2 * Copyright 2016 Facebook, Inc.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
17 #include <folly/experimental/exception_tracer/ExceptionTracer.h>
22 #include <glog/logging.h>
24 #include <folly/experimental/exception_tracer/ExceptionAbi.h>
25 #include <folly/experimental/exception_tracer/StackTrace.h>
26 #include <folly/experimental/symbolizer/Symbolizer.h>
27 #include <folly/String.h>
31 using namespace ::folly::exception_tracer;
32 using namespace ::folly::symbolizer;
33 using namespace __cxxabiv1;
36 StackTraceStack* getExceptionStackTraceStack(void) __attribute__((__weak__));
37 typedef StackTraceStack* (*GetExceptionStackTraceStackType)(void);
38 GetExceptionStackTraceStackType getExceptionStackTraceStackFn;
44 namespace exception_tracer {
46 std::ostream& operator<<(std::ostream& out, const ExceptionInfo& info) {
47 printExceptionInfo(out, info, SymbolizePrinter::COLOR_IF_TTY);
51 void printExceptionInfo(
53 const ExceptionInfo& info,
55 out << "Exception type: ";
57 out << folly::demangle(*info.type);
59 out << "(unknown type)";
61 out << " (" << info.frames.size()
62 << (info.frames.size() == 1 ? " frame" : " frames")
65 size_t frameCount = info.frames.size();
67 // Skip our own internal frames
68 static constexpr size_t kInternalFramesNumber = 3;
69 if (frameCount > kInternalFramesNumber) {
70 auto addresses = info.frames.data() + kInternalFramesNumber;
71 frameCount -= kInternalFramesNumber;
73 std::vector<SymbolizedFrame> frames;
74 frames.resize(frameCount);
76 Symbolizer symbolizer(
77 (options & SymbolizePrinter::NO_FILE_AND_LINE)
78 ? Dwarf::LocationInfoMode::DISABLED
79 : Symbolizer::kDefaultLocationInfoMode);
80 symbolizer.symbolize(addresses, frames.data(), frameCount);
82 OStreamSymbolizePrinter osp(out, options);
83 osp.println(addresses, frames.data(), frameCount);
85 } catch (const std::exception& e) {
86 out << "\n !! caught " << folly::exceptionStr(e) << "\n";
88 out << "\n !!! caught unexpected exception\n";
95 * Is this a standard C++ ABI exception?
97 * Dependent exceptions (thrown via std::rethrow_exception) aren't --
98 * exc doesn't actually point to a __cxa_exception structure, but
99 * the offset of unwindHeader is correct, so exc->unwindHeader actually
100 * returns a _Unwind_Exception object. Yeah, it's ugly like that.
102 bool isAbiCppException(const __cxa_exception* exc) {
103 // The least significant four bytes must be "C++\0"
104 static const uint64_t cppClass =
105 ((uint64_t)'C' << 24) |
106 ((uint64_t)'+' << 16) |
107 ((uint64_t)'+' << 8);
108 return (exc->unwindHeader.exception_class & 0xffffffff) == cppClass;
113 std::vector<ExceptionInfo> getCurrentExceptions() {
116 // See if linked in with us (getExceptionStackTraceStack is weak)
117 getExceptionStackTraceStackFn = getExceptionStackTraceStack;
119 if (!getExceptionStackTraceStackFn) {
120 // Nope, see if it's in a shared library
121 getExceptionStackTraceStackFn =
122 (GetExceptionStackTraceStackType)dlsym(
123 RTLD_NEXT, "getExceptionStackTraceStack");
129 std::vector<ExceptionInfo> exceptions;
130 auto currentException = __cxa_get_globals()->caughtExceptions;
131 if (!currentException) {
135 StackTraceStack* traceStack = nullptr;
136 if (!getExceptionStackTraceStackFn) {
137 static bool logged = false;
140 << "Exception tracer library not linked, stack traces not available";
143 } else if ((traceStack = getExceptionStackTraceStackFn()) == nullptr) {
144 static bool logged = false;
147 << "Exception stack trace invalid, stack traces not available";
152 StackTrace* trace = traceStack ? traceStack->top() : nullptr;
153 while (currentException) {
155 // Dependent exceptions (thrown via std::rethrow_exception) aren't
156 // standard ABI __cxa_exception objects, and are correctly labeled as
157 // such in the exception_class field. We could try to extract the
158 // primary exception type in horribly hacky ways, but, for now, NULL.
160 isAbiCppException(currentException) ?
161 currentException->exceptionType :
164 CHECK(trace) << "Invalid trace stack!";
165 info.frames.assign(trace->addresses,
166 trace->addresses + trace->frameCount);
167 trace = traceStack->next(trace);
169 currentException = currentException->nextException;
170 exceptions.push_back(std::move(info));
172 CHECK(!trace) << "Invalid trace stack!";
179 std::terminate_handler origTerminate = abort;
180 std::unexpected_handler origUnexpected = abort;
182 void dumpExceptionStack(const char* prefix) {
183 auto exceptions = getCurrentExceptions();
184 if (exceptions.empty()) {
187 LOG(ERROR) << prefix << ", exception stack follows";
188 for (auto& exc : exceptions) {
189 LOG(ERROR) << exc << "\n";
191 LOG(ERROR) << "exception stack complete";
194 void terminateHandler() {
195 dumpExceptionStack("terminate() called");
199 void unexpectedHandler() {
200 dumpExceptionStack("Unexpected exception");
206 void installHandlers() {
209 origTerminate = std::set_terminate(terminateHandler);
210 origUnexpected = std::set_unexpected(unexpectedHandler);
216 } // namespace exception_tracer