[sanitizer] Disable fast_unwind_on_malloc as default for arm-linux-gnu

[zatrazz]

Summary

This is an updated version of D83143. Instead of disable fast-unwinder
on arm-linux-gnu, it just disable it as *default* instead. It should fix the
possible false-positive malloc failures when iteracting with thumb build
object by GCC, with the expanse of the slowdown from using the slow
library based unwinder. However users still have the option to use the
fast-unwinder.

ARM thumb/thumb2 frame pointer is inconsistent on GCC and Clang [1]
and fast-unwider is also unreliable with mixing arm and thumb code [2].

The fast unwinder ARM tries to probe and compare the frame-pointer
in different stack layout position and it works reliable only on a
systems where all the libraries are built in arm mode (either with
gcc or clang) or with clang (which uses the same stack frame pointer
layout in arm and thumb).

However when mixing objects built with different abi mode the
fast unwinder is still problematic as shown by the failures on the
AddressSanitizer.ThreadStackReuseTest. For these failures, the
malloc is called by the loader itself and since it has been built
with a thum enabled gcc, the stack frame is not correctly obtained
and the suppression rule and thus not applied (resulting in a leak
warning).

The check for fast-unwinder-works is also changed: instead of checking
f it is explicit enabled in the compiler flags, it now checks if
compiler defined thumb pre-processore.

This should fix BZ#44158.

[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92172
[2] https://bugs.llvm.org/show_bug.cgi?id=44158

[eugenis]

I'm fine with this.

compiler-rt/CMakeLists.txt

if (COMPILER_RT_STANDALONE_BUILD)
   set(LLVM_LIT_ARGS "${LIT_ARGS_DEFAULT}" CACHE STRING "Default options for lit")
   set(LLVM_LIT_OUTPUT_DIR "${COMPILER_RT_EXEC_OUTPUT_DIR}")
 endif()
 
 construct_compiler_rt_default_triple()
 if ("${COMPILER_RT_DEFAULT_TARGET_TRIPLE}" MATCHES ".*hf$")
   if (${COMPILER_RT_DEFAULT_TARGET_ARCH} MATCHES "^arm")
     set(COMPILER_RT_DEFAULT_TARGET_ARCH "armhf")
+    CHECK_SYMBOL_EXISTS (__thumb__ "" COMPILER_RT_ARM_THUMB)
   endif()
 endif()
 if ("${COMPILER_RT_DEFAULT_TARGET_TRIPLE}" MATCHES ".*android.*")
   set(ANDROID 1)
 endif()
 pythonize_bool(ANDROID)
 
 set(ANDROID_NDK_VERSION 18

compiler-rt/lib/sanitizer_common/sanitizer_flags.inc

 //===-- sanitizer_flags.h ---------------------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This file describes common flags available in all sanitizers.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef COMMON_FLAG
 #error "Define COMMON_FLAG prior to including this file!"
 #endif
 
 // COMMON_FLAG(Type, Name, DefaultValue, Description)
 // Supported types: bool, const char *, int, uptr.
 // Default value must be a compile-time constant.
 // Description must be a string literal.
 
 COMMON_FLAG(
     bool, symbolize, true,
     "If set, use the online symbolizer from common sanitizer runtime to turn "
     "virtual addresses to file/line locations.")
 COMMON_FLAG(
     const char *, external_symbolizer_path, nullptr,
     "Path to external symbolizer. If empty, the tool will search $PATH for "
     "the symbolizer.")
 COMMON_FLAG(
     bool, allow_addr2line, false,
     "If set, allows online symbolizer to run addr2line binary to symbolize "
     "stack traces (addr2line will only be used if llvm-symbolizer binary is "
     "unavailable.")
 COMMON_FLAG(const char *, strip_path_prefix, "",
             "Strips this prefix from file paths in error reports.")
 COMMON_FLAG(bool, fast_unwind_on_check, false,
             "If available, use the fast frame-pointer-based unwinder on "
             "internal CHECK failures.")
 COMMON_FLAG(bool, fast_unwind_on_fatal, false,
             "If available, use the fast frame-pointer-based unwinder on fatal "
             "errors.")
-COMMON_FLAG(bool, fast_unwind_on_malloc, true,
+// ARM thumb/thumb2 frame pointer is inconsistent on GCC and Clang [1]
+// and fast-unwider is also unreliable with mixing arm and thumb code [2].
+// [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92172
+// [2] https://bugs.llvm.org/show_bug.cgi?id=44158
+COMMON_FLAG(bool, fast_unwind_on_malloc,
+      !(SANITIZER_LINUX && !SANITIZER_ANDROID && SANITIZER_ARM),
             "If available, use the fast frame-pointer-based unwinder on "
             "malloc/free.")
 COMMON_FLAG(bool, handle_ioctl, false, "Intercept and handle ioctl requests.")
 COMMON_FLAG(int, malloc_context_size, 1,
             "Max number of stack frames kept for each allocation/deallocation.")
 COMMON_FLAG(
     const char *, log_path, "stderr",
     "Write logs to \"log_path.pid\". The special values are \"stdout\" and "

compiler-rt/test/asan/TestCases/Linux/clang_gcc_abi.cpp

-// RUN: %clangxx_asan -O0 -x c %s -o %t && not %run %t 2>&1 | FileCheck %s
-// RUN: %clangxx_asan -O1 -x c %s -o %t && not %run %t 2>&1 | FileCheck %s
-// RUN: %clangxx_asan -O2 -x c %s -o %t && not %run %t 2>&1 | FileCheck %s
-// RUN: %clangxx_asan -O3 -x c %s -o %t && not %run %t 2>&1 | FileCheck %s
+// RUN: %clangxx_asan -O0 -x c %s -o %t && not %env_asan_opts=fast_unwind_on_malloc=1 %run %t 2>&1 | FileCheck %s
+// RUN: %clangxx_asan -O1 -x c %s -o %t && not %env_asan_opts=fast_unwind_on_malloc=1 %run %t 2>&1 | FileCheck %s
+// RUN: %clangxx_asan -O2 -x c %s -o %t && not %env_asan_opts=fast_unwind_on_malloc=1 %run %t 2>&1 | FileCheck %s
+// RUN: %clangxx_asan -O3 -x c %s -o %t && not %env_asan_opts=fast_unwind_on_malloc=1 %run %t 2>&1 | FileCheck %s
 
 // REQUIRES: (arm-target-arch || armhf-target-arch), fast-unwinder-works
 
 #include <stdlib.h>
 
 __attribute__((noinline))
 int boom() {
   volatile int three = 3;

compiler-rt/test/asan/lit.cfg.py

 
 config.substitutions.append( ('CHECK-%kernel_bits', ("CHECK-kernel-" + kernel_bits + "-bits")))
 
 config.substitutions.append( ("%libdl", libdl_flag) )
 
 config.available_features.add("asan-" + config.bits + "-bits")
 
 # Fast unwinder doesn't work with Thumb
-if re.search('mthumb', config.target_cflags) is None:
+if not config.arm_thumb:
   config.available_features.add('fast-unwinder-works')
 
 # Turn on leak detection on 64-bit Linux.
 leak_detection_linux = (config.host_os == 'Linux') and (not config.android) and (config.target_arch == 'x86_64' or config.target_arch == 'i386')
 leak_detection_mac = (config.host_os == 'Darwin') and (config.target_arch == 'x86_64')
 leak_detection_netbsd = (config.host_os == 'NetBSD') and (config.target_arch in ['x86_64', 'i386'])
 if leak_detection_linux or leak_detection_mac or leak_detection_netbsd:
   config.available_features.add('leak-detection')

compiler-rt/test/asan/lit.site.cfg.py.in

 @LIT_SITE_CFG_IN_HEADER@
 
 # Tool-specific config options.
 config.name_suffix = "@ASAN_TEST_CONFIG_SUFFIX@"
 config.target_cflags = "@ASAN_TEST_TARGET_CFLAGS@"
 config.clang = "@ASAN_TEST_TARGET_CC@"
 config.bits = "@ASAN_TEST_BITS@"
+config.arm_thumb = "@COMPILER_RT_ARM_THUMB@"
 config.apple_platform = "@ASAN_TEST_APPLE_PLATFORM@"
 config.apple_platform_min_deployment_target_flag = "@ASAN_TEST_MIN_DEPLOYMENT_TARGET_FLAG@"
 config.asan_dynamic = @ASAN_TEST_DYNAMIC@
 config.target_arch = "@ASAN_TEST_TARGET_ARCH@"
 
 # Load common config for all compiler-rt lit tests.
 lit_config.load_config(config, "@COMPILER_RT_BINARY_DIR@/test/lit.common.configured")
 
 # Load tool-specific config that would do the real work.
 lit_config.load_config(config, "@ASAN_LIT_SOURCE_DIR@/lit.cfg.py")