1 files changed, 259 insertions, 0 deletions
diff --git a/pkg/sentry/syscalls/linux/sys_stat.go b/pkg/sentry/syscalls/linux/sys_stat.go
new file mode 100644
index 000000000..10fc201ef
--- /dev/null
+++ b/pkg/sentry/syscalls/linux/sys_stat.go
@@ -0,0 +1,259 @@
+// 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.googlesource.com/gvisor/pkg/abi/linux"
+	"gvisor.googlesource.com/gvisor/pkg/binary"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel/kdefs"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+	"gvisor.googlesource.com/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) 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) 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) 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) 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
+}