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 }