Check in gVisor.

PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463

1 files changed, 148 insertions, 0 deletions

diff --git a/pkg/sentry/fs/ramfs/file.go b/pkg/sentry/fs/ramfs/file.go
new file mode 100644
index 000000000..e8363c3e2
--- /dev/null
+++ b/pkg/sentry/fs/ramfs/file.go
@@ -0,0 +1,148 @@
+// 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 ramfs
+
+import (
+	"io"
+	"sync"
+
+	"gvisor.googlesource.com/gvisor/pkg/secio"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/safemem"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+	"gvisor.googlesource.com/gvisor/pkg/syserror"
+)
+
+// File represents a unique file.  It uses a simple byte slice as storage, and
+// thus should only be used for small files.
+//
+// A File is not mappable.
+type File struct {
+	Entry
+
+	// mu protects the fields below.
+	mu sync.Mutex `state:"nosave"`
+
+	// data tracks backing data for the file.
+	data []byte
+}
+
+// InitFile initializes a file.
+func (f *File) InitFile(ctx context.Context, owner fs.FileOwner, perms fs.FilePermissions) {
+	f.InitEntry(ctx, owner, perms)
+}
+
+// UnstableAttr returns unstable attributes of this ramfs file.
+func (f *File) UnstableAttr(ctx context.Context, inode *fs.Inode) (fs.UnstableAttr, error) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+
+	uattr, _ := f.Entry.UnstableAttr(ctx, inode)
+	uattr.Size = int64(len(f.data))
+	uattr.Usage = f.usageLocked()
+
+	return uattr, nil
+}
+
+// usageLocked returns the disk usage. Caller must hold f.mu.
+func (f *File) usageLocked() int64 {
+	return int64(len(f.data))
+}
+
+// Append appends the given data. This is for internal use.
+func (f *File) Append(data []byte) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	f.data = append(f.data, data...)
+}
+
+// Truncate truncates this node.
+func (f *File) Truncate(ctx context.Context, inode *fs.Inode, l int64) error {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	if l < int64(len(f.data)) {
+		// Remove excess bytes.
+		f.data = f.data[:l]
+		return nil
+	} else if l > int64(len(f.data)) {
+		// Create a new slice with size l, and copy f.data into it.
+		d := make([]byte, l)
+		copy(d, f.data)
+		f.data = d
+	}
+	f.Entry.NotifyModification(ctx)
+	return nil
+}
+
+// ReadAt implements io.ReaderAt.
+func (f *File) ReadAt(data []byte, offset int64) (int, error) {
+	if offset < 0 {
+		return 0, ErrInvalidOp
+	}
+	if offset >= int64(len(f.data)) {
+		return 0, io.EOF
+	}
+	n := copy(data, f.data[offset:])
+	// Did we read past the end?
+	if offset+int64(len(data)) >= int64(len(f.data)) {
+		return n, io.EOF
+	}
+	return n, nil
+}
+
+// DeprecatedPreadv reads into a collection of slices from a given offset.
+func (f *File) DeprecatedPreadv(ctx context.Context, dst usermem.IOSequence, offset int64) (int64, error) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	if offset >= int64(len(f.data)) {
+		return 0, io.EOF
+	}
+	n, err := dst.CopyOut(ctx, f.data[offset:])
+	if n > 0 {
+		f.Entry.NotifyAccess(ctx)
+	}
+	return int64(n), err
+}
+
+// WriteAt implements io.WriterAt.
+func (f *File) WriteAt(data []byte, offset int64) (int, error) {
+	if offset < 0 {
+		return 0, ErrInvalidOp
+	}
+	newLen := offset + int64(len(data))
+	if newLen < 0 {
+		// Overflow.
+		return 0, syserror.EINVAL
+	}
+	if newLen > int64(len(f.data)) {
+		// Copy f.data into new slice with expanded length.
+		d := make([]byte, newLen)
+		copy(d, f.data)
+		f.data = d
+	}
+	return copy(f.data[offset:], data), nil
+}
+
+// DeprecatedPwritev writes from a collection of slices at a given offset.
+func (f *File) DeprecatedPwritev(ctx context.Context, src usermem.IOSequence, offset int64) (int64, error) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	n, err := src.CopyInTo(ctx, safemem.FromIOWriter{secio.NewOffsetWriter(f, offset)})
+	if n > 0 {
+		f.Entry.NotifyModification(ctx)
+	}
+	return n, err
+}