[GWP-ASan] Configuration options [3].

[hctim]

Summary

See D60593 for further information.

This patch introduces the configuration options for GWP-ASan. In general, we expect the supporting allocator to populate the options struct, and give that to GWP-ASan during initialisation. For allocators that are okay with pulling in sanitizer_common, we also provide an optional parser that populates the gwp_asan::Options struct with values provided in the GWP_ASAN_OPTIONS environment variable.

This patch contains very little logic, and all of the testable components (i.e. the optional parser's internal logic) is tested as part of the sanitizer_common testbed.

[morehouse]

compiler-rt/lib/gwp_asan/optional/options_parser.cpp

39

If the above functions are private, they can go in an unnamed namespace or be made static.

57

What does this do? Do we need it?

60

Should we return early? Maybe the user will later set Enabled = true. In that case, we skipped the below validation and Printf initialization.

89

I think this is unnecessary since we check __gwp_asan_default_options != nullptr before calling it.

compiler-rt/lib/gwp_asan/options.inc

31

I think 2^31 will overflow. So technically only 2^31 - 1 is supported.

42

This wording is a bit confusing. There are a few uses of the phrase "previously installed handler", but they refer to different handlers in each case.

[hctim]

compiler-rt/lib/gwp_asan/optional/options_parser.cpp

57

In this patchset, nothing. New patchest it initialises verbosity, which is used to report unrecognised flags.

60

I don't think we should be targeting live-enable/disable of GWP-ASan at this point in time, only at start time, unless I misunderstand the premise of the question.

@vlad.tsyrklevich WDYT?

compiler-rt/lib/gwp_asan/options.inc

31

Also added a sanity check in the optional parser.

42

Changed it. WDYT?

[hctim]

• Merge branch 'master' into gwp_asan/options
• Updated from Matt's comments.

[morehouse]

compiler-rt/lib/gwp_asan/optional/options_parser.cpp

60

In that case, why support modifying options at runtime at all?

getOptions should return a const-ref, not a pointer and all initialization should be done through initOptions.

82

Hm.. So now 2^31 - 1 is no longer supported?

compiler-rt/lib/gwp_asan/options.inc

39

"will forward the signal to any previously-installed handler, and user"

40

further signal

41

sam. Note

[vlad.tsyrklevich]

compiler-rt/lib/gwp_asan/optional/options_parser.cpp

60

Agree that live-enable/disable doesn't really make sense, and that we should change the interface to be a const ref instead.

[hctim]

• Matt's comments #3.

[morehouse]

compiler-rt/lib/gwp_asan/optional/options_parser.cpp

81

Isn't it impossible for SampleRate to be larger than INT_MAX?

[hctim]

• Matt's last round of comments.
• Merge branch 'master' into gwp_asan/options

compiler-rt/lib/gwp_asan/CMakeLists.txt

 add_compiler_rt_component(gwp_asan)
 
 include_directories(..)
 
 set(GWP_ASAN_SOURCES
   platform_specific/mutex_posix.cpp
   random.cpp
 )
 
 set(GWP_ASAN_HEADERS
   mutex.h
   random.h
+  options.h
+  options.inc
 )
 
 # Ensure that GWP-ASan meets the delegated requirements of some supporting
 # allocators. Some supporting allocators (e.g. scudo standalone) cannot use any
 # parts of the C++ standard library.
 set(GWP_ASAN_CFLAGS -fno-rtti -fno-exceptions -nostdinc++ -pthread)
 
 # Remove -stdlib= which is unused when passing -nostdinc++.
 string(REGEX REPLACE "-stdlib=[a-zA-Z+]*" "" CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS})
 
+# Options parsing support is optional. GwpAsan is totally independent of
+# sanitizer_common, the options parser is not. This is an optional library
+# that can be used by an allocator to automatically parse GwpAsan options from
+# the environment variable GWP_ASAN_FLAGS, but the allocator can choose to
+# implement its own options parsing and populate the Options struct itself.
+set(GWP_ASAN_OPTIONS_PARSER_SOURCES
+  optional/options_parser.cpp
+)
+set(GWP_ASAN_OPTIONS_PARSER_HEADERS
+  optional/options_parser.h
+  options.h
+  options.inc
+)
+set(GWP_ASAN_OPTIONS_PARSER_CFLAGS
+    ${GWP_ASAN_CFLAGS}
+    ${SANITIZER_COMMON_CFLAGS})
+set(GWP_ASAN_OPTIONS_PARSER_OBJECT_LIBS
+    RTSanitizerCommon
+    RTSanitizerCommonNoLibc)
+
 if (COMPILER_RT_HAS_GWP_ASAN)
   foreach(arch ${GWP_ASAN_SUPPORTED_ARCH})
     add_compiler_rt_runtime(
       clang_rt.gwp_asan
       STATIC
       ARCHS ${arch}
       SOURCES ${GWP_ASAN_SOURCES}
       ADDITIONAL_HEADERS ${GWP_ASAN_HEADERS}
       CFLAGS ${GWP_ASAN_CFLAGS}
       PARENT_TARGET gwp_asan
     )
   endforeach()
 
   add_compiler_rt_object_libraries(RTGwpAsan
       ARCHS ${GWP_ASAN_SUPPORTED_ARCH}
       SOURCES ${GWP_ASAN_SOURCES}
       ADDITIONAL_HEADERS ${GWP_ASAN_HEADERS}
       CFLAGS ${GWP_ASAN_CFLAGS})
+
+  # Note: If you choose to add this as an object library, ensure you also
+  # include the sanitizer_common flag parsing object lib (generally
+  # 'RTSanitizerCommonNoTermination').
+  add_compiler_rt_object_libraries(RTGwpAsanOptionsParser
+      ARCHS ${GWP_ASAN_SUPPORTED_ARCH}
+      SOURCES ${GWP_ASAN_OPTIONS_PARSER_SOURCES}
+      ADDITIONAL_HEADERS ${GWP_ASAN_OPTIONS_PARSER_HEADERS}
+      CFLAGS ${GWP_ASAN_OPTIONS_PARSER_CFLAGS})
+
+  # Ensure that the build for the options parser succeeds, as
+  # 'RTGwpAsanOptionsParser' may not be built if it's not needed. This library
+  # has only a very small amount of logic, all of the testable components are
+  # exercised in the sanitizer_common test suite.
+  foreach(arch ${GWP_ASAN_SUPPORTED_ARCH})
+    add_compiler_rt_runtime(
+      clang_rt.gwp_asan_options_parser
+      SHARED
+      ARCHS ${arch}
+      SOURCES ${GWP_ASAN_OPTIONS_PARSER_SOURCES}
+      ADDITIONAL_HEADERS ${GWP_ASAN_OPTIONS_PARSER_HEADERS}
+      CFLAGS ${GWP_ASAN_OPTIONS_PARSER_CFLAGS}
+      OBJECT_LIBS ${GWP_ASAN_OPTIONS_PARSER_OBJECT_LIBS}
+      PARENT_TARGET gwp_asan
+    )
+  endforeach()
 endif()
 
 if(COMPILER_RT_INCLUDE_TESTS)
   add_subdirectory(tests)
 endif()

compiler-rt/lib/gwp_asan/optional/options_parser.h

+//===-- options_parser.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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef GWP_ASAN_OPTIONAL_OPTIONS_PARSER_H_
+#define GWP_ASAN_OPTIONAL_OPTIONS_PARSER_H_
+
+#include "gwp_asan/options.h"
+#include "sanitizer_common/sanitizer_common.h"
+
+namespace gwp_asan {
+namespace options {
+
+// Parse the options from the GWP_ASAN_FLAGS environment variable.
+void initOptions();
+// Returns a pointer to the initialised options. Call initOptions() prior to
+// calling this function.
+Options *getOptions();
+
+} // namespace options
+} // namespace gwp_asan
+
+extern "C" {
+SANITIZER_INTERFACE_ATTRIBUTE SANITIZER_WEAK_ATTRIBUTE const char *
+__gwp_asan_default_options();
+}
+
+#endif // GWP_ASAN_OPTIONAL_OPTIONS_PARSER_H_

compiler-rt/lib/gwp_asan/optional/options_parser.cpp

+//===-- options_parser.cpp --------------------------------------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "gwp_asan/optional/options_parser.h"
+
+#include <stdarg.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "gwp_asan/options.h"
+#include "sanitizer_common/sanitizer_common.h"
+#include "sanitizer_common/sanitizer_flag_parser.h"
+#include "sanitizer_common/sanitizer_flags.h"
+
+namespace gwp_asan {
+namespace options {
+void registerGwpAsanFlags(__sanitizer::FlagParser *parser, Options *o) {
+#define GWP_ASAN_OPTION(Type, Name, DefaultValue, Description)                 \
+  RegisterFlag(parser, #Name, Description, &o->Name);
+#include "gwp_asan/options.inc"
+#undef GWP_ASAN_OPTION
+}
+
+const char *getCompileDefinitionGwpAsanDefaultOptions() {
+#ifdef GWP_ASAN_DEFAULT_OPTIONS
+  return SANITIZER_STRINGIFY(GWP_ASAN_DEFAULT_OPTIONS);
+#else
+  return "";
+#endif
+}
+
+const char *getGwpAsanDefaultOptions() {
+  return (__gwp_asan_default_options) ? __gwp_asan_default_options() : "";
+}
+
+void initOptions() {
+  Options *o = getOptions();
+  o->setDefaults();
+
+  __sanitizer::FlagParser Parser;
+  registerGwpAsanFlags(&Parser, o);
+
+  // Override from compile definition.
+  Parser.ParseString(getCompileDefinitionGwpAsanDefaultOptions());
+
+  // Override from user-specified string.
+  Parser.ParseString(getGwpAsanDefaultOptions());
+
+  // Override from environment.
+  Parser.ParseString(__sanitizer::GetEnv("GWP_ASAN_OPTIONS"));
+
+  __sanitizer::InitializeCommonFlags();
+
+  if (!o->Enabled)
+    return;
+
+  // Sanity checks for the parameters.
+  if (o->MaxSimultaneousAllocations <= 0) {
+    __sanitizer::Printf(
+        "GWP-ASan ERROR: MaxSimultaneousAllocations must be >= 0 when "
+        "GWP-ASan is enabled.\n");
+    exit(EXIT_FAILURE);
+  }
+
+  if (o->SampleRate < 1) {
+    __sanitizer::Printf("GWP-ASan ERROR: SampleRate must be >= 1 when "
+                        "GWP-ASan is enabled.\n");
+    exit(EXIT_FAILURE);
+  }
+
+  o->Printf = __sanitizer::Printf;
+}
+
+Options *getOptions() {
+  static Options GwpAsanFlags;
+  return &GwpAsanFlags;
+}
+
+} // namespace options
+} // namespace gwp_asan
+
+SANITIZER_INTERFACE_WEAK_DEF(const char *, __gwp_asan_default_options, void) {
+  return "";
+}

compiler-rt/lib/gwp_asan/options.h

+//===-- options.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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef GWP_ASAN_OPTIONS_H_
+#define GWP_ASAN_OPTIONS_H_
+
+namespace gwp_asan {
+namespace options {
+// The function pointer type for printf(). Follows the standard format from the
+// sanitizers library. If the supported allocator exposes printing via a
+// different function signature, please provide a wrapper which has this
+// printf() signature, and pass the wrapper instead.
+typedef void (*Printf_t)(const char *Format, ...);
+
+struct Options {
+  Printf_t Printf = nullptr;
+
+  // Read the options from the included definitions file.
+#define GWP_ASAN_OPTION(Type, Name, DefaultValue, Description)                 \
+  Type Name = DefaultValue;
+#include "gwp_asan/options.inc"
+#undef GWP_ASAN_OPTION
+
+  void setDefaults() {
+#define GWP_ASAN_OPTION(Type, Name, DefaultValue, Description)                 \
+  Name = DefaultValue;
+#include "gwp_asan/options.inc"
+#undef GWP_ASAN_OPTION
+
+    Printf = nullptr;
+  }
+};
+} // namespace options
+} // namespace gwp_asan
+
+#endif // GWP_ASAN_OPTIONS_H_

compiler-rt/lib/gwp_asan/options.inc

+//===-- options.inc ---------------------------------------------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef GWP_ASAN_OPTION
+#error "Define GWP_ASAN_OPTION prior to including this file!"
+#endif
+
+GWP_ASAN_OPTION(bool, Enabled, true, "Is GWP-ASan enabled? Defaults to true.")
+
+GWP_ASAN_OPTION(
+    bool, PerfectlyRightAlign, false,
+    "When allocations are right-aligned, should we perfectly align them up to "
+    "the page boundary? By default (false), we round up allocation size to the "
+    "nearest power of two (1, 2, 4, 8, 16) up to a maximum of 16-byte "
+    "alignment for performance reasons. Setting this to true can find single "
+    "byte buffer-overflows for multibyte allocations at the cost of "
+    "performance, and may be incompatible with some architectures.")
+
+GWP_ASAN_OPTION(
+    int, MaxSimultaneousAllocations, 16,
+    "Number of usable guarded slots in the allocation pool. Defaults to 16.")
+
+GWP_ASAN_OPTION(int, SampleRate, 5000,
+                "The probability (1 / SampleRate) that an allocation is "
+                "selected for GWP-ASan sampling. Default is 5000. Sample rates "
+                "up to 2^31 are supported.")
+
+GWP_ASAN_OPTION(
+    bool, InstallSignalHandlers, true,
+    "Install GWP-ASan signal handlers for SIGSEGV. This allows better error "
+    "reports by providing stack traces for allocation and deallocation when "
+    "reporting a memory error. These handlers are generally installed during "
+    "dynamic loading, and will ensure that the previously installed signal "
+    "handlers will be called. User programs that also install SIGSEGV handlers "
+    "should ensure that the previously-installed GWP-ASan handler is called. "
+    "Note, if the previously installed SIGSEGV handler is SIG_IGN, we "
+    "terminate the process after dumping the error report.")