GN: Add an explicit gn arg for recovery in CFI

build/config/sanitizers/sanitizers.gni

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/chrome_build.gni")
 import("//build/toolchain/toolchain.gni")
 
 declare_args() {
   # Compile for Address Sanitizer to find memory bugs.
   is_asan = false
@@ skipping 49 matching lines @@
   # 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 = false
 
   # 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 = false
 
-  # By default, Control Flow Integrity will crash the program if it detects a
-  # violation. Set this to true to print detailed diagnostics instead.
+  # 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

[Dirk Pranke, 2017/06/07 19:42:12]

Should we have an assert somewhere that `!use_cfi_recover || use_cfi_diag` ?

[Michael Achenbach, 2017/06/07 20:59:32]

Can add that tomorrow...

[Michael Achenbach, 2017/06/08 10:58:38]

Done in patch 3. Added it at the end of this file right after a bunch of other
similar asserts.

+
   # Compile for fuzzing with LLVM LibFuzzer.
   # See http://www.chromium.org/developers/testing/libfuzzer
   use_libfuzzer = false
 
   # Compile for fuzzing with AFL.
   use_afl = false
 
   # Enables core ubsan security features. Will later be removed once it matches
   # is_ubsan.
   is_ubsan_security = false
@@ skipping 31 matching lines @@
   is_tsan = false
   is_ubsan = false
   is_ubsan_null = false
   is_ubsan_no_recover = false
   is_ubsan_security = false
   is_ubsan_vptr = false
   msan_track_origins = 0
   sanitizer_coverage_flags = ""
   use_afl = false
   use_cfi_diag = false
+  use_cfi_recover = false
   use_custom_libcxx = false
   use_drfuzz = false
   use_libfuzzer = false
   use_prebuilt_instrumented_libraries = false
   use_locally_built_instrumented_libraries = false
   use_sanitizer_coverage = false
 }
 
 # 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
@@ skipping 59 matching lines @@
 assert(!is_debug || !(is_msan || is_ubsan || is_ubsan_null || is_ubsan_vptr),
        "Sanitizers should generally be used in release (set is_debug=false).")
 
 assert(!is_msan || (is_linux && current_cpu == "x64"),
        "MSan currently only works on 64-bit Linux and ChromeOS builds.")
 
 # 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).")