1 files changed, 76 insertions, 0 deletions
diff --git a/pkg/fdnotifier/poll_unsafe.go b/pkg/fdnotifier/poll_unsafe.go
new file mode 100644
index 000000000..bc5e0ac44
--- /dev/null
+++ b/pkg/fdnotifier/poll_unsafe.go
@@ -0,0 +1,76 @@
+// Copyright 2018 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build linux
+
+package fdnotifier
+
+import (
+	"syscall"
+	"unsafe"
+
+	"gvisor.googlesource.com/gvisor/pkg/waiter"
+)
+
+// NonBlockingPoll polls the given FD in non-blocking fashion. It is used just
+// to query the FD's current state.
+func NonBlockingPoll(fd int32, mask waiter.EventMask) waiter.EventMask {
+	e := struct {
+		fd      int32
+		events  int16
+		revents int16
+	}{
+		fd:     fd,
+		events: int16(mask.ToLinux()),
+	}
+
+	for {
+		n, _, err := syscall.RawSyscall(syscall.SYS_POLL, uintptr(unsafe.Pointer(&e)), 1, 0)
+		// Interrupted by signal, try again.
+		if err == syscall.EINTR {
+			continue
+		}
+		// If an error occur we'll conservatively say the FD is ready for
+		// whatever is being checked.
+		if err != 0 {
+			return mask
+		}
+
+		// If no FDs were returned, it wasn't ready for anything.
+		if n == 0 {
+			return 0
+		}
+
+		// Otherwise we got the ready events in the revents field.
+		return waiter.EventMaskFromLinux(uint32(e.revents))
+	}
+}
+
+// epollWait performs a blocking wait on epfd.
+//
+// Preconditions:
+//  * len(events) > 0
+func epollWait(epfd int, events []syscall.EpollEvent, msec int) (int, error) {
+	if len(events) == 0 {
+		panic("Empty events passed to EpollWait")
+	}
+
+	// We actually use epoll_pwait with NULL sigmask instead of epoll_wait
+	// since that is what the Go >= 1.11 runtime prefers.
+	r, _, e := syscall.Syscall6(syscall.SYS_EPOLL_PWAIT, uintptr(epfd), uintptr(unsafe.Pointer(&events[0])), uintptr(len(events)), uintptr(msec), 0, 0)
+	if e != 0 {
+		return 0, e
+	}
+	return int(r), nil
+}