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// Copyright 2018 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 linux
import (
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/binary"
"gvisor.dev/gvisor/pkg/sentry/arch"
"gvisor.dev/gvisor/pkg/sentry/fs"
"gvisor.dev/gvisor/pkg/sentry/kernel"
"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
"gvisor.dev/gvisor/pkg/sentry/usermem"
"gvisor.dev/gvisor/pkg/syserror"
)
// Stat implements linux syscall stat(2).
func Stat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
addr := args[0].Pointer()
statAddr := args[1].Pointer()
path, dirPath, err := copyInPath(t, addr, false /* allowEmpty */)
if err != nil {
return 0, nil, err
}
return 0, nil, fileOpOn(t, linux.AT_FDCWD, path, true /* resolve */, func(root *fs.Dirent, d *fs.Dirent, _ uint) error {
return stat(t, d, dirPath, statAddr)
})
}
// Fstatat implements linux syscall newfstatat, i.e. fstatat(2).
func Fstatat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
fd := kdefs.FD(args[0].Int())
addr := args[1].Pointer()
statAddr := args[2].Pointer()
flags := args[3].Int()
path, dirPath, err := copyInPath(t, addr, flags&linux.AT_EMPTY_PATH != 0)
if err != nil {
return 0, nil, err
}
if path == "" {
// Annoying. What's wrong with fstat?
file := t.FDMap().GetFile(fd)
if file == nil {
return 0, nil, syserror.EBADF
}
defer file.DecRef()
return 0, nil, fstat(t, file, statAddr)
}
// If the path ends in a slash (i.e. dirPath is true) or if AT_SYMLINK_NOFOLLOW is unset,
// then we must resolve the final component.
resolve := dirPath || flags&linux.AT_SYMLINK_NOFOLLOW == 0
return 0, nil, fileOpOn(t, fd, path, resolve, func(root *fs.Dirent, d *fs.Dirent, _ uint) error {
return stat(t, d, dirPath, statAddr)
})
}
// Lstat implements linux syscall lstat(2).
func Lstat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
addr := args[0].Pointer()
statAddr := args[1].Pointer()
path, dirPath, err := copyInPath(t, addr, false /* allowEmpty */)
if err != nil {
return 0, nil, err
}
// If the path ends in a slash (i.e. dirPath is true), then we *do*
// want to resolve the final component.
resolve := dirPath
return 0, nil, fileOpOn(t, linux.AT_FDCWD, path, resolve, func(root *fs.Dirent, d *fs.Dirent, _ uint) error {
return stat(t, d, dirPath, statAddr)
})
}
// Fstat implements linux syscall fstat(2).
func Fstat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
fd := kdefs.FD(args[0].Int())
statAddr := args[1].Pointer()
file := t.FDMap().GetFile(fd)
if file == nil {
return 0, nil, syserror.EBADF
}
defer file.DecRef()
return 0, nil, fstat(t, file, statAddr)
}
// stat implements stat from the given *fs.Dirent.
func stat(t *kernel.Task, d *fs.Dirent, dirPath bool, statAddr usermem.Addr) error {
if dirPath && !fs.IsDir(d.Inode.StableAttr) {
return syserror.ENOTDIR
}
uattr, err := d.Inode.UnstableAttr(t)
if err != nil {
return err
}
return copyOutStat(t, statAddr, d.Inode.StableAttr, uattr)
}
// fstat implements fstat for the given *fs.File.
func fstat(t *kernel.Task, f *fs.File, statAddr usermem.Addr) error {
uattr, err := f.UnstableAttr(t)
if err != nil {
return err
}
return copyOutStat(t, statAddr, f.Dirent.Inode.StableAttr, uattr)
}
// copyOutStat copies the attributes (sattr, uattr) to the struct stat at
// address dst in t's address space. It encodes the stat struct to bytes
// manually, as stat() is a very common syscall for many applications, and
// t.CopyObjectOut has noticeable performance impact due to its many slice
// allocations and use of reflection.
func copyOutStat(t *kernel.Task, dst usermem.Addr, sattr fs.StableAttr, uattr fs.UnstableAttr) error {
var mode uint32
switch sattr.Type {
case fs.RegularFile, fs.SpecialFile:
mode |= linux.ModeRegular
case fs.Symlink:
mode |= linux.ModeSymlink
case fs.Directory, fs.SpecialDirectory:
mode |= linux.ModeDirectory
case fs.Pipe:
mode |= linux.ModeNamedPipe
case fs.CharacterDevice:
mode |= linux.ModeCharacterDevice
case fs.BlockDevice:
mode |= linux.ModeBlockDevice
case fs.Socket:
mode |= linux.ModeSocket
}
b := t.CopyScratchBuffer(int(linux.SizeOfStat))[:0]
// Dev (uint64)
b = binary.AppendUint64(b, usermem.ByteOrder, uint64(sattr.DeviceID))
// Ino (uint64)
b = binary.AppendUint64(b, usermem.ByteOrder, uint64(sattr.InodeID))
// Nlink (uint64)
b = binary.AppendUint64(b, usermem.ByteOrder, uattr.Links)
// Mode (uint32)
b = binary.AppendUint32(b, usermem.ByteOrder, mode|uint32(uattr.Perms.LinuxMode()))
// UID (uint32)
b = binary.AppendUint32(b, usermem.ByteOrder, uint32(uattr.Owner.UID.In(t.UserNamespace()).OrOverflow()))
// GID (uint32)
b = binary.AppendUint32(b, usermem.ByteOrder, uint32(uattr.Owner.GID.In(t.UserNamespace()).OrOverflow()))
// Padding (uint32)
b = binary.AppendUint32(b, usermem.ByteOrder, 0)
// Rdev (uint64)
b = binary.AppendUint64(b, usermem.ByteOrder, uint64(linux.MakeDeviceID(sattr.DeviceFileMajor, sattr.DeviceFileMinor)))
// Size (uint64)
b = binary.AppendUint64(b, usermem.ByteOrder, uint64(uattr.Size))
// Blksize (uint64)
b = binary.AppendUint64(b, usermem.ByteOrder, uint64(sattr.BlockSize))
// Blocks (uint64)
b = binary.AppendUint64(b, usermem.ByteOrder, uint64(uattr.Usage/512))
// ATime
atime := uattr.AccessTime.Timespec()
b = binary.AppendUint64(b, usermem.ByteOrder, uint64(atime.Sec))
b = binary.AppendUint64(b, usermem.ByteOrder, uint64(atime.Nsec))
// MTime
mtime := uattr.ModificationTime.Timespec()
b = binary.AppendUint64(b, usermem.ByteOrder, uint64(mtime.Sec))
b = binary.AppendUint64(b, usermem.ByteOrder, uint64(mtime.Nsec))
// CTime
ctime := uattr.StatusChangeTime.Timespec()
b = binary.AppendUint64(b, usermem.ByteOrder, uint64(ctime.Sec))
b = binary.AppendUint64(b, usermem.ByteOrder, uint64(ctime.Nsec))
_, err := t.CopyOutBytes(dst, b)
return err
}
// Statfs implements linux syscall statfs(2).
func Statfs(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
addr := args[0].Pointer()
statfsAddr := args[1].Pointer()
path, _, err := copyInPath(t, addr, false /* allowEmpty */)
if err != nil {
return 0, nil, err
}
return 0, nil, fileOpOn(t, linux.AT_FDCWD, path, true /* resolve */, func(root *fs.Dirent, d *fs.Dirent, _ uint) error {
return statfsImpl(t, d, statfsAddr)
})
}
// Fstatfs implements linux syscall fstatfs(2).
func Fstatfs(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
fd := kdefs.FD(args[0].Int())
statfsAddr := args[1].Pointer()
file := t.FDMap().GetFile(fd)
if file == nil {
return 0, nil, syserror.EBADF
}
defer file.DecRef()
return 0, nil, statfsImpl(t, file.Dirent, statfsAddr)
}
// statfsImpl implements the linux syscall statfs and fstatfs based on a Dirent,
// copying the statfs structure out to addr on success, otherwise an error is
// returned.
func statfsImpl(t *kernel.Task, d *fs.Dirent, addr usermem.Addr) error {
info, err := d.Inode.StatFS(t)
if err != nil {
return err
}
// Construct the statfs structure and copy it out.
statfs := linux.Statfs{
Type: info.Type,
// Treat block size and fragment size as the same, as
// most consumers of this structure will expect one
// or the other to be filled in.
BlockSize: d.Inode.StableAttr.BlockSize,
Blocks: info.TotalBlocks,
// We don't have the concept of reserved blocks, so
// report blocks free the same as available blocks.
// This is a normal thing for filesystems, to do, see
// udf, hugetlbfs, tmpfs, among others.
BlocksFree: info.FreeBlocks,
BlocksAvailable: info.FreeBlocks,
Files: info.TotalFiles,
FilesFree: info.FreeFiles,
// Same as Linux for simple_statfs, see fs/libfs.c.
NameLength: linux.NAME_MAX,
FragmentSize: d.Inode.StableAttr.BlockSize,
// Leave other fields 0 like simple_statfs does.
}
if _, err := t.CopyOut(addr, &statfs); err != nil {
return err
}
return nil
}
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