unix: use pipe2 syscall on FreeBSD instead of pipe

The pipe syscall no longer exists in FreeBSD 11 and 12.
The pipe2 syscall exists in all currently supported FreeBSD
versions: 10, 11 and the upcoming 12.

Follow CL 38426

Change-Id: If908eecfd2662e6f32a229ac52f27d9a2ec2b9d7
Reviewed-on: https://go-review.googlesource.com/130995
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

unix/syscall_freebsd.go

@@ -57,14 +57,21 @@ func nametomib(name string) (mib []_C_int, err error) {
 	return buf[0 : n/siz], nil
 }
 
-//sysnb pipe() (r int, w int, err error)
-
 func Pipe(p []int) (err error) {
+	return Pipe2(p, 0)
+}
+
+//sysnb	pipe2(p *[2]_C_int, flags int) (err error)
+
+func Pipe2(p []int, flags int) error {
 	if len(p) != 2 {
 		return EINVAL
 	}
-	p[0], p[1], err = pipe()
-	return
+	var pp [2]_C_int
+	err := pipe2(&pp, flags)
+	p[0] = int(pp[0])
+	p[1] = int(pp[1])
+	return err
 }
 
 func GetsockoptIPMreqn(fd, level, opt int) (*IPMreqn, error) {

unix/zsyscall_freebsd_386.go

@@ -377,10 +377,8 @@ func Munlockall() (err error) {
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func pipe() (r int, w int, err error) {
-	r0, r1, e1 := RawSyscall(SYS_PIPE, 0, 0, 0)
-	r = int(r0)
-	w = int(r1)
+func pipe2(p *[2]_C_int, flags int) (err error) {
+	_, _, e1 := RawSyscall(SYS_PIPE2, uintptr(unsafe.Pointer(p)), uintptr(flags), 0)
 	if e1 != 0 {
 		err = errnoErr(e1)
 	}

unix/zsyscall_freebsd_amd64.go

@@ -377,10 +377,8 @@ func Munlockall() (err error) {
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func pipe() (r int, w int, err error) {
-	r0, r1, e1 := RawSyscall(SYS_PIPE, 0, 0, 0)
-	r = int(r0)
-	w = int(r1)
+func pipe2(p *[2]_C_int, flags int) (err error) {
+	_, _, e1 := RawSyscall(SYS_PIPE2, uintptr(unsafe.Pointer(p)), uintptr(flags), 0)
 	if e1 != 0 {
 		err = errnoErr(e1)
 	}

unix/zsyscall_freebsd_arm.go

@@ -377,10 +377,8 @@ func Munlockall() (err error) {
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func pipe() (r int, w int, err error) {
-	r0, r1, e1 := RawSyscall(SYS_PIPE, 0, 0, 0)
-	r = int(r0)
-	w = int(r1)
+func pipe2(p *[2]_C_int, flags int) (err error) {
+	_, _, e1 := RawSyscall(SYS_PIPE2, uintptr(unsafe.Pointer(p)), uintptr(flags), 0)
 	if e1 != 0 {
 		err = errnoErr(e1)
 	}