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1//===-- common.h ------------------------------------------------*- C++ -*-===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8 9// This file contains code that is common between the crash handler and the10// GuardedPoolAllocator.11 12#ifndef GWP_ASAN_COMMON_H_13#define GWP_ASAN_COMMON_H_14 15#include "gwp_asan/definitions.h"16#include "gwp_asan/options.h"17 18#include <stddef.h>19#include <stdint.h>20 21namespace gwp_asan {22 23// Magic header that resides in the AllocatorState so that GWP-ASan bugreports24// can be understood by tools at different versions. Out-of-process crash25// handlers, like crashpad on Fuchsia, take the raw contents of the26// AllocationMetatada array and the AllocatorState, and shove them into the27// minidump. Online unpacking of these structs needs to know from which version28// of GWP-ASan it's extracting the information, as the structures are not29// stable.30struct AllocatorVersionMagic {31 // The values are copied into the structure at runtime, during32 // `GuardedPoolAllocator::init()` so that GWP-ASan remains completely in the33 // `.bss` segment.34 static constexpr uint8_t kAllocatorVersionMagic[4] = {'A', 'S', 'A', 'N'};35 uint8_t Magic[4] = {};36 // Update the version number when the AllocatorState or AllocationMetadata37 // change.38 static constexpr uint16_t kAllocatorVersion = 2;39 uint16_t Version = 0;40 uint16_t Reserved = 0;41};42 43enum class Error : uint8_t {44 UNKNOWN,45 USE_AFTER_FREE,46 DOUBLE_FREE,47 INVALID_FREE,48 BUFFER_OVERFLOW,49 BUFFER_UNDERFLOW50};51 52const char *ErrorToString(const Error &E);53 54static constexpr uint64_t kInvalidThreadID = UINT64_MAX;55// Get the current thread ID, or kInvalidThreadID if failure. Note: This56// implementation is platform-specific.57uint64_t getThreadID();58 59// This struct contains all the metadata recorded about a single allocation made60// by GWP-ASan. If `AllocationMetadata.Addr` is zero, the metadata is non-valid.61struct AllocationMetadata {62 // The number of bytes used to store a compressed stack frame. On 64-bit63 // platforms, assuming a compression ratio of 50%, this should allow us to64 // store ~64 frames per trace.65 static constexpr size_t kStackFrameStorageBytes = 256;66 67 // Maximum number of stack frames to collect on allocation/deallocation. The68 // actual number of collected frames may be less than this as the stack69 // frames are compressed into a fixed memory range.70 static constexpr size_t kMaxTraceLengthToCollect = 128;71 72 // Records the given allocation metadata into this struct.73 void RecordAllocation(uintptr_t Addr, size_t RequestedSize);74 // Record that this allocation is now deallocated.75 void RecordDeallocation();76 77 struct CallSiteInfo {78 // Record the current backtrace to this callsite.79 void RecordBacktrace(options::Backtrace_t Backtrace);80 81 // The compressed backtrace to the allocation/deallocation.82 uint8_t CompressedTrace[kStackFrameStorageBytes];83 // The thread ID for this trace, or kInvalidThreadID if not available.84 uint64_t ThreadID = kInvalidThreadID;85 // The size of the compressed trace (in bytes). Zero indicates that no86 // trace was collected.87 size_t TraceSize = 0;88 };89 90 // The address of this allocation. If zero, the rest of this struct isn't91 // valid, as the allocation has never occurred.92 uintptr_t Addr = 0;93 // Represents the actual size of the allocation.94 size_t RequestedSize = 0;95 96 CallSiteInfo AllocationTrace;97 CallSiteInfo DeallocationTrace;98 99 // Whether this allocation has been deallocated yet.100 bool IsDeallocated = false;101 102 // In recoverable mode, whether this allocation has had a crash associated103 // with it. This has certain side effects, like meaning this allocation will104 // permanently occupy a slot, and won't ever have another crash reported from105 // it.106 bool HasCrashed = false;107};108 109// This holds the state that's shared between the GWP-ASan allocator and the110// crash handler. This, in conjunction with the Metadata array, forms the entire111// set of information required for understanding a GWP-ASan crash.112struct AllocatorState {113 constexpr AllocatorState() {}114 AllocatorVersionMagic VersionMagic{};115 116 // Returns whether the provided pointer is a current sampled allocation that117 // is owned by this pool.118 GWP_ASAN_ALWAYS_INLINE bool pointerIsMine(const void *Ptr) const {119 uintptr_t P = reinterpret_cast<uintptr_t>(Ptr);120 return P < GuardedPagePoolEnd && GuardedPagePool <= P;121 }122 123 // Returns the address of the N-th guarded slot.124 uintptr_t slotToAddr(size_t N) const;125 126 // Returns the largest allocation that is supported by this pool.127 size_t maximumAllocationSize() const;128 129 // Gets the nearest slot to the provided address.130 size_t getNearestSlot(uintptr_t Ptr) const;131 132 // Returns whether the provided pointer is a guard page or not. The pointer133 // must be within memory owned by this pool, else the result is undefined.134 bool isGuardPage(uintptr_t Ptr) const;135 136 // Returns the address that's used by __gwp_asan_get_internal_crash_address()137 // and GPA::raiseInternallyDetectedError() to communicate that the SEGV in138 // question comes from an internally-detected error.139 uintptr_t internallyDetectedErrorFaultAddress() const;140 141 // The number of guarded slots that this pool holds.142 size_t MaxSimultaneousAllocations = 0;143 144 // Pointer to the pool of guarded slots. Note that this points to the start of145 // the pool (which is a guard page), not a pointer to the first guarded page.146 uintptr_t GuardedPagePool = 0;147 uintptr_t GuardedPagePoolEnd = 0;148 149 // Cached page size for this system in bytes.150 size_t PageSize = 0;151 152 // The type and address of an internally-detected failure. For INVALID_FREE153 // and DOUBLE_FREE, these errors are detected in GWP-ASan, which will set154 // these values and terminate the process.155 Error FailureType = Error::UNKNOWN;156 uintptr_t FailureAddress = 0;157};158 159// Below are various compile-time checks that the layout of the internal160// GWP-ASan structures are undisturbed. If they are disturbed, the version magic161// number needs to be increased by one, and the asserts need to be updated.162// Out-of-process crash handlers, like breakpad/crashpad, may copy the internal163// GWP-ASan structures into a minidump for offline reconstruction of the crash.164// In order to accomplish this, the offline reconstructor needs to know the165// version of GWP-ASan internal structures that it's unpacking (along with the166// architecture-specific layout info, which is left as an exercise to the crash167// handler).168static_assert(offsetof(AllocatorState, VersionMagic) == 0, "");169static_assert(sizeof(AllocatorVersionMagic) == 8, "");170#if defined(__x86_64__)171static_assert(sizeof(AllocatorState) == 56, "");172static_assert(offsetof(AllocatorState, FailureAddress) == 48, "");173static_assert(sizeof(AllocationMetadata) == 568, "");174static_assert(offsetof(AllocationMetadata, IsDeallocated) == 560, "");175#elif defined(__aarch64__)176static_assert(sizeof(AllocatorState) == 56, "");177static_assert(offsetof(AllocatorState, FailureAddress) == 48, "");178static_assert(sizeof(AllocationMetadata) == 568, "");179static_assert(offsetof(AllocationMetadata, IsDeallocated) == 560, "");180#elif defined(__i386__)181static_assert(sizeof(AllocatorState) == 32, "");182static_assert(offsetof(AllocatorState, FailureAddress) == 28, "");183static_assert(sizeof(AllocationMetadata) == 548, "");184static_assert(offsetof(AllocationMetadata, IsDeallocated) == 544, "");185#elif defined(__arm__)186static_assert(sizeof(AllocatorState) == 32, "");187static_assert(offsetof(AllocatorState, FailureAddress) == 28, "");188static_assert(sizeof(AllocationMetadata) == 560, "");189static_assert(offsetof(AllocationMetadata, IsDeallocated) == 552, "");190#endif // defined($ARCHITECTURE)191 192} // namespace gwp_asan193#endif // GWP_ASAN_COMMON_H_194