sigchain: limit use of SetHandlingSignal.
The native bridge and user signal handlers are able to not return to
our signal handler, leaving the HandlingSignal flag set to true for the
rest of the lifetime of the thread. Fix this by only using
SetHandlingSignal for handlers that we know will return (i.e. the ART
fault handler).
This effectively reverts commit 90444558, which means sigprocmask's
behavior is back to filtering out claimed signals when inside a user
signal handler.
Include an update to test/115-native-bridge from Zhenhua Wang, to make
sure we keep handling signals when a signal handler longjmps away
instead of returning.
Bug: http://b/37988407
Test: m test-art-host
Test: m test-art-target
Change-Id: Ia7159ddfa38f1f055e5cd6089c849a208d335752
diff --git a/sigchainlib/sigchain.cc b/sigchainlib/sigchain.cc
index 13c03e8..df4372f 100644
--- a/sigchainlib/sigchain.cc
+++ b/sigchainlib/sigchain.cc
@@ -190,10 +190,10 @@
return action_;
}
- void AddSpecialHandler(SpecialSignalHandlerFn fn) {
- for (SpecialSignalHandlerFn& slot : special_handlers_) {
- if (slot == nullptr) {
- slot = fn;
+ void AddSpecialHandler(SigchainAction* sa) {
+ for (SigchainAction& slot : special_handlers_) {
+ if (slot.sc_sigaction == nullptr) {
+ slot = *sa;
return;
}
}
@@ -201,15 +201,15 @@
fatal("too many special signal handlers");
}
- void RemoveSpecialHandler(SpecialSignalHandlerFn fn) {
+ void RemoveSpecialHandler(bool (*fn)(int, siginfo_t*, void*)) {
// This isn't thread safe, but it's unlikely to be a real problem.
size_t len = sizeof(special_handlers_)/sizeof(*special_handlers_);
for (size_t i = 0; i < len; ++i) {
- if (special_handlers_[i] == fn) {
+ if (special_handlers_[i].sc_sigaction == fn) {
for (size_t j = i; j < len - 1; ++j) {
special_handlers_[j] = special_handlers_[j + 1];
}
- special_handlers_[len - 1] = nullptr;
+ special_handlers_[len - 1].sc_sigaction = nullptr;
return;
}
}
@@ -223,47 +223,37 @@
private:
bool claimed_;
struct sigaction action_;
- SpecialSignalHandlerFn special_handlers_[2];
+ SigchainAction special_handlers_[2];
};
static SignalChain chains[_NSIG];
-class ScopedSignalUnblocker {
- public:
- explicit ScopedSignalUnblocker(const std::initializer_list<int>& signals) {
- sigset_t new_mask;
- sigemptyset(&new_mask);
- for (int signal : signals) {
- sigaddset(&new_mask, signal);
- }
- if (sigprocmask(SIG_UNBLOCK, &new_mask, &previous_mask_) != 0) {
- fatal("failed to unblock signals: %s", strerror(errno));
- }
- }
-
- ~ScopedSignalUnblocker() {
- if (sigprocmask(SIG_SETMASK, &previous_mask_, nullptr) != 0) {
- fatal("failed to unblock signals: %s", strerror(errno));
- }
- }
-
- private:
- sigset_t previous_mask_;
-};
-
void SignalChain::Handler(int signo, siginfo_t* siginfo, void* ucontext_raw) {
- ScopedHandlingSignal handling_signal;
-
// Try the special handlers first.
// If one of them crashes, we'll reenter this handler and pass that crash onto the user handler.
if (!GetHandlingSignal()) {
- ScopedSignalUnblocker unblocked { SIGABRT, SIGBUS, SIGFPE, SIGILL, SIGSEGV }; // NOLINT
- SetHandlingSignal(true);
-
for (const auto& handler : chains[signo].special_handlers_) {
- if (handler != nullptr && handler(signo, siginfo, ucontext_raw)) {
+ if (handler.sc_sigaction == nullptr) {
+ break;
+ }
+
+ // The native bridge signal handler might not return.
+ // Avoid setting the thread local flag in this case, since we'll never
+ // get a chance to restore it.
+ bool handler_noreturn = (handler.sc_flags & SIGCHAIN_ALLOW_NORETURN);
+ sigset_t previous_mask;
+ linked_sigprocmask(SIG_SETMASK, &handler.sc_mask, &previous_mask);
+
+ ScopedHandlingSignal restorer;
+ if (!handler_noreturn) {
+ SetHandlingSignal(true);
+ }
+
+ if (handler.sc_sigaction(signo, siginfo, ucontext_raw)) {
return;
}
+
+ linked_sigprocmask(SIG_SETMASK, &previous_mask, nullptr);
}
}
@@ -275,7 +265,7 @@
if ((handler_flags & SA_NODEFER)) {
sigdelset(&mask, signo);
}
- sigprocmask(SIG_SETMASK, &mask, nullptr);
+ linked_sigprocmask(SIG_SETMASK, &mask, nullptr);
if ((handler_flags & SA_SIGINFO)) {
chains[signo].action_.sa_sigaction(signo, siginfo, ucontext_raw);
@@ -386,7 +376,7 @@
return linked_sigprocmask(how, new_set_ptr, bionic_old_set);
}
-extern "C" void AddSpecialSignalHandlerFn(int signal, SpecialSignalHandlerFn fn) {
+extern "C" void AddSpecialSignalHandlerFn(int signal, SigchainAction* sa) {
InitializeSignalChain();
if (signal <= 0 || signal >= _NSIG) {
@@ -394,11 +384,11 @@
}
// Set the managed_handler.
- chains[signal].AddSpecialHandler(fn);
+ chains[signal].AddSpecialHandler(sa);
chains[signal].Claim(signal);
}
-extern "C" void RemoveSpecialSignalHandlerFn(int signal, SpecialSignalHandlerFn fn) {
+extern "C" void RemoveSpecialSignalHandlerFn(int signal, bool (*fn)(int, siginfo_t*, void*)) {
InitializeSignalChain();
if (signal <= 0 || signal >= _NSIG) {