preparation for exec.

* syscall:
	add syscall.RawSyscall, which doesn't use sys.entersyscall/sys.exitsyscall
	add syscall.dup2
	add syscall.BytePtrPtr
	add syscall.Rusage, RusagePtr
	add syscall.F_GETFD, F_SETFD, FD_CLOEXEC

* runtime:
	clean up, correct signal handling.
	can now survive (continue running after) a signal.

R=r
DELTA=394  (286 added, 51 deleted, 57 changed)
OCL=20351
CL=20369

19 files changed, 349 insertions, 106 deletions

diff --git a/src/lib/syscall/Makefile b/src/lib/syscall/Makefile
index 8dd3d2fe0..5f613b9b4 100644
--- a/src/lib/syscall/Makefile
+++ b/src/lib/syscall/Makefile
@@ -5,7 +5,7 @@
 # DO NOT EDIT.  Automatically generated by gobuild.
 # gobuild -m errstr_darwin.go file_darwin.go socket_darwin.go\
 #    syscall_amd64_darwin.go time_amd64_darwin.go types_amd64_darwin.go\
-#    asm_amd64_darwin.s cast_amd64.s syscall.go >Makefile
+#    asm_amd64_darwin.s cast_amd64.s syscall.go signal_amd64_darwin.go >Makefile
 O=6
 GC=$(O)g
 CC=$(O)c -w
@@ -40,6 +40,7 @@ O1=\
 	asm_$(GOARCH)_$(GOOS).$O\
 	cast_$(GOARCH).$O\
 	syscall.$O\
+	signal_$(GOARCH)_$(GOOS).$O\
 
 O2=\
 	file_$(GOOS).$O\
@@ -49,7 +50,7 @@ O2=\
 syscall.a: a1 a2
 
 a1:	$(O1)
-	$(AR) grc syscall.a errstr_$(GOOS).$O syscall_$(GOARCH)_$(GOOS).$O types_$(GOARCH)_$(GOOS).$O asm_$(GOARCH)_$(GOOS).$O cast_$(GOARCH).$O syscall.$O
+	$(AR) grc syscall.a errstr_$(GOOS).$O syscall_$(GOARCH)_$(GOOS).$O types_$(GOARCH)_$(GOOS).$O asm_$(GOARCH)_$(GOOS).$O cast_$(GOARCH).$O syscall.$O signal_$(GOARCH)_$(GOOS).$O
 	rm -f $(O1)
 
 a2:	$(O2)
diff --git a/src/lib/syscall/asm_amd64_darwin.s b/src/lib/syscall/asm_amd64_darwin.s
index 3cf6aad83..dbc345c19 100644
--- a/src/lib/syscall/asm_amd64_darwin.s
+++ b/src/lib/syscall/asm_amd64_darwin.s
@@ -54,3 +54,21 @@ ok6:
 	MOVQ	$0, 80(SP)	// errno
 	CALL	sys·exitsyscall(SB)
 	RET
+
+TEXT syscall·RawSyscall(SB),7,$0
+	MOVQ	16(SP), DI
+	MOVQ	24(SP), SI
+	MOVQ	32(SP), DX
+	MOVQ	8(SP), AX	// syscall entry
+	ADDQ	$0x2000000, AX
+	SYSCALL
+	JCC	ok1
+	MOVQ	$-1, 40(SP)	// r1
+	MOVQ	$0, 48(SP)	// r2
+	MOVQ	AX, 56(SP)  // errno
+	RET
+ok1:
+	MOVQ	AX, 40(SP)	// r1
+	MOVQ	DX, 48(SP)	// r2
+	MOVQ	$0, 56(SP)	// errno
+	RET
diff --git a/src/lib/syscall/asm_amd64_linux.s b/src/lib/syscall/asm_amd64_linux.s
index e0c115387..2826c1b58 100644
--- a/src/lib/syscall/asm_amd64_linux.s
+++ b/src/lib/syscall/asm_amd64_linux.s
@@ -57,3 +57,22 @@ ok6:
 	MOVQ	$0, 80(SP)	// errno
 	CALL	sys·exitsyscall(SB)
 	RET
+
+TEXT syscall·RawSyscall(SB),7,$0
+	MOVQ	16(SP), DI
+	MOVQ	24(SP), SI
+	MOVQ	32(SP), DX
+	MOVQ	8(SP), AX	// syscall entry
+	SYSCALL
+	CMPQ	AX, $0xfffffffffffff001
+	JLS	ok1
+	MOVQ	$-1, 40(SP)	// r1
+	MOVQ	$0, 48(SP)	// r2
+	NEGQ	AX
+	MOVQ	AX, 56(SP)  // errno
+	RET
+ok1:
+	MOVQ	AX, 40(SP)	// r1
+	MOVQ	DX, 48(SP)	// r2
+	MOVQ	$0, 56(SP)	// errno
+	RET
diff --git a/src/lib/syscall/cast_amd64.s b/src/lib/syscall/cast_amd64.s
index c2205b990..3eaa5e70e 100644
--- a/src/lib/syscall/cast_amd64.s
+++ b/src/lib/syscall/cast_amd64.s
@@ -8,6 +8,11 @@ TEXT	syscall·BytePtr(SB),7,$-8
 	MOVQ	AX, 16(SP)
 	RET
 
+TEXT	syscall·BytePtrPtr(SB),7,$-8
+	MOVQ	8(SP), AX
+	MOVQ	AX, 16(SP)
+	RET
+
 TEXT	syscall·Int32Ptr(SB),7,$-8
 	MOVQ	8(SP), AX
 	MOVQ	AX, 16(SP)
@@ -53,6 +58,11 @@ TEXT	syscall·TimevalPtr(SB),7,$-8
 	MOVQ	AX, 16(SP)
 	RET
 
+TEXT	syscall·RusagePtr(SB),7,$-8
+	MOVQ	8(SP), AX
+	MOVQ	AX, 16(SP)
+	RET
+
 TEXT	syscall·SockaddrToSockaddrInet4(SB),7,$-8
 	MOVQ	8(SP), AX
 	MOVQ	AX, 16(SP)
diff --git a/src/lib/syscall/file_darwin.go b/src/lib/syscall/file_darwin.go
index 2cb78ffe5..0c6a38a3a 100644
--- a/src/lib/syscall/file_darwin.go
+++ b/src/lib/syscall/file_darwin.go
@@ -94,3 +94,9 @@ export func mkdir(name string, perm int64) (ret int64, errno int64) {
 	r1, r2, err := Syscall(SYS_MKDIR, BytePtr(&namebuf[0]), perm, 0);
 	return r1, err;
 }
+
+export func dup2(fd1, fd2 int64) (ret int64, errno int64) {
+	r1, r2, err := Syscall(SYS_DUP2, fd1, fd2, 0);
+	return r1, err;
+}
+
diff --git a/src/lib/syscall/file_linux.go b/src/lib/syscall/file_linux.go
index af7728a6b..3fa2588af 100644
--- a/src/lib/syscall/file_linux.go
+++ b/src/lib/syscall/file_linux.go
@@ -95,3 +95,9 @@ export func mkdir(name string, perm int64) (ret int64, errno int64) {
 	r1, r2, err := Syscall(SYS_MKDIR, BytePtr(&namebuf[0]), perm, 0);
 	return r1, err;
 }
+
+export func dup2(fd1, fd2 int64) (ret int64, errno int64) {
+	r1, r2, err := Syscall(SYS_DUP2, fd1, fd2, 0);
+	return r1, err;
+}
+
diff --git a/src/lib/syscall/syscall.go b/src/lib/syscall/syscall.go
index 6420684ce..eb1ad36a6 100644
--- a/src/lib/syscall/syscall.go
+++ b/src/lib/syscall/syscall.go
@@ -10,10 +10,12 @@ package syscall
 
 export func Syscall(trap int64, a1, a2, a3 int64) (r1, r2, err int64);
 export func Syscall6(trap int64, a1, a2, a3, a4, a5, a6 int64) (r1, r2, err int64);
+export func RawSyscall(trap int64, a1, a2, a3 int64) (r1, r2, err int64);
 
 export func BytePtr(b *byte) int64;
 export func Int32Ptr(p *int32) int64;
 export func Int64Ptr(p *int64) int64;
+export func BytePtrPtr(b **byte) int64;
 
 /*
  * Used to convert file names to byte arrays for passing to kernel,
diff --git a/src/lib/syscall/types_amd64_darwin.go b/src/lib/syscall/types_amd64_darwin.go
index bb715ccb1..2c98fd521 100644
--- a/src/lib/syscall/types_amd64_darwin.go
+++ b/src/lib/syscall/types_amd64_darwin.go
@@ -23,6 +23,29 @@ export type Timeval struct {
 export func TimevalPtr(t *Timeval) int64;
 
 
+// Processes
+
+export type Rusage struct {
+	utime	Timeval;
+	stime	Timeval;
+	maxrss	int64;
+	ixrss	int64;
+	idrss	int64;
+	isrss	int64;
+	minflt	int64;
+	majflt	int64;
+	nswap	int64;
+	inblock	int64;
+	oublock	int64;
+	msgsnd	int64;
+	msgrcv	int64;
+	nsignals	int64;
+	nvcsw	int64;
+	nivcsw	int64;
+}
+export func RusagePtr(r *Rusage) int64;
+
+
 // Files
 
 export const (
@@ -38,8 +61,13 @@ export const (
 	O_SYNC = 0x80;
 	O_TRUNC = 0x400;
 
+	F_GETFD = 1;
+	F_SETFD = 2;
+
 	F_GETFL = 3;
 	F_SETFL = 4;
+
+	FD_CLOEXEC = 1;
 )
 
 export type Stat struct {
diff --git a/src/lib/syscall/types_amd64_linux.go b/src/lib/syscall/types_amd64_linux.go
index 534827e3e..ccca2671c 100644
--- a/src/lib/syscall/types_amd64_linux.go
+++ b/src/lib/syscall/types_amd64_linux.go
@@ -23,6 +23,29 @@ export type Timeval struct {
 export func TimevalPtr(t *Timeval) int64;
 
 
+// Processes
+
+export type Rusage struct {
+	utime	Timeval;
+	stime	Timeval;
+	maxrss	int64;
+	ixrss	int64;
+	idrss	int64;
+	isrss	int64;
+	minflt	int64;
+	majflt	int64;
+	nswap	int64;
+	inblock	int64;
+	oublock	int64;
+	msgsnd	int64;
+	msgrcv	int64;
+	nsignals	int64;
+	nvcsw	int64;
+	nivcsw	int64;
+}
+export func RusagePtr(r *Rusage) int64;
+
+
 // Files
 
 export const (
@@ -38,8 +61,13 @@ export const (
 	O_SYNC = 0x1000;
 	O_TRUNC = 0x200;
 
+	F_GETFD = 1;
+	F_SETFD = 2;
+
 	F_GETFL = 3;
 	F_SETFL = 4;
+
+	FD_CLOEXEC = 1;
 )
 
 export type Stat struct {
diff --git a/src/runtime/rt1_amd64_darwin.c b/src/runtime/rt1_amd64_darwin.c
index 82999b89f..7bd7c78fd 100644
--- a/src/runtime/rt1_amd64_darwin.c
+++ b/src/runtime/rt1_amd64_darwin.c
@@ -4,7 +4,7 @@
 
 #include "runtime.h"
 #include "amd64_darwin.h"
-#include "signals.h"
+#include "signals_darwin.h"
 
 typedef uint64 __uint64_t;
 
@@ -100,15 +100,14 @@ static _STRUCT_X86_FLOAT_STATE64 *get___fs(_STRUCT_MCONTEXT64 *ptr) {
 
 /*
  * This assembler routine takes the args from registers, puts them on the stack,
- * and calls sighandler().
+ * and calls the registered handler.
  */
-extern void sigtramp();
-
+extern void sigtramp(void);
 /*
  * Rudimentary reverse-engineered definition of signal interface.
  * You'd think it would be documented.
  */
-typedef struct siginfo {
+struct siginfo {
 	int32	si_signo;		/* signal number */
 	int32	si_errno;		/* errno association */
 	int32	si_code;		/* signal code */
@@ -117,21 +116,17 @@ typedef struct siginfo {
 	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;
+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, siginfo *info, void *context)
+sighandler(int32 sig, struct siginfo *info, void *context)
 {
 	if(panicking)	// traceback already printed
 		sys·exit(2);
@@ -159,15 +154,17 @@ sighandler(int32 sig, siginfo *info, void *context)
 	sys·exit(2);
 }
 
+void
+sigignore(int32, struct siginfo*, void*)
+{
+}
+
 struct stack_t {
 	byte *sp;
 	int64 size;
 	int32 flags;
 };
 
-sigaction a;
-extern void sigtramp(void);
-
 void
 signalstack(byte *p, int32 n)
 {
@@ -179,21 +176,39 @@ signalstack(byte *p, int32 n)
 	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;
-
-	a.u.sa_sigaction = (void*)sigtramp;
-	a.sa_flags |= 0x41;  /* SA_SIGINFO, SA_ONSTACK */
-	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);
+	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
diff --git a/src/runtime/rt1_amd64_linux.c b/src/runtime/rt1_amd64_linux.c
index ff9245a20..30a041066 100644
--- a/src/runtime/rt1_amd64_linux.c
+++ b/src/runtime/rt1_amd64_linux.c
@@ -4,7 +4,7 @@
 
 #include "runtime.h"
 #include "amd64_linux.h"
-#include "signals.h"
+#include "signals_linux.h"
 
 /* From /usr/include/asm-x86_64/sigcontext.h */
 struct _fpstate {
@@ -105,37 +105,34 @@ print_sigcontext(struct sigcontext *sc)
  * This assembler routine takes the args from registers, puts them on the stack,
  * and calls sighandler().
  */
-extern void sigtramp();
+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 */
-typedef struct siginfo {
+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 */
-} siginfo;
-
+};
 
-/* From /usr/include/bits/sigaction.h */
-/* (gri) Is this correct? See e.g. /usr/include/asm-x86_64/signal.h */
-typedef struct sigaction {
- 	union {
-		void (*sa_handler)(int32);
-		void (*sa_sigaction)(int32, siginfo *, void *);
-	} u;				/* signal handler */
-	uint8 sa_mask[128];		/* signal mask to apply. 128? are they KIDDING? */
-	int32 sa_flags;			/* see signal options below */
-	void (*sa_restorer) (void);	/* unused here; needed to return from trap? */
-} sigaction;
+// 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, siginfo* info, void** context)
+sighandler(int32 sig, struct siginfo* info, void** context)
 {
 	if(panicking)	// traceback already printed
 		sys·exit(2);
@@ -182,21 +179,37 @@ signalstack(byte *p, int32 n)
 	sigaltstack(&st, nil);
 }
 
-static sigaction a;
+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;
-	a.u.sa_sigaction = (void*)sigtramp;
-	a.sa_flags = 0x08000004;  /* SA_ONSTACK,  SA_SIGINFO */
-	for(i=0; i<sizeof(a.sa_mask); i++)
-		a.sa_mask[i] = 0xFF;
-
-	for(i = 0; i<NSIG; i++)
-		if(sigtab[i].catch){
-			sys·rt_sigaction(i, &a, (void*)0, 8);
+	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/runtime.h b/src/runtime/runtime.h
index 4b282c126..e37786e4f 100644
--- a/src/runtime/runtime.h
+++ b/src/runtime/runtime.h
@@ -48,6 +48,7 @@ typedef	union	Note		Note;
 typedef	struct	Stktop		Stktop;
 typedef	struct	String		*string;
 typedef	struct	Usema		Usema;
+typedef	struct	SigTab	SigTab;
 
 /*
  * per cpu declaration
@@ -179,9 +180,15 @@ struct	Alg
 };
 struct	SigTab
 {
-	int32	catch;
+	int32	flags;
 	int8	*name;
 };
+enum
+{
+	SigCatch = 1<<0,
+	SigIgnore = 1<<1,
+	SigRestart = 1<<2,
+};
 
 // (will be) shared with go; edit ../cmd/6g/sys.go too.
 // should move out of sys.go eventually.
@@ -305,8 +312,6 @@ uint8*	sys·mmap(byte*, uint32, int32, int32, int32, uint32);
 void	sys·memclr(byte*, uint32);
 void	sys·setcallerpc(void*, void*);
 void*	sys·getcallerpc(void*);
-void	sys·sigaction(int64, void*, void*);
-void	sys·rt_sigaction(int64, void*, void*, uint64);
 
 /*
  * runtime go-called
diff --git a/src/runtime/signals.h b/src/runtime/signals.h
deleted file mode 100644
index 475f6752b..000000000
--- a/src/runtime/signals.h
+++ /dev/null
@@ -1,40 +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.
-
-
-static struct SigTab sigtab[] = {
-	/* 0 */	0, "SIGNONE: no trap",
-	/* 1 */	0, "SIGHUP: terminal line hangup",
-	/* 2 */	0, "SIGINT: interrupt program",
-	/* 3 */	1, "SIGQUIT: quit program",
-	/* 4 */	1, "SIGILL: illegal instruction",
-	/* 5 */	1, "SIGTRAP: trace trap",	/* used by panic and array out of bounds, etc. */
-	/* 6 */	1, "SIGABRT: abort program",
-	/* 7 */	1, "SIGEMT: emulate instruction executed",
-	/* 8 */	1, "SIGFPE: floating-point exception",
-	/* 9 */	0, "SIGKILL: kill program",
-	/* 10 */	1, "SIGBUS: bus error",
-	/* 11 */	1, "SIGSEGV: segmentation violation",
-	/* 12 */	1, "SIGSYS: non-existent system call invoked",
-	/* 13 */	0, "SIGPIPE: write on a pipe with no reader",
-	/* 14 */	0, "SIGALRM: real-time timer expired",
-	/* 15 */	0, "SIGTERM: software termination signal",
-	/* 16 */	0, "SIGURG: urgent condition present on socket",
-	/* 17 */	0, "SIGSTOP: stop",
-	/* 18 */	0, "SIGTSTP: stop signal generated from keyboard",
-	/* 19 */	0, "SIGCONT: continue after stop",
-	/* 20 */	0, "SIGCHLD: child status has changed",
-	/* 21 */	0, "SIGTTIN: background read attempted from control terminal",
-	/* 22 */	0, "SIGTTOU: background write attempted to control terminal",
-	/* 23 */	0, "SIGIO: I/O is possible on a descriptor",
-	/* 24 */	0, "SIGXCPU: cpu time limit exceeded",
-	/* 25 */	0, "SIGXFSZ: file size limit exceeded",
-	/* 26 */	0, "SIGVTALRM: virtual time alarm",
-	/* 27 */	0, "SIGPROF: profiling timer alarm",
-	/* 28 */	0, "SIGWINCH: Window size change",
-	/* 29 */	0, "SIGINFO: status request from keyboard",
-	/* 30 */	0, "SIGUSR1: User defined signal 1",
-	/* 31 */	0, "SIGUSR2: User defined signal 2",
-};
-#define	NSIG 32
diff --git a/src/runtime/signals_darwin.h b/src/runtime/signals_darwin.h
new file mode 100644
index 000000000..c4d586049
--- /dev/null
+++ b/src/runtime/signals_darwin.h
@@ -0,0 +1,48 @@
+// 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.
+
+
+#define C SigCatch
+#define I SigIgnore
+#define R SigRestart
+
+static SigTab sigtab[] = {
+	/* 0 */	0, "SIGNONE: no trap",
+	/* 1 */	0, "SIGHUP: terminal line hangup",
+	/* 2 */	0, "SIGINT: interrupt",
+	/* 3 */	C, "SIGQUIT: quit",
+	/* 4 */	C, "SIGILL: illegal instruction",
+	/* 5 */	C, "SIGTRAP: trace trap",	/* used by panic and array out of bounds, etc. */
+	/* 6 */	C, "SIGABRT: abort",
+	/* 7 */	C, "SIGEMT: emulate instruction executed",
+	/* 8 */	C, "SIGFPE: floating-point exception",
+	/* 9 */	0, "SIGKILL: kill",
+	/* 10 */	C, "SIGBUS: bus error",
+	/* 11 */	C, "SIGSEGV: segmentation violation",
+	/* 12 */	C, "SIGSYS: bad system call",
+	/* 13 */	0, "SIGPIPE: write to broken pipe",
+	/* 14 */	0, "SIGALRM: alarm clock",
+	/* 15 */	0, "SIGTERM: termination",
+	/* 16 */	0, "SIGURG: urgent condition on socket",
+	/* 17 */	0, "SIGSTOP: stop",
+	/* 18 */	0, "SIGTSTP: keyboard stop",
+	/* 19 */	0, "SIGCONT: continue after stop",
+	/* 20 */	I+R, "SIGCHLD: child status has changed",
+	/* 21 */	0, "SIGTTIN: background read from tty",
+	/* 22 */	0, "SIGTTOU: background write to tty",
+	/* 23 */	0, "SIGIO: i/o now possible",
+	/* 24 */	0, "SIGXCPU: cpu limit exceeded",
+	/* 25 */	0, "SIGXFSZ: file size limit exceeded",
+	/* 26 */	0, "SIGVTALRM: virtual alarm clock",
+	/* 27 */	0, "SIGPROF: profiling alarm clock",
+	/* 28 */	I+R, "SIGWINCH: window size change",
+	/* 29 */	0, "SIGINFO: status request from keyboard",
+	/* 30 */	0, "SIGUSR1: user-defined signal 1",
+	/* 31 */	0, "SIGUSR2: user-defined signal 2",
+};
+#undef C
+#undef I
+#undef R
+
+#define	NSIG 32
diff --git a/src/runtime/signals_linux.h b/src/runtime/signals_linux.h
new file mode 100644
index 000000000..9e770e92f
--- /dev/null
+++ b/src/runtime/signals_linux.h
@@ -0,0 +1,48 @@
+// 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.
+
+
+#define C SigCatch
+#define I SigIgnore
+#define R SigRestart
+
+static SigTab sigtab[] = {
+	/* 0 */	0, "SIGNONE: no trap",
+	/* 1 */	0, "SIGHUP: terminal line hangup",
+	/* 2 */	0, "SIGINT: interrupt",
+	/* 3 */	C, "SIGQUIT: quit",
+	/* 4 */	C, "SIGILL: illegal instruction",
+	/* 5 */	C, "SIGTRAP: trace trap",
+	/* 6 */	C, "SIGABRT: abort",
+	/* 7 */	C, "SIGBUS: bus error",
+	/* 8 */	C, "SIGFPE: floating-point exception",
+	/* 9 */	0, "SIGKILL: kill",
+	/* 10 */	0, "SIGUSR1: user-defined signal 1",
+	/* 11 */	C, "SIGSEGV: segmentation violation",
+	/* 12 */	0, "SIGUSR2: user-defined signal 2",
+	/* 13 */	0, "SIGPIPE: write to broken pipe",
+	/* 14 */	0, "SIGALRM: alarm clock",
+	/* 15 */	0, "SIGTERM: termination",
+	/* 16 */	0, "SIGSTKFLT: stack fault",
+	/* 17 */	I+R, "SIGCHLD: child status has changed",
+	/* 18 */	0, "SIGCONT: continue",
+	/* 19 */	0, "SIGSTOP: stop, unblockable",
+	/* 20 */	0, "SIGTSTP: keyboard stop",
+	/* 21 */	0, "SIGTTIN: background read from tty",
+	/* 22 */	0, "SIGTTOU: background write to tty",
+	/* 23 */	0, "SIGURG: urgent condition on socket",
+	/* 24 */	0, "SIGXCPU: cpu limit exceeded",
+	/* 25 */	0, "SIGXFSZ: file size limit exceeded",
+	/* 26 */	0, "SIGVTALRM: virtual alarm clock",
+	/* 27 */	0, "SIGPROF: profiling alarm clock",
+	/* 28 */	I+R, "SIGWINCH: window size change",
+	/* 29 */	0, "SIGIO: i/o now possible",
+	/* 30 */	0, "SIGPWR: power failure restart",
+	/* 31 */	C, "SIGSYS: bad system call",
+};
+#undef C
+#undef I
+#undef R
+
+#define	NSIG 32
diff --git a/src/runtime/sys_amd64_darwin.s b/src/runtime/sys_amd64_darwin.s
index 6110362a7..a276576d9 100644
--- a/src/runtime/sys_amd64_darwin.s
+++ b/src/runtime/sys_amd64_darwin.s
@@ -73,7 +73,7 @@ TEXT	write(SB),7,$-8
 	SYSCALL
 	RET
 
-TEXT	sys·sigaction(SB),7,$-8
+TEXT	sigaction(SB),7,$-8
 	MOVL	8(SP), DI		// arg 1 sig
 	MOVQ	16(SP), SI		// arg 2 act
 	MOVQ	24(SP), DX		// arg 3 oact
@@ -85,13 +85,19 @@ TEXT	sys·sigaction(SB),7,$-8
 	CALL	notok(SB)
 	RET
 
-TEXT sigtramp(SB),7,$24
+TEXT sigtramp(SB),7,$40
 	MOVQ	32(R14), R15	// g = m->gsignal
 	MOVL	DX,0(SP)
 	MOVQ	CX,8(SP)
 	MOVQ	R8,16(SP)
-	CALL	sighandler(SB)
-	RET
+	MOVQ	R8, 24(SP)	// save ucontext
+	MOVQ	SI, 32(SP)	// save infostyle
+	CALL	DI
+	MOVL	$(0x2000000+184), AX	// sigreturn(ucontext, infostyle)
+	MOVQ	24(SP), DI	// saved ucontext
+	MOVQ	32(SP), SI	// saved infostyle
+	SYSCALL
+	INT $3	// not reached
 
 TEXT	sys·mmap(SB),7,$-8
 	MOVQ	8(SP), DI		// arg 1 addr
diff --git a/src/runtime/sys_amd64_linux.s b/src/runtime/sys_amd64_linux.s
index 581bf15ab..d385bb43e 100644
--- a/src/runtime/sys_amd64_linux.s
+++ b/src/runtime/sys_amd64_linux.s
@@ -63,7 +63,7 @@ TEXT	sys·write(SB),7,$0-24
 	SYSCALL
 	RET
 
-TEXT	sys·rt_sigaction(SB),7,$0-32
+TEXT	rt_sigaction(SB),7,$0-32
 	MOVL	8(SP), DI
 	MOVQ	16(SP), SI
 	MOVQ	24(SP), DX
@@ -80,6 +80,14 @@ TEXT	sigtramp(SB),7,$24-16
 	CALL	sighandler(SB)
 	RET
 
+TEXT sigignore(SB),7,$0
+	RET
+
+TEXT sigreturn(SB),7,$0
+	MOVL	$15, AX	// rt_sigreturn
+	SYSCALL
+	INT $3	// not reached
+
 TEXT	sys·mmap(SB),7,$0-32
 	MOVQ	8(SP), DI
 	MOVQ	$0, SI
diff --git a/test/golden.out b/test/golden.out
index 24f56b63a..4489d69cb 100644
--- a/test/golden.out
+++ b/test/golden.out
@@ -56,6 +56,9 @@ BUG: errchk: command succeeded unexpectedly:  6g ./method2.go
 -9223372036854775808
 9223372036854775807
 
+=========== ./sigchld.go
+survived SIGCHLD
+
 =========== ./turing.go
 Hello World!
 
diff --git a/test/sigchld.go b/test/sigchld.go
new file mode 100644
index 000000000..417b833c7
--- /dev/null
+++ b/test/sigchld.go
@@ -0,0 +1,19 @@
+// $G $D/$F.go && $L $F.$A && ./$A.out
+
+// 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.
+
+package main
+
+import "syscall"
+
+func getpid() int64 {
+	r1, r2, err := syscall.Syscall(syscall.SYS_GETPID, 0, 0, 0);
+	return r1;
+}
+
+func main() {
+	syscall.Syscall(syscall.SYS_KILL, getpid(), syscall.SIGCHLD, 0);
+	println("survived SIGCHLD");
+}