syscall: fix FreeBSD 386 sendfile

The previous version was not handling an off_t (64 bit)
parameter on 32 bit i386 systems.  This patch splits sendfile
into two implementations in their respective arch-specific files.
Tested on FreeBSD amd64 and i386.

R=bradfitz
CC=golang-dev
https://golang.org/cl/6356048

src/pkg/syscall/syscall_freebsd.go

@@ -89,18 +89,6 @@ func Pipe(p []int) (err error) {
 	return
 }
 
-func Sendfile(outfd int, infd int, offset *int64, count int) (written int, err error) {
-	var writtenOut uint64 = 0
-	_, _, e1 := Syscall9(SYS_SENDFILE, uintptr(infd), uintptr(outfd), uintptr(*offset), uintptr(count), 0, uintptr(unsafe.Pointer(&writtenOut)), 0, 0, 0)
-
-	written = int(writtenOut)
-
-	if e1 != 0 {
-		err = e1
-	}
-	return
-}
-
 func GetsockoptIPMreqn(fd, level, opt int) (*IPMreqn, error) {
 	var value IPMreqn
 	vallen := _Socklen(SizeofIPMreqn)

src/pkg/syscall/syscall_freebsd_386.go

@@ -4,6 +4,8 @@
 
 package syscall
 
+import "unsafe"
+
 func Getpagesize() int { return 4096 }
 
 func TimespecToNsec(ts Timespec) int64 { return int64(ts.Sec)*1e9 + int64(ts.Nsec) }
@@ -41,4 +43,16 @@ func (cmsg *Cmsghdr) SetLen(length int) {
 	cmsg.Len = uint32(length)
 }
 
+func Sendfile(outfd int, infd int, offset *int64, count int) (written int, err error) {
+	var writtenOut uint64 = 0
+	_, _, e1 := Syscall9(SYS_SENDFILE, uintptr(infd), uintptr(outfd), uintptr(*offset), uintptr((*offset)>>32), uintptr(count), 0, uintptr(unsafe.Pointer(&writtenOut)), 0, 0)
+
+	written = int(writtenOut)
+
+	if e1 != 0 {
+		err = e1
+	}
+	return
+}
+
 func Syscall9(num, a1, a2, a3, a4, a5, a6, a7, a8, a9 uintptr) (r1, r2 uintptr, err Errno) // sic

src/pkg/syscall/syscall_freebsd_amd64.go

@@ -4,6 +4,8 @@
 
 package syscall
 
+import "unsafe"
+
 func Getpagesize() int { return 4096 }
 
 func TimespecToNsec(ts Timespec) int64 { return int64(ts.Sec)*1e9 + int64(ts.Nsec) }
@@ -41,4 +43,16 @@ func (cmsg *Cmsghdr) SetLen(length int) {
 	cmsg.Len = uint32(length)
 }
 
+func Sendfile(outfd int, infd int, offset *int64, count int) (written int, err error) {
+	var writtenOut uint64 = 0
+	_, _, e1 := Syscall9(SYS_SENDFILE, uintptr(infd), uintptr(outfd), uintptr(*offset), uintptr(count), 0, uintptr(unsafe.Pointer(&writtenOut)), 0, 0, 0)
+
+	written = int(writtenOut)
+
+	if e1 != 0 {
+		err = e1
+	}
+	return
+}
+
 func Syscall9(num, a1, a2, a3, a4, a5, a6, a7, a8, a9 uintptr) (r1, r2 uintptr, err Errno)