diff --git a/src/runtime/rt0_amd64_darwin.s b/src/runtime/rt0_amd64_darwin.s
index 824a602554e..16592b90ae2 100644
--- a/src/runtime/rt0_amd64_darwin.s
+++ b/src/runtime/rt0_amd64_darwin.s
@@ -52,6 +52,25 @@ TEXT	sys_write(SB),1,$-8
 	CALL	notok(SB)
 	RET
 
+TEXT	sys_sigaction(SB),1,$-8
+	MOVL	8(SP), DI		// arg 1 sig
+	MOVQ	16(SP), SI		// arg 2 act
+	MOVQ	24(SP), DX		// arg 3 oact
+	MOVQ	24(SP), CX		// arg 3 oact
+	MOVQ	24(SP), R10		// arg 3 oact
+	MOVL	$(0x2000000+46), AX	// syscall entry
+	SYSCALL
+	JCC	2(PC)
+	CALL	notok(SB)
+	RET
+
+TEXT sigtramp(SB),1,$-24
+	MOVL	DX,0(SP)
+	MOVQ	CX,8(SP)
+	MOVQ	R8,16(SP)
+	CALL	sighandler(SB)
+	RET
+
 TEXT	sys_breakpoint(SB),1,$-8
 	BYTE	$0xcc
 	RET
diff --git a/src/runtime/rt1_amd64_darwin.c b/src/runtime/rt1_amd64_darwin.c
index fe92d0b292f..c24b40fae5b 100644
--- a/src/runtime/rt1_amd64_darwin.c
+++ b/src/runtime/rt1_amd64_darwin.c
@@ -3,9 +3,75 @@
 // license that can be found in the LICENSE file.
 
 #include "runtime.h"
+#include "signals.h"
+
+/*
+ * This assembler routine takes the args from registers, puts them on the stack,
+ * and calls sighandler().
+ */
+extern void sigtramp();
+
+/*
+ * Rudimentary reverse-engineered definition of signal interface.
+ * You'd think it would be documented.
+ */
+typedef 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 */
+} siginfo;
+
+typedef struct  sigaction {
+ 	union {
+		void    (*sa_handler)(int32);
+		void    (*sa_sigaction)(int32, siginfo *, void *);
+	} u;		     /* signal handler */
+	void	(*sa_trampoline)(void);	/* kernel callback point; calls sighandler() */
+	uint8 sa_mask[4];		     /* signal mask to apply */
+	int32     sa_flags;		     /* see signal options below */
+} sigaction;
+
+void
+sighandler(int32 sig, siginfo* info, void** context) {
+	int32 i;
+
+	if(sig < 0 || sig >= NSIG){
+		prints("Signal ");
+		sys_printint(sig);
+	}else{
+		prints(sigtab[sig].name);
+	}
+	prints("\nFaulting address: 0x");
+	sys_printpointer(info->si_addr);
+	prints("\nPC: 0x");
+	sys_printpointer(((void**)((&sig)+1))[22]);
+	prints("\nSP: 0x");
+	sys_printpointer(((void**)((&sig)+1))[13]);
+	prints("\n");
+	traceback(((void**)((&sig)+1))[22], ((void**)((&sig)+1))[13]);	/* empirically discovered locations */
+	sys_exit(2);
+}
+
+sigaction a;
+extern void sigtramp(void);
 
 void
 initsig(void)
 {
-	/* no signal handler on mac yet */
+	int32 i;
+	a.u.sa_sigaction = (void*)sigtramp;
+	a.sa_flags |= 0x40;  /* SA_SIGINFO */
+	for(i=0; i<sizeof(a.sa_mask); i++)
+		a.sa_mask[i] = 0xFF;
+	a.sa_trampoline = sigtramp;
+
+	for(i = 0; i <NSIG; i++)
+		if(sigtab[i].catch){
+			sys_sigaction(i, &a, (void*)0);
+		}
 }