rev 55196 : 8225716: G1 GC: Undefined behaviour in G1BlockOffsetTablePart::block_at_or_preceding
Reviewed-by: duke
1 /*
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24
25 #ifndef SHARE_GC_G1_G1BLOCKOFFSETTABLE_INLINE_HPP
26 #define SHARE_GC_G1_G1BLOCKOFFSETTABLE_INLINE_HPP
27
28 #include "gc/g1/g1BlockOffsetTable.hpp"
29 #include "gc/g1/heapRegion.hpp"
30 #include "gc/shared/memset_with_concurrent_readers.hpp"
31 #include "gc/shared/space.hpp"
32
33 inline HeapWord* G1BlockOffsetTablePart::block_start(const void* addr) {
34 if (addr >= _space->bottom() && addr < _space->end()) {
35 HeapWord* q = block_at_or_preceding(addr, true, _next_offset_index-1);
36 return forward_to_block_containing_addr(q, addr);
37 } else {
38 return NULL;
39 }
40 }
41
42 inline HeapWord* G1BlockOffsetTablePart::block_start_const(const void* addr) const {
43 if (addr >= _space->bottom() && addr < _space->end()) {
44 HeapWord* q = block_at_or_preceding(addr, true, _next_offset_index-1);
45 HeapWord* n = q + block_size(q);
46 return forward_to_block_containing_addr_const(q, n, addr);
47 } else {
48 return NULL;
49 }
50 }
51
52 u_char G1BlockOffsetTable::offset_array(size_t index) const {
53 check_index(index, "index out of range");
54 return Atomic::load(&_offset_array[index]);
55 }
56
57 void G1BlockOffsetTable::set_offset_array(size_t index, u_char offset) {
58 check_index(index, "index out of range");
59 set_offset_array_raw(index, offset);
60 }
61
62 void G1BlockOffsetTable::set_offset_array(size_t index, HeapWord* high, HeapWord* low) {
63 check_index(index, "index out of range");
64 assert(high >= low, "addresses out of order");
65 size_t offset = pointer_delta(high, low);
66 check_offset(offset, "offset too large");
67 set_offset_array(index, (u_char)offset);
68 }
69
70 void G1BlockOffsetTable::set_offset_array(size_t left, size_t right, u_char offset) {
71 check_index(right, "right index out of range");
72 assert(left <= right, "indexes out of order");
73 size_t num_cards = right - left + 1;
74 memset_with_concurrent_readers(&_offset_array[left], offset, num_cards);
75 }
76
77 // Variant of index_for that does not check the index for validity.
78 inline size_t G1BlockOffsetTable::index_for_raw(const void* p) const {
79 return pointer_delta((char*)p, _reserved.start(), sizeof(char)) >> BOTConstants::LogN;
80 }
81
82 inline size_t G1BlockOffsetTable::index_for(const void* p) const {
83 char* pc = (char*)p;
84 assert(pc >= (char*)_reserved.start() &&
85 pc < (char*)_reserved.end(),
86 "p (" PTR_FORMAT ") not in reserved [" PTR_FORMAT ", " PTR_FORMAT ")",
87 p2i(p), p2i(_reserved.start()), p2i(_reserved.end()));
88 size_t result = index_for_raw(p);
89 check_index(result, "bad index from address");
90 return result;
91 }
92
93 inline HeapWord* G1BlockOffsetTable::address_for_index(size_t index) const {
94 check_index(index, "index out of range");
95 HeapWord* result = address_for_index_raw(index);
96 assert(result >= _reserved.start() && result < _reserved.end(),
97 "bad address from index result " PTR_FORMAT
98 " _reserved.start() " PTR_FORMAT " _reserved.end() " PTR_FORMAT,
99 p2i(result), p2i(_reserved.start()), p2i(_reserved.end()));
100 return result;
101 }
102
103 inline size_t G1BlockOffsetTablePart::block_size(const HeapWord* p) const {
104 return _space->block_size(p);
105 }
106
107 inline HeapWord* G1BlockOffsetTablePart::block_at_or_preceding(const void* addr,
108 bool has_max_index,
109 size_t max_index) const {
110 assert(_object_can_span || _bot->offset_array(_bot->index_for(_space->bottom())) == 0,
111 "Object crossed region boundary, found offset %u instead of 0",
112 (uint) _bot->offset_array(_bot->index_for(_space->bottom())));
113 size_t index = _bot->index_for(addr);
114 // We must make sure that the offset table entry we use is valid. If
115 // "addr" is past the end, start at the last known one and go forward.
116 if (has_max_index) {
117 index = MIN2(index, max_index);
118 }
119 HeapWord* q = _bot->address_for_index(index);
120
121 uint offset = _bot->offset_array(index); // Extend u_char to uint.
122 while (offset >= BOTConstants::N_words) {
123 // The excess of the offset from N_words indicates a power of Base
124 // to go back by.
125 size_t n_cards_back = BOTConstants::entry_to_cards_back(offset);
126 q -= (BOTConstants::N_words * n_cards_back);
127 index -= n_cards_back;
128 offset = _bot->offset_array(index);
129 }
130 assert(offset < BOTConstants::N_words, "offset too large");
131 q -= offset;
132 return q;
133 }
134
135 inline HeapWord* G1BlockOffsetTablePart::forward_to_block_containing_addr_const(HeapWord* q, HeapWord* n,
136 const void* addr) const {
137 if (addr >= _space->top()) return _space->top();
138 while (n <= addr) {
139 q = n;
140 oop obj = oop(q);
141 if (obj->klass_or_null_acquire() == NULL) {
142 return q;
143 }
144 n += block_size(q);
145 }
146 assert(q <= n, "wrong order for q and addr");
147 assert(addr < n, "wrong order for addr and n");
148 return q;
149 }
150
151 inline HeapWord* G1BlockOffsetTablePart::forward_to_block_containing_addr(HeapWord* q,
152 const void* addr) {
153 if (oop(q)->klass_or_null_acquire() == NULL) {
154 return q;
155 }
156 HeapWord* n = q + block_size(q);
157 // In the normal case, where the query "addr" is a card boundary, and the
158 // offset table chunks are the same size as cards, the block starting at
159 // "q" will contain addr, so the test below will fail, and we'll fall
160 // through quickly.
161 if (n <= addr) {
162 q = forward_to_block_containing_addr_slow(q, n, addr);
163 }
164 assert(q <= addr, "wrong order for current and arg");
165 return q;
166 }
167
168 #endif // SHARE_GC_G1_G1BLOCKOFFSETTABLE_INLINE_HPP
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