Check in gVisor.

PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463

1 files changed, 117 insertions, 0 deletions

diff --git a/pkg/sentry/fs/proc/sys.go b/pkg/sentry/fs/proc/sys.go
new file mode 100644
index 000000000..4323f3650
--- /dev/null
+++ b/pkg/sentry/fs/proc/sys.go
@@ -0,0 +1,117 @@
+// 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 proc
+
+import (
+	"fmt"
+	"io"
+
+	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs/proc/seqfile"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs/ramfs"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+)
+
+// hostname is a file containing the system hostname.
+type hostname struct {
+	ramfs.Entry
+}
+
+// DeprecatedPreadv implements fs.InodeOperations.DeprecatedPreadv.
+func (hostname) DeprecatedPreadv(ctx context.Context, dst usermem.IOSequence, offset int64) (int64, error) {
+	utsns := kernel.UTSNamespaceFromContext(ctx)
+	contents := []byte(utsns.HostName() + "\n")
+
+	if offset >= int64(len(contents)) {
+		return 0, io.EOF
+	}
+
+	n, err := dst.CopyOut(ctx, contents[offset:])
+	return int64(n), err
+}
+
+func (p *proc) newHostname(ctx context.Context, msrc *fs.MountSource) *fs.Inode {
+	h := &hostname{}
+	h.InitEntry(ctx, fs.RootOwner, fs.FilePermsFromMode(0444))
+	return newFile(h, msrc, fs.SpecialFile, nil)
+}
+
+// mmapMinAddrData backs /proc/sys/vm/mmap_min_addr.
+type mmapMinAddrData struct {
+	k *kernel.Kernel
+}
+
+// NeedsUpdate implements seqfile.SeqSource.NeedsUpdate.
+func (*mmapMinAddrData) NeedsUpdate(generation int64) bool {
+	return true
+}
+
+// ReadSeqFileData implements seqfile.SeqSource.ReadSeqFileData.
+func (d *mmapMinAddrData) ReadSeqFileData(h seqfile.SeqHandle) ([]seqfile.SeqData, int64) {
+	if h != nil {
+		return nil, 0
+	}
+	return []seqfile.SeqData{
+		{
+			Buf:    []byte(fmt.Sprintf("%d\n", d.k.Platform.MinUserAddress())),
+			Handle: (*mmapMinAddrData)(nil),
+		},
+	}, 0
+}
+
+type overcommitMemory struct{}
+
+func (*overcommitMemory) NeedsUpdate(generation int64) bool {
+	return true
+}
+
+// ReadSeqFileData implements seqfile.SeqSource.
+func (*overcommitMemory) ReadSeqFileData(h seqfile.SeqHandle) ([]seqfile.SeqData, int64) {
+	if h != nil {
+		return nil, 0
+	}
+	return []seqfile.SeqData{
+		{
+			Buf:    []byte("0\n"),
+			Handle: (*overcommitMemory)(nil),
+		},
+	}, 0
+}
+
+func (p *proc) newKernelDir(ctx context.Context, msrc *fs.MountSource) *fs.Inode {
+	d := &ramfs.Dir{}
+	d.InitDir(ctx, nil, fs.RootOwner, fs.FilePermsFromMode(0555))
+	d.AddChild(ctx, "hostname", p.newHostname(ctx, msrc))
+	return newFile(d, msrc, fs.SpecialDirectory, nil)
+}
+
+func (p *proc) newVMDir(ctx context.Context, msrc *fs.MountSource) *fs.Inode {
+	d := &ramfs.Dir{}
+	d.InitDir(ctx, nil, fs.RootOwner, fs.FilePermsFromMode(0555))
+	d.AddChild(ctx, "mmap_min_addr", seqfile.NewSeqFileInode(ctx, &mmapMinAddrData{p.k}, msrc))
+	d.AddChild(ctx, "overcommit_memory", seqfile.NewSeqFileInode(ctx, &overcommitMemory{}, msrc))
+	return newFile(d, msrc, fs.SpecialDirectory, nil)
+}
+
+func (p *proc) newSysDir(ctx context.Context, msrc *fs.MountSource) *fs.Inode {
+	d := &ramfs.Dir{}
+	d.InitDir(ctx, nil, fs.RootOwner, fs.FilePermsFromMode(0555))
+	d.AddChild(ctx, "kernel", p.newKernelDir(ctx, msrc))
+	d.AddChild(ctx, "vm", p.newVMDir(ctx, msrc))
+	d.AddChild(ctx, "net", p.newSysNetDir(ctx, msrc))
+	return newFile(d, msrc, fs.SpecialDirectory, nil)
+}