1 files changed, 42 insertions, 0 deletions
diff --git a/src/pkg/runtime/sys_x86.c b/src/pkg/runtime/sys_x86.c
new file mode 100644
index 000000000..e68ff514a
--- /dev/null
+++ b/src/pkg/runtime/sys_x86.c
@@ -0,0 +1,42 @@
+// Copyright 2013 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build amd64 386
+
+#include "runtime.h"
+
+// adjust Gobuf as it if executed a call to fn with context ctxt
+// and then did an immediate gosave.
+void
+runtime·gostartcall(Gobuf *gobuf, void (*fn)(void), void *ctxt)
+{
+	uintptr *sp;
+	
+	sp = (uintptr*)gobuf->sp;
+	*--sp = (uintptr)gobuf->pc;
+	gobuf->sp = (uintptr)sp;
+	gobuf->pc = (uintptr)fn;
+	gobuf->ctxt = ctxt;
+}
+
+// Called to rewind context saved during morestack back to beginning of function.
+// To help us, the linker emits a jmp back to the beginning right after the
+// call to morestack. We just have to decode and apply that jump.
+void
+runtime·rewindmorestack(Gobuf *gobuf)
+{
+	byte *pc;
+	
+	pc = (byte*)gobuf->pc;
+	if(pc[0] == 0xe9) { // jmp 4-byte offset
+		gobuf->pc = gobuf->pc + 5 + *(int32*)(pc+1);
+		return;
+	}
+	if(pc[0] == 0xeb) { // jmp 1-byte offset
+		gobuf->pc = gobuf->pc + 2 + *(int8*)(pc+1);
+		return;
+	}
+	runtime·printf("runtime: pc=%p %x %x %x %x %x\n", pc, pc[0], pc[1], pc[2], pc[3], pc[4]);
+	runtime·throw("runtime: misuse of rewindmorestack");
+}