Convert poll/select to operate more directly on linux.PollFD

Current, doPoll copies the user struct pollfd array into a
[]syscalls.PollFD, which contains internal kdefs.FD and
waiter.EventMask types. While these are currently binary-compatible with
the Linux versions, we generally discourage copying directly to internal
types (someone may inadvertantly change kdefs.FD to uint64).

Instead, copy directly to a []linux.PollFD, which will certainly be
binary compatible. Most of syscalls/polling.go is included directly into
syscalls/linux/sys_poll.go, as it can then operate directly on
linux.PollFD. The additional syscalls.PollFD type is providing little
value.

I've also added explicit conversion functions for waiter.EventMask,
which creates the possibility of a different binary format.

PiperOrigin-RevId: 244042947
Change-Id: I24e5b642002a32b3afb95a9dcb80d4acd1288abf

2 files changed, 8 insertions, 4 deletions

diff --git a/pkg/fdnotifier/fdnotifier.go b/pkg/fdnotifier/fdnotifier.go
index 624b1a0c5..aa4906ca0 100644
--- a/pkg/fdnotifier/fdnotifier.go
+++ b/pkg/fdnotifier/fdnotifier.go
@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build linux
+
 // Package fdnotifier contains an adapter that translates IO events (e.g., a
 // file became readable/writable) from native FDs to the notifications in the
 // waiter package. It uses epoll in edge-triggered mode to receive notifications
@@ -70,7 +72,7 @@ func (n *notifier) waitFD(fd int32, fi *fdInfo, mask waiter.EventMask) error {
 	}
 
 	e := syscall.EpollEvent{
-		Events: uint32(mask) | -syscall.EPOLLET,
+		Events: mask.ToLinux() | -syscall.EPOLLET,
 		Fd:     fd,
 	}
 
@@ -155,7 +157,7 @@ func (n *notifier) waitAndNotify() error {
 		n.mu.Lock()
 		for i := 0; i < v; i++ {
 			if fi, ok := n.fdMap[e[i].Fd]; ok {
-				fi.queue.Notify(waiter.EventMask(e[i].Events))
+				fi.queue.Notify(waiter.EventMaskFromLinux(e[i].Events))
 			}
 		}
 		n.mu.Unlock()
diff --git a/pkg/fdnotifier/poll_unsafe.go b/pkg/fdnotifier/poll_unsafe.go
index 8459d4c74..05be9aeb5 100644
--- a/pkg/fdnotifier/poll_unsafe.go
+++ b/pkg/fdnotifier/poll_unsafe.go
@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build linux
+
 package fdnotifier
 
 import (
@@ -30,7 +32,7 @@ func NonBlockingPoll(fd int32, mask waiter.EventMask) waiter.EventMask {
 		revents int16
 	}{
 		fd:     fd,
-		events: int16(mask),
+		events: int16(mask.ToLinux()),
 	}
 
 	for {
@@ -51,7 +53,7 @@ func NonBlockingPoll(fd int32, mask waiter.EventMask) waiter.EventMask {
 		}
 
 		// Otherwise we got the ready events in the revents field.
-		return waiter.EventMask(e.revents)
+		return waiter.EventMaskFromLinux(uint32(e.revents))
 	}
 }