Revert^2: "Make sigchain actually own the signal chain.""
This reverts commit 33dca562d5ed9f52f63ced2334c066333ca073e9.
Bug: http://b/36205469
Bug: http://b/36262089
Original-Change-Id: I416b13de800d3e23424cf20688ccfd7e4e48a111
Change-Id: I1267be72c32ed73d1079a572d0b8907556526dde
diff --git a/runtime/fault_handler.cc b/runtime/fault_handler.cc
index 64128cc..4220250 100644
--- a/runtime/fault_handler.cc
+++ b/runtime/fault_handler.cc
@@ -38,8 +38,8 @@
}
// Signal handler called on SIGSEGV.
-static void art_fault_handler(int sig, siginfo_t* info, void* context) {
- fault_manager.HandleFault(sig, info, context);
+static bool art_fault_handler(int sig, siginfo_t* info, void* context) {
+ return fault_manager.HandleFault(sig, info, context);
}
FaultManager::FaultManager() : initialized_(false) {
@@ -49,43 +49,15 @@
FaultManager::~FaultManager() {
}
-static void SetUpArtAction(struct sigaction* action) {
- action->sa_sigaction = art_fault_handler;
- sigemptyset(&action->sa_mask);
- action->sa_flags = SA_SIGINFO | SA_ONSTACK;
-#if !defined(__APPLE__) && !defined(__mips__)
- action->sa_restorer = nullptr;
-#endif
-}
-
-void FaultManager::EnsureArtActionInFrontOfSignalChain() {
- if (initialized_) {
- struct sigaction action;
- SetUpArtAction(&action);
- EnsureFrontOfChain(SIGSEGV, &action);
- } else {
- LOG(WARNING) << "Can't call " << __FUNCTION__ << " due to unitialized fault manager";
- }
-}
-
void FaultManager::Init() {
CHECK(!initialized_);
- struct sigaction action;
- SetUpArtAction(&action);
-
- // Set our signal handler now.
- int e = sigaction(SIGSEGV, &action, &oldaction_);
- if (e != 0) {
- VLOG(signals) << "Failed to claim SEGV: " << strerror(errno);
- }
- // Make sure our signal handler is called before any user handlers.
- ClaimSignalChain(SIGSEGV, &oldaction_);
+ AddSpecialSignalHandlerFn(SIGSEGV, art_fault_handler);
initialized_ = true;
}
void FaultManager::Release() {
if (initialized_) {
- UnclaimSignalChain(SIGSEGV);
+ RemoveSpecialSignalHandlerFn(SIGSEGV, art_fault_handler);
initialized_ = false;
}
}
@@ -118,93 +90,36 @@
return false;
}
-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) {
- PLOG(FATAL) << "failed to unblock signals";
- }
- }
-
- ~ScopedSignalUnblocker() {
- if (sigprocmask(SIG_SETMASK, &previous_mask_, nullptr) != 0) {
- PLOG(FATAL) << "failed to unblock signals";
- }
- }
-
- private:
- sigset_t previous_mask_;
-};
-
-class ScopedHandlingSignalSetter {
- public:
- explicit ScopedHandlingSignalSetter(Thread* thread) : thread_(thread) {
- CHECK(!thread->HandlingSignal());
- thread_->SetHandlingSignal(true);
- }
-
- ~ScopedHandlingSignalSetter() {
- CHECK(thread_->HandlingSignal());
- thread_->SetHandlingSignal(false);
- }
-
- private:
- Thread* thread_;
-};
-
-void FaultManager::HandleFault(int sig, siginfo_t* info, void* context) {
- // BE CAREFUL ALLOCATING HERE INCLUDING USING LOG(...)
- //
- // If malloc calls abort, it will be holding its lock.
- // If the handler tries to call malloc, it will deadlock.
-
- // Use a thread local field to track whether we're recursing, and fall back.
- // (e.g.. if one of our handlers crashed)
- Thread* thread = Thread::Current();
-
- if (thread != nullptr && !thread->HandlingSignal()) {
- // Unblock some signals and set thread->handling_signal_ to true,
- // so that we can catch crashes in our signal handler.
- ScopedHandlingSignalSetter setter(thread);
- ScopedSignalUnblocker unblocker { SIGABRT, SIGBUS, SIGSEGV }; // NOLINT
-
- VLOG(signals) << "Handling fault";
+bool FaultManager::HandleFault(int sig, siginfo_t* info, void* context) {
+ VLOG(signals) << "Handling fault";
#ifdef TEST_NESTED_SIGNAL
- // Simulate a crash in a handler.
- raise(SIGSEGV);
+ // Simulate a crash in a handler.
+ raise(SIGSEGV);
#endif
- if (IsInGeneratedCode(info, context, true)) {
- VLOG(signals) << "in generated code, looking for handler";
- for (const auto& handler : generated_code_handlers_) {
- VLOG(signals) << "invoking Action on handler " << handler;
- if (handler->Action(sig, info, context)) {
- // We have handled a signal so it's time to return from the
- // signal handler to the appropriate place.
- return;
- }
+ if (IsInGeneratedCode(info, context, true)) {
+ VLOG(signals) << "in generated code, looking for handler";
+ for (const auto& handler : generated_code_handlers_) {
+ VLOG(signals) << "invoking Action on handler " << handler;
+ if (handler->Action(sig, info, context)) {
+ // We have handled a signal so it's time to return from the
+ // signal handler to the appropriate place.
+ return true;
}
+ }
- // We hit a signal we didn't handle. This might be something for which
- // we can give more information about so call all registered handlers to
- // see if it is.
- if (HandleFaultByOtherHandlers(sig, info, context)) {
- return;
- }
+ // We hit a signal we didn't handle. This might be something for which
+ // we can give more information about so call all registered handlers to
+ // see if it is.
+ if (HandleFaultByOtherHandlers(sig, info, context)) {
+ return true;
}
}
// Set a breakpoint in this function to catch unhandled signals.
art_sigsegv_fault();
-
- // Pass this on to the next handler in the chain, or the default if none.
- InvokeUserSignalHandler(sig, info, context);
+ return false;
}
void FaultManager::AddHandler(FaultHandler* handler, bool generated_code) {
diff --git a/runtime/fault_handler.h b/runtime/fault_handler.h
index ce59ba7..d56cf17 100644
--- a/runtime/fault_handler.h
+++ b/runtime/fault_handler.h
@@ -42,9 +42,9 @@
// Unclaim signals and delete registered handlers.
void Shutdown();
- void EnsureArtActionInFrontOfSignalChain();
- void HandleFault(int sig, siginfo_t* info, void* context);
+ // Try to handle a fault, returns true if successful.
+ bool HandleFault(int sig, siginfo_t* info, void* context);
// Added handlers are owned by the fault handler and will be freed on Shutdown().
void AddHandler(FaultHandler* handler, bool generated_code);
diff --git a/runtime/java_vm_ext.cc b/runtime/java_vm_ext.cc
index a341cdb..b93b8f2 100644
--- a/runtime/java_vm_ext.cc
+++ b/runtime/java_vm_ext.cc
@@ -39,6 +39,7 @@
#include "runtime_options.h"
#include "ScopedLocalRef.h"
#include "scoped_thread_state_change-inl.h"
+#include "sigchain.h"
#include "thread-inl.h"
#include "thread_list.h"
@@ -900,7 +901,8 @@
int version = (*jni_on_load)(this, nullptr);
if (runtime_->GetTargetSdkVersion() != 0 && runtime_->GetTargetSdkVersion() <= 21) {
- fault_manager.EnsureArtActionInFrontOfSignalChain();
+ // Make sure that sigchain owns SIGSEGV.
+ EnsureFrontOfChain(SIGSEGV);
}
self->SetClassLoaderOverride(old_class_loader.get());
diff --git a/runtime/native_bridge_art_interface.cc b/runtime/native_bridge_art_interface.cc
index c58854b..d77cfa1 100644
--- a/runtime/native_bridge_art_interface.cc
+++ b/runtime/native_bridge_art_interface.cc
@@ -118,7 +118,7 @@
for (int signal = 0; signal < _NSIG; ++signal) {
android::NativeBridgeSignalHandlerFn fn = android::NativeBridgeGetSignalHandler(signal);
if (fn != nullptr) {
- SetSpecialSignalHandlerFn(signal, fn);
+ AddSpecialSignalHandlerFn(signal, fn);
}
}
#endif
diff --git a/sigchainlib/sigchain.cc b/sigchainlib/sigchain.cc
index c1efecd..ed6d7cd 100644
--- a/sigchainlib/sigchain.cc
+++ b/sigchainlib/sigchain.cc
@@ -25,6 +25,9 @@
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
+#include <ucontext.h>
+
+#include <utility>
#include "sigchain.h"
@@ -33,70 +36,24 @@
#define sighandler_t sig_t
#endif
-namespace art {
+// libsigchain provides an interception layer for signal handlers, to allow ART and others to give
+// their signal handlers the first stab at handling signals before passing them on to user code.
+//
+// It implements wrapper functions for signal, sigaction, and sigprocmask, and a handler that
+// forwards signals appropriately.
+//
+// In our handler, we start off with all signals blocked, fetch the original signal mask from the
+// passed in ucontext, and then adjust our signal mask appropriately for the user handler.
+//
+// It's somewhat tricky for us to properly handle some flag cases:
+// SA_NOCLDSTOP and SA_NOCLDWAIT: shouldn't matter, we don't have special handlers for SIGCHLD.
+// SA_NODEFER: unimplemented, we can manually change the signal mask appropriately.
+// ~SA_ONSTACK: always silently enable this
+// SA_RESETHAND: unimplemented, but we can probably do this?
+// ~SA_RESTART: unimplemented, maybe we can reserve an RT signal, register an empty handler that
+// doesn't have SA_RESTART, and raise the signal to avoid restarting syscalls that are
+// expected to be interrupted?
-typedef int (*SigActionFnPtr)(int, const struct sigaction*, struct sigaction*);
-
-class SignalAction {
- public:
- SignalAction() : claimed_(false), uses_old_style_(false), special_handler_(nullptr) {
- }
-
- // Claim the signal and keep the action specified.
- void Claim(const struct sigaction& action) {
- action_ = action;
- claimed_ = true;
- }
-
- // Unclaim the signal and restore the old action.
- void Unclaim(int signal) {
- claimed_ = false;
- sigaction(signal, &action_, nullptr); // Restore old action.
- }
-
- // Get the action associated with this signal.
- const struct sigaction& GetAction() const {
- return action_;
- }
-
- // Is the signal claimed?
- bool IsClaimed() const {
- return claimed_;
- }
-
- // Change the recorded action to that specified.
- // If oldstyle is true then this action is from an older style signal()
- // call as opposed to sigaction(). In this case the sa_handler is
- // used when invoking the user's handler.
- void SetAction(const struct sigaction& action, bool oldstyle) {
- action_ = action;
- uses_old_style_ = oldstyle;
- }
-
- bool OldStyle() const {
- return uses_old_style_;
- }
-
- void SetSpecialHandler(SpecialSignalHandlerFn fn) {
- special_handler_ = fn;
- }
-
- SpecialSignalHandlerFn GetSpecialHandler() {
- return special_handler_;
- }
-
- private:
- struct sigaction action_; // Action to be performed.
- bool claimed_; // Whether signal is claimed or not.
- bool uses_old_style_; // Action is created using signal(). Use sa_handler.
- SpecialSignalHandlerFn special_handler_; // A special handler executed before user handlers.
-};
-
-// User's signal handlers
-static SignalAction user_sigactions[_NSIG];
-static bool initialized;
-static void* linked_sigaction_sym;
-static void* linked_sigprocmask_sym;
static void log(const char* format, ...) {
char buf[256];
@@ -111,102 +68,185 @@
va_end(ap);
}
-static void CheckSignalValid(int signal) {
- if (signal <= 0 || signal >= _NSIG) {
- log("Invalid signal %d", signal);
- abort();
- }
-}
+#define fatal(...) log(__VA_ARGS__); abort()
-// Sigchainlib's own handler so we can ensure a managed handler is called first even if nobody
-// claimed a chain. Simply forward to InvokeUserSignalHandler.
-static void sigchainlib_managed_handler_sigaction(int sig, siginfo_t* info, void* context) {
- InvokeUserSignalHandler(sig, info, context);
-}
-
-// Claim a signal chain for a particular signal.
-extern "C" void ClaimSignalChain(int signal, struct sigaction* oldaction) {
- CheckSignalValid(signal);
-
- user_sigactions[signal].Claim(*oldaction);
-}
-
-extern "C" void UnclaimSignalChain(int signal) {
- CheckSignalValid(signal);
-
- user_sigactions[signal].Unclaim(signal);
-}
-
-// Invoke the user's signal handler.
-extern "C" void InvokeUserSignalHandler(int sig, siginfo_t* info, void* context) {
- // Check the arguments.
- CheckSignalValid(sig);
-
- // The signal must have been claimed in order to get here. Check it.
- if (!user_sigactions[sig].IsClaimed()) {
- abort();
- }
-
- // Do we have a managed handler? If so, run it first.
- SpecialSignalHandlerFn managed = user_sigactions[sig].GetSpecialHandler();
- if (managed != nullptr) {
- sigset_t mask, old_mask;
- sigfillset(&mask);
- sigprocmask(SIG_BLOCK, &mask, &old_mask);
- // Call the handler. If it succeeds, we're done.
- if (managed(sig, info, context)) {
- sigprocmask(SIG_SETMASK, &old_mask, nullptr);
- return;
+static int sigorset(sigset_t* dest, sigset_t* left, sigset_t* right) {
+ sigemptyset(dest);
+ for (size_t i = 0; i < sizeof(sigset_t) * CHAR_BIT; ++i) {
+ if (sigismember(left, i) == 1 || sigismember(right, i) == 1) {
+ sigaddset(dest, i);
}
- sigprocmask(SIG_SETMASK, &old_mask, nullptr);
+ }
+ return 0;
+}
+
+namespace art {
+
+static decltype(&sigaction) linked_sigaction;
+static decltype(&sigprocmask) linked_sigprocmask;
+__thread bool handling_signal;
+
+class SignalChain {
+ public:
+ SignalChain() : claimed_(false) {
}
- const struct sigaction& action = user_sigactions[sig].GetAction();
- if (user_sigactions[sig].OldStyle()) {
- if (action.sa_handler != nullptr) {
- action.sa_handler(sig);
- } else {
- signal(sig, SIG_DFL);
- raise(sig);
+ bool IsClaimed() {
+ return claimed_;
+ }
+
+ void Claim(int signo) {
+ if (!claimed_) {
+ Register(signo);
+ claimed_ = true;
}
+ }
+
+ // Register the signal chain with the kernel if needed.
+ void Register(int signo) {
+ struct sigaction handler_action = {};
+ handler_action.sa_sigaction = SignalChain::Handler;
+ handler_action.sa_flags = SA_RESTART | SA_SIGINFO | SA_ONSTACK;
+ sigfillset(&handler_action.sa_mask);
+ linked_sigaction(signo, &handler_action, &action_);
+ }
+
+ void SetAction(const struct sigaction* action) {
+ action_ = *action;
+ }
+
+ struct sigaction GetAction() {
+ return action_;
+ }
+
+ void AddSpecialHandler(SpecialSignalHandlerFn fn) {
+ for (SpecialSignalHandlerFn& slot : special_handlers_) {
+ if (slot == nullptr) {
+ slot = fn;
+ return;
+ }
+ }
+
+ fatal("too many special signal handlers");
+ }
+
+ void RemoveSpecialHandler(SpecialSignalHandlerFn fn) {
+ // 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) {
+ for (size_t j = i; j < len - 1; ++j) {
+ special_handlers_[j] = special_handlers_[j + 1];
+ }
+ special_handlers_[len - 1] = nullptr;
+ return;
+ }
+ }
+
+ fatal("failed to find special handler to remove");
+ }
+
+
+ static void Handler(int signo, siginfo_t* siginfo, void*);
+
+ private:
+ bool claimed_;
+ struct sigaction action_;
+ SpecialSignalHandlerFn special_handlers_[2];
+};
+
+static SignalChain chains[_NSIG];
+
+class ScopedFlagSetter {
+ public:
+ explicit ScopedFlagSetter(bool* flag) : flag_(flag) {
+ *flag_ = true;
+ }
+
+ ~ScopedFlagSetter() {
+ *flag_ = false;
+ }
+
+ private:
+ bool* flag_;
+};
+
+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) {
+ // Try the special handlers first.
+ // If one of them crashes, we'll reenter this handler and pass that crash onto the user handler.
+ if (!handling_signal) {
+ ScopedFlagSetter flag(&handling_signal);
+ ScopedSignalUnblocker unblocked { SIGABRT, SIGSEGV, SIGBUS }; // NOLINT
+
+ for (const auto& handler : chains[signo].special_handlers_) {
+ if (handler != nullptr && handler(signo, siginfo, ucontext_raw)) {
+ return;
+ }
+ }
+ }
+
+ // Forward to the user's signal handler.
+ int handler_flags = chains[signo].action_.sa_flags;
+ ucontext_t* ucontext = static_cast<ucontext_t*>(ucontext_raw);
+ sigset_t mask;
+ sigorset(&mask, &ucontext->uc_sigmask, &chains[signo].action_.sa_mask);
+ if ((handler_flags & SA_NODEFER)) {
+ sigdelset(&mask, signo);
+ }
+ sigprocmask(SIG_SETMASK, &mask, nullptr);
+
+ if ((handler_flags & SA_SIGINFO)) {
+ chains[signo].action_.sa_sigaction(signo, siginfo, ucontext_raw);
} else {
- if (action.sa_sigaction != nullptr) {
- sigset_t old_mask;
- sigprocmask(SIG_BLOCK, &action.sa_mask, &old_mask);
- action.sa_sigaction(sig, info, context);
- sigprocmask(SIG_SETMASK, &old_mask, nullptr);
+ auto handler = chains[signo].action_.sa_handler;
+ if (handler == SIG_IGN) {
+ return;
+ } else if (handler == SIG_DFL) {
+ raise(signo);
} else {
- signal(sig, SIG_DFL);
- raise(sig);
+ handler(signo);
}
}
}
-extern "C" void EnsureFrontOfChain(int signal, struct sigaction* expected_action) {
- CheckSignalValid(signal);
- // Read the current action without looking at the chain, it should be the expected action.
- SigActionFnPtr linked_sigaction = reinterpret_cast<SigActionFnPtr>(linked_sigaction_sym);
- struct sigaction current_action;
- linked_sigaction(signal, nullptr, ¤t_action);
- // If the sigactions don't match then we put the current action on the chain and make ourself as
- // the main action.
- if (current_action.sa_sigaction != expected_action->sa_sigaction) {
- log("Warning: Unexpected sigaction action found %p\n", current_action.sa_sigaction);
- user_sigactions[signal].Claim(current_action);
- linked_sigaction(signal, expected_action, nullptr);
- }
-}
-
extern "C" int sigaction(int signal, const struct sigaction* new_action, struct sigaction* old_action) {
// If this signal has been claimed as a signal chain, record the user's
// action but don't pass it on to the kernel.
// Note that we check that the signal number is in range here. An out of range signal
// number should behave exactly as the libc sigaction.
- if (signal > 0 && signal < _NSIG && user_sigactions[signal].IsClaimed() &&
- (new_action == nullptr || new_action->sa_handler != SIG_DFL)) {
- struct sigaction saved_action = user_sigactions[signal].GetAction();
+ if (signal < 0 || signal >= _NSIG) {
+ errno = EINVAL;
+ return -1;
+ }
+
+ if (chains[signal].IsClaimed() && new_action != nullptr) {
+ struct sigaction saved_action = chains[signal].GetAction();
if (new_action != nullptr) {
- user_sigactions[signal].SetAction(*new_action, false);
+ chains[signal].SetAction(new_action);
}
if (old_action != nullptr) {
*old_action = saved_action;
@@ -216,69 +256,43 @@
// Will only get here if the signal chain has not been claimed. We want
// to pass the sigaction on to the kernel via the real sigaction in libc.
-
- if (linked_sigaction_sym == nullptr) {
- // Perform lazy initialization.
- // This will only occur outside of a signal context since we have
- // not been initialized and therefore cannot be within the ART
- // runtime.
- InitializeSignalChain();
- }
-
- if (linked_sigaction_sym == nullptr) {
- log("Unable to find next sigaction in signal chain");
- abort();
- }
- SigActionFnPtr linked_sigaction = reinterpret_cast<SigActionFnPtr>(linked_sigaction_sym);
+ InitializeSignalChain();
return linked_sigaction(signal, new_action, old_action);
}
-static sighandler_t signal_impl(int signal, sighandler_t handler) {
- struct sigaction sa;
+extern "C" sighandler_t signal(int signo, sighandler_t handler) {
+ if (signo < 0 || signo > _NSIG) {
+ errno = EINVAL;
+ return SIG_ERR;
+ }
+
+ struct sigaction sa = {};
sigemptyset(&sa.sa_mask);
sa.sa_handler = handler;
- sa.sa_flags = SA_RESTART;
+ sa.sa_flags = SA_RESTART | SA_ONSTACK;
sighandler_t oldhandler;
// If this signal has been claimed as a signal chain, record the user's
// action but don't pass it on to the kernel.
- // Note that we check that the signal number is in range here. An out of range signal
- // number should behave exactly as the libc sigaction.
- if (signal > 0 && signal < _NSIG && user_sigactions[signal].IsClaimed() && handler != SIG_DFL) {
- oldhandler = reinterpret_cast<sighandler_t>(user_sigactions[signal].GetAction().sa_handler);
- user_sigactions[signal].SetAction(sa, true);
+ if (chains[signo].IsClaimed()) {
+ oldhandler = reinterpret_cast<sighandler_t>(chains[signo].GetAction().sa_handler);
+ chains[signo].SetAction(&sa);
return oldhandler;
}
// Will only get here if the signal chain has not been claimed. We want
// to pass the sigaction on to the kernel via the real sigaction in libc.
-
- if (linked_sigaction_sym == nullptr) {
- // Perform lazy initialization.
- InitializeSignalChain();
- }
-
- if (linked_sigaction_sym == nullptr) {
- log("Unable to find next sigaction in signal chain");
- abort();
- }
-
- typedef int (*SigAction)(int, const struct sigaction*, struct sigaction*);
- SigAction linked_sigaction = reinterpret_cast<SigAction>(linked_sigaction_sym);
- if (linked_sigaction(signal, &sa, &sa) == -1) {
+ InitializeSignalChain();
+ if (linked_sigaction(signo, &sa, &sa) == -1) {
return SIG_ERR;
}
return reinterpret_cast<sighandler_t>(sa.sa_handler);
}
-extern "C" sighandler_t signal(int signal, sighandler_t handler) {
- return signal_impl(signal, handler);
-}
-
#if !defined(__LP64__)
-extern "C" sighandler_t bsd_signal(int signal, sighandler_t handler) {
- return signal_impl(signal, handler);
+extern "C" sighandler_t bsd_signal(int signo, sighandler_t handler) {
+ return signal(signo, handler);
}
#endif
@@ -292,7 +306,7 @@
// Don't allow claimed signals in the mask. If a signal chain has been claimed
// we can't allow the user to block that signal.
for (int i = 0 ; i < _NSIG; ++i) {
- if (user_sigactions[i].IsClaimed() && sigismember(&tmpset, i)) {
+ if (chains[i].IsClaimed() && sigismember(&tmpset, i)) {
sigdelset(&tmpset, i);
}
}
@@ -300,18 +314,7 @@
new_set_ptr = &tmpset;
}
- if (linked_sigprocmask_sym == nullptr) {
- // Perform lazy initialization.
- InitializeSignalChain();
- }
-
- if (linked_sigprocmask_sym == nullptr) {
- log("Unable to find next sigprocmask in signal chain");
- abort();
- }
-
- typedef int (*SigProcMask)(int how, const sigset_t*, sigset_t*);
- SigProcMask linked_sigprocmask= reinterpret_cast<SigProcMask>(linked_sigprocmask_sym);
+ InitializeSignalChain();
return linked_sigprocmask(how, new_set_ptr, bionic_old_set);
}
@@ -322,49 +325,67 @@
// taken and if it so happens that a signal occurs while one of these
// locks is already taken, dlsym will block trying to reenter a
// mutex and we will never get out of it.
+ static bool initialized = false;
if (initialized) {
// Don't initialize twice.
return;
}
- linked_sigaction_sym = dlsym(RTLD_NEXT, "sigaction");
+
+ void* linked_sigaction_sym = dlsym(RTLD_NEXT, "sigaction");
if (linked_sigaction_sym == nullptr) {
linked_sigaction_sym = dlsym(RTLD_DEFAULT, "sigaction");
if (linked_sigaction_sym == nullptr ||
linked_sigaction_sym == reinterpret_cast<void*>(sigaction)) {
- linked_sigaction_sym = nullptr;
+ fatal("Unable to find next sigaction in signal chain");
}
}
- linked_sigprocmask_sym = dlsym(RTLD_NEXT, "sigprocmask");
+ void* linked_sigprocmask_sym = dlsym(RTLD_NEXT, "sigprocmask");
if (linked_sigprocmask_sym == nullptr) {
linked_sigprocmask_sym = dlsym(RTLD_DEFAULT, "sigprocmask");
if (linked_sigprocmask_sym == nullptr ||
linked_sigprocmask_sym == reinterpret_cast<void*>(sigprocmask)) {
- linked_sigprocmask_sym = nullptr;
+ fatal("Unable to find next sigprocmask in signal chain");
}
}
+
+ linked_sigaction = reinterpret_cast<decltype(linked_sigaction)>(linked_sigaction_sym);
+ linked_sigprocmask = reinterpret_cast<decltype(linked_sigprocmask)>(linked_sigprocmask_sym);
initialized = true;
}
-extern "C" void SetSpecialSignalHandlerFn(int signal, SpecialSignalHandlerFn fn) {
- CheckSignalValid(signal);
+extern "C" void AddSpecialSignalHandlerFn(int signal, SpecialSignalHandlerFn fn) {
+ if (signal <= 0 || signal >= _NSIG) {
+ fatal("Invalid signal %d", signal);
+ }
// Set the managed_handler.
- user_sigactions[signal].SetSpecialHandler(fn);
+ chains[signal].AddSpecialHandler(fn);
+ chains[signal].Claim(signal);
+}
- // In case the chain isn't claimed, claim it for ourself so we can ensure the managed handler
- // goes first.
- if (!user_sigactions[signal].IsClaimed()) {
- struct sigaction act, old_act;
- act.sa_sigaction = sigchainlib_managed_handler_sigaction;
- sigemptyset(&act.sa_mask);
- act.sa_flags = SA_SIGINFO | SA_ONSTACK;
-#if !defined(__APPLE__) && !defined(__mips__)
- act.sa_restorer = nullptr;
-#endif
- if (sigaction(signal, &act, &old_act) != -1) {
- user_sigactions[signal].Claim(old_act);
- }
+extern "C" void RemoveSpecialSignalHandlerFn(int signal, SpecialSignalHandlerFn fn) {
+ if (signal <= 0 || signal >= _NSIG) {
+ fatal("Invalid signal %d", signal);
+ }
+
+ chains[signal].RemoveSpecialHandler(fn);
+}
+
+extern "C" void EnsureFrontOfChain(int signal) {
+ if (signal <= 0 || signal >= _NSIG) {
+ fatal("Invalid signal %d", signal);
+ }
+
+ // Read the current action without looking at the chain, it should be the expected action.
+ struct sigaction current_action;
+ InitializeSignalChain();
+ linked_sigaction(signal, nullptr, ¤t_action);
+ // If the sigactions don't match then we put the current action on the chain and make ourself as
+ // the main action.
+ if (current_action.sa_sigaction != SignalChain::Handler) {
+ log("Warning: Unexpected sigaction action found %p\n", current_action.sa_sigaction);
+ chains[signal].Register(signal);
}
}
diff --git a/sigchainlib/sigchain.h b/sigchainlib/sigchain.h
index 01ccedf..960d221 100644
--- a/sigchainlib/sigchain.h
+++ b/sigchainlib/sigchain.h
@@ -23,16 +23,11 @@
extern "C" void InitializeSignalChain();
-extern "C" void ClaimSignalChain(int signal, struct sigaction* oldaction);
-
-extern "C" void UnclaimSignalChain(int signal);
-
typedef bool (*SpecialSignalHandlerFn)(int, siginfo_t*, void*);
-extern "C" void SetSpecialSignalHandlerFn(int signal, SpecialSignalHandlerFn fn);
+extern "C" void AddSpecialSignalHandlerFn(int signal, SpecialSignalHandlerFn fn);
+extern "C" void RemoveSpecialSignalHandlerFn(int signal, SpecialSignalHandlerFn fn);
-extern "C" void InvokeUserSignalHandler(int sig, siginfo_t* info, void* context);
-
-extern "C" void EnsureFrontOfChain(int signal, struct sigaction* expected_action);
+extern "C" void EnsureFrontOfChain(int signal);
} // namespace art
diff --git a/sigchainlib/sigchain_dummy.cc b/sigchainlib/sigchain_dummy.cc
index aa3c360..d6a5e12 100644
--- a/sigchainlib/sigchain_dummy.cc
+++ b/sigchainlib/sigchain_dummy.cc
@@ -48,37 +48,23 @@
namespace art {
-
-extern "C" void ClaimSignalChain(int signal ATTRIBUTE_UNUSED,
- struct sigaction* oldaction ATTRIBUTE_UNUSED) {
- log("ClaimSignalChain is not exported by the main executable.");
- abort();
-}
-
-extern "C" void UnclaimSignalChain(int signal ATTRIBUTE_UNUSED) {
- log("UnclaimSignalChain is not exported by the main executable.");
- abort();
-}
-
-extern "C" void InvokeUserSignalHandler(int sig ATTRIBUTE_UNUSED,
- siginfo_t* info ATTRIBUTE_UNUSED,
- void* context ATTRIBUTE_UNUSED) {
- log("InvokeUserSignalHandler is not exported by the main executable.");
- abort();
-}
-
extern "C" void InitializeSignalChain() {
log("InitializeSignalChain is not exported by the main executable.");
abort();
}
-extern "C" void EnsureFrontOfChain(int signal ATTRIBUTE_UNUSED,
- struct sigaction* expected_action ATTRIBUTE_UNUSED) {
+extern "C" void EnsureFrontOfChain(int signal ATTRIBUTE_UNUSED) {
log("EnsureFrontOfChain is not exported by the main executable.");
abort();
}
-extern "C" void SetSpecialSignalHandlerFn(int signal ATTRIBUTE_UNUSED,
+extern "C" void AddSpecialSignalHandlerFn(int signal ATTRIBUTE_UNUSED,
+ SpecialSignalHandlerFn fn ATTRIBUTE_UNUSED) {
+ log("SetSpecialSignalHandlerFn is not exported by the main executable.");
+ abort();
+}
+
+extern "C" void RemoveSpecialSignalHandlerFn(int signal ATTRIBUTE_UNUSED,
SpecialSignalHandlerFn fn ATTRIBUTE_UNUSED) {
log("SetSpecialSignalHandlerFn is not exported by the main executable.");
abort();
diff --git a/sigchainlib/version-script32.txt b/sigchainlib/version-script32.txt
index eec9103..f360efa 100644
--- a/sigchainlib/version-script32.txt
+++ b/sigchainlib/version-script32.txt
@@ -1,11 +1,9 @@
{
global:
- ClaimSignalChain;
- UnclaimSignalChain;
- InvokeUserSignalHandler;
InitializeSignalChain;
EnsureFrontOfChain;
- SetSpecialSignalHandlerFn;
+ AddSpecialSignalHandlerFn;
+ RemoveSpecialSignalHandlerFn;
bsd_signal;
sigaction;
signal;
diff --git a/sigchainlib/version-script64.txt b/sigchainlib/version-script64.txt
index 08c312e..319d1c6 100644
--- a/sigchainlib/version-script64.txt
+++ b/sigchainlib/version-script64.txt
@@ -1,11 +1,9 @@
{
global:
- ClaimSignalChain;
- UnclaimSignalChain;
- InvokeUserSignalHandler;
InitializeSignalChain;
EnsureFrontOfChain;
- SetSpecialSignalHandlerFn;
+ AddSpecialSignalHandlerFn;
+ RemoveSpecialSignalHandlerFn;
sigaction;
signal;
sigprocmask;
diff --git a/test/004-SignalTest/expected.txt b/test/004-SignalTest/expected.txt
index b3a0e1c..847b56f 100644
--- a/test/004-SignalTest/expected.txt
+++ b/test/004-SignalTest/expected.txt
@@ -3,4 +3,8 @@
Caught NullPointerException
Caught StackOverflowError
signal caught
+unblocked signal received
+unblocking blocked signal
+blocked signal received
+signal handler done
Signal test OK
diff --git a/test/004-SignalTest/signaltest.cc b/test/004-SignalTest/signaltest.cc
index 6dd6355..a115c0e 100644
--- a/test/004-SignalTest/signaltest.cc
+++ b/test/004-SignalTest/signaltest.cc
@@ -18,13 +18,14 @@
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
+#include <string.h>
#include <sys/ucontext.h>
#include <unistd.h>
#include "base/macros.h"
static int signal_count;
-static const int kMaxSignal = 2;
+static const int kMaxSignal = 1;
#if defined(__i386__) || defined(__x86_64__)
#if defined(__APPLE__)
@@ -47,6 +48,17 @@
#endif
#endif
+#define BLOCKED_SIGNAL SIGUSR1
+#define UNBLOCKED_SIGNAL SIGUSR2
+
+static void blocked_signal(int sig ATTRIBUTE_UNUSED) {
+ printf("blocked signal received\n");
+}
+
+static void unblocked_signal(int sig ATTRIBUTE_UNUSED) {
+ printf("unblocked signal received\n");
+}
+
static void signalhandler(int sig ATTRIBUTE_UNUSED, siginfo_t* info ATTRIBUTE_UNUSED,
void* context) {
printf("signal caught\n");
@@ -54,6 +66,16 @@
if (signal_count > kMaxSignal) {
abort();
}
+
+ raise(UNBLOCKED_SIGNAL);
+ raise(BLOCKED_SIGNAL);
+ printf("unblocking blocked signal\n");
+
+ sigset_t mask;
+ sigemptyset(&mask);
+ sigaddset(&mask, BLOCKED_SIGNAL);
+ sigprocmask(SIG_UNBLOCK, &mask, nullptr);
+
#if defined(__arm__)
struct ucontext *uc = reinterpret_cast<struct ucontext*>(context);
struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext);
@@ -71,6 +93,8 @@
#else
UNUSED(context);
#endif
+
+ printf("signal handler done\n");
}
static struct sigaction oldaction;
@@ -78,13 +102,16 @@
extern "C" JNIEXPORT void JNICALL Java_Main_initSignalTest(JNIEnv*, jclass) {
struct sigaction action;
action.sa_sigaction = signalhandler;
- sigemptyset(&action.sa_mask);
+ sigfillset(&action.sa_mask);
+ sigdelset(&action.sa_mask, UNBLOCKED_SIGNAL);
action.sa_flags = SA_SIGINFO | SA_ONSTACK;
#if !defined(__APPLE__) && !defined(__mips__)
action.sa_restorer = nullptr;
#endif
sigaction(SIGSEGV, &action, &oldaction);
+ signal(BLOCKED_SIGNAL, blocked_signal);
+ signal(UNBLOCKED_SIGNAL, unblocked_signal);
}
extern "C" JNIEXPORT void JNICALL Java_Main_terminateSignalTest(JNIEnv*, jclass) {
@@ -96,6 +123,12 @@
char *go_away_compiler = nullptr;
extern "C" JNIEXPORT jint JNICALL Java_Main_testSignal(JNIEnv*, jclass) {
+ // Unblock UNBLOCKED_SIGNAL.
+ sigset_t mask;
+ memset(&mask, 0, sizeof(mask));
+ sigaddset(&mask, UNBLOCKED_SIGNAL);
+ sigprocmask(SIG_UNBLOCK, &mask, nullptr);
+
#if defined(__arm__) || defined(__i386__) || defined(__aarch64__)
// On supported architectures we cause a real SEGV.
*go_away_compiler = 'a';