[asan] Disable fast unwinder on arm-linux-gnueabi with thumb

[zatrazz]

Summary

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 hacks to probe and compare the frame-pointer
in different stack layout position works reliable only on a system where
all the libraries are built in arm mode (either with gcc or clang).

However when mixing objects built with different abi mode the
fast unwinder is still problematic. The quarantine_size_mb.cpp
still fails on ARM on system with libraries built with thumb (Ubuntu
bionic for instance) so make is pass clean this patch forces it to
use the slow unwinder is to avoid a leak warning triggered by the
helper quarantine thread creation (the allocation is done by glibc
pthread_create). Without proper stack frame information libsanitizer
can not apply the expected suppresion in this case.

This should fix BZ#44158, however the leak sanitizier is still
unreliable on most distros where the system compiler defaults to
use thumb.

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

[eugenis]

Is unwinding actually broken on an all-clang, all-thumb system?

[zatrazz]

In D83134#2133857, @eugenis wrote:

Is unwinding actually broken on an all-clang, all-thumb system?

The issue is when instrumented objects interact with gcc object,, for instance running instrumented binaries on usual distros like Ubuntu. I haven't tested on a all-clang/all-thumb system, but from my understanding is clang thumb use the FP similar no arm mode (differerent than gcc), so it should work.

[vitalybuka]

Is this patch still needed?

[zatrazz]

In D83134#2225283, @vitalybuka wrote:

Is this patch still needed?

It is to at least make the unwinder not triggering testcase failures on some arm-linux-gnu distros [1]. The fast-unwinder on ARM does not work correctly when unwinding any thumb code built code by gcc, so it would potentially fail on some scenarios (for instance if system libraries or gcc-build ones call malloc). It should be mitigated by 'fast_unwind_on_check=0' and/or 'fast_unwind_on_malloc=0'.

This issues has come up multiple times and compiler-rt developers either state that Android (which is now built with clang) and clang built objects works and that _Unwind based unwind is too slow to be usable. I think we should at least document this issues with gcc built with thumb support and the possible mitigations and tradeoffs.

[1] http://lab.llvm.org:8011/builders/clang-cmake-armv7-full/builds/11561

[eugenis]

LGTM

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_platform.h

 # define SANITIZER_PPC32 0
 # define SANITIZER_PPC64 0
 # define SANITIZER_PPC64V1 0
 # define SANITIZER_PPC64V2 0
 #endif
 
 #if defined(__arm__)
 # define SANITIZER_ARM 1
+# ifdef __thumb__
+#  define SANITIZER_ARM_THUMB 1
+# endif
 #else
 # define SANITIZER_ARM 0
+# define SANITIZER_ARM_THUMB 0
 #endif
 
 #if SANITIZER_SOLARIS && SANITIZER_WORDSIZE == 32
 # define SANITIZER_SOLARIS32 1
 #else
 # define SANITIZER_SOLARIS32 0
 #endif
 
 #if defined(__myriad2__)
 # define SANITIZER_MYRIAD2 1
 #else
 # define SANITIZER_MYRIAD2 0
 #endif
 

 #if SANITIZER_GO == 0
 # define SANITIZER_GO 0
 #endif
 
 // On PowerPC and ARM Thumb, calling pthread_exit() causes LSan to detect leaks.
 // pthread_exit() performs unwinding that leads to dlopen'ing libgcc_s.so.
 // dlopen mallocs "libgcc_s.so" string which confuses LSan, it fails to realize
 // that this allocation happens in dynamic linker and should be ignored.
-#if SANITIZER_PPC || defined(__thumb__)
+#if SANITIZER_PPC || SANITIZER_ARM_THUMB
 # define SANITIZER_SUPPRESS_LEAK_ON_PTHREAD_EXIT 1
 #else
 # define SANITIZER_SUPPRESS_LEAK_ON_PTHREAD_EXIT 0
 #endif
 
 #if SANITIZER_FREEBSD || SANITIZER_MAC || SANITIZER_NETBSD || \
   SANITIZER_OPENBSD || SANITIZER_SOLARIS
 # define SANITIZER_MADVISE_DONTNEED MADV_FREE

compiler-rt/lib/sanitizer_common/sanitizer_stacktrace.h

 namespace __sanitizer {
 
 struct BufferedStackTrace;
 
 static const u32 kStackTraceMax = 256;
 
 #if SANITIZER_LINUX && defined(__mips__)
 # define SANITIZER_CAN_FAST_UNWIND 0
+#elif SANITIZER_LINUX && !SANITIZER_ANDROID && SANITIZER_ARM_THUMB
+# define SANITIZER_CAN_FAST_UNWIND 0
 #elif SANITIZER_WINDOWS
 # define SANITIZER_CAN_FAST_UNWIND 0
 #elif SANITIZER_OPENBSD
 # define SANITIZER_CAN_FAST_UNWIND 0
 #else
 # define SANITIZER_CAN_FAST_UNWIND 1
 #endif
 

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

 // Test quarantine_size_mb (and the deprecated quarantine_size)
 // RUN: %clangxx_asan  %s -o %t
-// RUN: %env_asan_opts=quarantine_size=10485760:verbosity=1:hard_rss_limit_mb=50 %run %t  2>&1 | FileCheck %s  --check-prefix=Q10
-// RUN: %env_asan_opts=quarantine_size_mb=10:verbosity=1:hard_rss_limit_mb=50    %run %t  2>&1 | FileCheck %s  --check-prefix=Q10
-// RUN: %env_asan_opts=quarantine_size_mb=10:quarantine_size=20:verbosity=1  not %run %t  2>&1 | FileCheck %s  --check-prefix=BOTH
-// RUN: %env_asan_opts=quarantine_size_mb=1000:hard_rss_limit_mb=50 not  %run %t          2>&1 | FileCheck %s  --check-prefix=RSS_LIMIT
-// RUN: %env_asan_opts=hard_rss_limit_mb=20                         not  %run %t          2>&1 | FileCheck %s  --check-prefix=RSS_LIMIT
+// RUN: %env_asan_opts=quarantine_size=10485760:verbosity=1:hard_rss_limit_mb=50:fast_unwind_on_malloc=0 %run %t  2>&1 | FileCheck %s  --check-prefix=Q10
+// RUN: %env_asan_opts=quarantine_size_mb=10:verbosity=1:hard_rss_limit_mb=50:fast_unwind_on_malloc=0    %run %t  2>&1 | FileCheck %s  --check-prefix=Q10
+// RUN: %env_asan_opts=quarantine_size_mb=10:quarantine_size=20:verbosity=1  not %run %t                          2>&1 | FileCheck %s  --check-prefix=BOTH
+// RUN: %env_asan_opts=quarantine_size_mb=1000:hard_rss_limit_mb=50 not  %run %t                                  2>&1 | FileCheck %s  --check-prefix=RSS_LIMIT
+// RUN: %env_asan_opts=hard_rss_limit_mb=20                         not  %run %t                                  2>&1 | FileCheck %s  --check-prefix=RSS_LIMIT
 
 // https://github.com/google/sanitizers/issues/981
 // UNSUPPORTED: android-26
 
 #include <string.h>
 char *g;
 
 static const int kNumAllocs = 1 << 11;

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")