net, syscall, os: set CLOEXEC flag on epoll/kqueue descriptor

Enable new test in os.

R=dave, iant, rsc
CC=golang-dev
https://golang.org/cl/5494061

src/pkg/net/fd_darwin.go

@@ -27,6 +27,7 @@ func newpollster() (p *pollster, err error) {
 	if p.kq, err = syscall.Kqueue(); err != nil {
 		return nil, os.NewSyscallError("kqueue", err)
 	}
+	syscall.CloseOnExec(p.kq)
 	p.events = p.eventbuf[0:0]
 	return p, nil
 }

src/pkg/net/fd_freebsd.go

@@ -26,6 +26,7 @@ func newpollster() (p *pollster, err error) {
 	if p.kq, err = syscall.Kqueue(); err != nil {
 		return nil, os.NewSyscallError("kqueue", err)
 	}
+	syscall.CloseOnExec(p.kq)
 	p.events = p.eventbuf[0:0]
 	return p, nil
 }

src/pkg/net/fd_linux.go

@@ -37,12 +37,18 @@ func newpollster() (p *pollster, err error) {
 	p = new(pollster)
 	var e error
 
+	if p.epfd, e = syscall.EpollCreate1(syscall.EPOLL_CLOEXEC); e != nil {
+		if e != syscall.ENOSYS {
+			return nil, os.NewSyscallError("epoll_create1", e)
+		}
 		// The arg to epoll_create is a hint to the kernel
 		// about the number of FDs we will care about.
 		// We don't know, and since 2.6.8 the kernel ignores it anyhow.
 		if p.epfd, e = syscall.EpollCreate(16); e != nil {
 			return nil, os.NewSyscallError("epoll_create", e)
 		}
+		syscall.CloseOnExec(p.epfd)
+	}
 	p.events = make(map[int]uint32)
 	return p, nil
 }

src/pkg/net/fd_netbsd.go

@@ -26,6 +26,7 @@ func newpollster() (p *pollster, err error) {
 	if p.kq, err = syscall.Kqueue(); err != nil {
 		return nil, os.NewSyscallError("kqueue", err)
 	}
+	syscall.CloseOnExec(p.kq)
 	p.events = p.eventbuf[0:0]
 	return p, nil
 }

src/pkg/net/fd_openbsd.go

@@ -26,6 +26,7 @@ func newpollster() (p *pollster, err error) {
 	if p.kq, err = syscall.Kqueue(); err != nil {
 		return nil, os.NewSyscallError("kqueue", err)
 	}
+	syscall.CloseOnExec(p.kq)
 	p.events = p.eventbuf[0:0]
 	return p, nil
 }

src/pkg/os/exec/exec_test.go

@@ -256,12 +256,6 @@ func TestHelperProcess(*testing.T) {
 			fmt.Printf("ReadAll from fd 3: %v", err)
 			os.Exit(1)
 		}
-		// TODO(bradfitz,iant): the rest of this test is disabled
-		// for now. remove this block once 5494061 is in.
-		{
-			os.Stderr.Write(bs)
-			os.Exit(0)
-		}
 		// Now verify that there are no other open fds.
 		var files []*os.File
 		for wantfd := os.Stderr.Fd() + 2; wantfd <= 100; wantfd++ {

src/pkg/syscall/syscall_linux.go

@@ -806,6 +806,7 @@ func Mount(source string, target string, fstype string, flags uintptr, data stri
 //sysnb	Dup(oldfd int) (fd int, err error)
 //sysnb	Dup2(oldfd int, newfd int) (fd int, err error)
 //sysnb	EpollCreate(size int) (fd int, err error)
+//sysnb	EpollCreate1(flag int) (fd int, err error)
 //sysnb	EpollCtl(epfd int, op int, fd int, event *EpollEvent) (err error)
 //sys	EpollWait(epfd int, events []EpollEvent, msec int) (n int, err error)
 //sys	Exit(code int) = SYS_EXIT_GROUP

src/pkg/syscall/zsyscall_linux_386.go

@@ -232,6 +232,17 @@ func EpollCreate(size int) (fd int, err error) {
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
+func EpollCreate1(flag int) (fd int, err error) {
+	r0, _, e1 := RawSyscall(SYS_EPOLL_CREATE1, uintptr(flag), 0, 0)
+	fd = int(r0)
+	if e1 != 0 {
+		err = e1
+	}
+	return
+}
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
 func EpollCtl(epfd int, op int, fd int, event *EpollEvent) (err error) {
 	_, _, e1 := RawSyscall6(SYS_EPOLL_CTL, uintptr(epfd), uintptr(op), uintptr(fd), uintptr(unsafe.Pointer(event)), 0, 0)
 	if e1 != 0 {

src/pkg/syscall/zsyscall_linux_amd64.go

@@ -232,6 +232,17 @@ func EpollCreate(size int) (fd int, err error) {
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
+func EpollCreate1(flag int) (fd int, err error) {
+	r0, _, e1 := RawSyscall(SYS_EPOLL_CREATE1, uintptr(flag), 0, 0)
+	fd = int(r0)
+	if e1 != 0 {
+		err = e1
+	}
+	return
+}
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
 func EpollCtl(epfd int, op int, fd int, event *EpollEvent) (err error) {
 	_, _, e1 := RawSyscall6(SYS_EPOLL_CTL, uintptr(epfd), uintptr(op), uintptr(fd), uintptr(unsafe.Pointer(event)), 0, 0)
 	if e1 != 0 {

src/pkg/syscall/zsyscall_linux_arm.go

@@ -232,6 +232,17 @@ func EpollCreate(size int) (fd int, err error) {
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
+func EpollCreate1(flag int) (fd int, err error) {
+	r0, _, e1 := RawSyscall(SYS_EPOLL_CREATE1, uintptr(flag), 0, 0)
+	fd = int(r0)
+	if e1 != 0 {
+		err = e1
+	}
+	return
+}
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
 func EpollCtl(epfd int, op int, fd int, event *EpollEvent) (err error) {
 	_, _, e1 := RawSyscall6(SYS_EPOLL_CTL, uintptr(epfd), uintptr(op), uintptr(fd), uintptr(unsafe.Pointer(event)), 0, 0)
 	if e1 != 0 {