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/10311
Reviewed-by: Rick Hudson <rlh@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

7 files changed, 56 insertions, 51 deletions

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)
 }