Implement sysfs.

PiperOrigin-RevId: 290822487

1 files changed, 124 insertions, 0 deletions

diff --git a/pkg/sentry/fsimpl/sys/sys.go b/pkg/sentry/fsimpl/sys/sys.go
new file mode 100644
index 000000000..1305ad01d
--- /dev/null
+++ b/pkg/sentry/fsimpl/sys/sys.go
@@ -0,0 +1,124 @@
+// Copyright 2019 The gVisor Authors.
+//
+// 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 sysfs.
+package sys
+
+import (
+	"bytes"
+	"fmt"
+
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/sentry/context"
+	"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/syserror"
+)
+
+// FilesystemType implements vfs.FilesystemType.
+type FilesystemType struct{}
+
+// filesystem implements vfs.FilesystemImpl.
+type filesystem struct {
+	kernfs.Filesystem
+}
+
+// GetFilesystem implements vfs.FilesystemType.GetFilesystem.
+func (FilesystemType) GetFilesystem(ctx context.Context, vfsObj *vfs.VirtualFilesystem, creds *auth.Credentials, source string, opts vfs.GetFilesystemOptions) (*vfs.Filesystem, *vfs.Dentry, error) {
+	fs := &filesystem{}
+	fs.Filesystem.Init(vfsObj)
+	k := kernel.KernelFromContext(ctx)
+	maxCPUCores := k.ApplicationCores()
+	defaultSysDirMode := linux.FileMode(0755)
+
+	root := fs.newDir(creds, defaultSysDirMode, map[string]*kernfs.Dentry{
+		"block": fs.newDir(creds, defaultSysDirMode, nil),
+		"bus":   fs.newDir(creds, defaultSysDirMode, nil),
+		"class": fs.newDir(creds, defaultSysDirMode, map[string]*kernfs.Dentry{
+			"power_supply": fs.newDir(creds, defaultSysDirMode, nil),
+		}),
+		"dev": fs.newDir(creds, defaultSysDirMode, nil),
+		"devices": fs.newDir(creds, defaultSysDirMode, map[string]*kernfs.Dentry{
+			"system": fs.newDir(creds, defaultSysDirMode, map[string]*kernfs.Dentry{
+				"cpu": fs.newDir(creds, defaultSysDirMode, map[string]*kernfs.Dentry{
+					"online":   fs.newCPUFile(creds, maxCPUCores, linux.FileMode(0444)),
+					"possible": fs.newCPUFile(creds, maxCPUCores, linux.FileMode(0444)),
+					"present":  fs.newCPUFile(creds, maxCPUCores, linux.FileMode(0444)),
+				}),
+			}),
+		}),
+		"firmware": fs.newDir(creds, defaultSysDirMode, nil),
+		"fs":       fs.newDir(creds, defaultSysDirMode, nil),
+		"kernel":   fs.newDir(creds, defaultSysDirMode, nil),
+		"module":   fs.newDir(creds, defaultSysDirMode, nil),
+		"power":    fs.newDir(creds, defaultSysDirMode, nil),
+	})
+	return fs.VFSFilesystem(), root.VFSDentry(), nil
+}
+
+// dir implements kernfs.Inode.
+type dir struct {
+	kernfs.InodeAttrs
+	kernfs.InodeNoDynamicLookup
+	kernfs.InodeNotSymlink
+	kernfs.InodeDirectoryNoNewChildren
+
+	kernfs.OrderedChildren
+	dentry kernfs.Dentry
+}
+
+func (fs *filesystem) newDir(creds *auth.Credentials, mode linux.FileMode, contents map[string]*kernfs.Dentry) *kernfs.Dentry {
+	d := &dir{}
+	d.InodeAttrs.Init(creds, fs.NextIno(), linux.ModeDirectory|0755)
+	d.OrderedChildren.Init(kernfs.OrderedChildrenOptions{})
+	d.dentry.Init(d)
+
+	d.IncLinks(d.OrderedChildren.Populate(&d.dentry, contents))
+
+	return &d.dentry
+}
+
+// SetStat implements kernfs.Inode.SetStat.
+func (d *dir) SetStat(fs *vfs.Filesystem, opts vfs.SetStatOptions) error {
+	return syserror.EPERM
+}
+
+// Open implements kernfs.Inode.Open.
+func (d *dir) Open(rp *vfs.ResolvingPath, vfsd *vfs.Dentry, flags uint32) (*vfs.FileDescription, error) {
+	fd := &kernfs.GenericDirectoryFD{}
+	fd.Init(rp.Mount(), vfsd, &d.OrderedChildren, flags)
+	return fd.VFSFileDescription(), nil
+}
+
+// cpuFile implements kernfs.Inode.
+type cpuFile struct {
+	kernfs.DynamicBytesFile
+	maxCores uint
+}
+
+// Generate implements vfs.DynamicBytesSource.Generate.
+func (c *cpuFile) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	fmt.Fprintf(buf, "0-%d", c.maxCores-1)
+	return nil
+}
+
+func (fs *filesystem) newCPUFile(creds *auth.Credentials, maxCores uint, mode linux.FileMode) *kernfs.Dentry {
+	c := &cpuFile{maxCores: maxCores}
+	c.DynamicBytesFile.Init(creds, fs.NextIno(), c, mode)
+	d := &kernfs.Dentry{}
+	d.Init(c)
+	return d
+}