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 bool have_mmap_lock(void)
  46 {
  47     return mmap_lock_count > 0 ? true : false;
  48 }
  49
  50 /* Grab lock to make sure things are in a consistent state after fork().  */
  51 void mmap_fork_start(void)
  52 {
  53     if (mmap_lock_count)
  54         abort();
  55     pthread_mutex_lock(&mmap_mutex);
  56 }
  57
  58 void mmap_fork_end(int child)
  59 {
  60     if (child)
  61         pthread_mutex_init(&mmap_mutex, NULL);
  62     else
  63         pthread_mutex_unlock(&mmap_mutex);
  64 }
  65 #else
  66 /* We aren't threadsafe to start with, so no need to worry about locking.  */
  67 void mmap_lock(void)
  68 {
  69 }
  70
  71 void mmap_unlock(void)
  72 {
  73 }
  74 #endif
  75
  76 /* NOTE: all the constants are the HOST ones, but addresses are target. */
  77 int target_mprotect(abi_ulong start, abi_ulong len, int prot)
  78 {
  79     abi_ulong end, host_start, host_end, addr;
  80     int prot1, ret;
  81
  82 #ifdef DEBUG_MMAP
  83     printf("mprotect: start=0x" TARGET_FMT_lx
  84            " len=0x" TARGET_FMT_lx " prot=%c%c%c\n", start, len,
  85            prot & PROT_READ ? 'r' : '-',
  86            prot & PROT_WRITE ? 'w' : '-',
  87            prot & PROT_EXEC ? 'x' : '-');
  88 #endif
  89
  90     if ((start & ~TARGET_PAGE_MASK) != 0)
  91         return -EINVAL;
  92     len = TARGET_PAGE_ALIGN(len);
  93     end = start + len;
  94     if (end < start)
  95         return -EINVAL;
  96     prot &= PROT_READ | PROT_WRITE | PROT_EXEC;
  97     if (len == 0)
  98         return 0;
  99
 100     mmap_lock();
 101     host_start = start & qemu_host_page_mask;
 102     host_end = HOST_PAGE_ALIGN(end);
 103     if (start > host_start) {
 104         /* handle host page containing start */
 105         prot1 = prot;
 106         for(addr = host_start; addr < start; addr += TARGET_PAGE_SIZE) {
 107             prot1 |= page_get_flags(addr);
 108         }
 109         if (host_end == host_start + qemu_host_page_size) {
 110             for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
 111                 prot1 |= page_get_flags(addr);
 112             }
 113             end = host_end;
 114         }
 115         ret = mprotect(g2h(host_start), qemu_host_page_size, prot1 & PAGE_BITS);
 116         if (ret != 0)
 117             goto error;
 118         host_start += qemu_host_page_size;
 119     }
 120     if (end < host_end) {
 121         prot1 = prot;
 122         for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
 123             prot1 |= page_get_flags(addr);
 124         }
 125         ret = mprotect(g2h(host_end - qemu_host_page_size), qemu_host_page_size,
 126                        prot1 & PAGE_BITS);
 127         if (ret != 0)
 128             goto error;
 129         host_end -= qemu_host_page_size;
 130     }
 131
 132     /* handle the pages in the middle */
 133     if (host_start < host_end) {
 134         ret = mprotect(g2h(host_start), host_end - host_start, prot);
 135         if (ret != 0)
 136             goto error;
 137     }
 138     page_set_flags(start, start + len, prot | PAGE_VALID);
 139     mmap_unlock();
 140     return 0;
 141 error:
 142     mmap_unlock();
 143     return ret;
 144 }
 145
 146 /* map an incomplete host page */
 147 static int mmap_frag(abi_ulong real_start,
 148                      abi_ulong start, abi_ulong end,
 149                      int prot, int flags, int fd, abi_ulong offset)
 150 {
 151     abi_ulong real_end, addr;
 152     void *host_start;
 153     int prot1, prot_new;
 154
 155     real_end = real_start + qemu_host_page_size;
 156     host_start = g2h(real_start);
 157
 158     /* get the protection of the target pages outside the mapping */
 159     prot1 = 0;
 160     for(addr = real_start; addr < real_end; addr++) {
 161         if (addr < start || addr >= end)
 162             prot1 |= page_get_flags(addr);
 163     }
 164
 165     if (prot1 == 0) {
 166         /* no page was there, so we allocate one */
 167         void *p = mmap(host_start, qemu_host_page_size, prot,
 168                        flags | MAP_ANON, -1, 0);
 169         if (p == MAP_FAILED)
 170             return -1;
 171         prot1 = prot;
 172     }
 173     prot1 &= PAGE_BITS;
 174
 175     prot_new = prot | prot1;
 176     if (!(flags & MAP_ANON)) {
 177         /* msync() won't work here, so we return an error if write is
 178            possible while it is a shared mapping */
 179         if ((flags & TARGET_BSD_MAP_FLAGMASK) == MAP_SHARED &&
 180             (prot & PROT_WRITE))
 181             return -1;
 182
 183         /* adjust protection to be able to read */
 184         if (!(prot1 & PROT_WRITE))
 185             mprotect(host_start, qemu_host_page_size, prot1 | PROT_WRITE);
 186
 187         /* read the corresponding file data */
 188         pread(fd, g2h(start), end - start, offset);
 189
 190         /* put final protection */
 191         if (prot_new != (prot1 | PROT_WRITE))
 192             mprotect(host_start, qemu_host_page_size, prot_new);
 193     } else {
 194         /* just update the protection */
 195         if (prot_new != prot1) {
 196             mprotect(host_start, qemu_host_page_size, prot_new);
 197         }
 198     }
 199     return 0;
 200 }
 201
 202 #if defined(__CYGWIN__)
 203 /* Cygwin doesn't have a whole lot of address space.  */
 204 static abi_ulong mmap_next_start = 0x18000000;
 205 #else
 206 static abi_ulong mmap_next_start = 0x40000000;
 207 #endif
 208
 209 unsigned long last_brk;
 210
 211 /* find a free memory area of size 'size'. The search starts at
 212    'start'. If 'start' == 0, then a default start address is used.
 213    Return -1 if error.
 214 */
 215 /* page_init() marks pages used by the host as reserved to be sure not
 216    to use them. */
 217 static abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size)
 218 {
 219     abi_ulong addr, addr1, addr_start;
 220     int prot;
 221     unsigned long new_brk;
 222
 223     new_brk = (unsigned long)sbrk(0);
 224     if (last_brk && last_brk < new_brk && last_brk == (target_ulong)last_brk) {
 225         /* This is a hack to catch the host allocating memory with brk().
 226            If it uses mmap then we loose.
 227            FIXME: We really want to avoid the host allocating memory in
 228            the first place, and maybe leave some slack to avoid switching
 229            to mmap.  */
 230         page_set_flags(last_brk & TARGET_PAGE_MASK,
 231                        TARGET_PAGE_ALIGN(new_brk),
 232                        PAGE_RESERVED);
 233     }
 234     last_brk = new_brk;
 235
 236     size = HOST_PAGE_ALIGN(size);
 237     start = start & qemu_host_page_mask;
 238     addr = start;
 239     if (addr == 0)
 240         addr = mmap_next_start;
 241     addr_start = addr;
 242     for(;;) {
 243         prot = 0;
 244         for(addr1 = addr; addr1 < (addr + size); addr1 += TARGET_PAGE_SIZE) {
 245             prot |= page_get_flags(addr1);
 246         }
 247         if (prot == 0)
 248             break;
 249         addr += qemu_host_page_size;
 250         /* we found nothing */
 251         if (addr == addr_start)
 252             return (abi_ulong)-1;
 253     }
 254     if (start == 0)
 255         mmap_next_start = addr + size;
 256     return addr;
 257 }
 258
 259 /* NOTE: all the constants are the HOST ones */
 260 abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,
 261                      int flags, int fd, abi_ulong offset)
 262 {
 263     abi_ulong ret, end, real_start, real_end, retaddr, host_offset, host_len;
 264     unsigned long host_start;
 265
 266     mmap_lock();
 267 #ifdef DEBUG_MMAP
 268     {
 269         printf("mmap: start=0x" TARGET_FMT_lx
 270                " len=0x" TARGET_FMT_lx " prot=%c%c%c flags=",
 271                start, len,
 272                prot & PROT_READ ? 'r' : '-',
 273                prot & PROT_WRITE ? 'w' : '-',
 274                prot & PROT_EXEC ? 'x' : '-');
 275         if (flags & MAP_FIXED)
 276             printf("MAP_FIXED ");
 277         if (flags & MAP_ANON)
 278             printf("MAP_ANON ");
 279         switch(flags & TARGET_BSD_MAP_FLAGMASK) {
 280         case MAP_PRIVATE:
 281             printf("MAP_PRIVATE ");
 282             break;
 283         case MAP_SHARED:
 284             printf("MAP_SHARED ");
 285             break;
 286         default:
 287             printf("[MAP_FLAGMASK=0x%x] ", flags & TARGET_BSD_MAP_FLAGMASK);
 288             break;
 289         }
 290         printf("fd=%d offset=" TARGET_FMT_lx "\n", fd, offset);
 291     }
 292 #endif
 293
 294     if (offset & ~TARGET_PAGE_MASK) {
 295         errno = EINVAL;
 296         goto fail;
 297     }
 298
 299     len = TARGET_PAGE_ALIGN(len);
 300     if (len == 0)
 301         goto the_end;
 302     real_start = start & qemu_host_page_mask;
 303
 304     if (!(flags & MAP_FIXED)) {
 305         abi_ulong mmap_start;
 306         void *p;
 307         host_offset = offset & qemu_host_page_mask;
 308         host_len = len + offset - host_offset;
 309         host_len = HOST_PAGE_ALIGN(host_len);
 310         mmap_start = mmap_find_vma(real_start, host_len);
 311         if (mmap_start == (abi_ulong)-1) {
 312             errno = ENOMEM;
 313             goto fail;
 314         }
 315         /* Note: we prefer to control the mapping address. It is
 316            especially important if qemu_host_page_size >
 317            qemu_real_host_page_size */
 318         p = mmap(g2h(mmap_start),
 319                  host_len, prot, flags | MAP_FIXED, fd, host_offset);
 320         if (p == MAP_FAILED)
 321             goto fail;
 322         /* update start so that it points to the file position at 'offset' */
 323         host_start = (unsigned long)p;
 324         if (!(flags & MAP_ANON))
 325             host_start += offset - host_offset;
 326         start = h2g(host_start);
 327     } else {
 328         int flg;
 329         target_ulong addr;
 330
 331         if (start & ~TARGET_PAGE_MASK) {
 332             errno = EINVAL;
 333             goto fail;
 334         }
 335         end = start + len;
 336         real_end = HOST_PAGE_ALIGN(end);
 337
 338         for(addr = real_start; addr < real_end; addr += TARGET_PAGE_SIZE) {
 339             flg = page_get_flags(addr);
 340             if (flg & PAGE_RESERVED) {
 341                 errno = ENXIO;
 342                 goto fail;
 343             }
 344         }
 345
 346         /* worst case: we cannot map the file because the offset is not
 347            aligned, so we read it */
 348         if (!(flags & MAP_ANON) &&
 349             (offset & ~qemu_host_page_mask) != (start & ~qemu_host_page_mask)) {
 350             /* msync() won't work here, so we return an error if write is
 351                possible while it is a shared mapping */
 352             if ((flags & TARGET_BSD_MAP_FLAGMASK) == MAP_SHARED &&
 353                 (prot & PROT_WRITE)) {
 354                 errno = EINVAL;
 355                 goto fail;
 356             }
 357             retaddr = target_mmap(start, len, prot | PROT_WRITE,
 358                                   MAP_FIXED | MAP_PRIVATE | MAP_ANON,
 359                                   -1, 0);
 360             if (retaddr == -1)
 361                 goto fail;
 362             pread(fd, g2h(start), len, offset);
 363             if (!(prot & PROT_WRITE)) {
 364                 ret = target_mprotect(start, len, prot);
 365                 if (ret != 0) {
 366                     start = ret;
 367                     goto the_end;
 368                 }
 369             }
 370             goto the_end;
 371         }
 372
 373         /* handle the start of the mapping */
 374         if (start > real_start) {
 375             if (real_end == real_start + qemu_host_page_size) {
 376                 /* one single host page */
 377                 ret = mmap_frag(real_start, start, end,
 378                                 prot, flags, fd, offset);
 379                 if (ret == -1)
 380                     goto fail;
 381                 goto the_end1;
 382             }
 383             ret = mmap_frag(real_start, start, real_start + qemu_host_page_size,
 384                             prot, flags, fd, offset);
 385             if (ret == -1)
 386                 goto fail;
 387             real_start += qemu_host_page_size;
 388         }
 389         /* handle the end of the mapping */
 390         if (end < real_end) {
 391             ret = mmap_frag(real_end - qemu_host_page_size,
 392                             real_end - qemu_host_page_size, real_end,
 393                             prot, flags, fd,
 394                             offset + real_end - qemu_host_page_size - start);
 395             if (ret == -1)
 396                 goto fail;
 397             real_end -= qemu_host_page_size;
 398         }
 399
 400         /* map the middle (easier) */
 401         if (real_start < real_end) {
 402             void *p;
 403             unsigned long offset1;
 404             if (flags & MAP_ANON)
 405                 offset1 = 0;
 406             else
 407                 offset1 = offset + real_start - start;
 408             p = mmap(g2h(real_start), real_end - real_start,
 409                      prot, flags, fd, offset1);
 410             if (p == MAP_FAILED)
 411                 goto fail;
 412         }
 413     }
 414  the_end1:
 415     page_set_flags(start, start + len, prot | PAGE_VALID);
 416  the_end:
 417 #ifdef DEBUG_MMAP
 418     printf("ret=0x" TARGET_FMT_lx "\n", start);
 419     page_dump(stdout);
 420     printf("\n");
 421 #endif
 422     mmap_unlock();
 423     return start;
 424 fail:
 425     mmap_unlock();
 426     return -1;
 427 }
 428
 429 int target_munmap(abi_ulong start, abi_ulong len)
 430 {
 431     abi_ulong end, real_start, real_end, addr;
 432     int prot, ret;
 433
 434 #ifdef DEBUG_MMAP
 435     printf("munmap: start=0x%lx len=0x%lx\n", start, len);
 436 #endif
 437     if (start & ~TARGET_PAGE_MASK)
 438         return -EINVAL;
 439     len = TARGET_PAGE_ALIGN(len);
 440     if (len == 0)
 441         return -EINVAL;
 442     mmap_lock();
 443     end = start + len;
 444     real_start = start & qemu_host_page_mask;
 445     real_end = HOST_PAGE_ALIGN(end);
 446
 447     if (start > real_start) {
 448         /* handle host page containing start */
 449         prot = 0;
 450         for(addr = real_start; addr < start; addr += TARGET_PAGE_SIZE) {
 451             prot |= page_get_flags(addr);
 452         }
 453         if (real_end == real_start + qemu_host_page_size) {
 454             for(addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
 455                 prot |= page_get_flags(addr);
 456             }
 457             end = real_end;
 458         }
 459         if (prot != 0)
 460             real_start += qemu_host_page_size;
 461     }
 462     if (end < real_end) {
 463         prot = 0;
 464         for(addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
 465             prot |= page_get_flags(addr);
 466         }
 467         if (prot != 0)
 468             real_end -= qemu_host_page_size;
 469     }
 470
 471     ret = 0;
 472     /* unmap what we can */
 473     if (real_start < real_end) {
 474         ret = munmap(g2h(real_start), real_end - real_start);
 475     }
 476
 477     if (ret == 0)
 478         page_set_flags(start, start + len, 0);
 479     mmap_unlock();
 480     return ret;
 481 }
 482
 483 int target_msync(abi_ulong start, abi_ulong len, int flags)
 484 {
 485     abi_ulong end;
 486
 487     if (start & ~TARGET_PAGE_MASK)
 488         return -EINVAL;
 489     len = TARGET_PAGE_ALIGN(len);
 490     end = start + len;
 491     if (end < start)
 492         return -EINVAL;
 493     if (end == start)
 494         return 0;
 495
 496     start &= qemu_host_page_mask;
 497     return msync(g2h(start), end - start, flags);
 498 }