From 4037c981ebb6455e6631c2a9c79800bce325b9e2 Mon Sep 17 00:00:00 2001
From: Joe Groff <arcata@gmail.com>
Date: Tue, 1 Nov 2011 18:22:46 -0700
Subject: [PATCH] vm: die if we fault in a fault

---
 vm/errors.cpp | 6 ++++++
 vm/vm.cpp     | 3 ++-
 vm/vm.hpp     | 3 +++
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/vm/errors.cpp b/vm/errors.cpp
index bbf02c2db2..dcc3a54eb2 100755
--- a/vm/errors.cpp
+++ b/vm/errors.cpp
@@ -29,6 +29,8 @@ void out_of_memory()
 
 void factor_vm::general_error(vm_error_type error, cell arg1, cell arg2)
 {
+	faulting_p = true;
+
 	/* Reset local roots before allocating anything */
 	data_roots.clear();
 	bignum_roots.clear();
@@ -57,6 +59,7 @@ void factor_vm::general_error(vm_error_type error, cell arg1, cell arg2)
 
 		ctx->push(error_object);
 
+		faulting_p = false;
 		unwind_native_frames(special_objects[ERROR_HANDLER_QUOT],
 			ctx->callstack_top);
 	}
@@ -68,6 +71,7 @@ void factor_vm::general_error(vm_error_type error, cell arg1, cell arg2)
 		std::cout << "error: " << error << std::endl;
 		std::cout << "arg 1: "; print_obj(arg1); std::cout << std::endl;
 		std::cout << "arg 2: "; print_obj(arg2); std::cout << std::endl;
+		faulting_p = false;
 		factorbug();
 	}
 }
@@ -86,6 +90,8 @@ void factor_vm::memory_protection_error(cell addr)
 {
 	if(code->safepoint_p(addr))
 		handle_safepoint();
+	else if(faulting_p)
+		fatal_error("Double fault", 0);
 	else if(ctx->datastack_seg->underflow_p(addr))
 		general_error(ERROR_DATASTACK_UNDERFLOW,false_object,false_object);
 	else if(ctx->datastack_seg->overflow_p(addr))
diff --git a/vm/vm.cpp b/vm/vm.cpp
index 287db660e5..0f921e76a0 100755
--- a/vm/vm.cpp
+++ b/vm/vm.cpp
@@ -18,7 +18,8 @@ factor_vm::factor_vm() :
 	fep_disabled(false),
 	full_output(false),
 	last_nano_count(0),
-	signal_callstack_seg(NULL)
+	signal_callstack_seg(NULL),
+	faulting_p(false)
 {
 	primitive_reset_dispatch_stats();
 }
diff --git a/vm/vm.hpp b/vm/vm.hpp
index a167e487e5..f4c765d645 100755
--- a/vm/vm.hpp
+++ b/vm/vm.hpp
@@ -134,6 +134,9 @@ struct factor_vm
 	/* Stack for signal handlers, only used on Unix */
 	segment *signal_callstack_seg;
 
+	/* Are we already handling a fault? Used to catch double memory faults */
+	bool faulting_p;
+
 	// contexts
 	context *new_context();
 	void init_context(context *ctx);