diff --git a/src/pkg/runtime/debug/garbage.go b/src/pkg/runtime/debug/garbage.go
index edb3643871e..30994f21962 100644
--- a/src/pkg/runtime/debug/garbage.go
+++ b/src/pkg/runtime/debug/garbage.go
@@ -19,14 +19,6 @@ type GCStats struct {
 	PauseQuantiles []time.Duration
 }
 
-// Implemented in package runtime.
-func readGCStats(*[]time.Duration)
-func enableGC(bool) bool
-func setGCPercent(int) int
-func freeOSMemory()
-func setMaxStack(int) int
-func setMaxThreads(int) int
-
 // ReadGCStats reads statistics about garbage collection into stats.
 // The number of entries in the pause history is system-dependent;
 // stats.Pause slice will be reused if large enough, reallocated otherwise.
@@ -91,9 +83,9 @@ func (x byDuration) Less(i, j int) bool { return x[i] < x[j] }
 // at startup, or 100 if the variable is not set.
 // A negative percentage disables garbage collection.
 func SetGCPercent(percent int) int {
-	old := setGCPercent(percent)
+	old := setGCPercent(int32(percent))
 	runtime.GC()
-	return old
+	return int(old)
 }
 
 // FreeOSMemory forces a garbage collection followed by an
@@ -145,7 +137,9 @@ func SetMaxThreads(threads int) int {
 // that the runtime trigger only a panic, not a crash.
 // SetPanicOnFault applies only to the current goroutine.
 // It returns the previous setting.
-func SetPanicOnFault(enabled bool) bool
+func SetPanicOnFault(enabled bool) bool {
+	return setPanicOnFault(enabled)
+}
 
 // WriteHeapDump writes a description of the heap and the objects in
 // it to the given file descriptor.
diff --git a/src/pkg/runtime/debug/stubs.go b/src/pkg/runtime/debug/stubs.go
new file mode 100644
index 00000000000..8fba6cf34b7
--- /dev/null
+++ b/src/pkg/runtime/debug/stubs.go
@@ -0,0 +1,20 @@
+// Copyright 2014 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.
+
+package debug
+
+import (
+	"time"
+)
+
+// Uses assembly to call corresponding runtime-internal functions.
+func setMaxStack(int) int
+func setGCPercent(int32) int32
+func setPanicOnFault(bool) bool
+func setMaxThreads(int) int
+
+// Implemented in package runtime.
+func readGCStats(*[]time.Duration)
+func enableGC(bool) bool
+func freeOSMemory()
diff --git a/src/pkg/runtime/debug/stubs.s b/src/pkg/runtime/debug/stubs.s
new file mode 100644
index 00000000000..d56274f2dc7
--- /dev/null
+++ b/src/pkg/runtime/debug/stubs.s
@@ -0,0 +1,21 @@
+// Copyright 2014 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.
+
+#include "textflag.h"
+
+#ifdef GOARCH_arm
+#define JMP B
+#endif
+
+TEXT ·setMaxStack(SB),NOSPLIT,$0-0
+  JMP runtime·setMaxStack(SB)
+
+TEXT ·setGCPercent(SB),NOSPLIT,$0-0
+  JMP runtime·setGCPercent(SB)
+
+TEXT ·setPanicOnFault(SB),NOSPLIT,$0-0
+  JMP runtime·setPanicOnFault(SB)
+
+TEXT ·setMaxThreads(SB),NOSPLIT,$0-0
+  JMP runtime·setMaxThreads(SB)
diff --git a/src/pkg/runtime/malloc.h b/src/pkg/runtime/malloc.h
index 48ec0260051..fb51a9e5dd2 100644
--- a/src/pkg/runtime/malloc.h
+++ b/src/pkg/runtime/malloc.h
@@ -586,7 +586,7 @@ void	runtime·gc_m_ptr(Eface*);
 void	runtime·gc_g_ptr(Eface*);
 void	runtime·gc_itab_ptr(Eface*);
 
-int32	runtime·setgcpercent(int32);
+void  runtime·setgcpercent_m(void);
 
 // Value we use to mark dead pointers when GODEBUG=gcdead=1.
 #define PoisonGC ((uintptr)0xf969696969696969ULL)
diff --git a/src/pkg/runtime/mgc0.c b/src/pkg/runtime/mgc0.c
index 2a476fae4d9..ded41510c4b 100644
--- a/src/pkg/runtime/mgc0.c
+++ b/src/pkg/runtime/mgc0.c
@@ -1621,17 +1621,21 @@ runtime∕debug·readGCStats(Slice *pauses)
 	pauses->len = n+3;
 }
 
-int32
-runtime·setgcpercent(int32 in) {
+void
+runtime·setgcpercent_m(void) {
+	int32 in;
 	int32 out;
 
+	in = (int32)(intptr)g->m->scalararg[0];
+
 	runtime·lock(&runtime·mheap.lock);
 	out = runtime·gcpercent;
 	if(in < 0)
 		in = -1;
 	runtime·gcpercent = in;
 	runtime·unlock(&runtime·mheap.lock);
-	return out;
+
+	g->m->scalararg[0] = (uintptr)(intptr)out;
 }
 
 static void
diff --git a/src/pkg/runtime/proc.c b/src/pkg/runtime/proc.c
index 722f44bb1b0..44757a8afd2 100644
--- a/src/pkg/runtime/proc.c
+++ b/src/pkg/runtime/proc.c
@@ -3199,17 +3199,21 @@ runtime·topofstack(Func *f)
 		(runtime·externalthreadhandlerp != 0 && f->entry == runtime·externalthreadhandlerp);
 }
 
-int32
-runtime·setmaxthreads(int32 in)
+void
+runtime·setmaxthreads_m(void)
 {
+	int32 in;
 	int32 out;
 
+	in = g->m->scalararg[0];
+
 	runtime·lock(&runtime·sched.lock);
 	out = runtime·sched.maxmcount;
 	runtime·sched.maxmcount = in;
 	checkmcount();
 	runtime·unlock(&runtime·sched.lock);
-	return out;
+
+	g->m->scalararg[0] = out;
 }
 
 static int8 experiment[] = GOEXPERIMENT; // defined in zaexperiment.h
diff --git a/src/pkg/runtime/rdebug.go b/src/pkg/runtime/rdebug.go
new file mode 100644
index 00000000000..3df73ce660f
--- /dev/null
+++ b/src/pkg/runtime/rdebug.go
@@ -0,0 +1,42 @@
+// Copyright 2014 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.
+
+package runtime
+
+func setMaxStack(in int) (out int) {
+	out = int(maxstacksize)
+	maxstacksize = uint(in)
+	return out
+}
+
+func setGCPercent(in int32) (out int32) {
+	mp := acquirem()
+	mp.scalararg[0] = uint(int(in))
+	onM(&setgcpercent_m)
+	out = int32(int(mp.scalararg[0]))
+	releasem(mp)
+	return out
+}
+
+func setPanicOnFault(newb bool) (old bool) {
+	new := uint8(0)
+	if newb {
+		new = 1
+	}
+
+	mp := acquirem()
+	old = mp.curg.paniconfault == 1
+	mp.curg.paniconfault = new
+	releasem(mp)
+	return old
+}
+
+func setMaxThreads(in int) (out int) {
+	mp := acquirem()
+	mp.scalararg[0] = uint(in)
+	onM(&setmaxthreads_m)
+	out = int(mp.scalararg[0])
+	releasem(mp)
+	return out
+}
diff --git a/src/pkg/runtime/rdebug.goc b/src/pkg/runtime/rdebug.goc
deleted file mode 100644
index 042b30ace9b..00000000000
--- a/src/pkg/runtime/rdebug.goc
+++ /dev/null
@@ -1,27 +0,0 @@
-// 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.
-
-package runtime∕debug
-#include "runtime.h"
-#include "arch_GOARCH.h"
-#include "malloc.h"
-#include "stack.h"
-
-func setMaxStack(in int) (out int) {
-	out = runtime·maxstacksize;
-	runtime·maxstacksize = in;
-}
-
-func setGCPercent(in int) (out int) {
-	out = runtime·setgcpercent(in);
-}
-
-func setMaxThreads(in int) (out int) {
-	out = runtime·setmaxthreads(in);
-}
-
-func SetPanicOnFault(enabled bool) (old bool) {
-	old = g->paniconfault;
-	g->paniconfault = enabled;
-}
diff --git a/src/pkg/runtime/runtime.h b/src/pkg/runtime/runtime.h
index f12e50cbfb1..c96fc814170 100644
--- a/src/pkg/runtime/runtime.h
+++ b/src/pkg/runtime/runtime.h
@@ -981,7 +981,7 @@ void	runtime·crash(void);
 void	runtime·parsedebugvars(void);
 void	_rt0_go(void);
 void*	runtime·funcdata(Func*, int32);
-int32	runtime·setmaxthreads(int32);
+void	runtime·setmaxthreads_m(void);
 G*	runtime·timejump(void);
 void	runtime·iterate_itabs(void (*callback)(Itab*));
 void	runtime·iterate_finq(void (*callback)(FuncVal*, byte*, uintptr, Type*, PtrType*));
diff --git a/src/pkg/runtime/stubs.go b/src/pkg/runtime/stubs.go
index 76f6faf53a3..37e768a4ec9 100644
--- a/src/pkg/runtime/stubs.go
+++ b/src/pkg/runtime/stubs.go
@@ -84,6 +84,8 @@ var (
 	unrollgcprog_m,
 	unrollgcproginplace_m,
 	gosched_m,
+	setgcpercent_m,
+	setmaxthreads_m,
 	ready_m,
 	park_m,
 	blockevent_m,