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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 fs
import (
"bytes"
"fmt"
"gvisor.googlesource.com/gvisor/pkg/sentry/context"
"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
)
// inotifyEventBaseSize is the base size of linux's struct inotify_event. This
// must be a power 2 for rounding below.
const inotifyEventBaseSize = 16
// Event represents a struct inotify_event from linux.
//
// +stateify savable
type Event struct {
eventEntry
wd int32
mask uint32
cookie uint32
// len is computed based on the name field is set automatically by
// Event.setName. It should be 0 when no name is set; otherwise it is the
// length of the name slice.
len uint32
// The name field has special padding requirements and should only be set by
// calling Event.setName.
name []byte
}
func newEvent(wd int32, name string, events, cookie uint32) *Event {
e := &Event{
wd: wd,
mask: events,
cookie: cookie,
}
if name != "" {
e.setName(name)
}
return e
}
// paddedBytes converts a go string to a null-terminated c-string, padded with
// null bytes to a total size of 'l'. 'l' must be large enough for all the bytes
// in the 's' plus at least one null byte.
func paddedBytes(s string, l uint32) []byte {
if l < uint32(len(s)+1) {
panic("Converting string to byte array results in truncation, this can lead to buffer-overflow due to the missing null-byte!")
}
b := make([]byte, l)
copy(b, s)
// b was zero-value initialized during make(), so the rest of the slice is
// already filled with null bytes.
return b
}
// setName sets the optional name for this event.
func (e *Event) setName(name string) {
// We need to pad the name such that the entire event length ends up a
// multiple of inotifyEventBaseSize.
unpaddedLen := len(name) + 1
// Round up to nearest multiple of inotifyEventBaseSize.
e.len = uint32((unpaddedLen + inotifyEventBaseSize - 1) & ^(inotifyEventBaseSize - 1))
// Make sure we haven't overflowed and wrapped around when rounding.
if unpaddedLen > int(e.len) {
panic("Overflow when rounding inotify event size, the 'name' field was too big.")
}
e.name = paddedBytes(name, e.len)
}
func (e *Event) sizeOf() int {
s := inotifyEventBaseSize + int(e.len)
if s < inotifyEventBaseSize {
panic("overflow")
}
return s
}
// CopyTo serializes this event to dst. buf is used as a scratch buffer to
// construct the output. We use a buffer allocated ahead of time for
// performance. buf must be at least inotifyEventBaseSize bytes.
func (e *Event) CopyTo(ctx context.Context, buf []byte, dst usermem.IOSequence) (int64, error) {
usermem.ByteOrder.PutUint32(buf[0:], uint32(e.wd))
usermem.ByteOrder.PutUint32(buf[4:], e.mask)
usermem.ByteOrder.PutUint32(buf[8:], e.cookie)
usermem.ByteOrder.PutUint32(buf[12:], e.len)
writeLen := 0
n, err := dst.CopyOut(ctx, buf)
if err != nil {
return 0, err
}
writeLen += n
dst = dst.DropFirst(n)
if e.len > 0 {
n, err = dst.CopyOut(ctx, e.name)
if err != nil {
return 0, err
}
writeLen += n
}
// Santiy check.
if writeLen != e.sizeOf() {
panic(fmt.Sprintf("Serialized unexpected amount of data for an event, expected %v, wrote %v.", e.sizeOf(), writeLen))
}
return int64(writeLen), nil
}
func (e *Event) equals(other *Event) bool {
return e.wd == other.wd &&
e.mask == other.mask &&
e.cookie == other.cookie &&
e.len == other.len &&
bytes.Equal(e.name, other.name)
}
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