Make use of sigchainlib for signal chaining for implicit checks

This adds a preload library that overrides sigaction and sigprocmask
to implement signal chaining.  Signal chaining allows us to chain
any signal so that the ART runtime receives it before any signal
handler registered in native code by an application.  If the
ART signal handler doesn't want it, it will pass it on to the
user's handler.

ART uses signals for null pointer checks, stack overflow checks and
suspend points.

Also adds an OAT test to test this in isolation.

Change-Id: I9545f9f7343774c091410eb810504d9855fd399f

1 files changed, 26 insertions, 1 deletions

diff --git a/runtime/fault_handler.cc b/runtime/fault_handler.cc
index 8d750c5bdd..15c38c1f4b 100644
--- a/runtime/fault_handler.cc
+++ b/runtime/fault_handler.cc
@@ -29,12 +29,22 @@
 #include "mirror/object-inl.h"
 #include "object_utils.h"
 #include "scoped_thread_state_change.h"
+#ifdef HAVE_ANDROID_OS
+#include "sigchain.h"
+#endif
 #include "verify_object-inl.h"
 
 namespace art {
 // Static fault manger object accessed by signal handler.
 FaultManager fault_manager;
 
+extern "C" {
+void art_sigsegv_fault() {
+  // Set a breakpoint here to be informed when a SIGSEGV is unhandled by ART.
+  VLOG(signals)<< "Caught unknown SIGSEGV in ART fault handler - chaining to next handler.";
+}
+}
+
 // Signal handler called on SIGSEGV.
 static void art_fault_handler(int sig, siginfo_t* info, void* context) {
   fault_manager.HandleFault(sig, info, context);
@@ -45,9 +55,13 @@ FaultManager::FaultManager() {
 }
 
 FaultManager::~FaultManager() {
+#ifdef HAVE_ANDROID_OS
+  UnclaimSignalChain(SIGSEGV);
+#endif
   sigaction(SIGSEGV, &oldaction_, nullptr);   // Restore old handler.
 }
 
+
 void FaultManager::Init() {
   struct sigaction action;
   action.sa_sigaction = art_fault_handler;
@@ -56,7 +70,13 @@ void FaultManager::Init() {
 #if !defined(__mips__)
   action.sa_restorer = nullptr;
 #endif
+
+  // Set our signal handler now.
   sigaction(SIGSEGV, &action, &oldaction_);
+#ifdef HAVE_ANDROID_OS
+  // Make sure our signal handler is called before any user handlers.
+  ClaimSignalChain(SIGSEGV, &oldaction_);
+#endif
 }
 
 void FaultManager::HandleFault(int sig, siginfo_t* info, void* context) {
@@ -79,8 +99,13 @@ void FaultManager::HandleFault(int sig, siginfo_t* info, void* context) {
       return;
     }
   }
-  VLOG(signals)<< "Caught unknown SIGSEGV in ART fault handler";
+  art_sigsegv_fault();
+
+#ifdef HAVE_ANDROID_OS
+  InvokeUserSignalHandler(sig, info, context);
+#else
   oldaction_.sa_sigaction(sig, info, context);
+#endif
 }
 
 void FaultManager::AddHandler(FaultHandler* handler, bool generated_code) {