From 7b0fdb52cdf40ed4310fd61e10f37e66f17c3bd5 Mon Sep 17 00:00:00 2001
From: comex <comexk@gmail.com>
Date: Sun, 7 Sep 2014 19:10:02 -0400
Subject: [PATCH] Run exception handlers on an alternate stack on Linux.

*Completely untested.*  Someone please test.
---
 Source/Core/Core/ArmMemTools.cpp |  3 +++
 Source/Core/Core/Core.cpp        |  4 ++++
 Source/Core/Core/MemTools.h      |  1 +
 Source/Core/Core/x64MemTools.cpp | 20 ++++++++++++++++++++
 4 files changed, 28 insertions(+)

diff --git a/Source/Core/Core/ArmMemTools.cpp b/Source/Core/Core/ArmMemTools.cpp
index ff7d77e4f4..c9816aba00 100644
--- a/Source/Core/Core/ArmMemTools.cpp
+++ b/Source/Core/Core/ArmMemTools.cpp
@@ -86,4 +86,7 @@ void InstallExceptionHandler()
 	sigemptyset(&sa.sa_mask);
 	sigaction(SIGSEGV, &sa, nullptr);
 }
+
+void UninstallExceptionHandler() {}
+
 }  // namespace
diff --git a/Source/Core/Core/Core.cpp b/Source/Core/Core/Core.cpp
index 3a764a4e63..5b6294d2c7 100644
--- a/Source/Core/Core/Core.cpp
+++ b/Source/Core/Core/Core.cpp
@@ -277,6 +277,10 @@ static void CpuThread()
 	if (!_CoreParameter.bCPUThread)
 		g_video_backend->Video_Cleanup();
 
+	#if _M_X86_64 || _M_ARM_32
+	EMM::UninstallExceptionHandler();
+	#endif
+
 	return;
 }
 
diff --git a/Source/Core/Core/MemTools.h b/Source/Core/Core/MemTools.h
index 276af3d887..fcc671b799 100644
--- a/Source/Core/Core/MemTools.h
+++ b/Source/Core/Core/MemTools.h
@@ -11,4 +11,5 @@ namespace EMM
 {
 	typedef u32 EAddr;
 	void InstallExceptionHandler();
+	void UninstallExceptionHandler();
 }
diff --git a/Source/Core/Core/x64MemTools.cpp b/Source/Core/Core/x64MemTools.cpp
index de298363df..057d3a83f0 100644
--- a/Source/Core/Core/x64MemTools.cpp
+++ b/Source/Core/Core/x64MemTools.cpp
@@ -125,6 +125,8 @@ void InstallExceptionHandler()
 	handlerInstalled = true;
 }
 
+void UninstallExceptionHandler() {}
+
 #elif defined(__APPLE__)
 
 void CheckKR(const char* name, kern_return_t kr)
@@ -243,6 +245,8 @@ void InstallExceptionHandler()
 	CheckKR("mach_port_request_notification", mach_port_request_notification(mach_task_self(), port, MACH_NOTIFY_NO_SENDERS, 0, port, MACH_MSG_TYPE_MAKE_SEND_ONCE, &previous));
 }
 
+void UninstallExceptionHandler() {}
+
 #elif defined(_POSIX_VERSION)
 
 static void sigsegv_handler(int sig, siginfo_t *info, void *raw_context)
@@ -273,6 +277,12 @@ static void sigsegv_handler(int sig, siginfo_t *info, void *raw_context)
 
 void InstallExceptionHandler()
 {
+	stack_t signal_stack;
+	signal_stack.ss_sp = malloc(SIGSTKSZ);
+	signal_stack.ss_size = SIGSTKSZ;
+	signal_stack.ss_flags = 0;
+	if (sigaltstack(&signal_stack, nullptr))
+		PanicAlert("sigaltstack failed");
 	struct sigaction sa;
 	sa.sa_handler = nullptr;
 	sa.sa_sigaction = &sigsegv_handler;
@@ -281,6 +291,16 @@ void InstallExceptionHandler()
 	sigaction(SIGSEGV, &sa, nullptr);
 }
 
+void UninstallExceptionHandler()
+{
+	stack_t signal_stack, old_stack;
+	signal_stack.ss_flags = SS_DISABLE;
+	if (!sigaltstack(&signal_stack, &old_stack) &&
+	    !(old_stack.ss_flags & SS_DISABLE))
+	{
+		free(old_stack.ss_sp);
+	}
+}
 #else
 
 #error Unsupported x86_64 platform! Report this if you support sigaction