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// 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/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"
)
// Name is the default filesystem name.
const Name = "sysfs"
// 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 Inode.SetStat not allowing inode attributes to be changed.
func (*dir) SetStat(*vfs.Filesystem, *auth.Credentials, vfs.SetStatOptions) error {
return syserror.EPERM
}
// Open implements kernfs.Inode.Open.
func (d *dir) Open(rp *vfs.ResolvingPath, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
fd := &kernfs.GenericDirectoryFD{}
if err := fd.Init(rp.Mount(), vfsd, &d.OrderedChildren, &opts); err != nil {
return nil, err
}
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
}
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