[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 ↗

(On Diff #202284)

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

57 ↗

(On Diff #202284)

What does this do? Do we need it?

60 ↗

(On Diff #202284)

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

89 ↗

(On Diff #202284)

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

compiler-rt/lib/gwp_asan/options.inc

31 ↗

(On Diff #202284)

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

42 ↗

(On Diff #202284)

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 ↗

(On Diff #202284)

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

60 ↗

(On Diff #202284)

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 ↗

(On Diff #202284)

Also added a sanity check in the optional parser.

42 ↗

(On Diff #202284)

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

81 ↗

(On Diff #202500)

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

60 ↗

(On Diff #202284)

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.

compiler-rt/lib/gwp_asan/options.inc

38 ↗

(On Diff #202500)

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

39 ↗

(On Diff #202500)

further signal

40 ↗

(On Diff #202500)

sam. Note

[vlad.tsyrklevich]

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

60 ↗

(On Diff #202284)

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

80 ↗

(On Diff #202751)

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/trunk/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/trunk/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.
+const 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/trunk/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 <stdint.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 {
+namespace {
+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() : "";
+}
+
+Options *getOptionsInternal() {
+  static Options GwpAsanFlags;
+  return &GwpAsanFlags;
+}
+} // anonymous namespace
+
+void initOptions() {
+  Options *o = getOptionsInternal();
+  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 (__sanitizer::Verbosity())
+    __sanitizer::ReportUnrecognizedFlags();
+
+  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 > 0 when GWP-ASan is enabled.\n");
+    exit(EXIT_FAILURE);
+  }
+
+  o->Printf = __sanitizer::Printf;
+}
+
+const Options &getOptions() { return *getOptionsInternal(); }
+
+} // namespace options
+} // namespace gwp_asan

compiler-rt/trunk/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/trunk/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 - 1) are supported.")
+
+GWP_ASAN_OPTION(
+    bool, InstallSignalHandlers, true,
+    "Install GWP-ASan signal handlers for SIGSEGV during dynamic loading. This "
+    "allows better error reports by providing stack traces for allocation and "
+    "deallocation when reporting a memory error. GWP-ASan's signal handler "
+    "will forward the signal to any previously-installed handler, and user "
+    "programs that install further signal handlers should make sure they do "
+    "the same. Note, if the previously installed SIGSEGV handler is SIG_IGN, "
+    "we terminate the process after dumping the error report.")