2 * Copyright 2012 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.
18 #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"
32 const StackTraceStack* getExceptionStackTraceStack(void) __attribute__((weak));
33 typedef const StackTraceStack* (*GetExceptionStackTraceStackType)(void);
34 GetExceptionStackTraceStackType getExceptionStackTraceStackFn;
39 using namespace ::facebook::symbolizer;
40 using namespace __cxxabiv1;
42 namespace exception_tracer {
44 std::ostream& operator<<(std::ostream& out, const ExceptionInfo& info) {
45 out << "Exception type: ";
47 out << folly::demangle(*info.type);
49 out << "(unknown type)";
51 out << " (" << info.frames.size()
52 << (info.frames.size() == 1 ? " frame" : " frames")
55 Symbolizer symbolizer;
56 folly::StringPiece symbolName;
57 Dwarf::LocationInfo location;
58 for (auto ip : info.frames) {
59 // Symbolize the previous address because the IP might be in the
60 // next function, per glog/src/signalhandler.cc
61 symbolizer.symbolize(ip-1, symbolName, location);
62 Symbolizer::write(out, ip, symbolName, location);
64 } catch (const std::exception& e) {
65 out << "\n !! caught " << folly::exceptionStr(e) << "\n";
67 out << "\n !!! caught unexpected exception\n";
75 * Is this a standard C++ ABI exception?
77 * Dependent exceptions (thrown via std::rethrow_exception) aren't --
78 * exc doesn't actually point to a __cxa_exception structure, but
79 * the offset of unwindHeader is correct, so exc->unwindHeader actually
80 * returns a _Unwind_Exception object. Yeah, it's ugly like that.
82 bool isAbiCppException(const __cxa_exception* exc) {
83 // The least significant four bytes must be "C++\0"
84 static const uint64_t cppClass =
85 ((uint64_t)'C' << 24) |
86 ((uint64_t)'+' << 16) |
88 return (exc->unwindHeader.exception_class & 0xffffffff) == cppClass;
93 std::vector<ExceptionInfo> getCurrentExceptions() {
96 // See if linked in with us (getExceptionStackTraceStack is weak)
97 getExceptionStackTraceStackFn = getExceptionStackTraceStack;
99 if (!getExceptionStackTraceStackFn) {
100 // Nope, see if it's in a shared library
101 getExceptionStackTraceStackFn =
102 (GetExceptionStackTraceStackType)dlsym(
103 RTLD_NEXT, "getExceptionStackTraceStack");
109 std::vector<ExceptionInfo> exceptions;
110 auto currentException = __cxa_get_globals()->caughtExceptions;
111 if (!currentException) {
115 bool hasTraceStack = false;
116 const StackTraceStack* traceStack = nullptr;
117 if (!getExceptionStackTraceStackFn) {
118 static bool logged = false;
121 << "Exception tracer library not linked, stack traces not available";
124 } else if ((traceStack = getExceptionStackTraceStackFn()) == nullptr) {
125 static bool logged = false;
128 << "Exception stack trace invalid, stack traces not available";
132 hasTraceStack = true;
135 while (currentException) {
137 // Dependent exceptions (thrown via std::rethrow_exception) aren't
138 // standard ABI __cxa_exception objects, and are correctly labeled as
139 // such in the exception_class field. We could try to extract the
140 // primary exception type in horribly hacky ways, but, for now, NULL.
142 isAbiCppException(currentException) ?
143 currentException->exceptionType :
146 CHECK(traceStack) << "Invalid trace stack!";
148 traceStack->trace.frameIPs,
149 traceStack->trace.frameIPs + traceStack->trace.frameCount);
150 traceStack = traceStack->next;
152 currentException = currentException->nextException;
153 exceptions.push_back(std::move(info));
156 CHECK(!traceStack) << "Invalid trace stack!";
163 std::terminate_handler origTerminate = abort;
164 std::unexpected_handler origUnexpected = abort;
166 void dumpExceptionStack(const char* prefix) {
167 auto exceptions = getCurrentExceptions();
168 if (exceptions.empty()) {
171 LOG(ERROR) << prefix << ", exception stack follows";
172 for (auto& exc : exceptions) {
173 LOG(ERROR) << exc << "\n";
175 LOG(ERROR) << "exception stack complete";
178 void terminateHandler() {
179 dumpExceptionStack("terminate() called");
183 void unexpectedHandler() {
184 dumpExceptionStack("Unexpected exception");
190 void installHandlers() {
193 origTerminate = std::set_terminate(terminateHandler);
194 origUnexpected = std::set_unexpected(unexpectedHandler);
200 } // namespace exception_tracer