150 lines
4.6 KiB
Go
150 lines
4.6 KiB
Go
// Copyright 2020 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 vfs2
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import (
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"fmt"
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"gvisor.dev/gvisor/pkg/sentry/arch"
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"gvisor.dev/gvisor/pkg/sentry/kernel"
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"gvisor.dev/gvisor/pkg/sentry/vfs"
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"gvisor.dev/gvisor/pkg/sync"
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"gvisor.dev/gvisor/pkg/syserror"
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"gvisor.dev/gvisor/pkg/usermem"
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)
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// Getdents implements Linux syscall getdents(2).
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func Getdents(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
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return getdents(t, args, false /* isGetdents64 */)
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}
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// Getdents64 implements Linux syscall getdents64(2).
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func Getdents64(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
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return getdents(t, args, true /* isGetdents64 */)
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}
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func getdents(t *kernel.Task, args arch.SyscallArguments, isGetdents64 bool) (uintptr, *kernel.SyscallControl, error) {
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fd := args[0].Int()
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addr := args[1].Pointer()
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size := int(args[2].Uint())
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file := t.GetFileVFS2(fd)
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if file == nil {
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return 0, nil, syserror.EBADF
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}
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defer file.DecRef()
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cb := getGetdentsCallback(t, addr, size, isGetdents64)
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err := file.IterDirents(t, cb)
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n := size - cb.remaining
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putGetdentsCallback(cb)
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if n == 0 {
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return 0, nil, err
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}
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return uintptr(n), nil, nil
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}
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type getdentsCallback struct {
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t *kernel.Task
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addr usermem.Addr
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remaining int
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isGetdents64 bool
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}
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var getdentsCallbackPool = sync.Pool{
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New: func() interface{} {
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return &getdentsCallback{}
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},
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}
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func getGetdentsCallback(t *kernel.Task, addr usermem.Addr, size int, isGetdents64 bool) *getdentsCallback {
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cb := getdentsCallbackPool.Get().(*getdentsCallback)
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*cb = getdentsCallback{
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t: t,
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addr: addr,
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remaining: size,
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isGetdents64: isGetdents64,
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}
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return cb
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}
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func putGetdentsCallback(cb *getdentsCallback) {
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cb.t = nil
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getdentsCallbackPool.Put(cb)
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}
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// Handle implements vfs.IterDirentsCallback.Handle.
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func (cb *getdentsCallback) Handle(dirent vfs.Dirent) error {
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var buf []byte
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if cb.isGetdents64 {
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// struct linux_dirent64 {
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// ino64_t d_ino; /* 64-bit inode number */
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// off64_t d_off; /* 64-bit offset to next structure */
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// unsigned short d_reclen; /* Size of this dirent */
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// unsigned char d_type; /* File type */
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// char d_name[]; /* Filename (null-terminated) */
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// };
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size := 8 + 8 + 2 + 1 + 1 + len(dirent.Name)
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if size < cb.remaining {
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return syserror.EINVAL
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}
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buf = cb.t.CopyScratchBuffer(size)
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usermem.ByteOrder.PutUint64(buf[0:8], dirent.Ino)
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usermem.ByteOrder.PutUint64(buf[8:16], uint64(dirent.NextOff))
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usermem.ByteOrder.PutUint16(buf[16:18], uint16(size))
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buf[18] = dirent.Type
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copy(buf[19:], dirent.Name)
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buf[size-1] = 0 // NUL terminator
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} else {
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// struct linux_dirent {
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// unsigned long d_ino; /* Inode number */
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// unsigned long d_off; /* Offset to next linux_dirent */
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// unsigned short d_reclen; /* Length of this linux_dirent */
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// char d_name[]; /* Filename (null-terminated) */
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// /* length is actually (d_reclen - 2 -
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// offsetof(struct linux_dirent, d_name)) */
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// /*
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// char pad; // Zero padding byte
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// char d_type; // File type (only since Linux
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// // 2.6.4); offset is (d_reclen - 1)
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// */
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// };
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if cb.t.Arch().Width() != 8 {
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panic(fmt.Sprintf("unsupported sizeof(unsigned long): %d", cb.t.Arch().Width()))
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}
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size := 8 + 8 + 2 + 1 + 1 + 1 + len(dirent.Name)
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if size < cb.remaining {
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return syserror.EINVAL
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}
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buf = cb.t.CopyScratchBuffer(size)
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usermem.ByteOrder.PutUint64(buf[0:8], dirent.Ino)
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usermem.ByteOrder.PutUint64(buf[8:16], uint64(dirent.NextOff))
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usermem.ByteOrder.PutUint16(buf[16:18], uint16(size))
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copy(buf[18:], dirent.Name)
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buf[size-3] = 0 // NUL terminator
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buf[size-2] = 0 // zero padding byte
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buf[size-1] = dirent.Type
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}
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n, err := cb.t.CopyOutBytes(cb.addr, buf)
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if err != nil {
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// Don't report partially-written dirents by advancing cb.addr or
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// cb.remaining.
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return err
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}
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cb.addr += usermem.Addr(n)
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cb.remaining -= n
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return nil
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}
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