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
|
// Copyright 2012 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "src/zone/zone.h"
#include <cstring>
#include "src/asan.h"
#include "src/utils.h"
#include "src/v8.h"
namespace v8 {
namespace internal {
namespace {
#ifdef V8_USE_ADDRESS_SANITIZER
constexpr size_t kASanRedzoneBytes = 24; // Must be a multiple of 8.
#else // !V8_USE_ADDRESS_SANITIZER
constexpr size_t kASanRedzoneBytes = 0;
#endif // V8_USE_ADDRESS_SANITIZER
} // namespace
Zone::Zone(AccountingAllocator* allocator, const char* name,
SegmentSize segment_size)
: allocation_size_(0),
segment_bytes_allocated_(0),
position_(0),
limit_(0),
allocator_(allocator),
segment_head_(nullptr),
name_(name),
sealed_(false),
segment_size_(segment_size) {
allocator_->ZoneCreation(this);
}
Zone::~Zone() {
allocator_->ZoneDestruction(this);
DeleteAll();
DCHECK_EQ(segment_bytes_allocated_, 0);
}
void* Zone::New(size_t size) {
CHECK(!sealed_);
// Round up the requested size to fit the alignment.
size = RoundUp(size, kAlignmentInBytes);
// Check if the requested size is available without expanding.
Address result = position_;
const size_t size_with_redzone = size + kASanRedzoneBytes;
DCHECK(limit_ >= position_);
if (size_with_redzone > limit_ - position_) {
result = NewExpand(size_with_redzone);
} else {
position_ += size_with_redzone;
}
Address redzone_position = result + size;
DCHECK_EQ(redzone_position + kASanRedzoneBytes, position_);
ASAN_POISON_MEMORY_REGION(reinterpret_cast<void*>(redzone_position),
kASanRedzoneBytes);
// Check that the result has the proper alignment and return it.
DCHECK(IsAddressAligned(result, kAlignmentInBytes, 0));
allocation_size_ += size;
return reinterpret_cast<void*>(result);
}
void Zone::DeleteAll() {
// Traverse the chained list of segments and return them all to the allocator.
for (Segment* current = segment_head_; current;) {
Segment* next = current->next();
size_t size = current->size();
// Un-poison the segment content so we can re-use or zap it later.
ASAN_UNPOISON_MEMORY_REGION(reinterpret_cast<void*>(current->start()),
current->capacity());
segment_bytes_allocated_ -= size;
allocator_->ReturnSegment(current);
current = next;
}
position_ = limit_ = 0;
allocation_size_ = 0;
segment_head_ = nullptr;
}
// Creates a new segment, sets it size, and pushes it to the front
// of the segment chain. Returns the new segment.
Segment* Zone::NewSegment(size_t requested_size) {
Segment* result = allocator_->GetSegment(requested_size);
if (result != nullptr) {
DCHECK_GE(result->size(), requested_size);
segment_bytes_allocated_ += result->size();
result->set_zone(this);
result->set_next(segment_head_);
segment_head_ = result;
}
return result;
}
Address Zone::NewExpand(size_t size) {
// Make sure the requested size is already properly aligned and that
// there isn't enough room in the Zone to satisfy the request.
DCHECK_EQ(size, RoundDown(size, kAlignmentInBytes));
DCHECK(limit_ - position_ < size);
// Compute the new segment size. We use a 'high water mark'
// strategy, where we increase the segment size every time we expand
// except that we employ a maximum segment size when we delete. This
// is to avoid excessive malloc() and free() overhead.
Segment* head = segment_head_;
const size_t old_size = (head == nullptr) ? 0 : head->size();
static const size_t kSegmentOverhead = sizeof(Segment) + kAlignmentInBytes;
const size_t new_size_no_overhead = size + (old_size << 1);
size_t new_size = kSegmentOverhead + new_size_no_overhead;
const size_t min_new_size = kSegmentOverhead + size;
// Guard against integer overflow.
if (new_size_no_overhead < size || new_size < kSegmentOverhead) {
V8::FatalProcessOutOfMemory(nullptr, "Zone");
return kNullAddress;
}
if (segment_size_ == SegmentSize::kLarge) {
new_size = kMaximumSegmentSize;
}
if (new_size < kMinimumSegmentSize) {
new_size = kMinimumSegmentSize;
} else if (new_size > kMaximumSegmentSize) {
// Limit the size of new segments to avoid growing the segment size
// exponentially, thus putting pressure on contiguous virtual address space.
// All the while making sure to allocate a segment large enough to hold the
// requested size.
new_size = Max(min_new_size, kMaximumSegmentSize);
}
if (new_size > INT_MAX) {
V8::FatalProcessOutOfMemory(nullptr, "Zone");
return kNullAddress;
}
Segment* segment = NewSegment(new_size);
if (segment == nullptr) {
V8::FatalProcessOutOfMemory(nullptr, "Zone");
return kNullAddress;
}
// Recompute 'top' and 'limit' based on the new segment.
Address result = RoundUp(segment->start(), kAlignmentInBytes);
position_ = result + size;
// Check for address overflow.
// (Should not happen since the segment is guaranteed to accommodate
// size bytes + header and alignment padding)
DCHECK(position_ >= result);
limit_ = segment->end();
DCHECK(position_ <= limit_);
return result;
}
} // namespace internal
} // namespace v8
|
