1 /* 2 * Stack-less Just-In-Time compiler 3 * 4 * Copyright Zoltan Herczeg (hzmester (at) 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 struct chunk_header { 72 void *executable; 73 int fd; 74 }; 75 76 /* 77 alloc_chunk / free_chunk : 78 * allocate executable system memory chunks 79 * the size is always divisible by CHUNK_SIZE 80 allocator_grab_lock / allocator_release_lock : 81 * make the allocator thread safe 82 * can be empty if the OS (or the application) does not support threading 83 * only the allocator requires this lock, sljit is fully thread safe 84 as it only uses local variables 85 */ 86 87 #include <fcntl.h> 88 89 #ifndef O_NOATIME 90 #define O_NOATIME 0 91 #endif 92 93 #ifdef __O_TMPFILE 94 #ifndef O_TMPFILE 95 #define O_TMPFILE (__O_TMPFILE | O_DIRECTORY) 96 #endif 97 #endif 98 99 int mkostemp(char *template, int flags); 100 char *secure_getenv(const char *name); 101 102 static SLJIT_INLINE int create_tempfile(void) 103 { 104 int fd; 105 106 char tmp_name[256]; 107 size_t tmp_name_len; 108 char *dir; 109 size_t len; 110 111 #ifdef P_tmpdir 112 len = (P_tmpdir != NULL) ? strlen(P_tmpdir) : 0; 113 114 if (len > 0 && len < sizeof(tmp_name)) { 115 strcpy(tmp_name, P_tmpdir); 116 tmp_name_len = len; 117 } 118 else { 119 strcpy(tmp_name, "/tmp"); 120 tmp_name_len = 4; 121 } 122 #else 123 strcpy(tmp_name, "/tmp"); 124 tmp_name_len = 4; 125 #endif 126 127 dir = secure_getenv("TMPDIR"); 128 if (dir) { 129 len = strlen(dir); 130 if (len > 0 && len < sizeof(tmp_name)) { 131 strcpy(tmp_name, dir); 132 tmp_name_len = len; 133 } 134 } 135 136 SLJIT_ASSERT(tmp_name_len > 0 && tmp_name_len < sizeof(tmp_name)); 137 138 while (tmp_name_len > 0 && tmp_name[tmp_name_len - 1] == '/') { 139 tmp_name_len--; 140 tmp_name[tmp_name_len] = '\0'; 141 } 142 143 #ifdef O_TMPFILE 144 fd = open(tmp_name, O_TMPFILE | O_EXCL | O_RDWR | O_NOATIME | O_CLOEXEC, S_IRUSR | S_IWUSR); 145 if (fd != -1) 146 return fd; 147 #endif 148 149 if (tmp_name_len + 7 >= sizeof(tmp_name)) 150 { 151 return -1; 152 } 153 154 strcpy(tmp_name + tmp_name_len, "/XXXXXX"); 155 fd = mkostemp(tmp_name, O_CLOEXEC | O_NOATIME); 156 157 if (fd == -1) 158 return fd; 159 160 if (unlink(tmp_name)) { 161 close(fd); 162 return -1; 163 } 164 165 return fd; 166 } 167 168 static SLJIT_INLINE struct chunk_header* alloc_chunk(sljit_uw size) 169 { 170 struct chunk_header *retval; 171 int fd; 172 173 fd = create_tempfile(); 174 if (fd == -1) 175 return NULL; 176 177 if (ftruncate(fd, size)) { 178 close(fd); 179 return NULL; 180 } 181 182 retval = (struct chunk_header *)mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); 183 184 if (retval == MAP_FAILED) { 185 close(fd); 186 return NULL; 187 } 188 189 retval->executable = mmap(NULL, size, PROT_READ | PROT_EXEC, MAP_SHARED, fd, 0); 190 191 if (retval->executable == MAP_FAILED) { 192 munmap(retval, size); 193 close(fd); 194 return NULL; 195 } 196 197 retval->fd = fd; 198 return retval; 199 } 200 201 static SLJIT_INLINE void free_chunk(void *chunk, sljit_uw size) 202 { 203 struct chunk_header *header = ((struct chunk_header *)chunk) - 1; 204 205 int fd = header->fd; 206 munmap(header->executable, size); 207 munmap(header, size); 208 close(fd); 209 } 210 211 /* --------------------------------------------------------------------- */ 212 /* Common functions */ 213 /* --------------------------------------------------------------------- */ 214 215 #define CHUNK_MASK (~(CHUNK_SIZE - 1)) 216 217 struct block_header { 218 sljit_uw size; 219 sljit_uw prev_size; 220 sljit_sw executable_offset; 221 }; 222 223 struct free_block { 224 struct block_header header; 225 struct free_block *next; 226 struct free_block *prev; 227 sljit_uw size; 228 }; 229 230 #define AS_BLOCK_HEADER(base, offset) \ 231 ((struct block_header*)(((sljit_u8*)base) + offset)) 232 #define AS_FREE_BLOCK(base, offset) \ 233 ((struct free_block*)(((sljit_u8*)base) + offset)) 234 #define MEM_START(base) ((void*)((base) + 1)) 235 #define ALIGN_SIZE(size) (((size) + sizeof(struct block_header) + 7) & ~7) 236 237 static struct free_block* free_blocks; 238 static sljit_uw allocated_size; 239 static sljit_uw total_size; 240 241 static SLJIT_INLINE void sljit_insert_free_block(struct free_block *free_block, sljit_uw size) 242 { 243 free_block->header.size = 0; 244 free_block->size = size; 245 246 free_block->next = free_blocks; 247 free_block->prev = NULL; 248 if (free_blocks) 249 free_blocks->prev = free_block; 250 free_blocks = free_block; 251 } 252 253 static SLJIT_INLINE void sljit_remove_free_block(struct free_block *free_block) 254 { 255 if (free_block->next) 256 free_block->next->prev = free_block->prev; 257 258 if (free_block->prev) 259 free_block->prev->next = free_block->next; 260 else { 261 SLJIT_ASSERT(free_blocks == free_block); 262 free_blocks = free_block->next; 263 } 264 } 265 266 SLJIT_API_FUNC_ATTRIBUTE void* sljit_malloc_exec(sljit_uw size) 267 { 268 struct chunk_header *chunk_header; 269 struct block_header *header; 270 struct block_header *next_header; 271 struct free_block *free_block; 272 sljit_uw chunk_size; 273 sljit_sw executable_offset; 274 275 allocator_grab_lock(); 276 if (size < (64 - sizeof(struct block_header))) 277 size = (64 - sizeof(struct block_header)); 278 size = ALIGN_SIZE(size); 279 280 free_block = free_blocks; 281 while (free_block) { 282 if (free_block->size >= size) { 283 chunk_size = free_block->size; 284 if (chunk_size > size + 64) { 285 /* We just cut a block from the end of the free block. */ 286 chunk_size -= size; 287 free_block->size = chunk_size; 288 header = AS_BLOCK_HEADER(free_block, chunk_size); 289 header->prev_size = chunk_size; 290 header->executable_offset = free_block->header.executable_offset; 291 AS_BLOCK_HEADER(header, size)->prev_size = size; 292 } 293 else { 294 sljit_remove_free_block(free_block); 295 header = (struct block_header*)free_block; 296 size = chunk_size; 297 } 298 allocated_size += size; 299 header->size = size; 300 allocator_release_lock(); 301 return MEM_START(header); 302 } 303 free_block = free_block->next; 304 } 305 306 chunk_size = sizeof(struct chunk_header) + sizeof(struct block_header); 307 chunk_size = (chunk_size + size + CHUNK_SIZE - 1) & CHUNK_MASK; 308 309 chunk_header = alloc_chunk(chunk_size); 310 if (!chunk_header) { 311 allocator_release_lock(); 312 return NULL; 313 } 314 315 executable_offset = (sljit_sw)((sljit_u8*)chunk_header->executable - (sljit_u8*)chunk_header); 316 317 chunk_size -= sizeof(struct chunk_header) + sizeof(struct block_header); 318 total_size += chunk_size; 319 320 header = (struct block_header *)(chunk_header + 1); 321 322 header->prev_size = 0; 323 header->executable_offset = executable_offset; 324 if (chunk_size > size + 64) { 325 /* Cut the allocated space into a free and a used block. */ 326 allocated_size += size; 327 header->size = size; 328 chunk_size -= size; 329 330 free_block = AS_FREE_BLOCK(header, size); 331 free_block->header.prev_size = size; 332 free_block->header.executable_offset = executable_offset; 333 sljit_insert_free_block(free_block, chunk_size); 334 next_header = AS_BLOCK_HEADER(free_block, chunk_size); 335 } 336 else { 337 /* All space belongs to this allocation. */ 338 allocated_size += chunk_size; 339 header->size = chunk_size; 340 next_header = AS_BLOCK_HEADER(header, chunk_size); 341 } 342 next_header->size = 1; 343 next_header->prev_size = chunk_size; 344 next_header->executable_offset = executable_offset; 345 allocator_release_lock(); 346 return MEM_START(header); 347 } 348 349 SLJIT_API_FUNC_ATTRIBUTE void sljit_free_exec(void* ptr) 350 { 351 struct block_header *header; 352 struct free_block* free_block; 353 354 allocator_grab_lock(); 355 header = AS_BLOCK_HEADER(ptr, -(sljit_sw)sizeof(struct block_header)); 356 header = AS_BLOCK_HEADER(header, -header->executable_offset); 357 allocated_size -= header->size; 358 359 /* Connecting free blocks together if possible. */ 360 361 /* If header->prev_size == 0, free_block will equal to header. 362 In this case, free_block->header.size will be > 0. */ 363 free_block = AS_FREE_BLOCK(header, -(sljit_sw)header->prev_size); 364 if (SLJIT_UNLIKELY(!free_block->header.size)) { 365 free_block->size += header->size; 366 header = AS_BLOCK_HEADER(free_block, free_block->size); 367 header->prev_size = free_block->size; 368 } 369 else { 370 free_block = (struct free_block*)header; 371 sljit_insert_free_block(free_block, header->size); 372 } 373 374 header = AS_BLOCK_HEADER(free_block, free_block->size); 375 if (SLJIT_UNLIKELY(!header->size)) { 376 free_block->size += ((struct free_block*)header)->size; 377 sljit_remove_free_block((struct free_block*)header); 378 header = AS_BLOCK_HEADER(free_block, free_block->size); 379 header->prev_size = free_block->size; 380 } 381 382 /* The whole chunk is free. */ 383 if (SLJIT_UNLIKELY(!free_block->header.prev_size && header->size == 1)) { 384 /* If this block is freed, we still have (allocated_size / 2) free space. */ 385 if (total_size - free_block->size > (allocated_size * 3 / 2)) { 386 total_size -= free_block->size; 387 sljit_remove_free_block(free_block); 388 free_chunk(free_block, free_block->size + sizeof(struct block_header)); 389 } 390 } 391 392 allocator_release_lock(); 393 } 394 395 SLJIT_API_FUNC_ATTRIBUTE void sljit_free_unused_memory_exec(void) 396 { 397 struct free_block* free_block; 398 struct free_block* next_free_block; 399 400 allocator_grab_lock(); 401 402 free_block = free_blocks; 403 while (free_block) { 404 next_free_block = free_block->next; 405 if (!free_block->header.prev_size && 406 AS_BLOCK_HEADER(free_block, free_block->size)->size == 1) { 407 total_size -= free_block->size; 408 sljit_remove_free_block(free_block); 409 free_chunk(free_block, free_block->size + sizeof(struct block_header)); 410 } 411 free_block = next_free_block; 412 } 413 414 SLJIT_ASSERT((total_size && free_blocks) || (!total_size && !free_blocks)); 415 allocator_release_lock(); 416 } 417 418 SLJIT_API_FUNC_ATTRIBUTE sljit_sw sljit_exec_offset(void* ptr) 419 { 420 return ((struct block_header *)(ptr))[-1].executable_offset; 421 } 422
