[GWP-ASan] Add version header.
Adds magic version header to AllocatorState. This can be used by
out-of-process crash handlers, like Crashpad on Fuchsia, to do offline
reconstruction of GWP-ASan crash metadata.
Crashpad on Fuchsia is intending on dumping the AllocationMetadata pool
and the AllocatorState directly into the minidump. Then, using the
version number, they can unpack the data on serverside using a versioned
unpack tool.
Also add some asserts to make sure the version number gets bumped if the
internal structs get changed.
Reviewed By: eugenis, mcgrathr
Differential Revision: https://reviews.llvm.org/D106690
GitOrigin-RevId: 8e167f66b27fe9d2573eb149f736700302675297
diff --git a/common.h b/common.h
index 7ce367e..520f577 100644
--- a/common.h
+++ b/common.h
@@ -19,7 +19,22 @@
#include <stdint.h>
namespace gwp_asan {
-enum class Error {
+
+// Magic header that resides in the AllocatorState so that GWP-ASan bugreports
+// can be understood by tools at different versions. Out-of-process crash
+// handlers, like crashpad on Fuchsia, take the raw conents of the
+// AllocationMetatada array and the AllocatorState, and shove them into the
+// minidump. Online unpacking of these structs needs to know from which version
+// of GWP-ASan its extracting the information, as the structures are not stable.
+struct AllocatorVersionMagic {
+ const uint8_t Magic[4] = {'A', 'S', 'A', 'N'};
+ // Update the version number when the AllocatorState or AllocationMetadata
+ // change.
+ const uint16_t Version = 1;
+ const uint16_t Reserved = 0;
+};
+
+enum class Error : uint8_t {
UNKNOWN,
USE_AFTER_FREE,
DOUBLE_FREE,
@@ -84,6 +99,7 @@
// set of information required for understanding a GWP-ASan crash.
struct AllocatorState {
constexpr AllocatorState() {}
+ const AllocatorVersionMagic VersionMagic{};
// Returns whether the provided pointer is a current sampled allocation that
// is owned by this pool.
@@ -123,5 +139,38 @@
uintptr_t FailureAddress = 0;
};
+// Below are various compile-time checks that the layout of the internal
+// GWP-ASan structures are undisturbed. If they are disturbed, the version magic
+// number needs to be increased by one, and the asserts need to be updated.
+// Out-of-process crash handlers, like breakpad/crashpad, may copy the internal
+// GWP-ASan structures into a minidump for offline reconstruction of the crash.
+// In order to accomplish this, the offline reconstructor needs to know the
+// version of GWP-ASan internal structures that it's unpacking (along with the
+// architecture-specific layout info, which is left as an exercise to the crash
+// handler).
+static_assert(offsetof(AllocatorState, VersionMagic) == 0, "");
+static_assert(sizeof(AllocatorVersionMagic) == 8, "");
+#if defined(__x86_64__)
+static_assert(sizeof(AllocatorState) == 56, "");
+static_assert(offsetof(AllocatorState, FailureAddress) == 48, "");
+static_assert(sizeof(AllocationMetadata) == 568, "");
+static_assert(offsetof(AllocationMetadata, IsDeallocated) == 560, "");
+#elif defined(__aarch64__)
+static_assert(sizeof(AllocatorState) == 56, "");
+static_assert(offsetof(AllocatorState, FailureAddress) == 48, "");
+static_assert(sizeof(AllocationMetadata) == 568, "");
+static_assert(offsetof(AllocationMetadata, IsDeallocated) == 560, "");
+#elif defined(__i386__)
+static_assert(sizeof(AllocatorState) == 32, "");
+static_assert(offsetof(AllocatorState, FailureAddress) == 28, "");
+static_assert(sizeof(AllocationMetadata) == 548, "");
+static_assert(offsetof(AllocationMetadata, IsDeallocated) == 544, "");
+#elif defined(__arm__)
+static_assert(sizeof(AllocatorState) == 32, "");
+static_assert(offsetof(AllocatorState, FailureAddress) == 28, "");
+static_assert(sizeof(AllocationMetadata) == 560, "");
+static_assert(offsetof(AllocationMetadata, IsDeallocated) == 552, "");
+#endif // defined($ARCHITECTURE)
+
} // namespace gwp_asan
#endif // GWP_ASAN_COMMON_H_
