Add way to ensure we are at the front of the sigaction chain
Calling this after jni_on_load fixes the unity apps. This is
not exactly correct since we may already have the following chain.
Start up:
Us -> debuggerd
After app goes in front:
App -> us -> debuggerd
After we put ourself back at the front:
Us -> app -> us -> app -> .... stack overflow.
Bug: 17620677
Change-Id: I9183997e3d5ebd51c320b5d51425be5142e938f3
diff --git a/runtime/fault_handler.cc b/runtime/fault_handler.cc
index 25f87c5..56d709a 100644
--- a/runtime/fault_handler.cc
+++ b/runtime/fault_handler.cc
@@ -94,16 +94,29 @@
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 @@
//
// 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 bb26780..89c9360 100644
--- a/runtime/fault_handler.h
+++ b/runtime/fault_handler.h
@@ -40,6 +40,7 @@
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 @@
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 73effca..bdda5c8 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 @@
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 386bbd6..4991891 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 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" {
// These functions are C linkage since they replace the functions in libc.
@@ -171,9 +188,7 @@
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 5bc4026..be69ca4 100644
--- a/sigchainlib/sigchain.h
+++ b/sigchainlib/sigchain.h
@@ -25,6 +25,8 @@
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);
