diff --git a/src/runtime/Makefile b/src/runtime/Makefile
index 8d3e431eca..d281a90f6f 100644
--- a/src/runtime/Makefile
+++ b/src/runtime/Makefile
@@ -32,12 +32,13 @@ OFILES=\
 	rune.$O\
 	runtime.$O\
 	rt0.$O\
-	rt1.$O\
 	sema.$O\
 	sema_go.$O\
+	signal.$O\
 	string.$O\
 	symtab.$O\
 	sys.$O\
+	thread.$O\
 	traceback.$O\
 
 OS_H=$(GOARCH)_$(GOOS).h
diff --git a/src/runtime/darwin/signal.c b/src/runtime/darwin/signal.c
new file mode 100644
index 0000000000..937f402e4b
--- /dev/null
+++ b/src/runtime/darwin/signal.c
@@ -0,0 +1,258 @@
+// 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"
+#include "signals.h"
+
+typedef uint64 __uint64_t;
+
+/* From /usr/include/mach/i386/_structs.h */
+#define	_STRUCT_X86_THREAD_STATE64	struct __darwin_x86_thread_state64
+_STRUCT_X86_THREAD_STATE64
+{
+	__uint64_t	__rax;
+	__uint64_t	__rbx;
+	__uint64_t	__rcx;
+	__uint64_t	__rdx;
+	__uint64_t	__rdi;
+	__uint64_t	__rsi;
+	__uint64_t	__rbp;
+	__uint64_t	__rsp;
+	__uint64_t	__r8;
+	__uint64_t	__r9;
+	__uint64_t	__r10;
+	__uint64_t	__r11;
+	__uint64_t	__r12;
+	__uint64_t	__r13;
+	__uint64_t	__r14;
+	__uint64_t	__r15;
+	__uint64_t	__rip;
+	__uint64_t	__rflags;
+	__uint64_t	__cs;
+	__uint64_t	__fs;
+	__uint64_t	__gs;
+};
+
+
+void
+print_thread_state(_STRUCT_X86_THREAD_STATE64* ss)
+{
+	prints("\nrax     ");  sys·printhex(ss->__rax);
+	prints("\nrbx     ");  sys·printhex(ss->__rbx);
+	prints("\nrcx     ");  sys·printhex(ss->__rcx);
+	prints("\nrdx     ");  sys·printhex(ss->__rdx);
+	prints("\nrdi     ");  sys·printhex(ss->__rdi);
+	prints("\nrsi     ");  sys·printhex(ss->__rsi);
+	prints("\nrbp     ");  sys·printhex(ss->__rbp);
+	prints("\nrsp     ");  sys·printhex(ss->__rsp);
+	prints("\nr8      ");  sys·printhex(ss->__r8 );
+	prints("\nr9      ");  sys·printhex(ss->__r9 );
+	prints("\nr10     ");  sys·printhex(ss->__r10);
+	prints("\nr11     ");  sys·printhex(ss->__r11);
+	prints("\nr12     ");  sys·printhex(ss->__r12);
+	prints("\nr13     ");  sys·printhex(ss->__r13);
+	prints("\nr14     ");  sys·printhex(ss->__r14);
+	prints("\nr15     ");  sys·printhex(ss->__r15);
+	prints("\nrip     ");  sys·printhex(ss->__rip);
+	prints("\nrflags  ");  sys·printhex(ss->__rflags);
+	prints("\ncs      ");  sys·printhex(ss->__cs);
+	prints("\nfs      ");  sys·printhex(ss->__fs);
+	prints("\ngs      ");  sys·printhex(ss->__gs);
+	prints("\n");
+}
+
+
+/* Code generated via: g++ -m64 gen_signals_support.cc && a.out */
+
+static void *adr_at(void *ptr, int32 offs) {
+  return (void *)((uint8 *)ptr + offs);
+}
+
+static void *ptr_at(void *ptr, int32 offs) {
+  return *(void **)((uint8 *)ptr + offs);
+}
+
+typedef void ucontext_t;
+typedef void _STRUCT_MCONTEXT64;
+typedef void _STRUCT_X86_EXCEPTION_STATE64;
+typedef void _STRUCT_X86_FLOAT_STATE64;
+
+static _STRUCT_MCONTEXT64 *get_uc_mcontext(ucontext_t *ptr) {
+  return (_STRUCT_MCONTEXT64 *)ptr_at(ptr, 48);
+}
+
+static _STRUCT_X86_EXCEPTION_STATE64 *get___es(_STRUCT_MCONTEXT64 *ptr) {
+  return (_STRUCT_X86_EXCEPTION_STATE64 *)adr_at(ptr, 0);
+}
+
+static _STRUCT_X86_THREAD_STATE64 *get___ss(_STRUCT_MCONTEXT64 *ptr) {
+  return (_STRUCT_X86_THREAD_STATE64 *)adr_at(ptr, 16);
+}
+
+static _STRUCT_X86_FLOAT_STATE64 *get___fs(_STRUCT_MCONTEXT64 *ptr) {
+  return (_STRUCT_X86_FLOAT_STATE64 *)adr_at(ptr, 184);
+}
+
+/* End of generated code */
+
+
+/*
+ * This assembler routine takes the args from registers, puts them on the stack,
+ * and calls the registered handler.
+ */
+extern void sigtramp(void);
+/*
+ * Rudimentary reverse-engineered definition of signal interface.
+ * You'd think it would be documented.
+ */
+struct siginfo {
+	int32	si_signo;		/* signal number */
+	int32	si_errno;		/* errno association */
+	int32	si_code;		/* signal code */
+	int32	si_pid;			/* sending process */
+	int32	si_uid;			/* sender's ruid */
+	int32	si_status;		/* exit value */
+	void	*si_addr;		/* faulting address */
+	/* more stuff here */
+};
+
+struct sigaction {
+	void (*sa_handler)(int32, struct siginfo*, void*);	// actual handler
+	void (*sa_trampoline)(void);	// assembly trampoline
+	uint32 sa_mask;		// signal mask during handler
+	int32 sa_flags;			// flags below
+};
+
+void
+sighandler(int32 sig, struct siginfo *info, void *context)
+{
+	if(panicking)	// traceback already printed
+		sys_Exit(2);
+	panicking = 1;
+
+        _STRUCT_MCONTEXT64 *uc_mcontext = get_uc_mcontext(context);
+        _STRUCT_X86_THREAD_STATE64 *ss = get___ss(uc_mcontext);
+
+	if(sig < 0 || sig >= NSIG){
+		prints("Signal ");
+		sys·printint(sig);
+	}else{
+		prints(sigtab[sig].name);
+	}
+
+	prints("\nFaulting address: ");  sys·printpointer(info->si_addr);
+	prints("\npc: ");  sys·printhex(ss->__rip);
+	prints("\n\n");
+
+	if(gotraceback()){
+		traceback((void *)ss->__rip, (void *)ss->__rsp, (void*)ss->__r15);
+		tracebackothers((void*)ss->__r15);
+		print_thread_state(ss);
+	}
+
+	sys_Exit(2);
+}
+
+void
+sigignore(int32, struct siginfo*, void*)
+{
+}
+
+struct stack_t {
+	byte *sp;
+	int64 size;
+	int32 flags;
+};
+
+void
+signalstack(byte *p, int32 n)
+{
+	struct stack_t st;
+
+	st.sp = p;
+	st.size = n;
+	st.flags = 0;
+	sigaltstack(&st, nil);
+}
+
+void	sigaction(int64, void*, void*);
+
+enum {
+	SA_SIGINFO = 0x40,
+	SA_RESTART = 0x02,
+	SA_ONSTACK = 0x01,
+	SA_USERTRAMP = 0x100,
+	SA_64REGSET = 0x200,
+};
+
+void
+initsig(void)
+{
+	int32 i;
+	static struct sigaction sa;
+
+	sa.sa_flags |= SA_SIGINFO|SA_ONSTACK;
+	sa.sa_mask = 0; // 0xFFFFFFFFU;
+	sa.sa_trampoline = sigtramp;
+	for(i = 0; i<NSIG; i++) {
+		if(sigtab[i].flags) {
+			if(sigtab[i].flags & SigCatch) {
+				sa.sa_handler = sighandler;
+			} else {
+				sa.sa_handler = sigignore;
+			}
+			if(sigtab[i].flags & SigRestart)
+				sa.sa_flags |= SA_RESTART;
+			else
+				sa.sa_flags &= ~SA_RESTART;
+			sigaction(i, &sa, nil);
+		}
+	}
+}
+
+static void
+unimplemented(int8 *name)
+{
+	prints(name);
+	prints(" not implemented\n");
+	*(int32*)1231 = 1231;
+}
+
+// Thread-safe allocation of a semaphore.
+// Psema points at a kernel semaphore key.
+// It starts out zero, meaning no semaphore.
+// Fill it in, being careful of others calling initsema
+// simultaneously.
+static void
+initsema(uint32 *psema)
+{
+	uint32 sema;
+
+	if(*psema != 0)	// already have one
+		return;
+
+	sema = mach_semcreate();
+	if(!cas(psema, 0, sema)){
+		// Someone else filled it in.  Use theirs.
+		mach_semdestroy(sema);
+		return;
+	}
+}
+
+
+// Atomic add and return new value.
+static uint32
+xadd(uint32 volatile *val, int32 delta)
+{
+	uint32 oval, nval;
+
+	for(;;){
+		oval = *val;
+		nval = oval + delta;
+		if(cas(val, oval, nval))
+			return nval;
+	}
+}
+
diff --git a/src/runtime/darwin/amd64/rt1.c b/src/runtime/darwin/thread.c
similarity index 68%
rename from src/runtime/darwin/amd64/rt1.c
rename to src/runtime/darwin/thread.c
index e9b5c20b2a..06bbde5ab4 100644
--- a/src/runtime/darwin/amd64/rt1.c
+++ b/src/runtime/darwin/thread.c
@@ -4,213 +4,6 @@
 
 #include "runtime.h"
 #include "defs.h"
-#include "signals.h"
-
-typedef uint64 __uint64_t;
-
-/* From /usr/include/mach/i386/_structs.h */
-#define	_STRUCT_X86_THREAD_STATE64	struct __darwin_x86_thread_state64
-_STRUCT_X86_THREAD_STATE64
-{
-	__uint64_t	__rax;
-	__uint64_t	__rbx;
-	__uint64_t	__rcx;
-	__uint64_t	__rdx;
-	__uint64_t	__rdi;
-	__uint64_t	__rsi;
-	__uint64_t	__rbp;
-	__uint64_t	__rsp;
-	__uint64_t	__r8;
-	__uint64_t	__r9;
-	__uint64_t	__r10;
-	__uint64_t	__r11;
-	__uint64_t	__r12;
-	__uint64_t	__r13;
-	__uint64_t	__r14;
-	__uint64_t	__r15;
-	__uint64_t	__rip;
-	__uint64_t	__rflags;
-	__uint64_t	__cs;
-	__uint64_t	__fs;
-	__uint64_t	__gs;
-};
-
-
-void
-print_thread_state(_STRUCT_X86_THREAD_STATE64* ss)
-{
-	prints("\nrax     ");  sys·printhex(ss->__rax);
-	prints("\nrbx     ");  sys·printhex(ss->__rbx);
-	prints("\nrcx     ");  sys·printhex(ss->__rcx);
-	prints("\nrdx     ");  sys·printhex(ss->__rdx);
-	prints("\nrdi     ");  sys·printhex(ss->__rdi);
-	prints("\nrsi     ");  sys·printhex(ss->__rsi);
-	prints("\nrbp     ");  sys·printhex(ss->__rbp);
-	prints("\nrsp     ");  sys·printhex(ss->__rsp);
-	prints("\nr8      ");  sys·printhex(ss->__r8 );
-	prints("\nr9      ");  sys·printhex(ss->__r9 );
-	prints("\nr10     ");  sys·printhex(ss->__r10);
-	prints("\nr11     ");  sys·printhex(ss->__r11);
-	prints("\nr12     ");  sys·printhex(ss->__r12);
-	prints("\nr13     ");  sys·printhex(ss->__r13);
-	prints("\nr14     ");  sys·printhex(ss->__r14);
-	prints("\nr15     ");  sys·printhex(ss->__r15);
-	prints("\nrip     ");  sys·printhex(ss->__rip);
-	prints("\nrflags  ");  sys·printhex(ss->__rflags);
-	prints("\ncs      ");  sys·printhex(ss->__cs);
-	prints("\nfs      ");  sys·printhex(ss->__fs);
-	prints("\ngs      ");  sys·printhex(ss->__gs);
-	prints("\n");
-}
-
-
-/* Code generated via: g++ -m64 gen_signals_support.cc && a.out */
-
-static void *adr_at(void *ptr, int32 offs) {
-  return (void *)((uint8 *)ptr + offs);
-}
-
-static void *ptr_at(void *ptr, int32 offs) {
-  return *(void **)((uint8 *)ptr + offs);
-}
-
-typedef void ucontext_t;
-typedef void _STRUCT_MCONTEXT64;
-typedef void _STRUCT_X86_EXCEPTION_STATE64;
-typedef void _STRUCT_X86_FLOAT_STATE64;
-
-static _STRUCT_MCONTEXT64 *get_uc_mcontext(ucontext_t *ptr) {
-  return (_STRUCT_MCONTEXT64 *)ptr_at(ptr, 48);
-}
-
-static _STRUCT_X86_EXCEPTION_STATE64 *get___es(_STRUCT_MCONTEXT64 *ptr) {
-  return (_STRUCT_X86_EXCEPTION_STATE64 *)adr_at(ptr, 0);
-}
-
-static _STRUCT_X86_THREAD_STATE64 *get___ss(_STRUCT_MCONTEXT64 *ptr) {
-  return (_STRUCT_X86_THREAD_STATE64 *)adr_at(ptr, 16);
-}
-
-static _STRUCT_X86_FLOAT_STATE64 *get___fs(_STRUCT_MCONTEXT64 *ptr) {
-  return (_STRUCT_X86_FLOAT_STATE64 *)adr_at(ptr, 184);
-}
-
-/* End of generated code */
-
-
-/*
- * This assembler routine takes the args from registers, puts them on the stack,
- * and calls the registered handler.
- */
-extern void sigtramp(void);
-/*
- * Rudimentary reverse-engineered definition of signal interface.
- * You'd think it would be documented.
- */
-struct siginfo {
-	int32	si_signo;		/* signal number */
-	int32	si_errno;		/* errno association */
-	int32	si_code;		/* signal code */
-	int32	si_pid;			/* sending process */
-	int32	si_uid;			/* sender's ruid */
-	int32	si_status;		/* exit value */
-	void	*si_addr;		/* faulting address */
-	/* more stuff here */
-};
-
-struct sigaction {
-	void (*sa_handler)(int32, struct siginfo*, void*);	// actual handler
-	void (*sa_trampoline)(void);	// assembly trampoline
-	uint32 sa_mask;		// signal mask during handler
-	int32 sa_flags;			// flags below
-};
-
-void
-sighandler(int32 sig, struct siginfo *info, void *context)
-{
-	if(panicking)	// traceback already printed
-		sys_Exit(2);
-	panicking = 1;
-
-        _STRUCT_MCONTEXT64 *uc_mcontext = get_uc_mcontext(context);
-        _STRUCT_X86_THREAD_STATE64 *ss = get___ss(uc_mcontext);
-
-	if(sig < 0 || sig >= NSIG){
-		prints("Signal ");
-		sys·printint(sig);
-	}else{
-		prints(sigtab[sig].name);
-	}
-
-	prints("\nFaulting address: ");  sys·printpointer(info->si_addr);
-	prints("\npc: ");  sys·printhex(ss->__rip);
-	prints("\n\n");
-
-	if(gotraceback()){
-		traceback((void *)ss->__rip, (void *)ss->__rsp, (void*)ss->__r15);
-		tracebackothers((void*)ss->__r15);
-		print_thread_state(ss);
-	}
-
-	sys_Exit(2);
-}
-
-void
-sigignore(int32, struct siginfo*, void*)
-{
-}
-
-struct stack_t {
-	byte *sp;
-	int64 size;
-	int32 flags;
-};
-
-void
-signalstack(byte *p, int32 n)
-{
-	struct stack_t st;
-
-	st.sp = p;
-	st.size = n;
-	st.flags = 0;
-	sigaltstack(&st, nil);
-}
-
-void	sigaction(int64, void*, void*);
-
-enum {
-	SA_SIGINFO = 0x40,
-	SA_RESTART = 0x02,
-	SA_ONSTACK = 0x01,
-	SA_USERTRAMP = 0x100,
-	SA_64REGSET = 0x200,
-};
-
-void
-initsig(void)
-{
-	int32 i;
-	static struct sigaction sa;
-
-	sa.sa_flags |= SA_SIGINFO|SA_ONSTACK;
-	sa.sa_mask = 0; // 0xFFFFFFFFU;
-	sa.sa_trampoline = sigtramp;
-	for(i = 0; i<NSIG; i++) {
-		if(sigtab[i].flags) {
-			if(sigtab[i].flags & SigCatch) {
-				sa.sa_handler = sighandler;
-			} else {
-				sa.sa_handler = sigignore;
-			}
-			if(sigtab[i].flags & SigRestart)
-				sa.sa_flags |= SA_RESTART;
-			else
-				sa.sa_flags &= ~SA_RESTART;
-			sigaction(i, &sa, nil);
-		}
-	}
-}
 
 static void
 unimplemented(int8 *name)
diff --git a/src/runtime/linux/signal.c b/src/runtime/linux/signal.c
new file mode 100644
index 0000000000..5805f35abf
--- /dev/null
+++ b/src/runtime/linux/signal.c
@@ -0,0 +1,214 @@
+// 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"
+#include "signals.h"
+
+/* From /usr/include/asm-x86_64/sigcontext.h */
+struct _fpstate {
+  uint16   cwd;
+  uint16   swd;
+  uint16   twd;    /* Note this is not the same as the 32bit/x87/FSAVE twd */
+  uint16   fop;
+  uint64   rip;
+  uint32   rdp;
+  uint32   mxcsr;
+  uint32   mxcsr_mask;
+  uint32   st_space[32];   /* 8*16 bytes for each FP-reg */
+  uint32   xmm_space[64];  /* 16*16 bytes for each XMM-reg  */
+  uint32   reserved2[24];
+};
+
+struct sigcontext {
+  uint64 r8;
+  uint64 r9;
+  uint64 r10;
+  uint64 r11;
+  uint64 r12;
+  uint64 r13;
+  uint64 r14;
+  uint64 r15;
+  uint64 rdi;
+  uint64 rsi;
+  uint64 rbp;
+  uint64 rbx;
+  uint64 rdx;
+  uint64 rax;
+  uint64 rcx;
+  uint64 rsp;
+  uint64 rip;
+  uint64 eflags;           /* RFLAGS */
+  uint16 cs;
+  uint16 gs;
+  uint16 fs;
+  uint16 __pad0;
+  uint64 err;
+  uint64 trapno;
+  uint64 oldmask;
+  uint64 cr2;
+  struct _fpstate *fpstate;       /* zero when no FPU context */
+  uint64 reserved1[8];
+};
+
+
+/* From /usr/include/asm-x86_64/signal.h */
+typedef struct sigaltstack {
+	void /*__user*/ *ss_sp;
+	int32 ss_flags;
+	uint64 ss_size;
+} stack_t;
+
+typedef uint64 sigset_t;
+
+
+/* From /usr/include/asm-x86_64/ucontext.h */
+struct ucontext {
+  uint64            uc_flags;
+  struct ucontext  *uc_link;
+  stack_t           uc_stack;
+  struct sigcontext uc_mcontext;
+  sigset_t          uc_sigmask;   /* mask last for extensibility */
+};
+
+
+void
+print_sigcontext(struct sigcontext *sc)
+{
+	prints("\nrax     ");  sys·printhex(sc->rax);
+	prints("\nrbx     ");  sys·printhex(sc->rbx);
+	prints("\nrcx     ");  sys·printhex(sc->rcx);
+	prints("\nrdx     ");  sys·printhex(sc->rdx);
+	prints("\nrdi     ");  sys·printhex(sc->rdi);
+	prints("\nrsi     ");  sys·printhex(sc->rsi);
+	prints("\nrbp     ");  sys·printhex(sc->rbp);
+	prints("\nrsp     ");  sys·printhex(sc->rsp);
+	prints("\nr8      ");  sys·printhex(sc->r8 );
+	prints("\nr9      ");  sys·printhex(sc->r9 );
+	prints("\nr10     ");  sys·printhex(sc->r10);
+	prints("\nr11     ");  sys·printhex(sc->r11);
+	prints("\nr12     ");  sys·printhex(sc->r12);
+	prints("\nr13     ");  sys·printhex(sc->r13);
+	prints("\nr14     ");  sys·printhex(sc->r14);
+	prints("\nr15     ");  sys·printhex(sc->r15);
+	prints("\nrip     ");  sys·printhex(sc->rip);
+	prints("\nrflags  ");  sys·printhex(sc->eflags);
+	prints("\ncs      ");  sys·printhex(sc->cs);
+	prints("\nfs      ");  sys·printhex(sc->fs);
+	prints("\ngs      ");  sys·printhex(sc->gs);
+	prints("\n");
+}
+
+
+/*
+ * This assembler routine takes the args from registers, puts them on the stack,
+ * and calls sighandler().
+ */
+extern void sigtramp(void);
+extern void sigignore(void);	// just returns
+extern void sigreturn(void);	// calls sigreturn
+
+/*
+ * Rudimentary reverse-engineered definition of signal interface.
+ * You'd think it would be documented.
+ */
+/* From /usr/include/bits/siginfo.h */
+struct siginfo {
+	int32	si_signo;		/* signal number */
+	int32	si_errno;		/* errno association */
+	int32	si_code;		/* signal code */
+	int32	si_status;		/* exit value */
+	void	*si_addr;		/* faulting address */
+	/* more stuff here */
+};
+
+// This is a struct sigaction from /usr/include/asm/signal.h
+struct sigaction {
+	void (*sa_handler)(int32, struct siginfo*, void*);
+	uint64 sa_flags;
+	void (*sa_restorer)(void);
+	uint64 sa_mask;
+};
+
+void
+sighandler(int32 sig, struct siginfo* info, void** context)
+{
+	if(panicking)	// traceback already printed
+		sys_Exit(2);
+
+	struct sigcontext *sc = &(((struct ucontext *)context)->uc_mcontext);
+
+	if(sig < 0 || sig >= NSIG){
+		prints("Signal ");
+		sys·printint(sig);
+	}else{
+		prints(sigtab[sig].name);
+	}
+
+	prints("\nFaulting address: ");  sys·printpointer(info->si_addr);
+	prints("\npc: ");  sys·printhex(sc->rip);
+	prints("\n\n");
+
+	if(gotraceback()){
+		traceback((void *)sc->rip, (void *)sc->rsp, (void *)sc->r15);
+		tracebackothers((void*)sc->r15);
+		print_sigcontext(sc);
+	}
+
+	sys·Breakpoint();
+	sys_Exit(2);
+}
+
+struct stack_t {
+	void *sp;
+	int32 flags;
+	int32 pad;
+	int64 size;
+};
+
+void
+signalstack(byte *p, int32 n)
+{
+	struct stack_t st;
+
+	st.sp = p;
+	st.size = n;
+	st.pad = 0;
+	st.flags = 0;
+	sigaltstack(&st, nil);
+}
+
+void	rt_sigaction(int64, void*, void*, uint64);
+
+enum {
+	SA_RESTART = 0x10000000,
+	SA_ONSTACK = 0x08000000,
+	SA_RESTORER = 0x04000000,
+	SA_SIGINFO = 0x00000004,
+};
+
+void
+initsig(void)
+{
+	static struct sigaction sa;
+
+	int32 i;
+	sa.sa_flags = SA_ONSTACK | SA_SIGINFO | SA_RESTORER;
+	sa.sa_mask = 0xFFFFFFFFFFFFFFFFULL;
+	sa.sa_restorer = (void*)sigreturn;
+	for(i = 0; i<NSIG; i++) {
+		if(sigtab[i].flags) {
+			if(sigtab[i].flags & SigCatch)
+				sa.sa_handler = (void*)sigtramp;
+			else
+				sa.sa_handler = (void*)sigignore;
+			if(sigtab[i].flags & SigRestart)
+				sa.sa_flags |= SA_RESTART;
+			else
+				sa.sa_flags &= ~SA_RESTART;
+			rt_sigaction(i, &sa, nil, 8);
+		}
+	}
+}
+
diff --git a/src/runtime/linux/amd64/rt1.c b/src/runtime/linux/thread.c
similarity index 54%
rename from src/runtime/linux/amd64/rt1.c
rename to src/runtime/linux/thread.c
index 5b3e458094..df24b0712d 100644
--- a/src/runtime/linux/amd64/rt1.c
+++ b/src/runtime/linux/thread.c
@@ -3,215 +3,8 @@
 // license that can be found in the LICENSE file.
 
 #include "runtime.h"
-#include "amd64_linux.h"
-#include "signals_linux.h"
-
-/* From /usr/include/asm-x86_64/sigcontext.h */
-struct _fpstate {
-  uint16   cwd;
-  uint16   swd;
-  uint16   twd;    /* Note this is not the same as the 32bit/x87/FSAVE twd */
-  uint16   fop;
-  uint64   rip;
-  uint32   rdp;
-  uint32   mxcsr;
-  uint32   mxcsr_mask;
-  uint32   st_space[32];   /* 8*16 bytes for each FP-reg */
-  uint32   xmm_space[64];  /* 16*16 bytes for each XMM-reg  */
-  uint32   reserved2[24];
-};
-
-struct sigcontext {
-  uint64 r8;
-  uint64 r9;
-  uint64 r10;
-  uint64 r11;
-  uint64 r12;
-  uint64 r13;
-  uint64 r14;
-  uint64 r15;
-  uint64 rdi;
-  uint64 rsi;
-  uint64 rbp;
-  uint64 rbx;
-  uint64 rdx;
-  uint64 rax;
-  uint64 rcx;
-  uint64 rsp;
-  uint64 rip;
-  uint64 eflags;           /* RFLAGS */
-  uint16 cs;
-  uint16 gs;
-  uint16 fs;
-  uint16 __pad0;
-  uint64 err;
-  uint64 trapno;
-  uint64 oldmask;
-  uint64 cr2;
-  struct _fpstate *fpstate;       /* zero when no FPU context */
-  uint64 reserved1[8];
-};
-
-
-/* From /usr/include/asm-x86_64/signal.h */
-typedef struct sigaltstack {
-	void /*__user*/ *ss_sp;
-	int32 ss_flags;
-	uint64 ss_size;
-} stack_t;
-
-typedef uint64 sigset_t;
-
-
-/* From /usr/include/asm-x86_64/ucontext.h */
-struct ucontext {
-  uint64            uc_flags;
-  struct ucontext  *uc_link;
-  stack_t           uc_stack;
-  struct sigcontext uc_mcontext;
-  sigset_t          uc_sigmask;   /* mask last for extensibility */
-};
-
-
-void
-print_sigcontext(struct sigcontext *sc)
-{
-	prints("\nrax     ");  sys·printhex(sc->rax);
-	prints("\nrbx     ");  sys·printhex(sc->rbx);
-	prints("\nrcx     ");  sys·printhex(sc->rcx);
-	prints("\nrdx     ");  sys·printhex(sc->rdx);
-	prints("\nrdi     ");  sys·printhex(sc->rdi);
-	prints("\nrsi     ");  sys·printhex(sc->rsi);
-	prints("\nrbp     ");  sys·printhex(sc->rbp);
-	prints("\nrsp     ");  sys·printhex(sc->rsp);
-	prints("\nr8      ");  sys·printhex(sc->r8 );
-	prints("\nr9      ");  sys·printhex(sc->r9 );
-	prints("\nr10     ");  sys·printhex(sc->r10);
-	prints("\nr11     ");  sys·printhex(sc->r11);
-	prints("\nr12     ");  sys·printhex(sc->r12);
-	prints("\nr13     ");  sys·printhex(sc->r13);
-	prints("\nr14     ");  sys·printhex(sc->r14);
-	prints("\nr15     ");  sys·printhex(sc->r15);
-	prints("\nrip     ");  sys·printhex(sc->rip);
-	prints("\nrflags  ");  sys·printhex(sc->eflags);
-	prints("\ncs      ");  sys·printhex(sc->cs);
-	prints("\nfs      ");  sys·printhex(sc->fs);
-	prints("\ngs      ");  sys·printhex(sc->gs);
-	prints("\n");
-}
-
-
-/*
- * This assembler routine takes the args from registers, puts them on the stack,
- * and calls sighandler().
- */
-extern void sigtramp(void);
-extern void sigignore(void);	// just returns
-extern void sigreturn(void);	// calls sigreturn
-
-/*
- * Rudimentary reverse-engineered definition of signal interface.
- * You'd think it would be documented.
- */
-/* From /usr/include/bits/siginfo.h */
-struct siginfo {
-	int32	si_signo;		/* signal number */
-	int32	si_errno;		/* errno association */
-	int32	si_code;		/* signal code */
-	int32	si_status;		/* exit value */
-	void	*si_addr;		/* faulting address */
-	/* more stuff here */
-};
-
-// This is a struct sigaction from /usr/include/asm/signal.h
-struct sigaction {
-	void (*sa_handler)(int32, struct siginfo*, void*);
-	uint64 sa_flags;
-	void (*sa_restorer)(void);
-	uint64 sa_mask;
-};
-
-void
-sighandler(int32 sig, struct siginfo* info, void** context)
-{
-	if(panicking)	// traceback already printed
-		sys_Exit(2);
-
-	struct sigcontext *sc = &(((struct ucontext *)context)->uc_mcontext);
-
-	if(sig < 0 || sig >= NSIG){
-		prints("Signal ");
-		sys·printint(sig);
-	}else{
-		prints(sigtab[sig].name);
-	}
-
-	prints("\nFaulting address: ");  sys·printpointer(info->si_addr);
-	prints("\npc: ");  sys·printhex(sc->rip);
-	prints("\n\n");
-
-	if(gotraceback()){
-		traceback((void *)sc->rip, (void *)sc->rsp, (void *)sc->r15);
-		tracebackothers((void*)sc->r15);
-		print_sigcontext(sc);
-	}
-
-	sys·Breakpoint();
-	sys_Exit(2);
-}
-
-struct stack_t {
-	void *sp;
-	int32 flags;
-	int32 pad;
-	int64 size;
-};
-
-void
-signalstack(byte *p, int32 n)
-{
-	struct stack_t st;
-
-	st.sp = p;
-	st.size = n;
-	st.pad = 0;
-	st.flags = 0;
-	sigaltstack(&st, nil);
-}
-
-void	rt_sigaction(int64, void*, void*, uint64);
-
-enum {
-	SA_RESTART = 0x10000000,
-	SA_ONSTACK = 0x08000000,
-	SA_RESTORER = 0x04000000,
-	SA_SIGINFO = 0x00000004,
-};
-
-void
-initsig(void)
-{
-	static struct sigaction sa;
-
-	int32 i;
-	sa.sa_flags = SA_ONSTACK | SA_SIGINFO | SA_RESTORER;
-	sa.sa_mask = 0xFFFFFFFFFFFFFFFFULL;
-	sa.sa_restorer = (void*)sigreturn;
-	for(i = 0; i<NSIG; i++) {
-		if(sigtab[i].flags) {
-			if(sigtab[i].flags & SigCatch)
-				sa.sa_handler = (void*)sigtramp;
-			else
-				sa.sa_handler = (void*)sigignore;
-			if(sigtab[i].flags & SigRestart)
-				sa.sa_flags |= SA_RESTART;
-			else
-				sa.sa_flags &= ~SA_RESTART;
-			rt_sigaction(i, &sa, nil, 8);
-		}
-	}
-}
-
+#include "defs.h"
+#include "signals.h"
 
 // Linux futex.
 //
diff --git a/src/runtime/sys_types.h b/src/runtime/sys_types.h
deleted file mode 100644
index cffdaa9f68..0000000000
--- a/src/runtime/sys_types.h
+++ /dev/null
@@ -1,13 +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.
-
-#ifdef amd64_linux
-	#include "amd64_linux.h"
-#else
-	#ifdef amd64_darwin
-		#include "amd64_darwin.h"
-	#else
-		You_need_to_write_the_syscall_header
-	#endif
-#endif