am 1f24296c: Add way to ensure we are at the front of the sigaction chain

* commit '1f24296c7c8a6501ee2388c0d20b48f471b48660':
  Add way to ensure we are at the front of the sigaction chain

5 files changed, 44 insertions, 11 deletions

diff --git a/runtime/fault_handler.cc b/runtime/fault_handler.cc
index 25f87c5d48..56d709ad2a 100644
--- a/runtime/fault_handler.cc
+++ b/runtime/fault_handler.cc
@@ -94,16 +94,29 @@ FaultManager::FaultManager() : initialized_(false) {
 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;
-  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
+  SetUpArtAction(&action);
 
   // Set our signal handler now.
   int e = sigaction(SIGSEGV, &action, &oldaction_);
@@ -127,7 +140,6 @@ void FaultManager::HandleFault(int sig, siginfo_t* info, void* context) {
   //
   // If malloc calls abort, it will be holding its lock.
   // If the handler tries to call malloc, it will deadlock.
-
   VLOG(signals) << "Handling fault";
   if (IsInGeneratedCode(info, context, true)) {
     VLOG(signals) << "in generated code, looking for handler";
diff --git a/runtime/fault_handler.h b/runtime/fault_handler.h
index bb26780bd9..89c9360717 100644
--- a/runtime/fault_handler.h
+++ b/runtime/fault_handler.h
@@ -40,6 +40,7 @@ class FaultManager {
 
   void Init();
   void Shutdown();
+  void EnsureArtActionInFrontOfSignalChain();
 
   void HandleFault(int sig, siginfo_t* info, void* context);
   void HandleNestedSignal(int sig, siginfo_t* info, void* context);
@@ -121,7 +122,6 @@ class JavaStackTraceHandler FINAL : public FaultHandler {
   DISALLOW_COPY_AND_ASSIGN(JavaStackTraceHandler);
 };
 
-
 // Statically allocated so the the signal handler can Get access to it.
 extern FaultManager fault_manager;
 
diff --git a/runtime/jni_internal.cc b/runtime/jni_internal.cc
index 73effca152..bdda5c8707 100644
--- a/runtime/jni_internal.cc
+++ b/runtime/jni_internal.cc
@@ -30,6 +30,7 @@
 #include "base/stl_util.h"
 #include "class_linker-inl.h"
 #include "dex_file-inl.h"
+#include "fault_handler.h"
 #include "gc_root.h"
 #include "gc/accounting/card_table-inl.h"
 #include "indirect_reference_table-inl.h"
@@ -3342,6 +3343,9 @@ bool JavaVMExt::LoadNativeLibrary(const std::string& path,
       version = (*jni_on_load)(this, nullptr);
     }
 
+    if (runtime->GetTargetSdkVersion() != 0 && runtime->GetTargetSdkVersion() <= 21) {
+      fault_manager.EnsureArtActionInFrontOfSignalChain();
+    }
     self->SetClassLoaderOverride(old_class_loader.Get());
 
     if (version == JNI_ERR) {
diff --git a/sigchainlib/sigchain.cc b/sigchainlib/sigchain.cc
index 386bbd608f..4991891cfd 100644
--- a/sigchainlib/sigchain.cc
+++ b/sigchainlib/sigchain.cc
@@ -34,6 +34,8 @@
 
 namespace art {
 
+typedef int (*SigActionFnPtr)(int, const struct sigaction*, struct sigaction*);
+
 class SignalAction {
  public:
   SignalAction() : claimed_(false) {
@@ -138,6 +140,21 @@ void InvokeUserSignalHandler(int sig, siginfo_t* info, void* context) {
   }
 }
 
+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, &current_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" {
 // These functions are C linkage since they replace the functions in libc.
 
@@ -171,9 +188,7 @@ int sigaction(int signal, const struct sigaction* new_action, struct sigaction*
     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);
+  SigActionFnPtr linked_sigaction = reinterpret_cast<SigActionFnPtr>(linked_sigaction_sym);
   return linked_sigaction(signal, new_action, old_action);
 }
 
diff --git a/sigchainlib/sigchain.h b/sigchainlib/sigchain.h
index 5bc4026850..be69ca4d7e 100644
--- a/sigchainlib/sigchain.h
+++ b/sigchainlib/sigchain.h
@@ -25,6 +25,8 @@ void InitializeSignalChain();
 
 void ClaimSignalChain(int signal, struct sigaction* oldaction);
 
+void EnsureFrontOfChain(int signal, struct sigaction* expected_action);
+
 void UnclaimSignalChain(int signal);
 
 void InvokeUserSignalHandler(int sig, siginfo_t* info, void* context);