1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
|
// Copyright 2018 Google Inc.
//
// 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 fsutil
import (
"fmt"
"io"
"math"
"gvisor.googlesource.com/gvisor/pkg/sentry/context"
"gvisor.googlesource.com/gvisor/pkg/sentry/memmap"
"gvisor.googlesource.com/gvisor/pkg/sentry/platform"
"gvisor.googlesource.com/gvisor/pkg/sentry/safemem"
"gvisor.googlesource.com/gvisor/pkg/sentry/usage"
"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
)
// FileRangeSet maps offsets into a memmap.Mappable to offsets into a
// platform.File. It is used to implement Mappables that store data in
// sparsely-allocated memory.
//
// type FileRangeSet <generated by go_generics>
// fileRangeSetFunctions implements segment.Functions for FileRangeSet.
type fileRangeSetFunctions struct{}
// MinKey implements segment.Functions.MinKey.
func (fileRangeSetFunctions) MinKey() uint64 {
return 0
}
// MaxKey implements segment.Functions.MaxKey.
func (fileRangeSetFunctions) MaxKey() uint64 {
return math.MaxUint64
}
// ClearValue implements segment.Functions.ClearValue.
func (fileRangeSetFunctions) ClearValue(_ *uint64) {
}
// Merge implements segment.Functions.Merge.
func (fileRangeSetFunctions) Merge(mr1 memmap.MappableRange, frstart1 uint64, _ memmap.MappableRange, frstart2 uint64) (uint64, bool) {
if frstart1+mr1.Length() != frstart2 {
return 0, false
}
return frstart1, true
}
// Split implements segment.Functions.Split.
func (fileRangeSetFunctions) Split(mr memmap.MappableRange, frstart uint64, split uint64) (uint64, uint64) {
return frstart, frstart + (split - mr.Start)
}
// FileRange returns the FileRange mapped by seg.
func (seg FileRangeIterator) FileRange() platform.FileRange {
return seg.FileRangeOf(seg.Range())
}
// FileRangeOf returns the FileRange mapped by mr.
//
// Preconditions: seg.Range().IsSupersetOf(mr). mr.Length() != 0.
func (seg FileRangeIterator) FileRangeOf(mr memmap.MappableRange) platform.FileRange {
frstart := seg.Value() + (mr.Start - seg.Start())
return platform.FileRange{frstart, frstart + mr.Length()}
}
// Fill attempts to ensure that all memmap.Mappable offsets in required are
// mapped to a platform.File offset, by allocating from mem with the given
// memory usage kind and invoking readAt to store data into memory. (If readAt
// returns a successful partial read, Fill will call it repeatedly until all
// bytes have been read.) EOF is handled consistently with the requirements of
// mmap(2): bytes after EOF on the same page are zeroed; pages after EOF are
// invalid.
//
// Fill may read offsets outside of required, but will never read offsets
// outside of optional. It returns a non-nil error if any error occurs, even
// if the error only affects offsets in optional, but not in required.
//
// Preconditions: required.Length() > 0. optional.IsSupersetOf(required).
// required and optional must be page-aligned.
func (frs *FileRangeSet) Fill(ctx context.Context, required, optional memmap.MappableRange, mem platform.Memory, kind usage.MemoryKind, readAt func(ctx context.Context, dsts safemem.BlockSeq, offset uint64) (uint64, error)) error {
gap := frs.LowerBoundGap(required.Start)
for gap.Ok() && gap.Start() < required.End {
if gap.Range().Length() == 0 {
gap = gap.NextGap()
continue
}
gr := gap.Range().Intersect(optional)
// Read data into the gap.
fr, err := platform.AllocateAndFill(mem, gr.Length(), kind, safemem.ReaderFunc(func(dsts safemem.BlockSeq) (uint64, error) {
var done uint64
for !dsts.IsEmpty() {
n, err := readAt(ctx, dsts, gr.Start+done)
done += n
dsts = dsts.DropFirst64(n)
if err != nil {
if err == io.EOF {
// platform.AllocateAndFill truncates down to a page
// boundary, but FileRangeSet.Fill is supposed to
// zero-fill to the end of the page in this case.
donepgaddr, ok := usermem.Addr(done).RoundUp()
if donepg := uint64(donepgaddr); ok && donepg != done {
dsts.DropFirst64(donepg - done)
done = donepg
if dsts.IsEmpty() {
return done, nil
}
}
}
return done, err
}
}
return done, nil
}))
// Store anything we managed to read into the cache.
if done := fr.Length(); done != 0 {
gr.End = gr.Start + done
gap = frs.Insert(gap, gr, fr.Start).NextGap()
}
if err != nil {
return err
}
}
return nil
}
// Drop removes segments for memmap.Mappable offsets in mr, freeing the
// corresponding platform.FileRanges.
//
// Preconditions: mr must be page-aligned.
func (frs *FileRangeSet) Drop(mr memmap.MappableRange, mem platform.Memory) {
seg := frs.LowerBoundSegment(mr.Start)
for seg.Ok() && seg.Start() < mr.End {
seg = frs.Isolate(seg, mr)
mem.DecRef(seg.FileRange())
seg = frs.Remove(seg).NextSegment()
}
}
// DropAll removes all segments in mr, freeing the corresponding
// platform.FileRanges.
func (frs *FileRangeSet) DropAll(mem platform.Memory) {
for seg := frs.FirstSegment(); seg.Ok(); seg = seg.NextSegment() {
mem.DecRef(seg.FileRange())
}
frs.RemoveAll()
}
// Truncate updates frs to reflect Mappable truncation to the given length:
// bytes after the new EOF on the same page are zeroed, and pages after the new
// EOF are freed.
func (frs *FileRangeSet) Truncate(end uint64, mem platform.Memory) {
pgendaddr, ok := usermem.Addr(end).RoundUp()
if ok {
pgend := uint64(pgendaddr)
// Free truncated pages.
frs.SplitAt(pgend)
seg := frs.LowerBoundSegment(pgend)
for seg.Ok() {
mem.DecRef(seg.FileRange())
seg = frs.Remove(seg).NextSegment()
}
if end == pgend {
return
}
}
// Here we know end < end.RoundUp(). If the new EOF lands in the
// middle of a page that we have, zero out its contents beyond the new
// length.
seg := frs.FindSegment(end)
if seg.Ok() {
fr := seg.FileRange()
fr.Start += end - seg.Start()
ims, err := mem.MapInternal(fr, usermem.Write)
if err != nil {
// There's no good recourse from here. This means
// that we can't keep cached memory consistent with
// the new end of file. The caller may have already
// updated the file size on their backing file system.
//
// We don't want to risk blindly continuing onward,
// so in the extremely rare cases this does happen,
// we abandon ship.
panic(fmt.Sprintf("Failed to map %v: %v", fr, err))
}
if _, err := safemem.ZeroSeq(ims); err != nil {
panic(fmt.Sprintf("Zeroing %v failed: %v", fr, err))
}
}
}
|
