2 * Copyright 2013 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"
23 #include <glog/logging.h>
25 #include "folly/experimental/exception_tracer/ExceptionAbi.h"
26 #include "folly/experimental/exception_tracer/StackTrace.h"
27 #include "folly/experimental/symbolizer/Symbolizer.h"
28 #include "folly/String.h"
33 const StackTraceStack* getExceptionStackTraceStack(void) __attribute__((weak));
34 typedef const StackTraceStack* (*GetExceptionStackTraceStackType)(void);
35 GetExceptionStackTraceStackType getExceptionStackTraceStackFn;
40 using namespace ::folly::symbolizer;
41 using namespace __cxxabiv1;
44 namespace exception_tracer {
46 std::ostream& operator<<(std::ostream& out, const ExceptionInfo& info) {
47 out << "Exception type: ";
49 out << folly::demangle(*info.type);
51 out << "(unknown type)";
53 out << " (" << info.frames.size()
54 << (info.frames.size() == 1 ? " frame" : " frames")
57 std::vector<FrameInfo> addresses;
58 addresses.reserve(info.frames.size());
59 for (auto ip : info.frames) {
60 // Symbolize the previous address because the IP might be in the
61 // next function, per glog/src/signalhandler.cc
62 addresses.emplace_back(ip - 1);
65 Symbolizer symbolizer;
66 symbolizer.symbolize(addresses.data(), addresses.size());
68 OStreamSymbolizePrinter osp(out);
69 osp.print(addresses.data(), addresses.size(), addresses.size());
70 } catch (const std::exception& e) {
71 out << "\n !! caught " << folly::exceptionStr(e) << "\n";
73 out << "\n !!! caught unexpected exception\n";
81 * Is this a standard C++ ABI exception?
83 * Dependent exceptions (thrown via std::rethrow_exception) aren't --
84 * exc doesn't actually point to a __cxa_exception structure, but
85 * the offset of unwindHeader is correct, so exc->unwindHeader actually
86 * returns a _Unwind_Exception object. Yeah, it's ugly like that.
88 bool isAbiCppException(const __cxa_exception* exc) {
89 // The least significant four bytes must be "C++\0"
90 static const uint64_t cppClass =
91 ((uint64_t)'C' << 24) |
92 ((uint64_t)'+' << 16) |
94 return (exc->unwindHeader.exception_class & 0xffffffff) == cppClass;
99 std::vector<ExceptionInfo> getCurrentExceptions() {
102 // See if linked in with us (getExceptionStackTraceStack is weak)
103 getExceptionStackTraceStackFn = getExceptionStackTraceStack;
105 if (!getExceptionStackTraceStackFn) {
106 // Nope, see if it's in a shared library
107 getExceptionStackTraceStackFn =
108 (GetExceptionStackTraceStackType)dlsym(
109 RTLD_NEXT, "getExceptionStackTraceStack");
115 std::vector<ExceptionInfo> exceptions;
116 auto currentException = __cxa_get_globals()->caughtExceptions;
117 if (!currentException) {
121 bool hasTraceStack = false;
122 const StackTraceStack* traceStack = nullptr;
123 if (!getExceptionStackTraceStackFn) {
124 static bool logged = false;
127 << "Exception tracer library not linked, stack traces not available";
130 } else if ((traceStack = getExceptionStackTraceStackFn()) == nullptr) {
131 static bool logged = false;
134 << "Exception stack trace invalid, stack traces not available";
138 hasTraceStack = true;
141 while (currentException) {
143 // Dependent exceptions (thrown via std::rethrow_exception) aren't
144 // standard ABI __cxa_exception objects, and are correctly labeled as
145 // such in the exception_class field. We could try to extract the
146 // primary exception type in horribly hacky ways, but, for now, NULL.
148 isAbiCppException(currentException) ?
149 currentException->exceptionType :
152 CHECK(traceStack) << "Invalid trace stack!";
154 traceStack->trace.frameIPs,
155 traceStack->trace.frameIPs + traceStack->trace.frameCount);
156 traceStack = traceStack->next;
158 currentException = currentException->nextException;
159 exceptions.push_back(std::move(info));
162 CHECK(!traceStack) << "Invalid trace stack!";
169 std::terminate_handler origTerminate = abort;
170 std::unexpected_handler origUnexpected = abort;
172 void dumpExceptionStack(const char* prefix) {
173 auto exceptions = getCurrentExceptions();
174 if (exceptions.empty()) {
177 LOG(ERROR) << prefix << ", exception stack follows";
178 for (auto& exc : exceptions) {
179 LOG(ERROR) << exc << "\n";
181 LOG(ERROR) << "exception stack complete";
184 void terminateHandler() {
185 dumpExceptionStack("terminate() called");
189 void unexpectedHandler() {
190 dumpExceptionStack("Unexpected exception");
196 void installHandlers() {
199 origTerminate = std::set_terminate(terminateHandler);
200 origUnexpected = std::set_unexpected(unexpectedHandler);
206 } // namespace exception_tracer