1 /*
2 * Copyright (c) 2019, 2023, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "logging/log.hpp"
27 #include "memory/metaspace.hpp"
28 #include "oops/compressedKlass.hpp"
29 #include "runtime/globals.hpp"
30 #include "runtime/os.hpp"
31 #include "utilities/debug.hpp"
32 #include "utilities/globalDefinitions.hpp"
33 #include "utilities/ostream.hpp"
34
35 address CompressedKlassPointers::_base = nullptr;
36 int CompressedKlassPointers::_shift = 0;
37 size_t CompressedKlassPointers::_range = 0;
38
39 #ifdef _LP64
40
41 #ifdef ASSERT
42 void CompressedKlassPointers::assert_is_valid_encoding(address addr, size_t len, address base, int shift) {
43 assert(base + nth_bit(32 + shift) >= addr + len, "Encoding (base=" PTR_FORMAT ", shift=%d) does not "
44 "fully cover the class range " PTR_FORMAT "-" PTR_FORMAT, p2i(base), shift, p2i(addr), p2i(addr + len));
45 }
46 #endif
47
48 // Given a klass range [addr, addr+len) and a given encoding scheme, assert that this scheme covers the range, then
49 // set this encoding scheme. Used by CDS at runtime to re-instate the scheme used to pre-compute klass ids for
50 // archived heap objects.
51 void CompressedKlassPointers::initialize_for_given_encoding(address addr, size_t len, address requested_base, int requested_shift) {
52 address const end = addr + len;
53
54 const int narrow_klasspointer_bits = sizeof(narrowKlass) * 8;
55 const size_t encoding_range_size = nth_bit(narrow_klasspointer_bits + requested_shift);
56 address encoding_range_end = requested_base + encoding_range_size;
57
58 // Note: it would be technically valid for the encoding base to precede the start of the Klass range. But we only call
59 // this function from CDS, and therefore know this to be true.
60 assert(requested_base == addr, "Invalid requested base");
61 assert(encoding_range_end >= end, "Encoding does not cover the full Klass range");
62
63 _base = requested_base;
64 _shift = requested_shift;
65 _range = encoding_range_size;
66
67 DEBUG_ONLY(assert_is_valid_encoding(addr, len, _base, _shift);)
68 }
69
70 char* CompressedKlassPointers::reserve_address_space_X(uintptr_t from, uintptr_t to, size_t size, size_t alignment, bool aslr) {
71 alignment = MAX2(Metaspace::reserve_alignment(), alignment);
72 return os::attempt_reserve_memory_between((char*)from, (char*)to, size, alignment, aslr);
73 }
74
75 char* CompressedKlassPointers::reserve_address_space_for_unscaled_encoding(size_t size, bool aslr) {
76 return reserve_address_space_X(0, nth_bit(32), size, Metaspace::reserve_alignment(), aslr);
77 }
78
79 char* CompressedKlassPointers::reserve_address_space_for_zerobased_encoding(size_t size, bool aslr) {
80 return reserve_address_space_X(nth_bit(32), nth_bit(32 + LogKlassAlignmentInBytes), size, Metaspace::reserve_alignment(), aslr);
81 }
82
83 char* CompressedKlassPointers::reserve_address_space_for_16bit_move(size_t size, bool aslr) {
84 return reserve_address_space_X(nth_bit(32), nth_bit(48), size, nth_bit(32), aslr);
85 }
86
87 #if !defined(AARCH64) || defined(ZERO)
88 // On aarch64 we have an own version; all other platforms use the default version
89 void CompressedKlassPointers::initialize(address addr, size_t len) {
90 // The default version of this code tries, in order of preference:
91 // -unscaled (base=0 shift=0)
92 // -zero-based (base=0 shift>0)
93 // -nonzero-base (base>0 shift=0)
94 // Note that base>0 shift>0 should never be needed, since the klass range will
95 // never exceed 4GB.
96 constexpr uintptr_t unscaled_max = nth_bit(32);
97 assert(len <= unscaled_max, "Klass range larger than 32 bits?");
98
99 constexpr uintptr_t zerobased_max = nth_bit(32 + LogKlassAlignmentInBytes);
100
101 address const end = addr + len;
102 if (end <= (address)unscaled_max) {
103 _base = nullptr;
104 _shift = 0;
105 } else {
106 if (end <= (address)zerobased_max) {
107 _base = nullptr;
108 _shift = LogKlassAlignmentInBytes;
109 } else {
110 _base = addr;
111 _shift = 0;
112 }
113 }
114 _range = end - _base;
115
116 DEBUG_ONLY(assert_is_valid_encoding(addr, len, _base, _shift);)
117 }
118 #endif // !AARCH64 || ZERO
119
120 void CompressedKlassPointers::print_mode(outputStream* st) {
121 st->print_cr("Narrow klass base: " PTR_FORMAT ", Narrow klass shift: %d, "
122 "Narrow klass range: " SIZE_FORMAT_X, p2i(base()), shift(),
123 range());
124 }
125
126 #endif // _LP64