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// Copyright 2020 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 vfs2
import (
"fmt"
"gvisor.dev/gvisor/pkg/errors/linuxerr"
"gvisor.dev/gvisor/pkg/hostarch"
"gvisor.dev/gvisor/pkg/sentry/arch"
"gvisor.dev/gvisor/pkg/sentry/kernel"
"gvisor.dev/gvisor/pkg/sentry/vfs"
"gvisor.dev/gvisor/pkg/sync"
)
// Getdents implements Linux syscall getdents(2).
func Getdents(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
return getdents(t, args, false /* isGetdents64 */)
}
// Getdents64 implements Linux syscall getdents64(2).
func Getdents64(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
return getdents(t, args, true /* isGetdents64 */)
}
func getdents(t *kernel.Task, args arch.SyscallArguments, isGetdents64 bool) (uintptr, *kernel.SyscallControl, error) {
fd := args[0].Int()
addr := args[1].Pointer()
size := int(args[2].Uint())
file := t.GetFileVFS2(fd)
if file == nil {
return 0, nil, linuxerr.EBADF
}
defer file.DecRef(t)
cb := getGetdentsCallback(t, addr, size, isGetdents64)
err := file.IterDirents(t, cb)
n := size - cb.remaining
putGetdentsCallback(cb)
if n == 0 {
return 0, nil, err
}
return uintptr(n), nil, nil
}
type getdentsCallback struct {
t *kernel.Task
addr hostarch.Addr
remaining int
isGetdents64 bool
}
var getdentsCallbackPool = sync.Pool{
New: func() interface{} {
return &getdentsCallback{}
},
}
func getGetdentsCallback(t *kernel.Task, addr hostarch.Addr, size int, isGetdents64 bool) *getdentsCallback {
cb := getdentsCallbackPool.Get().(*getdentsCallback)
*cb = getdentsCallback{
t: t,
addr: addr,
remaining: size,
isGetdents64: isGetdents64,
}
return cb
}
func putGetdentsCallback(cb *getdentsCallback) {
cb.t = nil
getdentsCallbackPool.Put(cb)
}
// Handle implements vfs.IterDirentsCallback.Handle.
func (cb *getdentsCallback) Handle(dirent vfs.Dirent) error {
var buf []byte
if cb.isGetdents64 {
// struct linux_dirent64 {
// ino64_t d_ino; /* 64-bit inode number */
// off64_t d_off; /* 64-bit offset to next structure */
// unsigned short d_reclen; /* Size of this dirent */
// unsigned char d_type; /* File type */
// char d_name[]; /* Filename (null-terminated) */
// };
size := 8 + 8 + 2 + 1 + 1 + len(dirent.Name)
size = (size + 7) &^ 7 // round up to multiple of 8
if size > cb.remaining {
return linuxerr.EINVAL
}
buf = cb.t.CopyScratchBuffer(size)
hostarch.ByteOrder.PutUint64(buf[0:8], dirent.Ino)
hostarch.ByteOrder.PutUint64(buf[8:16], uint64(dirent.NextOff))
hostarch.ByteOrder.PutUint16(buf[16:18], uint16(size))
buf[18] = dirent.Type
copy(buf[19:], dirent.Name)
// Zero out all remaining bytes in buf, including the NUL terminator
// after dirent.Name.
bufTail := buf[19+len(dirent.Name):]
for i := range bufTail {
bufTail[i] = 0
}
} else {
// struct linux_dirent {
// unsigned long d_ino; /* Inode number */
// unsigned long d_off; /* Offset to next linux_dirent */
// unsigned short d_reclen; /* Length of this linux_dirent */
// char d_name[]; /* Filename (null-terminated) */
// /* length is actually (d_reclen - 2 -
// offsetof(struct linux_dirent, d_name)) */
// /*
// char pad; // Zero padding byte
// char d_type; // File type (only since Linux
// // 2.6.4); offset is (d_reclen - 1)
// */
// };
if cb.t.Arch().Width() != 8 {
panic(fmt.Sprintf("unsupported sizeof(unsigned long): %d", cb.t.Arch().Width()))
}
size := 8 + 8 + 2 + 1 + 1 + len(dirent.Name)
size = (size + 7) &^ 7 // round up to multiple of sizeof(long)
if size > cb.remaining {
return linuxerr.EINVAL
}
buf = cb.t.CopyScratchBuffer(size)
hostarch.ByteOrder.PutUint64(buf[0:8], dirent.Ino)
hostarch.ByteOrder.PutUint64(buf[8:16], uint64(dirent.NextOff))
hostarch.ByteOrder.PutUint16(buf[16:18], uint16(size))
copy(buf[18:], dirent.Name)
// Zero out all remaining bytes in buf, including the NUL terminator
// after dirent.Name and the zero padding byte between the name and
// dirent type.
bufTail := buf[18+len(dirent.Name) : size-1]
for i := range bufTail {
bufTail[i] = 0
}
buf[size-1] = dirent.Type
}
n, err := cb.t.CopyOutBytes(cb.addr, buf)
if err != nil {
// Don't report partially-written dirents by advancing cb.addr or
// cb.remaining.
return err
}
cb.addr += hostarch.Addr(n)
cb.remaining -= n
return nil
}
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