mirror of
https://github.com/netbirdio/gvisor.git
synced 2026-05-22 17:12:49 -07:00
Add vfs.DynamicBytesFileDescriptionImpl.
This replaces fs/proc/seqfile for vfs2-based filesystems. PiperOrigin-RevId: 263254647
This commit is contained in:
Jamie Liu
gVisor bot
@@ -18,6 +18,7 @@ go_library(
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"permissions.go",
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"resolving_path.go",
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"syscalls.go",
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"testutil.go",
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"vfs.go",
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],
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importpath = "gvisor.dev/gvisor/pkg/sentry/vfs",
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@@ -40,7 +41,16 @@ go_test(
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name = "vfs_test",
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size = "small",
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srcs = [
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"file_description_impl_util_test.go",
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"mount_test.go",
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],
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embed = [":vfs"],
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deps = [
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"//pkg/abi/linux",
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"//pkg/sentry/context",
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"//pkg/sentry/context/contexttest",
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"//pkg/sentry/kernel/auth",
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"//pkg/sentry/usermem",
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"//pkg/syserror",
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],
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)
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@@ -15,6 +15,10 @@
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package vfs
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import (
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"bytes"
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"io"
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"sync"
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"gvisor.dev/gvisor/pkg/abi/linux"
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"gvisor.dev/gvisor/pkg/sentry/arch"
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"gvisor.dev/gvisor/pkg/sentry/context"
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@@ -140,3 +144,106 @@ func (DirectoryFileDescriptionDefaultImpl) PWrite(ctx context.Context, src userm
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func (DirectoryFileDescriptionDefaultImpl) Write(ctx context.Context, src usermem.IOSequence, opts WriteOptions) (int64, error) {
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return 0, syserror.EISDIR
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}
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// DynamicBytesFileDescriptionImpl may be embedded by implementations of
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// FileDescriptionImpl that represent read-only regular files whose contents
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// are backed by a bytes.Buffer that is regenerated when necessary, consistent
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// with Linux's fs/seq_file.c:single_open().
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//
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// DynamicBytesFileDescriptionImpl.SetDataSource() must be called before first
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// use.
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type DynamicBytesFileDescriptionImpl struct {
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FileDescriptionDefaultImpl
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data DynamicBytesSource // immutable
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mu sync.Mutex // protects the following fields
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buf bytes.Buffer
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off int64
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lastRead int64 // offset at which the last Read, PRead, or Seek ended
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}
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// DynamicBytesSource represents a data source for a
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// DynamicBytesFileDescriptionImpl.
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type DynamicBytesSource interface {
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// Generate writes the file's contents to buf.
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Generate(ctx context.Context, buf *bytes.Buffer) error
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}
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// SetDataSource must be called exactly once on fd before first use.
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func (fd *DynamicBytesFileDescriptionImpl) SetDataSource(data DynamicBytesSource) {
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fd.data = data
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}
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// Preconditions: fd.mu must be locked.
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func (fd *DynamicBytesFileDescriptionImpl) preadLocked(ctx context.Context, dst usermem.IOSequence, offset int64, opts *ReadOptions) (int64, error) {
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// Regenerate the buffer if it's empty, or before pread() at a new offset.
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// Compare fs/seq_file.c:seq_read() => traverse().
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switch {
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case offset != fd.lastRead:
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fd.buf.Reset()
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fallthrough
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case fd.buf.Len() == 0:
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if err := fd.data.Generate(ctx, &fd.buf); err != nil {
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fd.buf.Reset()
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// fd.off is not updated in this case.
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fd.lastRead = 0
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return 0, err
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}
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}
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bs := fd.buf.Bytes()
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if offset >= int64(len(bs)) {
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return 0, io.EOF
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}
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n, err := dst.CopyOut(ctx, bs[offset:])
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fd.lastRead = offset + int64(n)
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return int64(n), err
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}
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// PRead implements FileDescriptionImpl.PRead.
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func (fd *DynamicBytesFileDescriptionImpl) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts ReadOptions) (int64, error) {
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fd.mu.Lock()
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n, err := fd.preadLocked(ctx, dst, offset, &opts)
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fd.mu.Unlock()
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return n, err
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}
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// Read implements FileDescriptionImpl.Read.
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func (fd *DynamicBytesFileDescriptionImpl) Read(ctx context.Context, dst usermem.IOSequence, opts ReadOptions) (int64, error) {
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fd.mu.Lock()
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n, err := fd.preadLocked(ctx, dst, fd.off, &opts)
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fd.off += n
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fd.mu.Unlock()
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return n, err
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}
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// Seek implements FileDescriptionImpl.Seek.
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func (fd *DynamicBytesFileDescriptionImpl) Seek(ctx context.Context, offset int64, whence int32) (int64, error) {
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fd.mu.Lock()
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defer fd.mu.Unlock()
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switch whence {
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case linux.SEEK_SET:
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// Use offset as given.
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case linux.SEEK_CUR:
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offset += fd.off
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default:
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// fs/seq_file:seq_lseek() rejects SEEK_END etc.
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return 0, syserror.EINVAL
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}
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if offset < 0 {
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return 0, syserror.EINVAL
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}
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if offset != fd.lastRead {
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// Regenerate the file's contents immediately. Compare
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// fs/seq_file.c:seq_lseek() => traverse().
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fd.buf.Reset()
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if err := fd.data.Generate(ctx, &fd.buf); err != nil {
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fd.buf.Reset()
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fd.off = 0
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fd.lastRead = 0
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return 0, err
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}
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fd.lastRead = offset
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}
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fd.off = offset
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return offset, nil
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}
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@@ -0,0 +1,134 @@
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// Copyright 2019 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package vfs
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import (
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"bytes"
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"fmt"
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"io"
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"sync/atomic"
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"testing"
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"gvisor.dev/gvisor/pkg/abi/linux"
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"gvisor.dev/gvisor/pkg/sentry/context"
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"gvisor.dev/gvisor/pkg/sentry/context/contexttest"
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"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
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"gvisor.dev/gvisor/pkg/sentry/usermem"
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"gvisor.dev/gvisor/pkg/syserror"
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)
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// genCountFD is a read-only FileDescriptionImpl representing a regular file
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// that contains the number of times its DynamicBytesSource.Generate()
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// implementation has been called.
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type genCountFD struct {
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vfsfd FileDescription
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DynamicBytesFileDescriptionImpl
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count uint64 // accessed using atomic memory ops
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}
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func newGenCountFD(mnt *Mount, vfsd *Dentry) *FileDescription {
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var fd genCountFD
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fd.vfsfd.Init(&fd, mnt, vfsd)
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fd.DynamicBytesFileDescriptionImpl.SetDataSource(&fd)
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return &fd.vfsfd
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}
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// Release implements FileDescriptionImpl.Release.
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func (fd *genCountFD) Release() {
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}
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// StatusFlags implements FileDescriptionImpl.StatusFlags.
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func (fd *genCountFD) StatusFlags(ctx context.Context) (uint32, error) {
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return 0, nil
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}
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// SetStatusFlags implements FileDescriptionImpl.SetStatusFlags.
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func (fd *genCountFD) SetStatusFlags(ctx context.Context, flags uint32) error {
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return syserror.EPERM
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}
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// Stat implements FileDescriptionImpl.Stat.
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func (fd *genCountFD) Stat(ctx context.Context, opts StatOptions) (linux.Statx, error) {
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// Note that Statx.Mask == 0 in the return value.
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return linux.Statx{}, nil
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}
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// SetStat implements FileDescriptionImpl.SetStat.
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func (fd *genCountFD) SetStat(ctx context.Context, opts SetStatOptions) error {
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return syserror.EPERM
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}
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// Generate implements DynamicBytesSource.Generate.
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func (fd *genCountFD) Generate(ctx context.Context, buf *bytes.Buffer) error {
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fmt.Fprintf(buf, "%d", atomic.AddUint64(&fd.count, 1))
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return nil
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}
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func TestGenCountFD(t *testing.T) {
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ctx := contexttest.Context(t)
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creds := auth.CredentialsFromContext(ctx)
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vfsObj := New() // vfs.New()
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vfsObj.MustRegisterFilesystemType("testfs", FDTestFilesystemType{})
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mntns, err := vfsObj.NewMountNamespace(ctx, creds, "", "testfs", &NewFilesystemOptions{})
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if err != nil {
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t.Fatalf("failed to create testfs root mount: %v", err)
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}
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vd := mntns.Root()
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defer vd.DecRef()
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fd := newGenCountFD(vd.Mount(), vd.Dentry())
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defer fd.DecRef()
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// The first read causes Generate to be called to fill the FD's buffer.
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buf := make([]byte, 2)
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ioseq := usermem.BytesIOSequence(buf)
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n, err := fd.Impl().Read(ctx, ioseq, ReadOptions{})
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if n != 1 || (err != nil && err != io.EOF) {
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t.Fatalf("first Read: got (%d, %v), wanted (1, nil or EOF)", n, err)
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}
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if want := byte('1'); buf[0] != want {
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t.Errorf("first Read: got byte %c, wanted %c", buf[0], want)
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}
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// A second read without seeking is still at EOF.
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n, err = fd.Impl().Read(ctx, ioseq, ReadOptions{})
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if n != 0 || err != io.EOF {
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t.Fatalf("second Read: got (%d, %v), wanted (0, EOF)", n, err)
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}
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// Seeking to the beginning of the file causes it to be regenerated.
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n, err = fd.Impl().Seek(ctx, 0, linux.SEEK_SET)
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if n != 0 || err != nil {
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t.Fatalf("Seek: got (%d, %v), wanted (0, nil)", n, err)
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}
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n, err = fd.Impl().Read(ctx, ioseq, ReadOptions{})
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if n != 1 || (err != nil && err != io.EOF) {
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t.Fatalf("Read after Seek: got (%d, %v), wanted (1, nil or EOF)", n, err)
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}
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if want := byte('2'); buf[0] != want {
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t.Errorf("Read after Seek: got byte %c, wanted %c", buf[0], want)
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}
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// PRead at the beginning of the file also causes it to be regenerated.
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n, err = fd.Impl().PRead(ctx, ioseq, 0, ReadOptions{})
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if n != 1 || (err != nil && err != io.EOF) {
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t.Fatalf("PRead: got (%d, %v), wanted (1, nil or EOF)", n, err)
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}
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if want := byte('3'); buf[0] != want {
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t.Errorf("PRead: got byte %c, wanted %c", buf[0], want)
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}
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}
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@@ -0,0 +1,139 @@
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// Copyright 2019 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package vfs
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import (
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"gvisor.dev/gvisor/pkg/abi/linux"
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"gvisor.dev/gvisor/pkg/sentry/context"
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"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
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"gvisor.dev/gvisor/pkg/syserror"
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)
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// FDTestFilesystemType is a test-only FilesystemType that produces Filesystems
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// for which all FilesystemImpl methods taking a path return EPERM. It is used
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// to produce Mounts and Dentries for testing of FileDescriptionImpls that do
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// not depend on their originating Filesystem.
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type FDTestFilesystemType struct{}
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// FDTestFilesystem is a test-only FilesystemImpl produced by
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// FDTestFilesystemType.
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type FDTestFilesystem struct {
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vfsfs Filesystem
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}
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// NewFilesystem implements FilesystemType.NewFilesystem.
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func (fstype FDTestFilesystemType) NewFilesystem(ctx context.Context, creds *auth.Credentials, source string, opts NewFilesystemOptions) (*Filesystem, *Dentry, error) {
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var fs FDTestFilesystem
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fs.vfsfs.Init(&fs)
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return &fs.vfsfs, fs.NewDentry(), nil
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}
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// Release implements FilesystemImpl.Release.
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func (fs *FDTestFilesystem) Release() {
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}
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// Sync implements FilesystemImpl.Sync.
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func (fs *FDTestFilesystem) Sync(ctx context.Context) error {
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return nil
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}
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// GetDentryAt implements FilesystemImpl.GetDentryAt.
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func (fs *FDTestFilesystem) GetDentryAt(ctx context.Context, rp *ResolvingPath, opts GetDentryOptions) (*Dentry, error) {
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return nil, syserror.EPERM
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}
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// LinkAt implements FilesystemImpl.LinkAt.
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func (fs *FDTestFilesystem) LinkAt(ctx context.Context, rp *ResolvingPath, vd VirtualDentry) error {
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return syserror.EPERM
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}
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// MkdirAt implements FilesystemImpl.MkdirAt.
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func (fs *FDTestFilesystem) MkdirAt(ctx context.Context, rp *ResolvingPath, opts MkdirOptions) error {
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return syserror.EPERM
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}
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// MknodAt implements FilesystemImpl.MknodAt.
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func (fs *FDTestFilesystem) MknodAt(ctx context.Context, rp *ResolvingPath, opts MknodOptions) error {
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return syserror.EPERM
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}
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// OpenAt implements FilesystemImpl.OpenAt.
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func (fs *FDTestFilesystem) OpenAt(ctx context.Context, rp *ResolvingPath, opts OpenOptions) (*FileDescription, error) {
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return nil, syserror.EPERM
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}
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// ReadlinkAt implements FilesystemImpl.ReadlinkAt.
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func (fs *FDTestFilesystem) ReadlinkAt(ctx context.Context, rp *ResolvingPath) (string, error) {
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return "", syserror.EPERM
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}
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// RenameAt implements FilesystemImpl.RenameAt.
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func (fs *FDTestFilesystem) RenameAt(ctx context.Context, rp *ResolvingPath, vd VirtualDentry, opts RenameOptions) error {
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return syserror.EPERM
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}
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// RmdirAt implements FilesystemImpl.RmdirAt.
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func (fs *FDTestFilesystem) RmdirAt(ctx context.Context, rp *ResolvingPath) error {
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return syserror.EPERM
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}
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// SetStatAt implements FilesystemImpl.SetStatAt.
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func (fs *FDTestFilesystem) SetStatAt(ctx context.Context, rp *ResolvingPath, opts SetStatOptions) error {
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return syserror.EPERM
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}
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// StatAt implements FilesystemImpl.StatAt.
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func (fs *FDTestFilesystem) StatAt(ctx context.Context, rp *ResolvingPath, opts StatOptions) (linux.Statx, error) {
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return linux.Statx{}, syserror.EPERM
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}
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// StatFSAt implements FilesystemImpl.StatFSAt.
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func (fs *FDTestFilesystem) StatFSAt(ctx context.Context, rp *ResolvingPath) (linux.Statfs, error) {
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return linux.Statfs{}, syserror.EPERM
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}
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// SymlinkAt implements FilesystemImpl.SymlinkAt.
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func (fs *FDTestFilesystem) SymlinkAt(ctx context.Context, rp *ResolvingPath, target string) error {
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return syserror.EPERM
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}
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// UnlinkAt implements FilesystemImpl.UnlinkAt.
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func (fs *FDTestFilesystem) UnlinkAt(ctx context.Context, rp *ResolvingPath) error {
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return syserror.EPERM
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}
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type fdTestDentry struct {
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vfsd Dentry
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}
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// NewDentry returns a new Dentry.
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func (fs *FDTestFilesystem) NewDentry() *Dentry {
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var d fdTestDentry
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d.vfsd.Init(&d)
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return &d.vfsd
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}
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// IncRef implements DentryImpl.IncRef.
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func (d *fdTestDentry) IncRef(vfsfs *Filesystem) {
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}
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// TryIncRef implements DentryImpl.TryIncRef.
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func (d *fdTestDentry) TryIncRef(vfsfs *Filesystem) bool {
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return true
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}
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// DecRef implements DentryImpl.DecRef.
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func (d *fdTestDentry) DecRef(vfsfs *Filesystem) {
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}
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