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 #include <sys/mman.h>
  21
  22 #include "qemu.h"
  23 #include "qemu-common.h"
  24 #include "bsd-mman.h"
  25
  26 //#define DEBUG_MMAP
  27
  28 #if defined(CONFIG_USE_NPTL)
  29 pthread_mutex_t mmap_mutex;
  30 static int __thread mmap_lock_count;
  31
  32 void mmap_lock(void)
  33 {
  34     if (mmap_lock_count++ == 0) {
  35         pthread_mutex_lock(&mmap_mutex);
  36     }
  37 }
  38
  39 void mmap_unlock(void)
  40 {
  41     if (--mmap_lock_count == 0) {
  42         pthread_mutex_unlock(&mmap_mutex);
  43     }
  44 }
  45
  46 /* Grab lock to make sure things are in a consistent state after fork().  */
  47 void mmap_fork_start(void)
  48 {
  49     if (mmap_lock_count)
  50         abort();
  51     pthread_mutex_lock(&mmap_mutex);
  52 }
  53
  54 void mmap_fork_end(int child)
  55 {
  56     if (child)
  57         pthread_mutex_init(&mmap_mutex, NULL);
  58     else
  59         pthread_mutex_unlock(&mmap_mutex);
  60 }
  61 #else
  62 /* We aren't threadsafe to start with, so no need to worry about locking.  */
  63 void mmap_lock(void)
  64 {
  65 }
  66
  67 void mmap_unlock(void)
  68 {
  69 }
  70 #endif
  71
  72 /* NOTE: all the constants are the HOST ones, but addresses are target. */
  73 int target_mprotect(abi_ulong start, abi_ulong len, int prot)
  74 {
  75     abi_ulong end, host_start, host_end, addr;
  76     int prot1, ret;
  77
  78 #ifdef DEBUG_MMAP
  79     printf("mprotect: start=0x" TARGET_FMT_lx
  80            " len=0x" TARGET_FMT_lx " prot=%c%c%c\n", start, len,
  81            prot & PROT_READ ? 'r' : '-',
  82            prot & PROT_WRITE ? 'w' : '-',
  83            prot & PROT_EXEC ? 'x' : '-');
  84 #endif
  85
  86     if ((start & ~TARGET_PAGE_MASK) != 0)
  87         return -EINVAL;
  88     len = TARGET_PAGE_ALIGN(len);
  89     end = start + len;
  90     if (end < start)
  91         return -EINVAL;
  92     prot &= PROT_READ | PROT_WRITE | PROT_EXEC;
  93     if (len == 0)
  94         return 0;
  95
  96     mmap_lock();
  97     host_start = start & qemu_host_page_mask;
  98     host_end = HOST_PAGE_ALIGN(end);
  99     if (start > host_start) {
 100         /* handle host page containing start */
 101         prot1 = prot;
 102         for(addr = host_start; addr < start; addr += TARGET_PAGE_SIZE) {
 103             prot1 |= page_get_flags(addr);
 104         }
 105         if (host_end == host_start + qemu_host_page_size) {
 106             for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
 107                 prot1 |= page_get_flags(addr);
 108             }
 109             end = host_end;
 110         }
 111         ret = mprotect(g2h(host_start), qemu_host_page_size, prot1 & PAGE_BITS);
 112         if (ret != 0)
 113             goto error;
 114         host_start += qemu_host_page_size;
 115     }
 116     if (end < host_end) {
 117         prot1 = prot;
 118         for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
 119             prot1 |= page_get_flags(addr);
 120         }
 121         ret = mprotect(g2h(host_end - qemu_host_page_size), qemu_host_page_size,
 122                        prot1 & PAGE_BITS);
 123         if (ret != 0)
 124             goto error;
 125         host_end -= qemu_host_page_size;
 126     }
 127
 128     /* handle the pages in the middle */
 129     if (host_start < host_end) {
 130         ret = mprotect(g2h(host_start), host_end - host_start, prot);
 131         if (ret != 0)
 132             goto error;
 133     }
 134     page_set_flags(start, start + len, prot | PAGE_VALID);
 135     mmap_unlock();
 136     return 0;
 137 error:
 138     mmap_unlock();
 139     return ret;
 140 }
 141
 142 /* map an incomplete host page */
 143 static int mmap_frag(abi_ulong real_start,
 144                      abi_ulong start, abi_ulong end,
 145                      int prot, int flags, int fd, abi_ulong offset)
 146 {
 147     abi_ulong real_end, addr;
 148     void *host_start;
 149     int prot1, prot_new;
 150
 151     real_end = real_start + qemu_host_page_size;
 152     host_start = g2h(real_start);
 153
 154     /* get the protection of the target pages outside the mapping */
 155     prot1 = 0;
 156     for(addr = real_start; addr < real_end; addr++) {
 157         if (addr < start || addr >= end)
 158             prot1 |= page_get_flags(addr);
 159     }
 160
 161     if (prot1 == 0) {
 162         /* no page was there, so we allocate one */
 163         void *p = mmap(host_start, qemu_host_page_size, prot,
 164                        flags | MAP_ANON, -1, 0);
 165         if (p == MAP_FAILED)
 166             return -1;
 167         prot1 = prot;
 168     }
 169     prot1 &= PAGE_BITS;
 170
 171     prot_new = prot | prot1;
 172     if (!(flags & MAP_ANON)) {
 173         /* msync() won't work here, so we return an error if write is
 174            possible while it is a shared mapping */
 175         if ((flags & TARGET_BSD_MAP_FLAGMASK) == MAP_SHARED &&
 176             (prot & PROT_WRITE))
 177             return -1;
 178
 179         /* adjust protection to be able to read */
 180         if (!(prot1 & PROT_WRITE))
 181             mprotect(host_start, qemu_host_page_size, prot1 | PROT_WRITE);
 182
 183         /* read the corresponding file data */
 184         pread(fd, g2h(start), end - start, offset);
 185
 186         /* put final protection */
 187         if (prot_new != (prot1 | PROT_WRITE))
 188             mprotect(host_start, qemu_host_page_size, prot_new);
 189     } else {
 190         /* just update the protection */
 191         if (prot_new != prot1) {
 192             mprotect(host_start, qemu_host_page_size, prot_new);
 193         }
 194     }
 195     return 0;
 196 }
 197
 198 #if defined(__CYGWIN__)
 199 /* Cygwin doesn't have a whole lot of address space.  */
 200 static abi_ulong mmap_next_start = 0x18000000;
 201 #else
 202 static abi_ulong mmap_next_start = 0x40000000;
 203 #endif
 204
 205 unsigned long last_brk;
 206
 207 /* find a free memory area of size 'size'. The search starts at
 208    'start'. If 'start' == 0, then a default start address is used.
 209    Return -1 if error.
 210 */
 211 /* page_init() marks pages used by the host as reserved to be sure not
 212    to use them. */
 213 static abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size)
 214 {
 215     abi_ulong addr, addr1, addr_start;
 216     int prot;
 217     unsigned long new_brk;
 218
 219     new_brk = (unsigned long)sbrk(0);
 220     if (last_brk && last_brk < new_brk && last_brk == (target_ulong)last_brk) {
 221         /* This is a hack to catch the host allocating memory with brk().
 222            If it uses mmap then we loose.
 223            FIXME: We really want to avoid the host allocating memory in
 224            the first place, and maybe leave some slack to avoid switching
 225            to mmap.  */
 226         page_set_flags(last_brk & TARGET_PAGE_MASK,
 227                        TARGET_PAGE_ALIGN(new_brk),
 228                        PAGE_RESERVED);
 229     }
 230     last_brk = new_brk;
 231
 232     size = HOST_PAGE_ALIGN(size);
 233     start = start & qemu_host_page_mask;
 234     addr = start;
 235     if (addr == 0)
 236         addr = mmap_next_start;
 237     addr_start = addr;
 238     for(;;) {
 239         prot = 0;
 240         for(addr1 = addr; addr1 < (addr + size); addr1 += TARGET_PAGE_SIZE) {
 241             prot |= page_get_flags(addr1);
 242         }
 243         if (prot == 0)
 244             break;
 245         addr += qemu_host_page_size;
 246         /* we found nothing */
 247         if (addr == addr_start)
 248             return (abi_ulong)-1;
 249     }
 250     if (start == 0)
 251         mmap_next_start = addr + size;
 252     return addr;
 253 }
 254
 255 /* NOTE: all the constants are the HOST ones */
 256 abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,
 257                      int flags, int fd, abi_ulong offset)
 258 {
 259     abi_ulong ret, end, real_start, real_end, retaddr, host_offset, host_len;
 260     unsigned long host_start;
 261
 262     mmap_lock();
 263 #ifdef DEBUG_MMAP
 264     {
 265         printf("mmap: start=0x" TARGET_FMT_lx
 266                " len=0x" TARGET_FMT_lx " prot=%c%c%c flags=",
 267                start, len,
 268                prot & PROT_READ ? 'r' : '-',
 269                prot & PROT_WRITE ? 'w' : '-',
 270                prot & PROT_EXEC ? 'x' : '-');
 271         if (flags & MAP_FIXED)
 272             printf("MAP_FIXED ");
 273         if (flags & MAP_ANON)
 274             printf("MAP_ANON ");
 275         switch(flags & TARGET_BSD_MAP_FLAGMASK) {
 276         case MAP_PRIVATE:
 277             printf("MAP_PRIVATE ");
 278             break;
 279         case MAP_SHARED:
 280             printf("MAP_SHARED ");
 281             break;
 282         default:
 283             printf("[MAP_FLAGMASK=0x%x] ", flags & TARGET_BSD_MAP_FLAGMASK);
 284             break;
 285         }
 286         printf("fd=%d offset=" TARGET_FMT_lx "\n", fd, offset);
 287     }
 288 #endif
 289
 290     if (offset & ~TARGET_PAGE_MASK) {
 291         errno = EINVAL;
 292         goto fail;
 293     }
 294
 295     len = TARGET_PAGE_ALIGN(len);
 296     if (len == 0)
 297         goto the_end;
 298     real_start = start & qemu_host_page_mask;
 299
 300     if (!(flags & MAP_FIXED)) {
 301         abi_ulong mmap_start;
 302         void *p;
 303         host_offset = offset & qemu_host_page_mask;
 304         host_len = len + offset - host_offset;
 305         host_len = HOST_PAGE_ALIGN(host_len);
 306         mmap_start = mmap_find_vma(real_start, host_len);
 307         if (mmap_start == (abi_ulong)-1) {
 308             errno = ENOMEM;
 309             goto fail;
 310         }
 311         /* Note: we prefer to control the mapping address. It is
 312            especially important if qemu_host_page_size >
 313            qemu_real_host_page_size */
 314         p = mmap(g2h(mmap_start),
 315                  host_len, prot, flags | MAP_FIXED, fd, host_offset);
 316         if (p == MAP_FAILED)
 317             goto fail;
 318         /* update start so that it points to the file position at 'offset' */
 319         host_start = (unsigned long)p;
 320         if (!(flags & MAP_ANON))
 321             host_start += offset - host_offset;
 322         start = h2g(host_start);
 323     } else {
 324         int flg;
 325         target_ulong addr;
 326
 327         if (start & ~TARGET_PAGE_MASK) {
 328             errno = EINVAL;
 329             goto fail;
 330         }
 331         end = start + len;
 332         real_end = HOST_PAGE_ALIGN(end);
 333
 334         for(addr = real_start; addr < real_end; addr += TARGET_PAGE_SIZE) {
 335             flg = page_get_flags(addr);
 336             if (flg & PAGE_RESERVED) {
 337                 errno = ENXIO;
 338                 goto fail;
 339             }
 340         }
 341
 342         /* worst case: we cannot map the file because the offset is not
 343            aligned, so we read it */
 344         if (!(flags & MAP_ANON) &&
 345             (offset & ~qemu_host_page_mask) != (start & ~qemu_host_page_mask)) {
 346             /* msync() won't work here, so we return an error if write is
 347                possible while it is a shared mapping */
 348             if ((flags & TARGET_BSD_MAP_FLAGMASK) == MAP_SHARED &&
 349                 (prot & PROT_WRITE)) {
 350                 errno = EINVAL;
 351                 goto fail;
 352             }
 353             retaddr = target_mmap(start, len, prot | PROT_WRITE,
 354                                   MAP_FIXED | MAP_PRIVATE | MAP_ANON,
 355                                   -1, 0);
 356             if (retaddr == -1)
 357                 goto fail;
 358             pread(fd, g2h(start), len, offset);
 359             if (!(prot & PROT_WRITE)) {
 360                 ret = target_mprotect(start, len, prot);
 361                 if (ret != 0) {
 362                     start = ret;
 363                     goto the_end;
 364                 }
 365             }
 366             goto the_end;
 367         }
 368
 369         /* handle the start of the mapping */
 370         if (start > real_start) {
 371             if (real_end == real_start + qemu_host_page_size) {
 372                 /* one single host page */
 373                 ret = mmap_frag(real_start, start, end,
 374                                 prot, flags, fd, offset);
 375                 if (ret == -1)
 376                     goto fail;
 377                 goto the_end1;
 378             }
 379             ret = mmap_frag(real_start, start, real_start + qemu_host_page_size,
 380                             prot, flags, fd, offset);
 381             if (ret == -1)
 382                 goto fail;
 383             real_start += qemu_host_page_size;
 384         }
 385         /* handle the end of the mapping */
 386         if (end < real_end) {
 387             ret = mmap_frag(real_end - qemu_host_page_size,
 388                             real_end - qemu_host_page_size, real_end,
 389                             prot, flags, fd,
 390                             offset + real_end - qemu_host_page_size - start);
 391             if (ret == -1)
 392                 goto fail;
 393             real_end -= qemu_host_page_size;
 394         }
 395
 396         /* map the middle (easier) */
 397         if (real_start < real_end) {
 398             void *p;
 399             unsigned long offset1;
 400             if (flags & MAP_ANON)
 401                 offset1 = 0;
 402             else
 403                 offset1 = offset + real_start - start;
 404             p = mmap(g2h(real_start), real_end - real_start,
 405                      prot, flags, fd, offset1);
 406             if (p == MAP_FAILED)
 407                 goto fail;
 408         }
 409     }
 410  the_end1:
 411     page_set_flags(start, start + len, prot | PAGE_VALID);
 412  the_end:
 413 #ifdef DEBUG_MMAP
 414     printf("ret=0x" TARGET_FMT_lx "\n", start);
 415     page_dump(stdout);
 416     printf("\n");
 417 #endif
 418     mmap_unlock();
 419     return start;
 420 fail:
 421     mmap_unlock();
 422     return -1;
 423 }
 424
 425 int target_munmap(abi_ulong start, abi_ulong len)
 426 {
 427     abi_ulong end, real_start, real_end, addr;
 428     int prot, ret;
 429
 430 #ifdef DEBUG_MMAP
 431     printf("munmap: start=0x%lx len=0x%lx\n", start, len);
 432 #endif
 433     if (start & ~TARGET_PAGE_MASK)
 434         return -EINVAL;
 435     len = TARGET_PAGE_ALIGN(len);
 436     if (len == 0)
 437         return -EINVAL;
 438     mmap_lock();
 439     end = start + len;
 440     real_start = start & qemu_host_page_mask;
 441     real_end = HOST_PAGE_ALIGN(end);
 442
 443     if (start > real_start) {
 444         /* handle host page containing start */
 445         prot = 0;
 446         for(addr = real_start; addr < start; addr += TARGET_PAGE_SIZE) {
 447             prot |= page_get_flags(addr);
 448         }
 449         if (real_end == real_start + qemu_host_page_size) {
 450             for(addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
 451                 prot |= page_get_flags(addr);
 452             }
 453             end = real_end;
 454         }
 455         if (prot != 0)
 456             real_start += qemu_host_page_size;
 457     }
 458     if (end < real_end) {
 459         prot = 0;
 460         for(addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
 461             prot |= page_get_flags(addr);
 462         }
 463         if (prot != 0)
 464             real_end -= qemu_host_page_size;
 465     }
 466
 467     ret = 0;
 468     /* unmap what we can */
 469     if (real_start < real_end) {
 470         ret = munmap(g2h(real_start), real_end - real_start);
 471     }
 472
 473     if (ret == 0)
 474         page_set_flags(start, start + len, 0);
 475     mmap_unlock();
 476     return ret;
 477 }
 478
 479 int target_msync(abi_ulong start, abi_ulong len, int flags)
 480 {
 481     abi_ulong end;
 482
 483     if (start & ~TARGET_PAGE_MASK)
 484         return -EINVAL;
 485     len = TARGET_PAGE_ALIGN(len);
 486     end = start + len;
 487     if (end < start)
 488         return -EINVAL;
 489     if (end == start)
 490         return 0;
 491
 492     start &= qemu_host_page_mask;
 493     return msync(g2h(start), end - start, flags);
 494 }