_fns_escaped) + r").*)\s+(\S+:\d+)$"
)
for line in lines:
m = re.search(alloc_lines_re, line)
if m:
print(
"check_vanilla_allocations.py:", m.group(1), "called at", m.group(3)
)
if has_failed:
sys.exit(1)
print("TEST-PASS | check_vanilla_allocations.py | ok")
sys.exit(0)
if __name__ == "__main__":
main()
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