1 files changed, 228 insertions, 0 deletions
diff --git a/pkg/sentry/syscalls/linux/vfs2/epoll.go b/pkg/sentry/syscalls/linux/vfs2/epoll.go
new file mode 100644
index 000000000..34c90ae3e
--- /dev/null
+++ b/pkg/sentry/syscalls/linux/vfs2/epoll.go
@@ -0,0 +1,228 @@
+// Copyright 2020 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.
+
+package vfs2
+
+import (
+	"math"
+	"time"
+
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/sentry/arch"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/syserror"
+	"gvisor.dev/gvisor/pkg/usermem"
+	"gvisor.dev/gvisor/pkg/waiter"
+)
+
+var sizeofEpollEvent = (*linux.EpollEvent)(nil).SizeBytes()
+
+// EpollCreate1 implements Linux syscall epoll_create1(2).
+func EpollCreate1(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	flags := args[0].Int()
+	if flags&^linux.EPOLL_CLOEXEC != 0 {
+		return 0, nil, syserror.EINVAL
+	}
+
+	file, err := t.Kernel().VFS().NewEpollInstanceFD()
+	if err != nil {
+		return 0, nil, err
+	}
+	defer file.DecRef()
+
+	fd, err := t.NewFDFromVFS2(0, file, kernel.FDFlags{
+		CloseOnExec: flags&linux.EPOLL_CLOEXEC != 0,
+	})
+	if err != nil {
+		return 0, nil, err
+	}
+	return uintptr(fd), nil, nil
+}
+
+// EpollCreate implements Linux syscall epoll_create(2).
+func EpollCreate(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	size := args[0].Int()
+
+	// "Since Linux 2.6.8, the size argument is ignored, but must be greater
+	// than zero" - epoll_create(2)
+	if size <= 0 {
+		return 0, nil, syserror.EINVAL
+	}
+
+	file, err := t.Kernel().VFS().NewEpollInstanceFD()
+	if err != nil {
+		return 0, nil, err
+	}
+	defer file.DecRef()
+
+	fd, err := t.NewFDFromVFS2(0, file, kernel.FDFlags{})
+	if err != nil {
+		return 0, nil, err
+	}
+	return uintptr(fd), nil, nil
+}
+
+// EpollCtl implements Linux syscall epoll_ctl(2).
+func EpollCtl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	epfd := args[0].Int()
+	op := args[1].Int()
+	fd := args[2].Int()
+	eventAddr := args[3].Pointer()
+
+	epfile := t.GetFileVFS2(epfd)
+	if epfile == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer epfile.DecRef()
+	ep, ok := epfile.Impl().(*vfs.EpollInstance)
+	if !ok {
+		return 0, nil, syserror.EINVAL
+	}
+	file := t.GetFileVFS2(fd)
+	if file == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer file.DecRef()
+	if epfile == file {
+		return 0, nil, syserror.EINVAL
+	}
+
+	var event linux.EpollEvent
+	switch op {
+	case linux.EPOLL_CTL_ADD:
+		if _, err := event.CopyIn(t, eventAddr); err != nil {
+			return 0, nil, err
+		}
+		return 0, nil, ep.AddInterest(file, fd, event)
+	case linux.EPOLL_CTL_DEL:
+		return 0, nil, ep.DeleteInterest(file, fd)
+	case linux.EPOLL_CTL_MOD:
+		if _, err := event.CopyIn(t, eventAddr); err != nil {
+			return 0, nil, err
+		}
+		return 0, nil, ep.ModifyInterest(file, fd, event)
+	default:
+		return 0, nil, syserror.EINVAL
+	}
+}
+
+// EpollWait implements Linux syscall epoll_wait(2).
+func EpollWait(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	epfd := args[0].Int()
+	eventsAddr := args[1].Pointer()
+	maxEvents := int(args[2].Int())
+	timeout := int(args[3].Int())
+
+	var _EP_MAX_EVENTS = math.MaxInt32 / sizeofEpollEvent // Linux: fs/eventpoll.c:EP_MAX_EVENTS
+	if maxEvents <= 0 || maxEvents > _EP_MAX_EVENTS {
+		return 0, nil, syserror.EINVAL
+	}
+
+	epfile := t.GetFileVFS2(epfd)
+	if epfile == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer epfile.DecRef()
+	ep, ok := epfile.Impl().(*vfs.EpollInstance)
+	if !ok {
+		return 0, nil, syserror.EINVAL
+	}
+
+	// Use a fixed-size buffer in a loop, instead of make([]linux.EpollEvent,
+	// maxEvents), so that the buffer can be allocated on the stack.
+	var (
+		events       [16]linux.EpollEvent
+		total        int
+		ch           chan struct{}
+		haveDeadline bool
+		deadline     ktime.Time
+	)
+	for {
+		batchEvents := len(events)
+		if batchEvents > maxEvents {
+			batchEvents = maxEvents
+		}
+		n := ep.ReadEvents(events[:batchEvents])
+		maxEvents -= n
+		if n != 0 {
+			// Copy what we read out.
+			copiedBytes, err := linux.CopyEpollEventSliceOut(t, eventsAddr, events[:n])
+			copiedEvents := copiedBytes / sizeofEpollEvent // rounded down
+			eventsAddr += usermem.Addr(copiedEvents * sizeofEpollEvent)
+			total += copiedEvents
+			if err != nil {
+				if total != 0 {
+					return uintptr(total), nil, nil
+				}
+				return 0, nil, err
+			}
+			// If we've filled the application's event buffer, we're done.
+			if maxEvents == 0 {
+				return uintptr(total), nil, nil
+			}
+			// Loop if we read a full batch, under the expectation that there
+			// may be more events to read.
+			if n == batchEvents {
+				continue
+			}
+		}
+		// We get here if n != batchEvents. If we read any number of events
+		// (just now, or in a previous iteration of this loop), or if timeout
+		// is 0 (such that epoll_wait should be non-blocking), return the
+		// events we've read so far to the application.
+		if total != 0 || timeout == 0 {
+			return uintptr(total), nil, nil
+		}
+		// In the first iteration of this loop, register with the epoll
+		// instance for readability events, but then immediately continue the
+		// loop since we need to retry ReadEvents() before blocking. In all
+		// subsequent iterations, block until events are available, the timeout
+		// expires, or an interrupt arrives.
+		if ch == nil {
+			var w waiter.Entry
+			w, ch = waiter.NewChannelEntry(nil)
+			epfile.EventRegister(&w, waiter.EventIn)
+			defer epfile.EventUnregister(&w)
+		} else {
+			// Set up the timer if a timeout was specified.
+			if timeout > 0 && !haveDeadline {
+				timeoutDur := time.Duration(timeout) * time.Millisecond
+				deadline = t.Kernel().MonotonicClock().Now().Add(timeoutDur)
+				haveDeadline = true
+			}
+			if err := t.BlockWithDeadline(ch, haveDeadline, deadline); err != nil {
+				if err == syserror.ETIMEDOUT {
+					err = nil
+				}
+				// total must be 0 since otherwise we would have returned
+				// above.
+				return 0, nil, err
+			}
+		}
+	}
+}
+
+// EpollPwait implements Linux syscall epoll_pwait(2).
+func EpollPwait(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	maskAddr := args[4].Pointer()
+	maskSize := uint(args[5].Uint())
+
+	if err := setTempSignalSet(t, maskAddr, maskSize); err != nil {
+		return 0, nil, err
+	}
+
+	return EpollWait(t, args)
+}