1/*
2 * Copyright (C) 2017-2018 Apple Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
17 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
18 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
20 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
23 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#include "config.h"
27#include "WasmFaultSignalHandler.h"
28
29#if ENABLE(WEBASSEMBLY)
30
31#include "ExecutableAllocator.h"
32#include "MachineContext.h"
33#include "WasmCapabilities.h"
34#include "WasmExceptionType.h"
35#include "WasmMemory.h"
36#include "WasmThunks.h"
37
38#include <wtf/HashSet.h>
39#include <wtf/Lock.h>
40#include <wtf/NeverDestroyed.h>
41#include <wtf/threads/Signals.h>
42
43namespace JSC { namespace Wasm {
44
45namespace {
46namespace WasmFaultSignalHandlerInternal {
47static const bool verbose = false;
48}
49}
50
51static Lock codeLocationsLock;
52static LazyNeverDestroyed<HashSet<std::tuple<void*, void*>>> codeLocations; // (start, end)
53
54static bool fastHandlerInstalled { false };
55
56#if ENABLE(WEBASSEMBLY_FAST_MEMORY)
57
58static SignalAction trapHandler(Signal, SigInfo& sigInfo, PlatformRegisters& context)
59{
60 auto instructionPointer = MachineContext::instructionPointer(context);
61 if (!instructionPointer)
62 return SignalAction::NotHandled;
63 void* faultingInstruction = instructionPointer->untaggedExecutableAddress();
64 dataLogLnIf(WasmFaultSignalHandlerInternal::verbose, "starting handler for fault at: ", RawPointer(faultingInstruction));
65
66 dataLogLnIf(WasmFaultSignalHandlerInternal::verbose, "JIT memory start: ", RawPointer(startOfFixedExecutableMemoryPool()), " end: ", RawPointer(endOfFixedExecutableMemoryPool()));
67 // First we need to make sure we are in JIT code before we can aquire any locks. Otherwise,
68 // we might have crashed in code that is already holding one of the locks we want to aquire.
69 assertIsNotTagged(faultingInstruction);
70 if (isJITPC(faultingInstruction)) {
71 bool faultedInActiveFastMemory = false;
72 {
73 void* faultingAddress = sigInfo.faultingAddress;
74 dataLogLnIf(WasmFaultSignalHandlerInternal::verbose, "checking faulting address: ", RawPointer(faultingAddress), " is in an active fast memory");
75 faultedInActiveFastMemory = Wasm::Memory::addressIsInActiveFastMemory(faultingAddress);
76 }
77 if (faultedInActiveFastMemory) {
78 dataLogLnIf(WasmFaultSignalHandlerInternal::verbose, "found active fast memory for faulting address");
79 LockHolder locker(codeLocationsLock);
80 for (auto range : codeLocations.get()) {
81 void* start;
82 void* end;
83 std::tie(start, end) = range;
84 dataLogLnIf(WasmFaultSignalHandlerInternal::verbose, "function start: ", RawPointer(start), " end: ", RawPointer(end));
85 if (start <= faultingInstruction && faultingInstruction < end) {
86 dataLogLnIf(WasmFaultSignalHandlerInternal::verbose, "found match");
87 MacroAssemblerCodeRef<JITThunkPtrTag> exceptionStub = Thunks::singleton().existingStub(throwExceptionFromWasmThunkGenerator);
88 // If for whatever reason we don't have a stub then we should just treat this like a regular crash.
89 if (!exceptionStub)
90 break;
91 dataLogLnIf(WasmFaultSignalHandlerInternal::verbose, "found stub: ", RawPointer(exceptionStub.code().executableAddress()));
92 MachineContext::argumentPointer<1>(context) = reinterpret_cast<void*>(ExceptionType::OutOfBoundsMemoryAccess);
93 MachineContext::setInstructionPointer(context, exceptionStub.code().retagged<CFunctionPtrTag>());
94 return SignalAction::Handled;
95 }
96 }
97 }
98 }
99 return SignalAction::NotHandled;
100}
101
102#endif // ENABLE(WEBASSEMBLY_FAST_MEMORY)
103
104void registerCode(void* start, void* end)
105{
106 if (!fastMemoryEnabled())
107 return;
108 LockHolder locker(codeLocationsLock);
109 codeLocations->add(std::make_tuple(start, end));
110}
111
112void unregisterCode(void* start, void* end)
113{
114 if (!fastMemoryEnabled())
115 return;
116 LockHolder locker(codeLocationsLock);
117 codeLocations->remove(std::make_tuple(start, end));
118}
119
120bool fastMemoryEnabled()
121{
122 return fastHandlerInstalled;
123}
124
125void enableFastMemory()
126{
127#if ENABLE(WEBASSEMBLY_FAST_MEMORY)
128 static std::once_flag once;
129 std::call_once(once, [] {
130 if (!Wasm::isSupported())
131 return;
132
133 if (!Options::useWebAssemblyFastMemory())
134 return;
135
136 installSignalHandler(Signal::BadAccess, [] (Signal signal, SigInfo& sigInfo, PlatformRegisters& ucontext) {
137 return trapHandler(signal, sigInfo, ucontext);
138 });
139
140 codeLocations.construct();
141 fastHandlerInstalled = true;
142 });
143#endif // ENABLE(WEBASSEMBLY_FAST_MEMORY)
144}
145
146} } // namespace JSC::Wasm
147
148#endif // ENABLE(WEBASSEMBLY)
149
150