bsd-user/mmap.c

   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 #if defined(CONFIG_USE_NPTL)
  28 pthread_mutex_t mmap_mutex;
  29 static int __thread mmap_lock_count;
  30
  31 void mmap_lock(void)
  32 {
  33     if (mmap_lock_count++ == 0) {
  34         pthread_mutex_lock(&mmap_mutex);
  35     }
  36 }
  37
  38 void mmap_unlock(void)
  39 {
  40     if (--mmap_lock_count == 0) {
  41         pthread_mutex_unlock(&mmap_mutex);
  42     }
  43 }
  44
  45 /* Grab lock to make sure things are in a consistent state after fork().  */
  46 void mmap_fork_start(void)
  47 {
  48     if (mmap_lock_count)
  49         abort();
  50     pthread_mutex_lock(&mmap_mutex);
  51 }
  52
  53 void mmap_fork_end(int child)
  54 {
  55     if (child)
  56         pthread_mutex_init(&mmap_mutex, NULL);
  57     else
  58         pthread_mutex_unlock(&mmap_mutex);
  59 }
  60 #else
  61 /* We aren't threadsafe to start with, so no need to worry about locking.  */
  62 void mmap_lock(void)
  63 {
  64 }
  65
  66 void mmap_unlock(void)
  67 {
  68 }
  69 #endif
  70
  71 /* NOTE: all the constants are the HOST ones, but addresses are target. */
  72 int target_mprotect(abi_ulong start, abi_ulong len, int prot)
  73 {
  74     abi_ulong end, host_start, host_end, addr;
  75     int prot1, ret;
  76
  77 #ifdef DEBUG_MMAP
  78     printf("mprotect: start=0x" TARGET_FMT_lx
  79            " len=0x" TARGET_FMT_lx " prot=%c%c%c\n", start, len,
  80            prot & PROT_READ ? 'r' : '-',
  81            prot & PROT_WRITE ? 'w' : '-',
  82            prot & PROT_EXEC ? 'x' : '-');
  83 #endif
  84
  85     if ((start & ~TARGET_PAGE_MASK) != 0)
  86         return -EINVAL;
  87     len = TARGET_PAGE_ALIGN(len);
  88     end = start + len;
  89     if (end < start)
  90         return -EINVAL;
  91     prot &= PROT_READ | PROT_WRITE | PROT_EXEC;
  92     if (len == 0)
  93         return 0;
  94
  95     mmap_lock();
  96     host_start = start & qemu_host_page_mask;
  97     host_end = HOST_PAGE_ALIGN(end);
  98     if (start > host_start) {
  99         /* handle host page containing start */
 100         prot1 = prot;
 101         for(addr = host_start; addr < start; addr += TARGET_PAGE_SIZE) {
 102             prot1 |= page_get_flags(addr);
 103         }
 104         if (host_end == host_start + qemu_host_page_size) {
 105             for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
 106                 prot1 |= page_get_flags(addr);
 107             }
 108             end = host_end;
 109         }
 110         ret = mprotect(g2h(host_start), qemu_host_page_size, prot1 & PAGE_BITS);
 111         if (ret != 0)
 112             goto error;
 113         host_start += qemu_host_page_size;
 114     }
 115     if (end < host_end) {
 116         prot1 = prot;
 117         for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
 118             prot1 |= page_get_flags(addr);
 119         }
 120         ret = mprotect(g2h(host_end - qemu_host_page_size), qemu_host_page_size,
 121                        prot1 & PAGE_BITS);
 122         if (ret != 0)
 123             goto error;
 124         host_end -= qemu_host_page_size;
 125     }
 126
 127     /* handle the pages in the middle */
 128     if (host_start < host_end) {
 129         ret = mprotect(g2h(host_start), host_end - host_start, prot);
 130         if (ret != 0)
 131             goto error;
 132     }
 133     page_set_flags(start, start + len, prot | PAGE_VALID);
 134     mmap_unlock();
 135     return 0;
 136 error:
 137     mmap_unlock();
 138     return ret;
 139 }
 140
 141 /* map an incomplete host page */
 142 static int mmap_frag(abi_ulong real_start,
 143                      abi_ulong start, abi_ulong end,
 144                      int prot, int flags, int fd, abi_ulong offset)
 145 {
 146     abi_ulong real_end, addr;
 147     void *host_start;
 148     int prot1, prot_new;
 149
 150     real_end = real_start + qemu_host_page_size;
 151     host_start = g2h(real_start);
 152
 153     /* get the protection of the target pages outside the mapping */
 154     prot1 = 0;
 155     for(addr = real_start; addr < real_end; addr++) {
 156         if (addr < start || addr >= end)
 157             prot1 |= page_get_flags(addr);
 158     }
 159
 160     if (prot1 == 0) {
 161         /* no page was there, so we allocate one */
 162         void *p = mmap(host_start, qemu_host_page_size, prot,
 163                        flags | MAP_ANON, -1, 0);
 164         if (p == MAP_FAILED)
 165             return -1;
 166         prot1 = prot;
 167     }
 168     prot1 &= PAGE_BITS;
 169
 170     prot_new = prot | prot1;
 171     if (!(flags & MAP_ANON)) {
 172         /* msync() won't work here, so we return an error if write is
 173            possible while it is a shared mapping */
 174         if ((flags & TARGET_BSD_MAP_FLAGMASK) == MAP_SHARED &&
 175             (prot & PROT_WRITE))
 176             return -1;
 177
 178         /* adjust protection to be able to read */
 179         if (!(prot1 & PROT_WRITE))
 180             mprotect(host_start, qemu_host_page_size, prot1 | PROT_WRITE);
 181
 182         /* read the corresponding file data */
 183         pread(fd, g2h(start), end - start, offset);
 184
 185         /* put final protection */
 186         if (prot_new != (prot1 | PROT_WRITE))
 187             mprotect(host_start, qemu_host_page_size, prot_new);
 188     } else {
 189         /* just update the protection */
 190         if (prot_new != prot1) {
 191             mprotect(host_start, qemu_host_page_size, prot_new);
 192         }
 193     }
 194     return 0;
 195 }
 196
 197 #if defined(__CYGWIN__)
 198 /* Cygwin doesn't have a whole lot of address space.  */
 199 static abi_ulong mmap_next_start = 0x18000000;
 200 #else
 201 static abi_ulong mmap_next_start = 0x40000000;
 202 #endif
 203
 204 unsigned long last_brk;
 205
 206 /* find a free memory area of size 'size'. The search starts at
 207    'start'. If 'start' == 0, then a default start address is used.
 208    Return -1 if error.
 209 */
 210 /* page_init() marks pages used by the host as reserved to be sure not
 211    to use them. */
 212 static abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size)
 213 {
 214     abi_ulong addr, addr1, addr_start;
 215     int prot;
 216     unsigned long new_brk;
 217
 218     new_brk = (unsigned long)sbrk(0);
 219     if (last_brk && last_brk < new_brk && last_brk == (target_ulong)last_brk) {
 220         /* This is a hack to catch the host allocating memory with brk().
 221            If it uses mmap then we loose.
 222            FIXME: We really want to avoid the host allocating memory in
 223            the first place, and maybe leave some slack to avoid switching
 224            to mmap.  */
 225         page_set_flags(last_brk & TARGET_PAGE_MASK,
 226                        TARGET_PAGE_ALIGN(new_brk),
 227                        PAGE_RESERVED);
 228     }
 229     last_brk = new_brk;
 230
 231     size = HOST_PAGE_ALIGN(size);
 232     start = start & qemu_host_page_mask;
 233     addr = start;
 234     if (addr == 0)
 235         addr = mmap_next_start;
 236     addr_start = addr;
 237     for(;;) {
 238         prot = 0;
 239         for(addr1 = addr; addr1 < (addr + size); addr1 += TARGET_PAGE_SIZE) {
 240             prot |= page_get_flags(addr1);
 241         }
 242         if (prot == 0)
 243             break;
 244         addr += qemu_host_page_size;
 245         /* we found nothing */
 246         if (addr == addr_start)
 247             return (abi_ulong)-1;
 248     }
 249     if (start == 0)
 250         mmap_next_start = addr + size;
 251     return addr;
 252 }
 253
 254 /* NOTE: all the constants are the HOST ones */
 255 abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,
 256                      int flags, int fd, abi_ulong offset)
 257 {
 258     abi_ulong ret, end, real_start, real_end, retaddr, host_offset, host_len;
 259     unsigned long host_start;
 260
 261     mmap_lock();
 262 #ifdef DEBUG_MMAP
 263     {
 264         printf("mmap: start=0x" TARGET_FMT_lx
 265                " len=0x" TARGET_FMT_lx " prot=%c%c%c flags=",
 266                start, len,
 267                prot & PROT_READ ? 'r' : '-',
 268                prot & PROT_WRITE ? 'w' : '-',
 269                prot & PROT_EXEC ? 'x' : '-');
 270         if (flags & MAP_FIXED)
 271             printf("MAP_FIXED ");
 272         if (flags & MAP_ANON)
 273             printf("MAP_ANON ");
 274         switch(flags & TARGET_BSD_MAP_FLAGMASK) {
 275         case MAP_PRIVATE:
 276             printf("MAP_PRIVATE ");
 277             break;
 278         case MAP_SHARED:
 279             printf("MAP_SHARED ");
 280             break;
 281         default:
 282             printf("[MAP_FLAGMASK=0x%x] ", flags & TARGET_BSD_MAP_FLAGMASK);
 283             break;
 284         }
 285         printf("fd=%d offset=" TARGET_FMT_lx "\n", fd, offset);
 286     }
 287 #endif
 288
 289     if (offset & ~TARGET_PAGE_MASK) {
 290         errno = EINVAL;
 291         goto fail;
 292     }
 293
 294     len = TARGET_PAGE_ALIGN(len);
 295     if (len == 0)
 296         goto the_end;
 297     real_start = start & qemu_host_page_mask;
 298
 299     if (!(flags & MAP_FIXED)) {
 300         abi_ulong mmap_start;
 301         void *p;
 302         host_offset = offset & qemu_host_page_mask;
 303         host_len = len + offset - host_offset;
 304         host_len = HOST_PAGE_ALIGN(host_len);
 305         mmap_start = mmap_find_vma(real_start, host_len);
 306         if (mmap_start == (abi_ulong)-1) {
 307             errno = ENOMEM;
 308             goto fail;
 309         }
 310         /* Note: we prefer to control the mapping address. It is
 311            especially important if qemu_host_page_size >
 312            qemu_real_host_page_size */
 313         p = mmap(g2h(mmap_start),
 314                  host_len, prot, flags | MAP_FIXED, fd, host_offset);
 315         if (p == MAP_FAILED)
 316             goto fail;
 317         /* update start so that it points to the file position at 'offset' */
 318         host_start = (unsigned long)p;
 319         if (!(flags & MAP_ANON))
 320             host_start += offset - host_offset;
 321         start = h2g(host_start);
 322     } else {
 323         int flg;
 324         target_ulong addr;
 325
 326         if (start & ~TARGET_PAGE_MASK) {
 327             errno = EINVAL;
 328             goto fail;
 329         }
 330         end = start + len;
 331         real_end = HOST_PAGE_ALIGN(end);
 332
 333         for(addr = real_start; addr < real_end; addr += TARGET_PAGE_SIZE) {
 334             flg = page_get_flags(addr);
 335             if (flg & PAGE_RESERVED) {
 336                 errno = ENXIO;
 337                 goto fail;
 338             }
 339         }
 340
 341         /* worst case: we cannot map the file because the offset is not
 342            aligned, so we read it */
 343         if (!(flags & MAP_ANON) &&
 344             (offset & ~qemu_host_page_mask) != (start & ~qemu_host_page_mask)) {
 345             /* msync() won't work here, so we return an error if write is
 346                possible while it is a shared mapping */
 347             if ((flags & TARGET_BSD_MAP_FLAGMASK) == MAP_SHARED &&
 348                 (prot & PROT_WRITE)) {
 349                 errno = EINVAL;
 350                 goto fail;
 351             }
 352             retaddr = target_mmap(start, len, prot | PROT_WRITE,
 353                                   MAP_FIXED | MAP_PRIVATE | MAP_ANON,
 354                                   -1, 0);
 355             if (retaddr == -1)
 356                 goto fail;
 357             pread(fd, g2h(start), len, offset);
 358             if (!(prot & PROT_WRITE)) {
 359                 ret = target_mprotect(start, len, prot);
 360                 if (ret != 0) {
 361                     start = ret;
 362                     goto the_end;
 363                 }
 364             }
 365             goto the_end;
 366         }
 367
 368         /* handle the start of the mapping */
 369         if (start > real_start) {
 370             if (real_end == real_start + qemu_host_page_size) {
 371                 /* one single host page */
 372                 ret = mmap_frag(real_start, start, end,
 373                                 prot, flags, fd, offset);
 374                 if (ret == -1)
 375                     goto fail;
 376                 goto the_end1;
 377             }
 378             ret = mmap_frag(real_start, start, real_start + qemu_host_page_size,
 379                             prot, flags, fd, offset);
 380             if (ret == -1)
 381                 goto fail;
 382             real_start += qemu_host_page_size;
 383         }
 384         /* handle the end of the mapping */
 385         if (end < real_end) {
 386             ret = mmap_frag(real_end - qemu_host_page_size,
 387                             real_end - qemu_host_page_size, real_end,
 388                             prot, flags, fd,
 389                             offset + real_end - qemu_host_page_size - start);
 390             if (ret == -1)
 391                 goto fail;
 392             real_end -= qemu_host_page_size;
 393         }
 394
 395         /* map the middle (easier) */
 396         if (real_start < real_end) {
 397             void *p;
 398             unsigned long offset1;
 399             if (flags & MAP_ANON)
 400                 offset1 = 0;
 401             else
 402                 offset1 = offset + real_start - start;
 403             p = mmap(g2h(real_start), real_end - real_start,
 404                      prot, flags, fd, offset1);
 405             if (p == MAP_FAILED)
 406                 goto fail;
 407         }
 408     }
 409  the_end1:
 410     page_set_flags(start, start + len, prot | PAGE_VALID);
 411  the_end:
 412 #ifdef DEBUG_MMAP
 413     printf("ret=0x" TARGET_FMT_lx "\n", start);
 414     page_dump(stdout);
 415     printf("\n");
 416 #endif
 417     mmap_unlock();
 418     return start;
 419 fail:
 420     mmap_unlock();
 421     return -1;
 422 }
 423
 424 int target_munmap(abi_ulong start, abi_ulong len)
 425 {
 426     abi_ulong end, real_start, real_end, addr;
 427     int prot, ret;
 428
 429 #ifdef DEBUG_MMAP
 430     printf("munmap: start=0x%lx len=0x%lx\n", start, len);
 431 #endif
 432     if (start & ~TARGET_PAGE_MASK)
 433         return -EINVAL;
 434     len = TARGET_PAGE_ALIGN(len);
 435     if (len == 0)
 436         return -EINVAL;
 437     mmap_lock();
 438     end = start + len;
 439     real_start = start & qemu_host_page_mask;
 440     real_end = HOST_PAGE_ALIGN(end);
 441
 442     if (start > real_start) {
 443         /* handle host page containing start */
 444         prot = 0;
 445         for(addr = real_start; addr < start; addr += TARGET_PAGE_SIZE) {
 446             prot |= page_get_flags(addr);
 447         }
 448         if (real_end == real_start + qemu_host_page_size) {
 449             for(addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
 450                 prot |= page_get_flags(addr);
 451             }
 452             end = real_end;
 453         }
 454         if (prot != 0)
 455             real_start += qemu_host_page_size;
 456     }
 457     if (end < real_end) {
 458         prot = 0;
 459         for(addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
 460             prot |= page_get_flags(addr);
 461         }
 462         if (prot != 0)
 463             real_end -= qemu_host_page_size;
 464     }
 465
 466     ret = 0;
 467     /* unmap what we can */
 468     if (real_start < real_end) {
 469         ret = munmap(g2h(real_start), real_end - real_start);
 470     }
 471
 472     if (ret == 0)
 473         page_set_flags(start, start + len, 0);
 474     mmap_unlock();
 475     return ret;
 476 }
 477
 478 int target_msync(abi_ulong start, abi_ulong len, int flags)
 479 {
 480     abi_ulong end;
 481
 482     if (start & ~TARGET_PAGE_MASK)
 483         return -EINVAL;
 484     len = TARGET_PAGE_ALIGN(len);
 485     end = start + len;
 486     if (end < start)
 487         return -EINVAL;
 488     if (end == start)
 489         return 0;
 490
 491     start &= qemu_host_page_mask;
 492     return msync(g2h(start), end - start, flags);
 493 }