diff -r de64b19b480e libgo/runtime/proc.c
--- a/libgo/runtime/proc.c	Thu Mar 06 16:00:18 2014 -0800
+++ b/libgo/runtime/proc.c	Thu Mar 06 20:55:49 2014 -0800
@@ -1857,10 +1857,30 @@
 // entersyscall is going to return immediately after.
 
 void runtime_entersyscall(void) __attribute__ ((no_split_stack));
+static void doentersyscall(void) __attribute__ ((no_split_stack, noinline));
 
 void
 runtime_entersyscall()
 {
+	// Save the registers in the g structure so that any pointers
+	// held in registers will be seen by the garbage collector.
+	getcontext(&g->gcregs);
+
+	// Do the work in a separate function, so that this function
+	// doesn't save any registers on its own stack.  If this
+	// function does save any registers, we might store the wrong
+	// value in the call to getcontext.
+	//
+	// FIXME: This assumes that we do not need to save any
+	// callee-saved registers to access the TLS variable g.  We
+	// don't want to put the ucontext_t on the stack because it is
+	// large and we can not split the stack here.
+	doentersyscall();
+}
+
+static void
+doentersyscall()
+{
 	// Disable preemption because during this function g is in Gsyscall status,
 	// but can have inconsistent g->sched, do not let GC observe it.
 	m->locks++;
@@ -1878,10 +1898,6 @@
 	}
 #endif
 
-	// Save the registers in the g structure so that any pointers
-	// held in registers will be seen by the garbage collector.
-	getcontext(&g->gcregs);
-
 	g->status = Gsyscall;
 
 	if(runtime_atomicload(&runtime_sched.sysmonwait)) {  // TODO: fast atomic