1 /*
2 * Copyright (c) 2006, 2025, 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 "utilities/copy.hpp"
26 #include "runtime/sharedRuntime.hpp"
27 #include "utilities/align.hpp"
28 #include "utilities/byteswap.hpp"
29 #include "utilities/copy.hpp"
30
31
32 // Copy bytes; larger units are filled atomically if everything is aligned.
33 void Copy::conjoint_memory_atomic(const void* from, void* to, size_t size) {
34 uintptr_t bits = (uintptr_t) from | (uintptr_t) to | (uintptr_t) size;
35
36 // (Note: We could improve performance by ignoring the low bits of size,
37 // and putting a short cleanup loop after each bulk copy loop.
38 // There are plenty of other ways to make this faster also,
39 // and it's a slippery slope. For now, let's keep this code simple
40 // since the simplicity helps clarify the atomicity semantics of
41 // this operation. There are also CPU-specific assembly versions
42 // which may or may not want to include such optimizations.)
43
44 if (bits % sizeof(jlong) == 0) {
45 Copy::conjoint_jlongs_atomic((const jlong*) from, (jlong*) to, size / sizeof(jlong));
46 } else if (bits % sizeof(jint) == 0) {
47 Copy::conjoint_jints_atomic((const jint*) from, (jint*) to, size / sizeof(jint));
48 } else if (bits % sizeof(jshort) == 0) {
49 Copy::conjoint_jshorts_atomic((const jshort*) from, (jshort*) to, size / sizeof(jshort));
50 } else {
51 // Not aligned, so no need to be atomic.
52 Copy::conjoint_jbytes((const void*) from, (void*) to, size);
53 }
54 }
55
56 class CopySwap : AllStatic {
57 public:
58 /**
59 * Copy and optionally byte swap elements
60 *
61 * <swap> - true if elements should be byte swapped
62 *
63 * @param src address of source
64 * @param dst address of destination
65 * @param byte_count number of bytes to copy
66 * @param elem_size size of the elements to copy-swap
67 */
68 template<bool swap>
69 static void conjoint_swap_if_needed(const void* src, void* dst, size_t byte_count, size_t elem_size) {
70 assert(src != nullptr, "address must not be null");
71 assert(dst != nullptr, "address must not be null");
72 assert(elem_size == 2 || elem_size == 4 || elem_size == 8,
73 "incorrect element size: %zu", elem_size);
74 assert(is_aligned(byte_count, elem_size),
75 "byte_count %zu must be multiple of element size %zu", byte_count, elem_size);
76
77 address src_end = (address)src + byte_count;
78
79 if (dst <= src || dst >= src_end) {
80 do_conjoint_swap<RIGHT,swap>(src, dst, byte_count, elem_size);
81 } else {
82 do_conjoint_swap<LEFT,swap>(src, dst, byte_count, elem_size);
83 }
84 }
85
86 private:
87 enum CopyDirection {
88 RIGHT, // lower -> higher address
89 LEFT // higher -> lower address
90 };
91
92 /**
93 * Copy and byte swap elements
94 *
95 * <T> - type of element to copy
96 * <D> - copy direction
97 * <is_src_aligned> - true if src argument is aligned to element size
98 * <is_dst_aligned> - true if dst argument is aligned to element size
99 *
100 * @param src address of source
101 * @param dst address of destination
102 * @param byte_count number of bytes to copy
103 */
104 template <typename T, CopyDirection D, bool swap, bool is_src_aligned, bool is_dst_aligned>
105 static void do_conjoint_swap(const void* src, void* dst, size_t byte_count) {
106 const char* cur_src;
107 char* cur_dst;
108
109 switch (D) {
110 case RIGHT:
111 cur_src = (const char*)src;
112 cur_dst = (char*)dst;
113 break;
114 case LEFT:
115 cur_src = (const char*)src + byte_count - sizeof(T);
116 cur_dst = (char*)dst + byte_count - sizeof(T);
117 break;
118 }
119
120 for (size_t i = 0; i < byte_count / sizeof(T); i++) {
121 T tmp;
122
123 if (is_src_aligned) {
124 tmp = *(T*)cur_src;
125 } else {
126 memcpy(&tmp, cur_src, sizeof(T));
127 }
128
129 if (swap) {
130 tmp = byteswap(tmp);
131 }
132
133 if (is_dst_aligned) {
134 *(T*)cur_dst = tmp;
135 } else {
136 memcpy(cur_dst, &tmp, sizeof(T));
137 }
138
139 switch (D) {
140 case RIGHT:
141 cur_src += sizeof(T);
142 cur_dst += sizeof(T);
143 break;
144 case LEFT:
145 cur_src -= sizeof(T);
146 cur_dst -= sizeof(T);
147 break;
148 }
149 }
150 }
151
152 /**
153 * Copy and byte swap elements
154 *
155 * <T> - type of element to copy
156 * <D> - copy direction
157 * <swap> - true if elements should be byte swapped
158 *
159 * @param src address of source
160 * @param dst address of destination
161 * @param byte_count number of bytes to copy
162 */
163 template <typename T, CopyDirection direction, bool swap>
164 static void do_conjoint_swap(const void* src, void* dst, size_t byte_count) {
165 if (is_aligned(src, sizeof(T))) {
166 if (is_aligned(dst, sizeof(T))) {
167 do_conjoint_swap<T,direction,swap,true,true>(src, dst, byte_count);
168 } else {
169 do_conjoint_swap<T,direction,swap,true,false>(src, dst, byte_count);
170 }
171 } else {
172 if (is_aligned(dst, sizeof(T))) {
173 do_conjoint_swap<T,direction,swap,false,true>(src, dst, byte_count);
174 } else {
175 do_conjoint_swap<T,direction,swap,false,false>(src, dst, byte_count);
176 }
177 }
178 }
179
180
181 /**
182 * Copy and byte swap elements
183 *
184 * <D> - copy direction
185 * <swap> - true if elements should be byte swapped
186 *
187 * @param src address of source
188 * @param dst address of destination
189 * @param byte_count number of bytes to copy
190 * @param elem_size size of the elements to copy-swap
191 */
192 template <CopyDirection D, bool swap>
193 static void do_conjoint_swap(const void* src, void* dst, size_t byte_count, size_t elem_size) {
194 switch (elem_size) {
195 case 2: do_conjoint_swap<uint16_t,D,swap>(src, dst, byte_count); break;
196 case 4: do_conjoint_swap<uint32_t,D,swap>(src, dst, byte_count); break;
197 case 8: do_conjoint_swap<uint64_t,D,swap>(src, dst, byte_count); break;
198 default: guarantee(false, "do_conjoint_swap: Invalid elem_size %zu\n", elem_size);
199 }
200 }
201 };
202
203 void Copy::conjoint_copy(const void* src, void* dst, size_t byte_count, size_t elem_size) {
204 CopySwap::conjoint_swap_if_needed<false>(src, dst, byte_count, elem_size);
205 }
206
207 void Copy::conjoint_swap(const void* src, void* dst, size_t byte_count, size_t elem_size) {
208 CopySwap::conjoint_swap_if_needed<true>(src, dst, byte_count, elem_size);
209 }
210
211 // Fill bytes; larger units are filled atomically if everything is aligned.
212 void Copy::fill_to_memory_atomic(void* to, size_t size, jubyte value) {
213 address dst = (address)to;
214 uintptr_t bits = (uintptr_t)to | (uintptr_t)size;
215 if (bits % sizeof(jlong) == 0) {
216 jlong fill = (julong)((jubyte)value); // zero-extend
217 if (fill != 0) {
218 fill += fill << 8;
219 fill += fill << 16;
220 fill += fill << 32;
221 }
222 // Copy::fill_to_jlongs_atomic((jlong*) dst, size / sizeof(jlong));
223 for (uintptr_t off = 0; off < size; off += sizeof(jlong)) {
224 *(jlong*)(dst + off) = fill;
225 }
226 } else if (bits % sizeof(jint) == 0) {
227 jint fill = (juint)((jubyte)value); // zero-extend
228 if (fill != 0) {
229 fill += fill << 8;
230 fill += fill << 16;
231 }
232 // Copy::fill_to_jints_atomic((jint*) dst, size / sizeof(jint));
233 for (uintptr_t off = 0; off < size; off += sizeof(jint)) {
234 *(jint*)(dst + off) = fill;
235 }
236 } else if (bits % sizeof(jshort) == 0) {
237 jshort fill = (jushort)((jubyte)value); // zero-extend
238 fill += (jshort)(fill << 8);
239 // Copy::fill_to_jshorts_atomic((jshort*) dst, size / sizeof(jshort));
240 for (uintptr_t off = 0; off < size; off += sizeof(jshort)) {
241 *(jshort*)(dst + off) = fill;
242 }
243 } else {
244 // Not aligned, so no need to be atomic.
245 #ifdef MUSL_LIBC
246 // This code is used by Unsafe and may hit the next page after truncation
247 // of mapped memory. Therefore, we use volatile to prevent compilers from
248 // replacing the loop by memset which may not trigger SIGBUS as needed
249 // (observed on Alpine Linux x86_64)
250 jbyte fill = value;
251 for (uintptr_t off = 0; off < size; off += sizeof(jbyte)) {
252 *(volatile jbyte*)(dst + off) = fill;
253 }
254 #else
255 Copy::fill_to_bytes(dst, size, value);
256 #endif
257 }
258 }