diff --git a/src/runtime/os1_darwin.go b/src/runtime/os1_darwin.go
index 1b74e3e653..06bc2c79a5 100644
--- a/src/runtime/os1_darwin.go
+++ b/src/runtime/os1_darwin.go
@@ -138,7 +138,7 @@ func msigsave(mp *m) {
 func minit() {
 	// Initialize signal handling.
 	_g_ := getg()
-	signalstack((*byte)(unsafe.Pointer(_g_.m.gsignal.stack.lo)), 32*1024)
+	signalstack(&_g_.m.gsignal.stack)
 
 	// restore signal mask from m.sigmask and unblock essential signals
 	nmask := *(*uint32)(unsafe.Pointer(&_g_.m.sigmask))
@@ -155,7 +155,7 @@ func unminit() {
 	_g_ := getg()
 	smask := (*uint32)(unsafe.Pointer(&_g_.m.sigmask))
 	sigprocmask(_SIG_SETMASK, smask, nil)
-	signalstack(nil, 0)
+	signalstack(nil)
 }
 
 // Mach IPC, to get at semaphores
@@ -454,13 +454,14 @@ func getsig(i int32) uintptr {
 	return *(*uintptr)(unsafe.Pointer(&sa.__sigaction_u))
 }
 
-func signalstack(p *byte, n int32) {
+func signalstack(s *stack) {
 	var st stackt
-	st.ss_sp = p
-	st.ss_size = uintptr(n)
-	st.ss_flags = 0
-	if p == nil {
+	if s == nil {
 		st.ss_flags = _SS_DISABLE
+	} else {
+		st.ss_sp = (*byte)(unsafe.Pointer(s.lo))
+		st.ss_size = s.hi - s.lo
+		st.ss_flags = 0
 	}
 	sigaltstack(&st, nil)
 }
diff --git a/src/runtime/os1_dragonfly.go b/src/runtime/os1_dragonfly.go
index eb42b54e2b..a4c11d4fbf 100644
--- a/src/runtime/os1_dragonfly.go
+++ b/src/runtime/os1_dragonfly.go
@@ -136,7 +136,7 @@ func minit() {
 	_g_.m.procid = uint64(*(*int32)(unsafe.Pointer(&_g_.m.procid)))
 
 	// Initialize signal handling
-	signalstack((*byte)(unsafe.Pointer(_g_.m.gsignal.stack.lo)), 32*1024)
+	signalstack(&_g_.m.gsignal.stack)
 
 	// restore signal mask from m.sigmask and unblock essential signals
 	nmask := *(*sigset)(unsafe.Pointer(&_g_.m.sigmask))
@@ -153,7 +153,7 @@ func unminit() {
 	_g_ := getg()
 	smask := (*sigset)(unsafe.Pointer(&_g_.m.sigmask))
 	sigprocmask(smask, nil)
-	signalstack(nil, 0)
+	signalstack(nil)
 }
 
 func memlimit() uintptr {
@@ -222,13 +222,14 @@ func getsig(i int32) uintptr {
 	return sa.sa_sigaction
 }
 
-func signalstack(p *byte, n int32) {
+func signalstack(s *stack) {
 	var st sigaltstackt
-	st.ss_sp = uintptr(unsafe.Pointer(p))
-	st.ss_size = uintptr(n)
-	st.ss_flags = 0
-	if p == nil {
+	if s == nil {
 		st.ss_flags = _SS_DISABLE
+	} else {
+		st.ss_sp = s.lo
+		st.ss_size = s.hi - s.lo
+		st.ss_flags = 0
 	}
 	sigaltstack(&st, nil)
 }
diff --git a/src/runtime/os1_freebsd.go b/src/runtime/os1_freebsd.go
index f7f34bd386..6dbf8299b4 100644
--- a/src/runtime/os1_freebsd.go
+++ b/src/runtime/os1_freebsd.go
@@ -138,7 +138,7 @@ func minit() {
 	}
 
 	// Initialize signal handling.
-	signalstack((*byte)(unsafe.Pointer(_g_.m.gsignal.stack.lo)), 32*1024)
+	signalstack(&_g_.m.gsignal.stack)
 
 	// restore signal mask from m.sigmask and unblock essential signals
 	nmask := *(*sigset)(unsafe.Pointer(&_g_.m.sigmask))
@@ -155,7 +155,7 @@ func unminit() {
 	_g_ := getg()
 	smask := (*sigset)(unsafe.Pointer(&_g_.m.sigmask))
 	sigprocmask(smask, nil)
-	signalstack(nil, 0)
+	signalstack(nil)
 }
 
 func memlimit() uintptr {
@@ -224,13 +224,14 @@ func getsig(i int32) uintptr {
 	return sa.sa_handler
 }
 
-func signalstack(p *byte, n int32) {
+func signalstack(s *stack) {
 	var st stackt
-	st.ss_sp = uintptr(unsafe.Pointer(p))
-	st.ss_size = uintptr(n)
-	st.ss_flags = 0
-	if p == nil {
+	if s == nil {
 		st.ss_flags = _SS_DISABLE
+	} else {
+		st.ss_sp = s.lo
+		st.ss_size = s.hi - s.lo
+		st.ss_flags = 0
 	}
 	sigaltstack(&st, nil)
 }
diff --git a/src/runtime/os1_linux.go b/src/runtime/os1_linux.go
index 02f98d7c5f..8aa0804860 100644
--- a/src/runtime/os1_linux.go
+++ b/src/runtime/os1_linux.go
@@ -202,7 +202,7 @@ func msigsave(mp *m) {
 func minit() {
 	// Initialize signal handling.
 	_g_ := getg()
-	signalstack((*byte)(unsafe.Pointer(_g_.m.gsignal.stack.lo)), 32*1024)
+	signalstack(&_g_.m.gsignal.stack)
 
 	// restore signal mask from m.sigmask and unblock essential signals
 	nmask := *(*sigset)(unsafe.Pointer(&_g_.m.sigmask))
@@ -219,7 +219,7 @@ func unminit() {
 	_g_ := getg()
 	smask := (*sigset)(unsafe.Pointer(&_g_.m.sigmask))
 	rtsigprocmask(_SIG_SETMASK, smask, nil, int32(unsafe.Sizeof(*smask)))
-	signalstack(nil, 0)
+	signalstack(nil)
 }
 
 func memlimit() uintptr {
@@ -311,13 +311,14 @@ func getsig(i int32) uintptr {
 	return sa.sa_handler
 }
 
-func signalstack(p *byte, n int32) {
+func signalstack(s *stack) {
 	var st sigaltstackt
-	st.ss_sp = p
-	st.ss_size = uintptr(n)
-	st.ss_flags = 0
-	if p == nil {
+	if s == nil {
 		st.ss_flags = _SS_DISABLE
+	} else {
+		st.ss_sp = (*byte)(unsafe.Pointer(s.lo))
+		st.ss_size = s.hi - s.lo
+		st.ss_flags = 0
 	}
 	sigaltstack(&st, nil)
 }
diff --git a/src/runtime/os1_netbsd.go b/src/runtime/os1_netbsd.go
index 3fb05989e7..2a579b8694 100644
--- a/src/runtime/os1_netbsd.go
+++ b/src/runtime/os1_netbsd.go
@@ -153,7 +153,7 @@ func minit() {
 	_g_.m.procid = uint64(lwp_self())
 
 	// Initialize signal handling
-	signalstack((*byte)(unsafe.Pointer(_g_.m.gsignal.stack.lo)), 32*1024)
+	signalstack(&_g_.m.gsignal.stack)
 
 	// restore signal mask from m.sigmask and unblock essential signals
 	nmask := *(*sigset)(unsafe.Pointer(&_g_.m.sigmask))
@@ -171,7 +171,7 @@ func unminit() {
 	smask := (*sigset)(unsafe.Pointer(&_g_.m.sigmask))
 	sigprocmask(_SIG_SETMASK, smask, nil)
 
-	signalstack(nil, 0)
+	signalstack(nil)
 }
 
 func memlimit() uintptr {
@@ -213,14 +213,14 @@ func getsig(i int32) uintptr {
 	return sa.sa_sigaction
 }
 
-func signalstack(p *byte, n int32) {
+func signalstack(s *stack) {
 	var st sigaltstackt
-
-	st.ss_sp = uintptr(unsafe.Pointer(p))
-	st.ss_size = uintptr(n)
-	st.ss_flags = 0
-	if p == nil {
+	if s == nil {
 		st.ss_flags = _SS_DISABLE
+	} else {
+		st.ss_sp = s.lo
+		st.ss_size = s.hi - s.lo
+		st.ss_flags = 0
 	}
 	sigaltstack(&st, nil)
 }
diff --git a/src/runtime/os1_openbsd.go b/src/runtime/os1_openbsd.go
index 5ccf642468..c07cd243be 100644
--- a/src/runtime/os1_openbsd.go
+++ b/src/runtime/os1_openbsd.go
@@ -165,7 +165,7 @@ func minit() {
 	_g_.m.procid = uint64(*(*int32)(unsafe.Pointer(&_g_.m.procid)))
 
 	// Initialize signal handling
-	signalstack((*byte)(unsafe.Pointer(_g_.m.gsignal.stack.lo)), 32*1024)
+	signalstack(&_g_.m.gsignal.stack)
 
 	// restore signal mask from m.sigmask and unblock essential signals
 	nmask := *(*uint32)(unsafe.Pointer(&_g_.m.sigmask))
@@ -182,7 +182,7 @@ func unminit() {
 	_g_ := getg()
 	smask := *(*uint32)(unsafe.Pointer(&_g_.m.sigmask))
 	sigprocmask(_SIG_SETMASK, smask)
-	signalstack(nil, 0)
+	signalstack(nil)
 }
 
 func memlimit() uintptr {
@@ -224,14 +224,14 @@ func getsig(i int32) uintptr {
 	return sa.sa_sigaction
 }
 
-func signalstack(p *byte, n int32) {
+func signalstack(s *stack) {
 	var st stackt
-
-	st.ss_sp = uintptr(unsafe.Pointer(p))
-	st.ss_size = uintptr(n)
-	st.ss_flags = 0
-	if p == nil {
+	if s == nil {
 		st.ss_flags = _SS_DISABLE
+	} else {
+		st.ss_sp = s.lo
+		st.ss_size = s.hi - s.lo
+		st.ss_flags = 0
 	}
 	sigaltstack(&st, nil)
 }
diff --git a/src/runtime/os3_solaris.go b/src/runtime/os3_solaris.go
index e4fe92de41..53d7b96b0f 100644
--- a/src/runtime/os3_solaris.go
+++ b/src/runtime/os3_solaris.go
@@ -203,7 +203,7 @@ func minit() {
 	_g_ := getg()
 	asmcgocall(unsafe.Pointer(funcPC(miniterrno)), unsafe.Pointer(&libc____errno))
 	// Initialize signal handling
-	signalstack((*byte)(unsafe.Pointer(_g_.m.gsignal.stack.lo)), 32*1024)
+	signalstack(&_g_.m.gsignal.stack)
 
 	// restore signal mask from m.sigmask and unblock essential signals
 	nmask := *(*sigset)(unsafe.Pointer(&_g_.m.sigmask))
@@ -221,7 +221,7 @@ func unminit() {
 	smask := (*sigset)(unsafe.Pointer(&_g_.m.sigmask))
 	sigprocmask(_SIG_SETMASK, smask, nil)
 
-	signalstack(nil, 0)
+	signalstack(nil)
 }
 
 func memlimit() uintptr {
@@ -286,13 +286,14 @@ func getsig(i int32) uintptr {
 	return *((*uintptr)(unsafe.Pointer(&sa._funcptr)))
 }
 
-func signalstack(p *byte, n int32) {
+func signalstack(s *stack) {
 	var st sigaltstackt
-	st.ss_sp = (*byte)(unsafe.Pointer(p))
-	st.ss_size = uint64(n)
-	st.ss_flags = 0
-	if p == nil {
+	if s == nil {
 		st.ss_flags = _SS_DISABLE
+	} else {
+		st.ss_sp = (*byte)(unsafe.Pointer(s.lo))
+		st.ss_size = uint64(s.hi - s.lo)
+		st.ss_flags = 0
 	}
 	sigaltstack(&st, nil)
 }