1 //===-- common.cpp ----------------------------------------------*- 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-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "gwp_asan/common.h"
10 #include "gwp_asan/stack_trace_compressor.h"
11 
12 #include <assert.h>
13 
14 using AllocationMetadata = gwp_asan::AllocationMetadata;
15 using Error = gwp_asan::Error;
16 
17 namespace gwp_asan {
18 
19 const char *ErrorToString(const Error &E) {
20   switch (E) {
21   case Error::UNKNOWN:
22     return "Unknown";
23   case Error::USE_AFTER_FREE:
24     return "Use After Free";
25   case Error::DOUBLE_FREE:
26     return "Double Free";
27   case Error::INVALID_FREE:
28     return "Invalid (Wild) Free";
29   case Error::BUFFER_OVERFLOW:
30     return "Buffer Overflow";
31   case Error::BUFFER_UNDERFLOW:
32     return "Buffer Underflow";
33   }
34   __builtin_trap();
35 }
36 
37 constexpr size_t AllocationMetadata::kStackFrameStorageBytes;
38 constexpr size_t AllocationMetadata::kMaxTraceLengthToCollect;
39 
40 void AllocationMetadata::RecordAllocation(uintptr_t AllocAddr,
41                                           size_t AllocSize) {
42   Addr = AllocAddr;
43   RequestedSize = AllocSize;
44   IsDeallocated = false;
45 
46   AllocationTrace.ThreadID = getThreadID();
47   DeallocationTrace.TraceSize = 0;
48   DeallocationTrace.ThreadID = kInvalidThreadID;
49 }
50 
51 void AllocationMetadata::RecordDeallocation() {
52   IsDeallocated = true;
53   DeallocationTrace.ThreadID = getThreadID();
54 }
55 
56 void AllocationMetadata::CallSiteInfo::RecordBacktrace(
57     options::Backtrace_t Backtrace) {
58   TraceSize = 0;
59   if (!Backtrace)
60     return;
61 
62   uintptr_t UncompressedBuffer[kMaxTraceLengthToCollect];
63   size_t BacktraceLength =
64       Backtrace(UncompressedBuffer, kMaxTraceLengthToCollect);
65   // Backtrace() returns the number of available frames, which may be greater
66   // than the number of frames in the buffer. In this case, we need to only pack
67   // the number of frames that are in the buffer.
68   if (BacktraceLength > kMaxTraceLengthToCollect)
69     BacktraceLength = kMaxTraceLengthToCollect;
70   TraceSize =
71       compression::pack(UncompressedBuffer, BacktraceLength, CompressedTrace,
72                         AllocationMetadata::kStackFrameStorageBytes);
73 }
74 
75 size_t AllocatorState::maximumAllocationSize() const { return PageSize; }
76 
77 uintptr_t AllocatorState::slotToAddr(size_t N) const {
78   return GuardedPagePool + (PageSize * (1 + N)) + (maximumAllocationSize() * N);
79 }
80 
81 bool AllocatorState::isGuardPage(uintptr_t Ptr) const {
82   assert(pointerIsMine(reinterpret_cast<void *>(Ptr)));
83   size_t PageOffsetFromPoolStart = (Ptr - GuardedPagePool) / PageSize;
84   size_t PagesPerSlot = maximumAllocationSize() / PageSize;
85   return (PageOffsetFromPoolStart % (PagesPerSlot + 1)) == 0;
86 }
87 
88 static size_t addrToSlot(const AllocatorState *State, uintptr_t Ptr) {
89   size_t ByteOffsetFromPoolStart = Ptr - State->GuardedPagePool;
90   return ByteOffsetFromPoolStart /
91          (State->maximumAllocationSize() + State->PageSize);
92 }
93 
94 size_t AllocatorState::getNearestSlot(uintptr_t Ptr) const {
95   if (Ptr <= GuardedPagePool + PageSize)
96     return 0;
97   if (Ptr > GuardedPagePoolEnd - PageSize)
98     return MaxSimultaneousAllocations - 1;
99 
100   if (!isGuardPage(Ptr))
101     return addrToSlot(this, Ptr);
102 
103   if (Ptr % PageSize <= PageSize / 2)
104     return addrToSlot(this, Ptr - PageSize); // Round down.
105   return addrToSlot(this, Ptr + PageSize);   // Round up.
106 }
107 
108 } // namespace gwp_asan
109