1 /* 2 * mmap support for qemu 3 * 4 * Copyright (c) 2003 - 2008 Fabrice Bellard 5 * 6 * This program is free software; you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License as published by 8 * the Free Software Foundation; either version 2 of the License, or 9 * (at your option) any later version. 10 * 11 * This program is distributed in the hope that it will be useful, 12 * but WITHOUT ANY WARRANTY; without even the implied warranty of 13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 * GNU General Public License for more details. 15 * 16 * You should have received a copy of the GNU General Public License 17 * along with this program; if not, see <http://www.gnu.org/licenses/>. 18 */ 19 #include "qemu/osdep.h" 20 21 #include "qemu.h" 22 #include "qemu-common.h" 23 #include "bsd-mman.h" 24 25 //#define DEBUG_MMAP 26 27 static pthread_mutex_t mmap_mutex = PTHREAD_MUTEX_INITIALIZER; 28 static __thread int mmap_lock_count; 29 30 void mmap_lock(void) 31 { 32 if (mmap_lock_count++ == 0) { 33 pthread_mutex_lock(&mmap_mutex); 34 } 35 } 36 37 void mmap_unlock(void) 38 { 39 if (--mmap_lock_count == 0) { 40 pthread_mutex_unlock(&mmap_mutex); 41 } 42 } 43 44 bool have_mmap_lock(void) 45 { 46 return mmap_lock_count > 0 ? true : false; 47 } 48 49 /* Grab lock to make sure things are in a consistent state after fork(). */ 50 void mmap_fork_start(void) 51 { 52 if (mmap_lock_count) 53 abort(); 54 pthread_mutex_lock(&mmap_mutex); 55 } 56 57 void mmap_fork_end(int child) 58 { 59 if (child) 60 pthread_mutex_init(&mmap_mutex, NULL); 61 else 62 pthread_mutex_unlock(&mmap_mutex); 63 } 64 65 /* NOTE: all the constants are the HOST ones, but addresses are target. */ 66 int target_mprotect(abi_ulong start, abi_ulong len, int prot) 67 { 68 abi_ulong end, host_start, host_end, addr; 69 int prot1, ret; 70 71 #ifdef DEBUG_MMAP 72 printf("mprotect: start=0x" TARGET_FMT_lx 73 " len=0x" TARGET_FMT_lx " prot=%c%c%c\n", start, len, 74 prot & PROT_READ ? 'r' : '-', 75 prot & PROT_WRITE ? 'w' : '-', 76 prot & PROT_EXEC ? 'x' : '-'); 77 #endif 78 79 if ((start & ~TARGET_PAGE_MASK) != 0) 80 return -EINVAL; 81 len = TARGET_PAGE_ALIGN(len); 82 end = start + len; 83 if (end < start) 84 return -EINVAL; 85 prot &= PROT_READ | PROT_WRITE | PROT_EXEC; 86 if (len == 0) 87 return 0; 88 89 mmap_lock(); 90 host_start = start & qemu_host_page_mask; 91 host_end = HOST_PAGE_ALIGN(end); 92 if (start > host_start) { 93 /* handle host page containing start */ 94 prot1 = prot; 95 for(addr = host_start; addr < start; addr += TARGET_PAGE_SIZE) { 96 prot1 |= page_get_flags(addr); 97 } 98 if (host_end == host_start + qemu_host_page_size) { 99 for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) { 100 prot1 |= page_get_flags(addr); 101 } 102 end = host_end; 103 } 104 ret = mprotect(g2h(host_start), qemu_host_page_size, prot1 & PAGE_BITS); 105 if (ret != 0) 106 goto error; 107 host_start += qemu_host_page_size; 108 } 109 if (end < host_end) { 110 prot1 = prot; 111 for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) { 112 prot1 |= page_get_flags(addr); 113 } 114 ret = mprotect(g2h(host_end - qemu_host_page_size), qemu_host_page_size, 115 prot1 & PAGE_BITS); 116 if (ret != 0) 117 goto error; 118 host_end -= qemu_host_page_size; 119 } 120 121 /* handle the pages in the middle */ 122 if (host_start < host_end) { 123 ret = mprotect(g2h(host_start), host_end - host_start, prot); 124 if (ret != 0) 125 goto error; 126 } 127 page_set_flags(start, start + len, prot | PAGE_VALID); 128 mmap_unlock(); 129 return 0; 130 error: 131 mmap_unlock(); 132 return ret; 133 } 134 135 /* map an incomplete host page */ 136 static int mmap_frag(abi_ulong real_start, 137 abi_ulong start, abi_ulong end, 138 int prot, int flags, int fd, abi_ulong offset) 139 { 140 abi_ulong real_end, addr; 141 void *host_start; 142 int prot1, prot_new; 143 144 real_end = real_start + qemu_host_page_size; 145 host_start = g2h(real_start); 146 147 /* get the protection of the target pages outside the mapping */ 148 prot1 = 0; 149 for(addr = real_start; addr < real_end; addr++) { 150 if (addr < start || addr >= end) 151 prot1 |= page_get_flags(addr); 152 } 153 154 if (prot1 == 0) { 155 /* no page was there, so we allocate one */ 156 void *p = mmap(host_start, qemu_host_page_size, prot, 157 flags | MAP_ANON, -1, 0); 158 if (p == MAP_FAILED) 159 return -1; 160 prot1 = prot; 161 } 162 prot1 &= PAGE_BITS; 163 164 prot_new = prot | prot1; 165 if (!(flags & MAP_ANON)) { 166 /* msync() won't work here, so we return an error if write is 167 possible while it is a shared mapping */ 168 if ((flags & TARGET_BSD_MAP_FLAGMASK) == MAP_SHARED && 169 (prot & PROT_WRITE)) 170 return -1; 171 172 /* adjust protection to be able to read */ 173 if (!(prot1 & PROT_WRITE)) 174 mprotect(host_start, qemu_host_page_size, prot1 | PROT_WRITE); 175 176 /* read the corresponding file data */ 177 pread(fd, g2h(start), end - start, offset); 178 179 /* put final protection */ 180 if (prot_new != (prot1 | PROT_WRITE)) 181 mprotect(host_start, qemu_host_page_size, prot_new); 182 } else { 183 /* just update the protection */ 184 if (prot_new != prot1) { 185 mprotect(host_start, qemu_host_page_size, prot_new); 186 } 187 } 188 return 0; 189 } 190 191 static abi_ulong mmap_next_start = 0x40000000; 192 193 unsigned long last_brk; 194 195 /* find a free memory area of size 'size'. The search starts at 196 'start'. If 'start' == 0, then a default start address is used. 197 Return -1 if error. 198 */ 199 /* page_init() marks pages used by the host as reserved to be sure not 200 to use them. */ 201 static abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size) 202 { 203 abi_ulong addr, addr1, addr_start; 204 int prot; 205 unsigned long new_brk; 206 207 new_brk = (unsigned long)sbrk(0); 208 if (last_brk && last_brk < new_brk && last_brk == (target_ulong)last_brk) { 209 /* This is a hack to catch the host allocating memory with brk(). 210 If it uses mmap then we loose. 211 FIXME: We really want to avoid the host allocating memory in 212 the first place, and maybe leave some slack to avoid switching 213 to mmap. */ 214 page_set_flags(last_brk & TARGET_PAGE_MASK, 215 TARGET_PAGE_ALIGN(new_brk), 216 PAGE_RESERVED); 217 } 218 last_brk = new_brk; 219 220 size = HOST_PAGE_ALIGN(size); 221 start = start & qemu_host_page_mask; 222 addr = start; 223 if (addr == 0) 224 addr = mmap_next_start; 225 addr_start = addr; 226 for(;;) { 227 prot = 0; 228 for(addr1 = addr; addr1 < (addr + size); addr1 += TARGET_PAGE_SIZE) { 229 prot |= page_get_flags(addr1); 230 } 231 if (prot == 0) 232 break; 233 addr += qemu_host_page_size; 234 /* we found nothing */ 235 if (addr == addr_start) 236 return (abi_ulong)-1; 237 } 238 if (start == 0) 239 mmap_next_start = addr + size; 240 return addr; 241 } 242 243 /* NOTE: all the constants are the HOST ones */ 244 abi_long target_mmap(abi_ulong start, abi_ulong len, int prot, 245 int flags, int fd, abi_ulong offset) 246 { 247 abi_ulong ret, end, real_start, real_end, retaddr, host_offset, host_len; 248 unsigned long host_start; 249 250 mmap_lock(); 251 #ifdef DEBUG_MMAP 252 { 253 printf("mmap: start=0x" TARGET_FMT_lx 254 " len=0x" TARGET_FMT_lx " prot=%c%c%c flags=", 255 start, len, 256 prot & PROT_READ ? 'r' : '-', 257 prot & PROT_WRITE ? 'w' : '-', 258 prot & PROT_EXEC ? 'x' : '-'); 259 if (flags & MAP_FIXED) 260 printf("MAP_FIXED "); 261 if (flags & MAP_ANON) 262 printf("MAP_ANON "); 263 switch(flags & TARGET_BSD_MAP_FLAGMASK) { 264 case MAP_PRIVATE: 265 printf("MAP_PRIVATE "); 266 break; 267 case MAP_SHARED: 268 printf("MAP_SHARED "); 269 break; 270 default: 271 printf("[MAP_FLAGMASK=0x%x] ", flags & TARGET_BSD_MAP_FLAGMASK); 272 break; 273 } 274 printf("fd=%d offset=" TARGET_FMT_lx "\n", fd, offset); 275 } 276 #endif 277 278 if (offset & ~TARGET_PAGE_MASK) { 279 errno = EINVAL; 280 goto fail; 281 } 282 283 len = TARGET_PAGE_ALIGN(len); 284 if (len == 0) 285 goto the_end; 286 real_start = start & qemu_host_page_mask; 287 288 if (!(flags & MAP_FIXED)) { 289 abi_ulong mmap_start; 290 void *p; 291 host_offset = offset & qemu_host_page_mask; 292 host_len = len + offset - host_offset; 293 host_len = HOST_PAGE_ALIGN(host_len); 294 mmap_start = mmap_find_vma(real_start, host_len); 295 if (mmap_start == (abi_ulong)-1) { 296 errno = ENOMEM; 297 goto fail; 298 } 299 /* Note: we prefer to control the mapping address. It is 300 especially important if qemu_host_page_size > 301 qemu_real_host_page_size */ 302 p = mmap(g2h(mmap_start), 303 host_len, prot, flags | MAP_FIXED, fd, host_offset); 304 if (p == MAP_FAILED) 305 goto fail; 306 /* update start so that it points to the file position at 'offset' */ 307 host_start = (unsigned long)p; 308 if (!(flags & MAP_ANON)) 309 host_start += offset - host_offset; 310 start = h2g(host_start); 311 } else { 312 int flg; 313 target_ulong addr; 314 315 if (start & ~TARGET_PAGE_MASK) { 316 errno = EINVAL; 317 goto fail; 318 } 319 end = start + len; 320 real_end = HOST_PAGE_ALIGN(end); 321 322 for(addr = real_start; addr < real_end; addr += TARGET_PAGE_SIZE) { 323 flg = page_get_flags(addr); 324 if (flg & PAGE_RESERVED) { 325 errno = ENXIO; 326 goto fail; 327 } 328 } 329 330 /* worst case: we cannot map the file because the offset is not 331 aligned, so we read it */ 332 if (!(flags & MAP_ANON) && 333 (offset & ~qemu_host_page_mask) != (start & ~qemu_host_page_mask)) { 334 /* msync() won't work here, so we return an error if write is 335 possible while it is a shared mapping */ 336 if ((flags & TARGET_BSD_MAP_FLAGMASK) == MAP_SHARED && 337 (prot & PROT_WRITE)) { 338 errno = EINVAL; 339 goto fail; 340 } 341 retaddr = target_mmap(start, len, prot | PROT_WRITE, 342 MAP_FIXED | MAP_PRIVATE | MAP_ANON, 343 -1, 0); 344 if (retaddr == -1) 345 goto fail; 346 pread(fd, g2h(start), len, offset); 347 if (!(prot & PROT_WRITE)) { 348 ret = target_mprotect(start, len, prot); 349 if (ret != 0) { 350 start = ret; 351 goto the_end; 352 } 353 } 354 goto the_end; 355 } 356 357 /* handle the start of the mapping */ 358 if (start > real_start) { 359 if (real_end == real_start + qemu_host_page_size) { 360 /* one single host page */ 361 ret = mmap_frag(real_start, start, end, 362 prot, flags, fd, offset); 363 if (ret == -1) 364 goto fail; 365 goto the_end1; 366 } 367 ret = mmap_frag(real_start, start, real_start + qemu_host_page_size, 368 prot, flags, fd, offset); 369 if (ret == -1) 370 goto fail; 371 real_start += qemu_host_page_size; 372 } 373 /* handle the end of the mapping */ 374 if (end < real_end) { 375 ret = mmap_frag(real_end - qemu_host_page_size, 376 real_end - qemu_host_page_size, real_end, 377 prot, flags, fd, 378 offset + real_end - qemu_host_page_size - start); 379 if (ret == -1) 380 goto fail; 381 real_end -= qemu_host_page_size; 382 } 383 384 /* map the middle (easier) */ 385 if (real_start < real_end) { 386 void *p; 387 unsigned long offset1; 388 if (flags & MAP_ANON) 389 offset1 = 0; 390 else 391 offset1 = offset + real_start - start; 392 p = mmap(g2h(real_start), real_end - real_start, 393 prot, flags, fd, offset1); 394 if (p == MAP_FAILED) 395 goto fail; 396 } 397 } 398 the_end1: 399 page_set_flags(start, start + len, prot | PAGE_VALID); 400 the_end: 401 #ifdef DEBUG_MMAP 402 printf("ret=0x" TARGET_FMT_lx "\n", start); 403 page_dump(stdout); 404 printf("\n"); 405 #endif 406 mmap_unlock(); 407 return start; 408 fail: 409 mmap_unlock(); 410 return -1; 411 } 412 413 int target_munmap(abi_ulong start, abi_ulong len) 414 { 415 abi_ulong end, real_start, real_end, addr; 416 int prot, ret; 417 418 #ifdef DEBUG_MMAP 419 printf("munmap: start=0x%lx len=0x%lx\n", start, len); 420 #endif 421 if (start & ~TARGET_PAGE_MASK) 422 return -EINVAL; 423 len = TARGET_PAGE_ALIGN(len); 424 if (len == 0) 425 return -EINVAL; 426 mmap_lock(); 427 end = start + len; 428 real_start = start & qemu_host_page_mask; 429 real_end = HOST_PAGE_ALIGN(end); 430 431 if (start > real_start) { 432 /* handle host page containing start */ 433 prot = 0; 434 for(addr = real_start; addr < start; addr += TARGET_PAGE_SIZE) { 435 prot |= page_get_flags(addr); 436 } 437 if (real_end == real_start + qemu_host_page_size) { 438 for(addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) { 439 prot |= page_get_flags(addr); 440 } 441 end = real_end; 442 } 443 if (prot != 0) 444 real_start += qemu_host_page_size; 445 } 446 if (end < real_end) { 447 prot = 0; 448 for(addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) { 449 prot |= page_get_flags(addr); 450 } 451 if (prot != 0) 452 real_end -= qemu_host_page_size; 453 } 454 455 ret = 0; 456 /* unmap what we can */ 457 if (real_start < real_end) { 458 ret = munmap(g2h(real_start), real_end - real_start); 459 } 460 461 if (ret == 0) 462 page_set_flags(start, start + len, 0); 463 mmap_unlock(); 464 return ret; 465 } 466 467 int target_msync(abi_ulong start, abi_ulong len, int flags) 468 { 469 abi_ulong end; 470 471 if (start & ~TARGET_PAGE_MASK) 472 return -EINVAL; 473 len = TARGET_PAGE_ALIGN(len); 474 end = start + len; 475 if (end < start) 476 return -EINVAL; 477 if (end == start) 478 return 0; 479 480 start &= qemu_host_page_mask; 481 return msync(g2h(start), end - start, flags); 482 } 483