4 files changed, 167 insertions, 0 deletions
diff --git a/pkg/sentry/fs/sys/BUILD b/pkg/sentry/fs/sys/BUILD
new file mode 100644
index 000000000..0ae2cbac8
--- /dev/null
+++ b/pkg/sentry/fs/sys/BUILD
@@ -0,0 +1,34 @@
+package(licenses = ["notice"])  # Apache 2.0
+
+load("@io_bazel_rules_go//go:def.bzl", "go_library")
+load("//tools/go_stateify:defs.bzl", "go_stateify")
+
+go_stateify(
+    name = "sys_state",
+    srcs = [
+        "fs.go",
+        "sys.go",
+    ],
+    out = "sys_state.go",
+    package = "sys",
+)
+
+go_library(
+    name = "sys",
+    srcs = [
+        "device.go",
+        "fs.go",
+        "sys.go",
+        "sys_state.go",
+    ],
+    importpath = "gvisor.googlesource.com/gvisor/pkg/sentry/fs/sys",
+    visibility = ["//pkg/sentry:internal"],
+    deps = [
+        "//pkg/sentry/context",
+        "//pkg/sentry/device",
+        "//pkg/sentry/fs",
+        "//pkg/sentry/fs/ramfs",
+        "//pkg/sentry/usermem",
+        "//pkg/state",
+    ],
+)
diff --git a/pkg/sentry/fs/sys/device.go b/pkg/sentry/fs/sys/device.go
new file mode 100644
index 000000000..54e414d1b
--- /dev/null
+++ b/pkg/sentry/fs/sys/device.go
@@ -0,0 +1,20 @@
+// 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 sys
+
+import "gvisor.googlesource.com/gvisor/pkg/sentry/device"
+
+// sysfsDevice is the sysfs virtual device.
+var sysfsDevice = device.NewAnonDevice()
diff --git a/pkg/sentry/fs/sys/fs.go b/pkg/sentry/fs/sys/fs.go
new file mode 100644
index 000000000..f25f648c3
--- /dev/null
+++ b/pkg/sentry/fs/sys/fs.go
@@ -0,0 +1,56 @@
+// 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 sys
+
+import (
+	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
+)
+
+// filesystem is a sysfs.
+type filesystem struct{}
+
+func init() {
+	fs.RegisterFilesystem(&filesystem{})
+}
+
+// FilesystemName is the name underwhich the filesystem is registered.
+// Name matches fs/sysfs/mount.c:sysfs_fs_type.name.
+const FilesystemName = "sysfs"
+
+// Name is the name of the file system.
+func (*filesystem) Name() string {
+	return FilesystemName
+}
+
+// AllowUserMount allows users to mount(2) this file system.
+func (*filesystem) AllowUserMount() bool {
+	return true
+}
+
+// Flags returns that there is nothing special about this file system.
+//
+// In Linux, sysfs returns FS_USERNS_VISIBLE | FS_USERNS_MOUNT, see fs/sysfs/mount.c.
+func (*filesystem) Flags() fs.FilesystemFlags {
+	return 0
+}
+
+// Mount returns a sysfs root which can be positioned in the vfs.
+func (f *filesystem) Mount(ctx context.Context, device string, flags fs.MountSourceFlags, data string) (*fs.Inode, error) {
+	// device is always ignored.
+	// sysfs ignores data, see fs/sysfs/mount.c:sysfs_mount.
+
+	return New(ctx, fs.NewNonCachingMountSource(f, flags)), nil
+}
diff --git a/pkg/sentry/fs/sys/sys.go b/pkg/sentry/fs/sys/sys.go
new file mode 100644
index 000000000..ccf56f644
--- /dev/null
+++ b/pkg/sentry/fs/sys/sys.go
@@ -0,0 +1,57 @@
+// 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 sys implements a sysfs filesystem.
+package sys
+
+import (
+	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs/ramfs"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+)
+
+type Dir struct {
+	ramfs.Dir
+}
+
+func newDir(ctx context.Context, msrc *fs.MountSource, contents map[string]*fs.Inode) *fs.Inode {
+	d := &Dir{}
+	d.InitDir(ctx, contents, fs.RootOwner, fs.FilePermsFromMode(0555))
+	return fs.NewInode(d, msrc, fs.StableAttr{
+		DeviceID:  sysfsDevice.DeviceID(),
+		InodeID:   sysfsDevice.NextIno(),
+		BlockSize: usermem.PageSize,
+		Type:      fs.SpecialDirectory,
+	})
+}
+
+// New returns the root node of a partial simple sysfs.
+func New(ctx context.Context, msrc *fs.MountSource) *fs.Inode {
+	return newDir(ctx, msrc, map[string]*fs.Inode{
+		// Add a basic set of top-level directories. In Linux, these
+		// are dynamically added depending on the KConfig. Here we just
+		// add the most common ones.
+		"block":    newDir(ctx, msrc, nil),
+		"bus":      newDir(ctx, msrc, nil),
+		"class":    newDir(ctx, msrc, nil),
+		"dev":      newDir(ctx, msrc, nil),
+		"devices":  newDir(ctx, msrc, nil),
+		"firmware": newDir(ctx, msrc, nil),
+		"fs":       newDir(ctx, msrc, nil),
+		"kernel":   newDir(ctx, msrc, nil),
+		"module":   newDir(ctx, msrc, nil),
+		"power":    newDir(ctx, msrc, nil),
+	})
+}