1 /* 2 * Stack-less Just-In-Time compiler 3 * 4 * Copyright 2009-2012 Zoltan Herczeg (hzmester@freemail.hu). All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without modification, are 7 * permitted provided that the following conditions are met: 8 * 9 * 1. Redistributions of source code must retain the above copyright notice, this list of 10 * conditions and the following disclaimer. 11 * 12 * 2. Redistributions in binary form must reproduce the above copyright notice, this list 13 * of conditions and the following disclaimer in the documentation and/or other materials 14 * provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) AND CONTRIBUTORS ``AS IS'' AND ANY 17 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT 19 * SHALL THE COPYRIGHT HOLDER(S) OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED 21 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR 22 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 23 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 24 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 */ 26 27 /* 28 This file contains a simple executable memory allocator 29 30 It is assumed, that executable code blocks are usually medium (or sometimes 31 large) memory blocks, and the allocator is not too frequently called (less 32 optimized than other allocators). Thus, using it as a generic allocator is 33 not suggested. 34 35 How does it work: 36 Memory is allocated in continuous memory areas called chunks by alloc_chunk() 37 Chunk format: 38 [ block ][ block ] ... [ block ][ block terminator ] 39 40 All blocks and the block terminator is started with block_header. The block 41 header contains the size of the previous and the next block. These sizes 42 can also contain special values. 43 Block size: 44 0 - The block is a free_block, with a different size member. 45 1 - The block is a block terminator. 46 n - The block is used at the moment, and the value contains its size. 47 Previous block size: 48 0 - This is the first block of the memory chunk. 49 n - The size of the previous block. 50 51 Using these size values we can go forward or backward on the block chain. 52 The unused blocks are stored in a chain list pointed by free_blocks. This 53 list is useful if we need to find a suitable memory area when the allocator 54 is called. 55 56 When a block is freed, the new free block is connected to its adjacent free 57 blocks if possible. 58 59 [ free block ][ used block ][ free block ] 60 and "used block" is freed, the three blocks are connected together: 61 [ one big free block ] 62 */ 63 64 /* --------------------------------------------------------------------- */ 65 /* System (OS) functions */ 66 /* --------------------------------------------------------------------- */ 67 68 /* 64 KByte. */ 69 #define CHUNK_SIZE 0x10000 70 71 /* 72 alloc_chunk / free_chunk : 73 * allocate executable system memory chunks 74 * the size is always divisible by CHUNK_SIZE 75 allocator_grab_lock / allocator_release_lock : 76 * make the allocator thread safe 77 * can be empty if the OS (or the application) does not support threading 78 * only the allocator requires this lock, sljit is fully thread safe 79 as it only uses local variables 80 */ 81 82 #ifdef _WIN32 83 84 static SLJIT_INLINE void* alloc_chunk(sljit_uw size) 85 { 86 return VirtualAlloc(0, size, MEM_COMMIT | MEM_RESERVE, PAGE_EXECUTE_READWRITE); 87 } 88 89 static SLJIT_INLINE void free_chunk(void* chunk, sljit_uw size) 90 { 91 SLJIT_UNUSED_ARG(size); 92 VirtualFree(chunk, 0, MEM_RELEASE); 93 } 94 95 #else 96 97 #include <sys/mman.h> 98 99 static SLJIT_INLINE void* alloc_chunk(sljit_uw size) 100 { 101 void* retval = mmap(0, size, PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE | MAP_ANON, -1, 0); 102 return (retval != MAP_FAILED) ? retval : NULL; 103 } 104 105 static SLJIT_INLINE void free_chunk(void* chunk, sljit_uw size) 106 { 107 munmap(chunk, size); 108 } 109 110 #endif 111 112 /* --------------------------------------------------------------------- */ 113 /* Common functions */ 114 /* --------------------------------------------------------------------- */ 115 116 #define CHUNK_MASK (~(CHUNK_SIZE - 1)) 117 118 struct block_header { 119 sljit_uw size; 120 sljit_uw prev_size; 121 }; 122 123 struct free_block { 124 struct block_header header; 125 struct free_block *next; 126 struct free_block *prev; 127 sljit_uw size; 128 }; 129 130 #define AS_BLOCK_HEADER(base, offset) \ 131 ((struct block_header*)(((sljit_ub*)base) + offset)) 132 #define AS_FREE_BLOCK(base, offset) \ 133 ((struct free_block*)(((sljit_ub*)base) + offset)) 134 #define MEM_START(base) ((void*)(((sljit_ub*)base) + sizeof(struct block_header))) 135 #define ALIGN_SIZE(size) (((size) + sizeof(struct block_header) + 7) & ~7) 136 137 static struct free_block* free_blocks; 138 static sljit_uw allocated_size; 139 static sljit_uw total_size; 140 141 static SLJIT_INLINE void sljit_insert_free_block(struct free_block *free_block, sljit_uw size) 142 { 143 free_block->header.size = 0; 144 free_block->size = size; 145 146 free_block->next = free_blocks; 147 free_block->prev = 0; 148 if (free_blocks) 149 free_blocks->prev = free_block; 150 free_blocks = free_block; 151 } 152 153 static SLJIT_INLINE void sljit_remove_free_block(struct free_block *free_block) 154 { 155 if (free_block->next) 156 free_block->next->prev = free_block->prev; 157 158 if (free_block->prev) 159 free_block->prev->next = free_block->next; 160 else { 161 SLJIT_ASSERT(free_blocks == free_block); 162 free_blocks = free_block->next; 163 } 164 } 165 166 SLJIT_API_FUNC_ATTRIBUTE void* sljit_malloc_exec(sljit_uw size) 167 { 168 struct block_header *header; 169 struct block_header *next_header; 170 struct free_block *free_block; 171 sljit_uw chunk_size; 172 173 allocator_grab_lock(); 174 if (size < sizeof(struct free_block)) 175 size = sizeof(struct free_block); 176 size = ALIGN_SIZE(size); 177 178 free_block = free_blocks; 179 while (free_block) { 180 if (free_block->size >= size) { 181 chunk_size = free_block->size; 182 if (chunk_size > size + 64) { 183 /* We just cut a block from the end of the free block. */ 184 chunk_size -= size; 185 free_block->size = chunk_size; 186 header = AS_BLOCK_HEADER(free_block, chunk_size); 187 header->prev_size = chunk_size; 188 AS_BLOCK_HEADER(header, size)->prev_size = size; 189 } 190 else { 191 sljit_remove_free_block(free_block); 192 header = (struct block_header*)free_block; 193 size = chunk_size; 194 } 195 allocated_size += size; 196 header->size = size; 197 allocator_release_lock(); 198 return MEM_START(header); 199 } 200 free_block = free_block->next; 201 } 202 203 chunk_size = (size + sizeof(struct block_header) + CHUNK_SIZE - 1) & CHUNK_MASK; 204 header = (struct block_header*)alloc_chunk(chunk_size); 205 PTR_FAIL_IF(!header); 206 207 chunk_size -= sizeof(struct block_header); 208 total_size += chunk_size; 209 210 header->prev_size = 0; 211 if (chunk_size > size + 64) { 212 /* Cut the allocated space into a free and a used block. */ 213 allocated_size += size; 214 header->size = size; 215 chunk_size -= size; 216 217 free_block = AS_FREE_BLOCK(header, size); 218 free_block->header.prev_size = size; 219 sljit_insert_free_block(free_block, chunk_size); 220 next_header = AS_BLOCK_HEADER(free_block, chunk_size); 221 } 222 else { 223 /* All space belongs to this allocation. */ 224 allocated_size += chunk_size; 225 header->size = chunk_size; 226 next_header = AS_BLOCK_HEADER(header, chunk_size); 227 } 228 next_header->size = 1; 229 next_header->prev_size = chunk_size; 230 allocator_release_lock(); 231 return MEM_START(header); 232 } 233 234 SLJIT_API_FUNC_ATTRIBUTE void sljit_free_exec(void* ptr) 235 { 236 struct block_header *header; 237 struct free_block* free_block; 238 239 allocator_grab_lock(); 240 header = AS_BLOCK_HEADER(ptr, -(sljit_w)sizeof(struct block_header)); 241 allocated_size -= header->size; 242 243 /* Connecting free blocks together if possible. */ 244 245 /* If header->prev_size == 0, free_block will equal to header. 246 In this case, free_block->header.size will be > 0. */ 247 free_block = AS_FREE_BLOCK(header, -(sljit_w)header->prev_size); 248 if (SLJIT_UNLIKELY(!free_block->header.size)) { 249 free_block->size += header->size; 250 header = AS_BLOCK_HEADER(free_block, free_block->size); 251 header->prev_size = free_block->size; 252 } 253 else { 254 free_block = (struct free_block*)header; 255 sljit_insert_free_block(free_block, header->size); 256 } 257 258 header = AS_BLOCK_HEADER(free_block, free_block->size); 259 if (SLJIT_UNLIKELY(!header->size)) { 260 free_block->size += ((struct free_block*)header)->size; 261 sljit_remove_free_block((struct free_block*)header); 262 header = AS_BLOCK_HEADER(free_block, free_block->size); 263 header->prev_size = free_block->size; 264 } 265 266 /* The whole chunk is free. */ 267 if (SLJIT_UNLIKELY(!free_block->header.prev_size && header->size == 1)) { 268 /* If this block is freed, we still have (allocated_size / 2) free space. */ 269 if (total_size - free_block->size > (allocated_size * 3 / 2)) { 270 total_size -= free_block->size; 271 sljit_remove_free_block(free_block); 272 free_chunk(free_block, free_block->size + sizeof(struct block_header)); 273 } 274 } 275 276 allocator_release_lock(); 277 } 278