diff --git a/sys/include/libc.h b/sys/include/libc.h
index 079c7eb..bb0756f 100644
--- a/sys/include/libc.h
+++ b/sys/include/libc.h
@@ -355,7 +355,7 @@ extern	int32_t	jehanne_strtol(const char*, char**, int);
 extern	uint32_t	jehanne_strtoul(const char*, char**, int);
 extern	int64_t	jehanne_strtoll(const char*, char**, int);
 extern	uint64_t	jehanne_strtoull(const char*, char**, int);
-extern	void	jehanne_sysfatal(const char*, ...);
+extern	void	jehanne_sysfatal(const char*, ...) __attribute__ ((noreturn));
 extern	void	jehanne_syslog(int, const char*, const char*, ...);
 extern	int32_t	jehanne_time(int32_t*);
 extern	int	jehanne_tolower(int);
diff --git a/sys/include/posix.h b/sys/include/posix.h
index 98e6e64..7b7bb65 100644
--- a/sys/include/posix.h
+++ b/sys/include/posix.h
@@ -64,30 +64,62 @@ extern void POSIX_free(void *ptr);
 extern unsigned int POSIX_sleep(unsigned int seconds);
 extern int POSIX_pipe(int *errnop, int fildes[2]);
 
-typedef enum PosixSignalDisposition
-{
-	SignalHandled = 0,	/* the application handled the signal */
-	TerminateTheProcess,
-	TerminateTheProcessAndCoreDump,
-	StopTheProcess,
-	ResumeTheProcess
-} PosixSignalDisposition;
-
-/* Executes a PosixSignalDisposition for pid.
- *
- * MUST be called instead of POSIX_kill for unblockable signals.
- */
-extern int POSIX_signal_execute(int sig, PosixSignalDisposition action, int pid);
-
 
 /* Library initialization
  */
 #define _ERRNO_H	// skip the Posix part, we just need the enum
 #include <apw/errno.h>
 
+typedef enum PosixSignals
+{
+	PosixSIGABRT = 1,
+	PosixSIGALRM,
+	PosixSIGBUS,
+	PosixSIGCHLD,
+	PosixSIGCONT,
+	PosixSIGFPE,
+	PosixSIGHUP,
+	PosixSIGILL,
+	PosixSIGINT,
+	PosixSIGKILL,
+	PosixSIGPIPE,
+	PosixSIGQUIT,
+	PosixSIGSEGV,
+	PosixSIGSTOP,
+	PosixSIGTERM,
+	PosixSIGTSTP,
+	PosixSIGTTIN,
+	PosixSIGTTOU,
+	PosixSIGUSR1,
+	PosixSIGUSR2,
+	PosixSIGPOLL,
+	PosixSIGPROF,
+	PosixSIGSYS,
+	PosixSIGTRAP,
+	PosixSIGURG,
+	PosixSIGVTALRM,
+	PosixSIGXCPU,
+	PosixSIGXFSZ,
+
+	/* Optional Signals */
+	PosixSIGIOT,
+	PosixSIGEMT,
+	PosixSIGSTKFLT,
+	PosixSIGIO,
+	PosixSIGCLD,
+	PosixSIGPWR,
+	PosixSIGINFO,
+	PosixSIGLOST,
+	PosixSIGWINCH,
+	PosixSIGUNUSED,
+
+	PosixNumberOfSignals
+} PosixSignals;
+
 /* Initialize libposix. Should call
  *
  *	libposix_define_errno to set the value of each PosixError
+ *	libposix_define_signal to set the value of each PosixSignal
  *	libposix_translate_error to translate error strings to PosixError
  * 	libposix_set_signal_trampoline to dispatch signal received as notes
  *	libposix_set_stat_reader
@@ -181,10 +213,14 @@ extern int libposix_translate_exit_status(PosixExitStatusTranslator translator);
 
 /* Dispatch the signal to the registered handlers.
  */
-typedef PosixSignalDisposition (*PosixSignalTrampoline)(int signal);
+typedef int (*PosixSignalTrampoline)(int signal);
 
 extern int libposix_set_signal_trampoline(PosixSignalTrampoline trampoline);
 
+extern int libposix_define_signal(PosixSignals signal, int code);
+
+extern int libposix_define_realtime_signals(int sigrtmin, int sigrtmax);
+
 /* Define of WCONTINUED, WNOHANG and WUNTRACED bit flags.
  *
  * Note that WCONTINUED and WUNTRACED are not yet supported by libposix
diff --git a/sys/src/lib/posix/initlib.c b/sys/src/lib/posix/initlib.c
index 74f769e..da40f33 100644
--- a/sys/src/lib/posix/initlib.c
+++ b/sys/src/lib/posix/initlib.c
@@ -37,9 +37,16 @@ void
 libposix_init(int argc, char *argv[], PosixInit init)
 {
 	extern int main(int, char**);
+	extern unsigned char *__signals_to_code_map;
+	extern unsigned char *__code_to_signal_map;
+	extern int *__handling_external_signal;
+
 	WaitList *wait_list;
 	int status;
 	int error_codes[ERRNO_LAST-ERRNO_FIRST];
+	unsigned char signals_to_code[256];
+	unsigned char code_to_signal[256];
+	int handling_signal;
 
 	assert(__initialized == 0);
 
@@ -51,6 +58,13 @@ libposix_init(int argc, char *argv[], PosixInit init)
 	wait_list = nil;
 	__libposix_wait_list = &wait_list;
 
+	/* initialize signal handling */
+	memset(signals_to_code, 0, sizeof(signals_to_code));
+	memset(code_to_signal, 0, sizeof(code_to_signal));
+	handling_signal = 0;
+	__signals_to_code_map = signals_to_code;
+	__code_to_signal_map = code_to_signal;
+	__handling_external_signal = &handling_signal;
 	if(!atnotify(__libposix_note_handler, 1))
 		sysfatal("libposix: atnotify");
 
diff --git a/sys/src/lib/posix/internal.h b/sys/src/lib/posix/internal.h
index 19ca01d..20c1346 100644
--- a/sys/src/lib/posix/internal.h
+++ b/sys/src/lib/posix/internal.h
@@ -38,3 +38,6 @@ extern int __libposix_translate_errstr(uintptr_t caller);
 extern int __libposix_note_handler(void *ureg, char *note);
 
 extern void __libposix_free_wait_list(void);
+
+
+
diff --git a/sys/src/lib/posix/signals.c b/sys/src/lib/posix/signals.c
index 3bfab8f..ab3ef09 100644
--- a/sys/src/lib/posix/signals.c
+++ b/sys/src/lib/posix/signals.c
@@ -22,8 +22,25 @@
 
 #define __POSIX_SIGNAL_PREFIX_LEN (sizeof(__POSIX_SIGNAL_PREFIX)-1)
 
+unsigned char *__signals_to_code_map;
+unsigned char *__code_to_signal_map;
+int *__handling_external_signal;
+
+static int __sigrtmin;
+static int __sigrtmax;
+static int __min_known_sig;
+static int __max_known_sig;
 static PosixSignalTrampoline __libposix_signal_trampoline;
 
+typedef enum PosixSignalDisposition
+{
+	SignalHandled = 0,	/* the application handled the signal */
+	TerminateTheProcess,
+	TerminateTheProcessAndCoreDump,
+	StopTheProcess,
+	ResumeTheProcess
+} PosixSignalDisposition;
+
 static int
 note_all_writable_processes(int *errnop, char *note)
 {
@@ -32,52 +49,6 @@ note_all_writable_processes(int *errnop, char *note)
 	return -1;
 }
 
-int
-POSIX_kill(int *errnop, int pid, int sig)
-{
-	char msg[64], file[128];
-	int mode;
-	int ret;
-
-	snprint(msg, sizeof(msg), __POSIX_SIGNAL_PREFIX "%d", sig);
-	switch(pid){
-	case 0:
-		mode = PNGROUP;
-		break;
-	case -1:
-		return note_all_writable_processes(errnop, msg);
-	default:
-		if(pid < 0){
-			mode = PNGROUP;
-			pid = -pid;
-		} else {
-			mode = PNPROC;
-		}
-	}
-
-	snprint(file, sizeof(file), "/proc/%d/note", pid);
-	if(access(file, AWRITE) != 0){
-		if(access(file, AEXIST) == 0)
-			*errnop = __libposix_get_errno(PosixEPERM);
-		else
-			*errnop = __libposix_get_errno(PosixESRCH);
-		return -1;
-	}
-	ret = postnote(mode, pid, msg);
-	if(ret != 0){
-		*errnop = __libposix_translate_errstr((uintptr_t)POSIX_kill);
-		return -1;
-	}
-	return 0;
-}
-
-static int
-translate_jehanne_note(char *note)
-{
-	// TODO: implement
-	return 0;
-}
-
 static void
 terminated_by_signal(int sig)
 {
@@ -115,8 +86,12 @@ ErrorBeforeOpen:
 	return 0;
 }
 
-int
-POSIX_signal_execute(int sig, PosixSignalDisposition action, int pid)
+/* Executes a PosixSignalDisposition for pid.
+ *
+ * MUST be called by POSIX_kill for unblockable signals.
+ */
+static int
+execute_disposition(int sig, PosixSignalDisposition action, int pid)
 {
 	switch(action){
 	case SignalHandled:
@@ -137,16 +112,203 @@ POSIX_signal_execute(int sig, PosixSignalDisposition action, int pid)
 	return 0;
 }
 
+static int
+send_signal(int *errnop, int pid, int signal)
+{
+	char msg[64], file[128];
+	int mode;
+	int ret;
+
+	snprint(msg, sizeof(msg), __POSIX_SIGNAL_PREFIX "%d", signal);
+	switch(pid){
+	case 0:
+		mode = PNGROUP;
+		break;
+	case -1:
+		return note_all_writable_processes(errnop, msg);
+	default:
+		if(pid < 0){
+			mode = PNGROUP;
+			pid = -pid;
+		} else {
+			mode = PNPROC;
+		}
+	}
+
+	snprint(file, sizeof(file), "/proc/%d/note", pid);
+	if(access(file, AWRITE) != 0){
+		if(access(file, AEXIST) == 0)
+			*errnop = __libposix_get_errno(PosixEPERM);
+		else
+			*errnop = __libposix_get_errno(PosixESRCH);
+		return -1;
+	}
+	ret = postnote(mode, pid, msg);
+	if(ret != 0){
+		*errnop = __libposix_translate_errstr((uintptr_t)POSIX_kill);
+		return -1;
+	}
+	return 0;
+}
+
+
+static PosixSignalDisposition
+default_signal_disposition(int signal)
+{
+	// see http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/signal.h.html
+	switch(signal){
+	default:
+		if(signal >= __sigrtmin || signal <= __sigrtmin)
+			return TerminateTheProcess;
+		break;
+
+	case PosixSIGALRM:
+	case PosixSIGHUP:
+	case PosixSIGINT:
+	case PosixSIGKILL:
+	case PosixSIGPIPE:
+	case PosixSIGTERM:
+	case PosixSIGUSR1:
+	case PosixSIGUSR2:
+	case PosixSIGPOLL:
+	case PosixSIGPROF:
+	case PosixSIGVTALRM:
+		return TerminateTheProcess;
+	case PosixSIGSTOP:
+	case PosixSIGTSTP:
+	case PosixSIGTTIN:
+	case PosixSIGTTOU:
+		return StopTheProcess;
+	case PosixSIGABRT:
+	case PosixSIGILL:
+	case PosixSIGFPE:
+	case PosixSIGBUS:
+	case PosixSIGQUIT:
+	case PosixSIGSEGV:
+	case PosixSIGSYS:
+	case PosixSIGTRAP:
+	case PosixSIGXCPU:
+	case PosixSIGXFSZ:
+		return TerminateTheProcessAndCoreDump;
+	case PosixSIGCHLD:
+	case PosixSIGURG:
+		return SignalHandled;
+	case PosixSIGCONT:
+		return ResumeTheProcess;
+	}
+	sysfatal("libposix: unknown PosixSignal %d", signal);
+}
+
+int
+POSIX_kill(int *errnop, int pid, int sig)
+{
+	PosixSignals signal;
+	PosixSignalDisposition action;
+
+	signal = __code_to_signal_map[sig];
+	if(signal == 0
+	&&(sig < __sigrtmin || sig > __sigrtmax))
+		sysfatal("libposix: undefined signal %d", sig);
+	if(pid == getpid()){
+		if(__libposix_signal_trampoline(sig))
+			action = SignalHandled;
+		else
+			action = default_signal_disposition(sig);
+		if(!execute_disposition(sig, action, -1)){
+			*errnop = __libposix_get_errno(PosixEPERM);
+			return -1;
+		}
+	}
+
+	switch(signal){
+	case PosixSIGKILL:
+		if(pid > 0)
+		if(!send_control_msg(pid, "kill")){
+			*errnop = __libposix_get_errno(PosixEPERM);
+			return -1;
+		}
+		break;
+	case PosixSIGSTOP:
+		if(pid > 0)
+		if(!send_control_msg(pid, "stop")){
+			*errnop = __libposix_get_errno(PosixEPERM);
+			return -1;
+		}
+		break;
+	case PosixSIGCONT:
+		if(pid > 0)
+		if(!send_control_msg(pid, "start")){
+			*errnop = __libposix_get_errno(PosixEPERM);
+			return -1;
+		}
+		break;
+	default:
+		break;
+	}
+	return send_signal(errnop, pid, sig);
+}
+
+static int
+translate_jehanne_note(char *note)
+{
+	// TODO: implement
+	return 0;
+}
+
+
 int
 __libposix_note_handler(void *ureg, char *note)
 {
-	int sig;
+	int sig, ret;
 	PosixSignalDisposition action;
 	if(strncmp(note, __POSIX_SIGNAL_PREFIX, __POSIX_SIGNAL_PREFIX_LEN) != 0)
 		return translate_jehanne_note(note); // TODO: should we translate common notes?
 	sig = atoi(note+__POSIX_SIGNAL_PREFIX_LEN);
+	if(sig < __min_known_sig || sig > __max_known_sig)
+		sysfatal("libposix: '%s' does not carry a signal", note);
+	*__handling_external_signal = 1;
 	action = __libposix_signal_trampoline(sig);
-	return POSIX_signal_execute(sig, action, -1);
+	ret = execute_disposition(sig, action, -1);
+	*__handling_external_signal = 0;
+	return ret;
+}
+
+int
+libposix_define_realtime_signals(int sigrtmin, int sigrtmax)
+{
+	if(sigrtmin >= 256 || sigrtmin <=0)
+		sysfatal("libposix: invalid SIGRTMIN %d (must be positive and less then 256)", sigrtmin);
+	if(sigrtmax >= 256 || sigrtmax <=0)
+		sysfatal("libposix: invalid SIGRTMAX %d (must be positive and less then 256)", sigrtmax);
+	if(sigrtmax <= sigrtmin)
+		sysfatal("libposix: invalid SIGRTMAX %d (must be greater than SIGRTMIN %d)", sigrtmax, sigrtmin);
+	if(__libposix_initialized())
+		return 0;
+	__sigrtmin = sigrtmin;
+	__sigrtmax = sigrtmax;
+	if(sigrtmin < __min_known_sig || __min_known_sig == 0)
+		__min_known_sig = sigrtmin;
+	if(sigrtmax > __max_known_sig || __max_known_sig == 0)
+		__max_known_sig = sigrtmax;
+	return 1;
+}
+
+int
+libposix_define_signal(PosixSignals signal, int code)
+{
+	if(signal >= PosixNumberOfSignals)
+		sysfatal("libposix: unknown PosixSignal %d", signal);
+	if(code >= 256 || code <=0)
+		sysfatal("libposix: invalid signal number %d (must be positive and less then 256)", code);
+	if(__libposix_initialized())
+		return 0;
+	__signals_to_code_map[signal] = (unsigned char)code;
+	__code_to_signal_map[code] = (unsigned char)signal;
+	if(code < __min_known_sig || __min_known_sig == 0)
+		__min_known_sig = code;
+	if(code > __max_known_sig || __max_known_sig == 0)
+		__max_known_sig = code;
+	return 1;
 }
 
 int