syscall: remove/update outdated TODO comments

Error returns for linux/arm syscalls are handled since a long time.

Remove another list of unimplemented syscalls, following CL 96315.

The root-only check in TestSyscallNoError was shown to be sufficient as
part of CL 84485 already.

NetBSD and OpenBSD do not implement the sendfile syscall (yet), so add a
link to golang.org/issue/5847

Change-Id: I07efc3c3203537a4142707385f31b59dc0ecca42
Reviewed-on: https://go-review.googlesource.com/97115Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/syscall/asm_linux_arm.s

@@ -9,8 +9,6 @@
 // System calls for arm, Linux
 //
 
-// TODO(kaib): handle error returns
-
 // func Syscall(syscall uintptr, a1, a2, a3 uintptr) (r1, r2, err uintptr);
 TEXT ·Syscall(SB),NOSPLIT,$0-28
 	BL	runtime·entersyscall(SB)

src/syscall/syscall_bsd.go

@@ -539,14 +539,6 @@ func Futimes(fd int, tv []Timeval) (err error) {
 
 //sys	fcntl(fd int, cmd int, arg int) (val int, err error)
 
-// TODO: wrap
-//	Acct(name nil-string) (err error)
-//	Gethostuuid(uuid *byte, timeout *Timespec) (err error)
-//	Madvise(addr *byte, len int, behav int) (err error)
-//	Mprotect(addr *byte, len int, prot int) (err error)
-//	Msync(addr *byte, len int, flags int) (err error)
-//	Ptrace(req int, pid int, addr uintptr, data int) (ret uintptr, err error)
-
 var mapper = &mmapper{
 	active: make(map[*byte][]byte),
 	mmap:   mmap,

src/syscall/syscall_linux_test.go

@@ -180,8 +180,6 @@ func TestSyscallNoError(t *testing.T) {
 		t.Skip("skipping on non-32bit architecture")
 	}
 
-	// TODO(tklauser) is this check enough? Otherwise test for being in a non-k8s
-	// Linux VM via testenv.Builder().
 	if os.Getuid() != 0 {
 		t.Skip("skipping root only test")
 	}

src/syscall/syscall_netbsd.go

@@ -142,7 +142,7 @@ func Getdirentries(fd int, buf []byte, basep *uintptr) (n int, err error) {
 	return getdents(fd, buf)
 }
 
-// TODO
+// TODO, see golang.org/issue/5847
 func sendfile(outfd int, infd int, offset *int64, count int) (written int, err error) {
 	return -1, ENOSYS
 }

src/syscall/syscall_openbsd.go

@@ -98,7 +98,7 @@ func Getdirentries(fd int, buf []byte, basep *uintptr) (n int, err error) {
 	return getdents(fd, buf)
 }
 
-// TODO
+// TODO, see golang.org/issue/5847
 func sendfile(outfd int, infd int, offset *int64, count int) (written int, err error) {
 	return -1, ENOSYS
 }