runtime: clean up signalstack API

Currently signalstack takes a lower limit and a length and all calls
hard-code the passed length. Change the API to take a *stack and
compute the lower limit and length from the passed stack.

This will make it easier for the runtime to steal some space from the
top of the stack since it eliminates the hard-coded stack sizes.

Change-Id: I7d2a9f45894b221f4e521628c2165530bbc57d53
Reviewed-on: https://go-review.googlesource.com/10311Reviewed-by: Rick Hudson <rlh@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

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)
 }

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)
 }

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)
 }

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)
 }

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)
 }

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)
 }

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)
 }