3 files changed, 168 insertions, 0 deletions
diff --git a/pkg/sentry/kernel/fasync/BUILD b/pkg/sentry/kernel/fasync/BUILD
new file mode 100644
index 000000000..8d06e1182
--- /dev/null
+++ b/pkg/sentry/kernel/fasync/BUILD
@@ -0,0 +1,18 @@
+package(licenses = ["notice"])  # Apache 2.0
+
+load("@io_bazel_rules_go//go:def.bzl", "go_library")
+
+go_library(
+    name = "fasync",
+    srcs = ["fasync.go"],
+    importpath = "gvisor.googlesource.com/gvisor/pkg/sentry/kernel/fasync",
+    visibility = ["//:sandbox"],
+    deps = [
+        "//pkg/abi/linux",
+        "//pkg/sentry/arch",
+        "//pkg/sentry/fs",
+        "//pkg/sentry/kernel",
+        "//pkg/sentry/kernel/auth",
+        "//pkg/waiter",
+    ],
+)
diff --git a/pkg/sentry/kernel/fasync/fasync.go b/pkg/sentry/kernel/fasync/fasync.go
new file mode 100644
index 000000000..028d6766f
--- /dev/null
+++ b/pkg/sentry/kernel/fasync/fasync.go
@@ -0,0 +1,145 @@
+// Copyright 2018 Google Inc.
+//
+// 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 fasync provides FIOASYNC related functionality.
+package fasync
+
+import (
+	"sync"
+
+	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.googlesource.com/gvisor/pkg/waiter"
+)
+
+// New creates a new FileAsync.
+func New() fs.FileAsync {
+	return &FileAsync{}
+}
+
+// FileAsync sends signals when the registered file is ready for IO.
+type FileAsync struct {
+	mu        sync.Mutex
+	e         waiter.Entry
+	requester auth.Credentials
+
+	// Only one of the following is allowed to be non-nil.
+	recipientPG *kernel.ProcessGroup
+	recipientTG *kernel.ThreadGroup
+	recipientT  *kernel.Task
+}
+
+// Callback sends a signal.
+func (a *FileAsync) Callback(e *waiter.Entry) {
+	a.mu.Lock()
+	if a.e.Callback == nil {
+		return
+	}
+	t := a.recipientT
+	tg := a.recipientTG
+	if a.recipientPG != nil {
+		tg = a.recipientPG.Originator()
+	}
+	if tg != nil {
+		t = tg.Leader()
+	}
+	c := t.Credentials()
+	// Logic from sigio_perm in fs/fcntl.c.
+	if a.requester.EffectiveKUID == 0 ||
+		a.requester.EffectiveKUID == c.SavedKUID ||
+		a.requester.EffectiveKUID == c.RealKUID ||
+		a.requester.RealKUID == c.SavedKUID ||
+		a.requester.RealKUID == c.RealKUID {
+		t.SendSignal(&arch.SignalInfo{
+			Signo: int32(linux.SIGIO),
+			// SEND_SIG_PRIV
+			Code: arch.SignalInfoKernel,
+		})
+	}
+	a.mu.Unlock()
+}
+
+// Register sets the file which will be monitored for IO events.
+//
+// The file must not be currently registered.
+func (a *FileAsync) Register(w waiter.Waitable) {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+
+	if a.e.Callback != nil {
+		panic("registering already registered file")
+	}
+
+	a.e.Callback = a
+	w.EventRegister(&a.e, waiter.EventIn|waiter.EventOut|waiter.EventErr|waiter.EventHUp)
+}
+
+// Unregister stops monitoring a file.
+//
+// The file must be currently registered.
+func (a *FileAsync) Unregister(w waiter.Waitable) {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+
+	if a.e.Callback == nil {
+		panic("unregistering unregistered file")
+	}
+
+	w.EventUnregister(&a.e)
+	a.e.Callback = nil
+}
+
+// Owner returns who is currently getting signals. All return values will be
+// nil if no one is set to receive signals.
+func (a *FileAsync) Owner() (*kernel.Task, *kernel.ThreadGroup, *kernel.ProcessGroup) {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+	return a.recipientT, a.recipientTG, a.recipientPG
+}
+
+// SetOwnerTask sets the owner (who will receive signals) to a specified task.
+// Only this owner will receive signals.
+func (a *FileAsync) SetOwnerTask(requester *kernel.Task, recipient *kernel.Task) {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+	a.requester = requester.Credentials()
+	a.recipientT = recipient
+	a.recipientTG = nil
+	a.recipientPG = nil
+}
+
+// SetOwnerThreadGroup sets the owner (who will receive signals) to a specified
+// thread group. Only this owner will receive signals.
+func (a *FileAsync) SetOwnerThreadGroup(requester *kernel.Task, recipient *kernel.ThreadGroup) {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+	a.requester = requester.Credentials()
+	a.recipientT = nil
+	a.recipientTG = recipient
+	a.recipientPG = nil
+}
+
+// SetOwnerProcessGroup sets the owner (who will receive signals) to a
+// specified process group. Only this owner will receive signals.
+func (a *FileAsync) SetOwnerProcessGroup(requester *kernel.Task, recipient *kernel.ProcessGroup) {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+	a.requester = requester.Credentials()
+	a.recipientT = nil
+	a.recipientTG = nil
+	a.recipientPG = recipient
+}
diff --git a/pkg/sentry/kernel/sessions.go b/pkg/sentry/kernel/sessions.go
index 53d8fb844..fa4c7b8f6 100644
--- a/pkg/sentry/kernel/sessions.go
+++ b/pkg/sentry/kernel/sessions.go
@@ -110,6 +110,11 @@ type ProcessGroup struct {
 	processGroupEntry
 }
 
+// Originator retuns the originator of the process group.
+func (pg *ProcessGroup) Originator() *ThreadGroup {
+	return pg.originator
+}
+
 // incRefWithParent grabs a reference.
 //
 // This function is called when this ProcessGroup is being associated with some