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/ExceptionTracerLib.h>
23 #include <folly/Indestructible.h>
24 #include <folly/Portability.h>
25 #include <folly/SharedMutex.h>
26 #include <folly/Synchronized.h>
28 namespace __cxxabiv1 {
32 void* thrownException,
34 void (*destructor)(void*)) __attribute__((__noreturn__));
35 void* __cxa_begin_catch(void* excObj) throw();
36 void __cxa_rethrow(void) __attribute__((__noreturn__));
37 void __cxa_rethrow(void);
38 void __cxa_end_catch(void);
41 } // namespace __cxxabiv1
43 using namespace folly::exception_tracer;
47 template <typename Function>
48 class CallbackHolder {
50 void registerCallback(Function f) {
51 SYNCHRONIZED(callbacks_) { callbacks_.push_back(std::move(f)); }
54 // always inline to enforce kInternalFramesNumber
55 template <typename... Args>
56 FOLLY_ALWAYS_INLINE void invoke(Args... args) {
57 SYNCHRONIZED_CONST(callbacks_) {
58 for (auto& cb : callbacks_) {
65 folly::Synchronized<std::vector<Function>> callbacks_;
71 namespace exception_tracer {
73 #define DECLARE_CALLBACK(NAME) \
74 CallbackHolder<NAME##Type>& get##NAME##Callbacks() { \
75 static Indestructible<CallbackHolder<NAME##Type>> Callbacks; \
78 void register##NAME##Callback(NAME##Type callback) { \
79 get##NAME##Callbacks().registerCallback(callback); \
82 DECLARE_CALLBACK(CxaThrow);
83 DECLARE_CALLBACK(CxaBeginCatch);
84 DECLARE_CALLBACK(CxaRethrow);
85 DECLARE_CALLBACK(CxaEndCatch);
86 DECLARE_CALLBACK(RethrowException);
91 namespace __cxxabiv1 {
93 void __cxa_throw(void* thrownException,
95 void (*destructor)(void*)) {
96 static auto orig_cxa_throw =
97 reinterpret_cast<decltype(&__cxa_throw)>(dlsym(RTLD_NEXT, "__cxa_throw"));
98 getCxaThrowCallbacks().invoke(thrownException, type, destructor);
99 orig_cxa_throw(thrownException, type, destructor);
100 __builtin_unreachable(); // orig_cxa_throw never returns
103 void __cxa_rethrow() {
104 // __cxa_rethrow leaves the current exception on the caught stack,
105 // and __cxa_begin_catch recognizes that case. We could do the same, but
106 // we'll implement something simpler (and slower): we pop the exception from
107 // the caught stack, and push it back onto the active stack; this way, our
108 // implementation of __cxa_begin_catch doesn't have to do anything special.
109 static auto orig_cxa_rethrow = reinterpret_cast<decltype(&__cxa_rethrow)>(
110 dlsym(RTLD_NEXT, "__cxa_rethrow"));
111 getCxaRethrowCallbacks().invoke();
113 __builtin_unreachable(); // orig_cxa_rethrow never returns
116 void* __cxa_begin_catch(void* excObj) throw() {
117 // excObj is a pointer to the unwindHeader in __cxa_exception
118 static auto orig_cxa_begin_catch =
119 reinterpret_cast<decltype(&__cxa_begin_catch)>(
120 dlsym(RTLD_NEXT, "__cxa_begin_catch"));
121 getCxaBeginCatchCallbacks().invoke(excObj);
122 return orig_cxa_begin_catch(excObj);
125 void __cxa_end_catch() {
126 static auto orig_cxa_end_catch = reinterpret_cast<decltype(&__cxa_end_catch)>(
127 dlsym(RTLD_NEXT, "__cxa_end_catch"));
128 getCxaEndCatchCallbacks().invoke();
129 orig_cxa_end_catch();
132 } // namespace __cxxabiv1
136 void rethrow_exception(std::exception_ptr ep) {
137 // Mangled name for std::rethrow_exception
138 // TODO(tudorb): Dicey, as it relies on the fact that std::exception_ptr
139 // is typedef'ed to a type in namespace __exception_ptr
140 static auto orig_rethrow_exception =
141 reinterpret_cast<decltype(&rethrow_exception)>(
143 "_ZSt17rethrow_exceptionNSt15__exception_ptr13exception_ptrE"));
144 getRethrowExceptionCallbacks().invoke(ep);
145 orig_rethrow_exception(ep);
146 __builtin_unreachable(); // orig_rethrow_exception never returns