diff --git a/src/pkg/runtime/Makefile b/src/pkg/runtime/Makefile
index 80bb521b31a..370a97309f6 100644
--- a/src/pkg/runtime/Makefile
+++ b/src/pkg/runtime/Makefile
@@ -62,6 +62,7 @@ OFILES=\
 	reflect.$O\
 	rune.$O\
 	runtime.$O\
+	runtime1.$O\
 	rt0.$O\
 	sema.$O\
 	signal.$O\
@@ -73,6 +74,7 @@ OFILES=\
 	thread.$O\
 	traceback.$O\
 	$(OFILES_$(GOARCH))\
+	$(OFILES_$(GOOS))\
 
 HFILES=\
 	cgocall.h\
@@ -84,6 +86,8 @@ HFILES=\
 	$(GOOS)/signals.h\
 	$(GOOS)/$(GOARCH)/defs.h\
 
+GOFILES+=$(GOFILES_$(GOOS))
+
 include ../../Make.pkg
 
 clean: clean-local
diff --git a/src/pkg/runtime/darwin/mem.c b/src/pkg/runtime/darwin/mem.c
new file mode 100644
index 00000000000..52e351a7d7e
--- /dev/null
+++ b/src/pkg/runtime/darwin/mem.c
@@ -0,0 +1,28 @@
+#include "runtime.h"
+#include "defs.h"
+#include "os.h"
+#include "malloc.h"
+
+void*
+SysAlloc(uintptr n)
+{
+	mstats.sys += n;
+	return runtime_mmap(nil, n, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_ANON|MAP_PRIVATE, -1, 0);
+}
+
+void
+SysUnused(void *v, uintptr n)
+{
+	USED(v);
+	USED(n);
+	// TODO(rsc): call madvise MADV_DONTNEED
+}
+
+void
+SysFree(void *v, uintptr n)
+{
+	USED(v);
+	USED(n);
+	// TODO(rsc): call munmap
+}
+
diff --git a/src/pkg/runtime/freebsd/mem.c b/src/pkg/runtime/freebsd/mem.c
new file mode 100644
index 00000000000..52e351a7d7e
--- /dev/null
+++ b/src/pkg/runtime/freebsd/mem.c
@@ -0,0 +1,28 @@
+#include "runtime.h"
+#include "defs.h"
+#include "os.h"
+#include "malloc.h"
+
+void*
+SysAlloc(uintptr n)
+{
+	mstats.sys += n;
+	return runtime_mmap(nil, n, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_ANON|MAP_PRIVATE, -1, 0);
+}
+
+void
+SysUnused(void *v, uintptr n)
+{
+	USED(v);
+	USED(n);
+	// TODO(rsc): call madvise MADV_DONTNEED
+}
+
+void
+SysFree(void *v, uintptr n)
+{
+	USED(v);
+	USED(n);
+	// TODO(rsc): call munmap
+}
+
diff --git a/src/pkg/runtime/linux/mem.c b/src/pkg/runtime/linux/mem.c
new file mode 100644
index 00000000000..7f837bd45ed
--- /dev/null
+++ b/src/pkg/runtime/linux/mem.c
@@ -0,0 +1,40 @@
+#include "runtime.h"
+#include "defs.h"
+#include "os.h"
+#include "malloc.h"
+
+void*
+SysAlloc(uintptr n)
+{
+	void *p;
+
+	mstats.sys += n;
+	p = runtime_mmap(nil, n, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_ANON|MAP_PRIVATE, -1, 0);
+	if(p < (void*)4096) {
+		if(p == (void*)EACCES) {
+			printf("mmap: access denied\n");
+			printf("If you're running SELinux, enable execmem for this process.\n");
+		} else {
+			printf("mmap: errno=%p\n", p);
+		}
+		exit(2);
+	}
+	return p;
+}
+
+void
+SysUnused(void *v, uintptr n)
+{
+	USED(v);
+	USED(n);
+	// TODO(rsc): call madvise MADV_DONTNEED
+}
+
+void
+SysFree(void *v, uintptr n)
+{
+	USED(v);
+	USED(n);
+	// TODO(rsc): call munmap
+}
+
diff --git a/src/pkg/runtime/malloc.cgo b/src/pkg/runtime/malloc.cgo
index a85c39d83d3..6acbac2eb09 100644
--- a/src/pkg/runtime/malloc.cgo
+++ b/src/pkg/runtime/malloc.cgo
@@ -205,41 +205,6 @@ mallocinit(void)
 	free(malloc(1));
 }
 
-void*
-SysAlloc(uintptr n)
-{
-	void *p;
-
-	mstats.sys += n;
-	p = runtime_mmap(nil, n, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_ANON|MAP_PRIVATE, -1, 0);
-	if(p < (void*)4096) {
-		if(p == (void*)EACCES) {
-			printf("mmap: access denied\n");
-			printf("If you're running SELinux, enable execmem for this process.\n");
-		} else {
-			printf("mmap: errno=%p\n", p);
-		}
-		exit(2);
-	}
-	return p;
-}
-
-void
-SysUnused(void *v, uintptr n)
-{
-	USED(v);
-	USED(n);
-	// TODO(rsc): call madvise MADV_DONTNEED
-}
-
-void
-SysFree(void *v, uintptr n)
-{
-	USED(v);
-	USED(n);
-	// TODO(rsc): call munmap
-}
-
 // Runtime stubs.
 
 void*
diff --git a/src/pkg/runtime/malloc.h b/src/pkg/runtime/malloc.h
index b3fa8e0dfb2..e07faf39f18 100644
--- a/src/pkg/runtime/malloc.h
+++ b/src/pkg/runtime/malloc.h
@@ -303,6 +303,10 @@ void*	mallocgc(uintptr size, uint32 flag, int32 dogc);
 int32	mlookup(void *v, byte **base, uintptr *size, uint32 **ref);
 void	gc(int32 force);
 
+void*	SysAlloc(uintptr);
+void	SysUnused(void*, uintptr);
+void	SysFree(void*, uintptr);
+
 enum
 {
 	RefcountOverhead = 4,	// one uint32 per object
diff --git a/src/pkg/runtime/mem.c b/src/pkg/runtime/mem.c
deleted file mode 100644
index f2796b7295e..00000000000
--- a/src/pkg/runtime/mem.c
+++ /dev/null
@@ -1,21 +0,0 @@
-// Copyright 2009 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 "runtime.h"
-#include "defs.h"
-
-// Stubs for memory management.
-// In a separate file so they can be overridden during testing of gc.
-
-enum
-{
-	NHUNK		= 20<<20,
-};
-
-void
-runtime·mal(uint32 n, uint8 *ret)
-{
-	ret = mal(n);
-	FLUSH(&ret);
-}
diff --git a/src/pkg/runtime/mingw/mem.c b/src/pkg/runtime/mingw/mem.c
new file mode 100644
index 00000000000..256ad9a7b4f
--- /dev/null
+++ b/src/pkg/runtime/mingw/mem.c
@@ -0,0 +1,29 @@
+// Copyright 2010 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 "runtime.h"
+#include "os.h"
+#include "defs.h"
+#include "malloc.h"
+
+void*
+SysAlloc(uintptr n)
+{
+	return stdcall(VirtualAlloc, nil, n, 0x3000, 0x40);
+}
+
+void
+SysUnused(void *v, uintptr n)
+{
+	USED(v);
+	USED(n);
+}
+
+void
+SysFree(void *v, uintptr n)
+{
+	USED(v);
+	USED(n);
+}
+
diff --git a/src/pkg/runtime/mingw/os.h b/src/pkg/runtime/mingw/os.h
index 8470cc0e587..3864dbf8f12 100644
--- a/src/pkg/runtime/mingw/os.h
+++ b/src/pkg/runtime/mingw/os.h
@@ -11,6 +11,8 @@ void *get_proc_addr(void *library, void *name);
 void *stdcall(void *fn, ...);
 void *stdcall_raw(void *fn, ...);
 
+extern void *VirtualAlloc;
+
 #define goargs mingw_goargs
 void mingw_goargs(void);
 
diff --git a/src/pkg/runtime/mingw/thread.c b/src/pkg/runtime/mingw/thread.c
index 979fd422473..89f33f8a4a1 100644
--- a/src/pkg/runtime/mingw/thread.c
+++ b/src/pkg/runtime/mingw/thread.c
@@ -15,13 +15,13 @@ void *ExitProcess;
 void *GetStdHandle;
 void *SetEvent;
 void *WriteFile;
+void *VirtualAlloc;
 
 static void *CreateEvent;
 static void *CreateThread;
 static void *GetModuleHandle;
 static void *GetProcAddress;
 static void *LoadLibraryEx;
-static void *VirtualAlloc;
 static void *WaitForSingleObject;
 
 static void*
@@ -148,14 +148,6 @@ write(int32 fd, void *buf, int32 n)
 	return written;
 }
 
-uint8*
-runtime_mmap(byte *addr, uint32 len, int32 prot,
-	int32 flags, int32 fd, uint32 off)
-{
-	USED(prot, flags, fd, off);
-	return stdcall(VirtualAlloc, addr, len, 0x3000, 0x40);
-}
-
 void*
 get_symdat_addr(void)
 {
diff --git a/src/pkg/runtime/runtime1.cgo b/src/pkg/runtime/runtime1.cgo
new file mode 100644
index 00000000000..7e5f323c12b
--- /dev/null
+++ b/src/pkg/runtime/runtime1.cgo
@@ -0,0 +1,11 @@
+// Copyright 2010 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
+#include "runtime.h"
+
+func mal(n uint32) (ret *uint8) {
+	ret = mal(n);
+}
+
diff --git a/src/pkg/runtime/string.cgo b/src/pkg/runtime/string.cgo
index 03b05618d81..c615768f3c6 100644
--- a/src/pkg/runtime/string.cgo
+++ b/src/pkg/runtime/string.cgo
@@ -31,7 +31,7 @@ findnullw(uint16 *s)
 	return l;
 }
 
-int32 maxstring;
+int32 maxstring = 256;
 
 String
 gostringsize(int32 l)