config/sanitizers/sanitizers.gni

# Copyright 2015 The Chromium Authors
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

import("//build/config/cast.gni")
import("//build/config/chrome_build.gni")
import("//build/config/chromeos/args.gni")
import("//build/config/chromeos/ui_mode.gni")
import("//build/config/profiling/profiling.gni")
import("//build/toolchain/toolchain.gni")

declare_args() {
  # Compile for Address Sanitizer to find memory bugs.
  is_asan = false

  # Compile for Hardware-Assisted Address Sanitizer to find memory bugs
  # (android/arm64 only).
  # See http://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html
  is_hwasan = false

  # Compile for Leak Sanitizer to find leaks.
  is_lsan = false

  # Compile for Memory Sanitizer to find uninitialized reads.
  is_msan = false

  # Compile for Thread Sanitizer to find threading bugs.
  is_tsan = false

  # Compile for Undefined Behaviour Sanitizer to find various types of
  # undefined behaviour (excludes vptr checks).
  is_ubsan = false

  # Halt the program if a problem is detected.
  is_ubsan_no_recover = false

  # Track where uninitialized memory originates from. From fastest to slowest:
  # 0 - no tracking, 1 - track only the initial allocation site, 2 - track the
  # chain of stores leading from allocation site to use site.
  msan_track_origins = 2

  # Use dynamic libraries instrumented by one of the sanitizers instead of the
  # standard system libraries. Set this flag to build the libraries from source.
  use_locally_built_instrumented_libraries = false

  # Compile with Control Flow Integrity to protect virtual calls and casts.
  # See http://clang.llvm.org/docs/ControlFlowIntegrity.html
  #
  # TODO(pcc): Remove this flag if/when CFI is enabled in all official builds.
  is_cfi = is_official_build && is_clang &&
           ((target_os == "linux" && target_cpu == "x64") ||
            (is_chromeos && is_chromeos_device))

  # Enable checks for indirect function calls via a function pointer.
  # TODO(pcc): remove this when we're ready to add these checks by default.
  # https://crbug.com/701919
  use_cfi_icall =
      target_os == "linux" && target_cpu == "x64" && is_official_build

  # Print detailed diagnostics when Control Flow Integrity detects a violation.
  use_cfi_diag = false

  # Let Control Flow Integrity continue execution instead of crashing when
  # printing diagnostics (use_cfi_diag = true).
  use_cfi_recover = false

  # Compile for fuzzing with LLVM LibFuzzer.
  # See http://www.chromium.org/developers/testing/libfuzzer
  use_libfuzzer = false

  # Compile for fuzzing with centipede.
  # See https://github.com/google/centipede
  use_centipede = false

  # Compile for fuzzing with AFL.
  use_afl = false

  # Compile for fuzzing with an external engine (e.g., Grammarinator).
  use_external_fuzzing_engine = false

  # Enables core ubsan security features. Will later be removed once it matches
  # is_ubsan.
  is_ubsan_security = false

  # Helper variable for testing builds with disabled libfuzzer.
  # Not for client use.
  disable_libfuzzer = false

  # Value for -fsanitize-coverage flag. Setting this causes
  # use_sanitizer_coverage to be enabled.
  # This flag is not used for libFuzzer (use_libfuzzer=true). Instead, we use:
  #     -fsanitize=fuzzer-no-link
  # Default value when unset and use_fuzzing_engine=true:
  #     trace-pc-guard
  # Default value when unset and use_sanitizer_coverage=true:
  #     trace-pc-guard,indirect-calls
  sanitizer_coverage_flags = ""

  # When enabled, only relevant sanitizer defines are set, but compilation
  # happens with no extra flags. This is useful when in component build
  # enabling sanitizers only in some of the components.
  use_sanitizer_configs_without_instrumentation = false

  # When true, seed corpora archives are built.
  archive_seed_corpus = true

  # When true, sanitizer warnings will cause test case failures.
  fail_on_san_warnings = false

  # The fuzztest library builds only on some platforms, so for now,
  # all targets depending on fuzztest need to be configured according
  # to this.
  # TODO(crbug.com/1494445): remove this when all build permutations
  # work
  fuzztest_supported = !(is_win && is_component_build)
}

declare_args() {
  # Enable checks for bad casts: derived cast and unrelated cast.
  # TODO(krasin): remove this, when we're ready to add these checks by default.
  # https://crbug.com/626794
  use_cfi_cast = is_cfi && is_chromeos

  # Compile for Undefined Behaviour Sanitizer's vptr checks.
  is_ubsan_vptr = is_ubsan_security
}

declare_args() {
  # Builds fuzztest test executables such that they support the
  # --fuzz= argument, which requires some sanitizer coverage.
  # We want to enable this only when we're *NOT* using a fuzzing
  # engine such as libfuzzer or centipede. It's generally a
  # useful option, but it requires sanitizer coverage, and that
  # could conceivably disrupt normal unit testing workflows, so we'll
  # enable it by default only in sanitizer builds.
  # Also be sure not to enable this on non-Chromium builds where
  # the required //third_party/fuzztest dependency may be absent.
  # TODO(crbug.com/1495713): enable on component builds
  enable_fuzztest_fuzz =
      !(use_libfuzzer || use_afl || use_centipede ||
        use_external_fuzzing_engine) &&
      (is_asan || is_hwasan || is_lsan || is_tsan || is_msan || is_ubsan ||
       is_ubsan_vptr || is_ubsan_security) && !is_component_build && is_linux &&
      build_with_chromium
}

assert(!is_hwasan || (target_os == "android" && target_cpu == "arm64"),
       "HWASan only supported on Android ARM64 builds.")

assert(
    !(enable_fuzztest_fuzz && use_libfuzzer),
    "Can't specify enable_fuzztest_fuzz and use_libfuzzer. When libfuzzer is enabled, fuzztest executables automatically support --fuzz but provide output that's libfuzzer compatible.")

assert(
    !(enable_fuzztest_fuzz && use_centipede),
    "Can't specify enable_fuzztest_fuzz and use_centipede. The same binaries are built in a different mode to add centipede support.")

assert(
    !(enable_fuzztest_fuzz && is_component_build),
    "Can't specify enable_fuzztest_fuzz in component builds; fuzztest doesn't yet support it. Consider using use_libfuzzer=true instead which provides superficially similar functionality.")

# Disable sanitizers for non-target toolchains, and for the toolchain using
# the prebuilt Rust stdlib which has no sanitizer support with it.
if (!is_a_target_toolchain || toolchain_for_rust_host_build_tools) {
  is_asan = false
  is_cfi = false
  is_hwasan = false
  is_lsan = false
  is_msan = false
  is_tsan = false
  is_ubsan = false
  is_ubsan_no_recover = false
  is_ubsan_security = false
  is_ubsan_vptr = false
  fail_on_san_warnings = false
  msan_track_origins = 0
  sanitizer_coverage_flags = ""
  use_afl = false
  use_centipede = false
  use_cfi_diag = false
  use_cfi_recover = false
  use_libfuzzer = false
  use_locally_built_instrumented_libraries = false
  use_sanitizer_coverage = false
  enable_fuzztest_fuzz = false
} else if (current_cpu != "arm64") {
  is_hwasan = false
}

# Use dynamic libraries instrumented by one of the sanitizers instead of the
# standard system libraries. We have instrumented system libraries for msan,
# which requires them to prevent false positives.
# TODO(thakis): Maybe remove this variable.
use_prebuilt_instrumented_libraries = is_msan

# Whether we are doing a fuzzer build. Normally this should be checked instead
# of checking "use_libfuzzer || use_afl" because often developers forget to
# check for "use_afl", and "use_centipede" is new.
use_fuzzing_engine =
    use_libfuzzer || use_afl || use_centipede || use_external_fuzzing_engine

# Whether the current fuzzing engine supports libprotobuf_mutator. Right now
# this is just libfuzzer, but others are likely to support this in future,
# so it's preferable to check this.
use_fuzzing_engine_with_lpm = use_libfuzzer || use_centipede

# Whether the fuzzing engine supports fuzzers which supply their own
# "main" function.
fuzzing_engine_supports_custom_main = use_libfuzzer || use_centipede

# Args that are in turn dependent on other args must be in a separate
# declare_args block. User overrides are only applied at the end of a
# declare_args block.
declare_args() {
  # Generates an owners file for each fuzzer test.
  # TODO(crbug.com/1194183): Remove this arg when finding OWNERS is faster.
  generate_fuzzer_owners = use_fuzzing_engine

  use_sanitizer_coverage =
      !use_clang_coverage && (use_fuzzing_engine || enable_fuzztest_fuzz ||
                              sanitizer_coverage_flags != "")

  # https://crbug.com/1002058: Code coverage works inside the sandbox via the
  # help of several helper IPCs. Unfortunately, the sandbox-only path does not
  # work well for fuzzing builds. Since fuzzing builds already disable the
  # sandbox when dumping coverage, limit the sandbox-only path to non-fuzzing
  # builds.
  # Everything is IPC on Fuchsia, so this workaround for code coverage inside
  # the sandbox does not apply.
  use_clang_profiling_inside_sandbox =
      use_clang_profiling && !use_fuzzing_engine && !is_fuchsia
}

if (sanitizer_coverage_flags == "") {
  if (enable_fuzztest_fuzz) {
    # ./fuzztest_executable --fuzz=
    # requires only this single type of coverage
    sanitizer_coverage_flags = "inline-8bit-counters"
  } else if (use_fuzzing_engine) {
    sanitizer_coverage_flags = "trace-pc-guard"
    if (use_centipede) {
      # Centipede's minimal flags are listed in //third_party/fuzztest/src/centipede/clang-flags.txt.
      # But, for users like Chromium using an up-to-date clang, we can also
      # enable extra optional types of coverage which may make Centipede more
      # effective. This list is not currently documented and has been derived
      # from discussion with centipede creators (though one is warned about at
      # https://github.com/google/centipede/blob/main/centipede_callbacks.cc#L68)
      sanitizer_coverage_flags = sanitizer_coverage_flags +
                                 ",pc-table,trace-cmp,control-flow,trace-loads"
    }
  } else if (use_sanitizer_coverage) {
    sanitizer_coverage_flags = "trace-pc-guard,indirect-calls"
  }
}

# Whether we are linking against a sanitizer runtime library. Among other
# things, this changes the default symbol level and other settings in order to
# prepare to create stack traces "live" using the sanitizer runtime.
using_sanitizer =
    is_asan || is_hwasan || is_lsan || is_tsan || is_msan || is_ubsan ||
    is_ubsan_vptr || is_ubsan_security || use_sanitizer_coverage || use_cfi_diag

assert(!using_sanitizer || is_clang,
       "Sanitizers (is_*san) require setting is_clang = true in 'gn args'")

assert(!is_cfi || is_clang,
       "is_cfi requires setting is_clang = true in 'gn args'")

prebuilt_instrumented_libraries_available =
    is_msan && (msan_track_origins == 0 || msan_track_origins == 2)

if (use_libfuzzer && (is_linux || is_chromeos)) {
  if (is_asan) {
    # We do leak checking with libFuzzer on Linux. Set is_lsan for code that
    # relies on LEAK_SANITIZER define to avoid false positives.
    is_lsan = true
  }
}

# MSan only links Chrome properly in release builds (brettw -- 9/1/2015). The
# same is possibly true for the other non-ASan sanitizers. But regardless of
# whether it links, one would normally never run a sanitizer in debug mode.
# Running in debug mode probably indicates you forgot to set the "is_debug =
# false" flag in the build args. ASan seems to run fine in debug mode.
#
# If you find a use-case where you want to compile a sanitizer in debug mode
# and have verified it works, ask brettw and we can consider removing it from
# this condition. We may also be able to find another way to enable your case
# without having people accidentally get broken builds by compiling an
# unsupported or unadvisable configurations.
#
# For one-off testing, just comment this assertion out.
assert(!is_debug || !(is_msan || is_ubsan || is_ubsan_vptr),
       "Sanitizers should generally be used in release (set is_debug=false).")

assert(!is_msan || ((is_linux || is_chromeos) && current_cpu == "x64"),
       "MSan currently only works on 64-bit Linux and ChromeOS builds.")

assert(!is_lsan || is_asan, "is_lsan = true requires is_asan = true also.")

# ASAN build on Windows is not working in debug mode. Intercepting memory
# allocation functions is hard on Windows and not yet implemented in LLVM.
assert(!is_win || !is_debug || !is_asan,
       "ASan on Windows doesn't work in debug (set is_debug=false).")

# libFuzzer targets can fail to build or behave incorrectly when built without
# ASAN on Windows.
assert(!is_win || !use_libfuzzer || is_asan,
       "use_libfuzzer on Windows requires setting is_asan = true")

# Make sure that if we recover on detection (i.e. not crash), diagnostics are
# printed.
assert(!use_cfi_recover || use_cfi_diag,
       "Only use CFI recovery together with diagnostics.")

# TODO(crbug.com/753445): the use_sanitizer_coverage arg is currently
# not supported by the Chromium mac_clang_x64 toolchain on iOS distribution.
# The coverage works with iOS toolchain but it is broken when the mac
# toolchain is used as a secondary one on iOS distribution. E.g., it should be
# possible to build the "net" target for iOS with the sanitizer coverage
# enabled.
assert(
    !(use_sanitizer_coverage && is_mac && target_os == "ios"),
    "crbug.com/753445: use_sanitizer_coverage=true is not supported by the " +
        "Chromium mac_clang_x64 toolchain on iOS distribution. Please set " +
        "the argument value to false.")

# Use these lists of configs to disable instrumenting code that is part of a
# fuzzer, but which isn't being targeted (such as libprotobuf-mutator, *.pb.cc
# and libprotobuf when they are built as part of a proto fuzzer). Adding or
# removing these lists does not have any effect if use_libfuzzer or use_afl are
# not passed as arguments to gn.
not_fuzzed_remove_configs = []
not_fuzzed_remove_nonasan_configs = []

if (use_fuzzing_engine) {
  # Removing coverage should always just work.
  not_fuzzed_remove_configs += [ "//build/config/coverage:default_coverage" ]
  not_fuzzed_remove_nonasan_configs +=
      [ "//build/config/coverage:default_coverage" ]

  if (!is_msan) {
    # Allow sanitizer instrumentation to be removed if we are not using MSan
    # since binaries cannot be partially instrumented with MSan.
    not_fuzzed_remove_configs +=
        [ "//build/config/sanitizers:default_sanitizer_flags" ]

    # Certain parts of binaries must be instrumented with ASan if the rest of
    # the binary is. For these, only remove non-ASan sanitizer instrumentation.
    if (!is_asan) {
      not_fuzzed_remove_nonasan_configs +=
          [ "//build/config/sanitizers:default_sanitizer_flags" ]

      assert(not_fuzzed_remove_nonasan_configs == not_fuzzed_remove_configs)
    }
  }
}

# Options common to different fuzzer engines.
# Engine should be compiled without coverage (infinite loop in trace_cmp).
fuzzing_engine_remove_configs = [
  "//build/config/coverage:default_coverage",
  "//build/config/sanitizers:default_sanitizer_flags",
]

# Add any sanitizer flags back. In MSAN builds, instrumenting libfuzzer with
# MSAN is necessary since all parts of the binary need to be instrumented for it
# to work. ASAN builds are more subtle: libfuzzer depends on features from the
# C++ STL. If it were not instrumented, templates would be insantiated without
# ASAN from libfuzzer and with ASAN in other TUs. The linker might merge
# instrumented template instantiations with non-instrumented ones (which could
# have a different ABI) in the final binary, which is problematic for TUs
# expecting one particular ABI (https://crbug.com/915422). The other sanitizers
# are added back for the same reason.
fuzzing_engine_add_configs =
    [ "//build/config/sanitizers:default_sanitizer_flags_but_coverage" ]