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 <stdlib.h>
  20 #include <stdio.h>
  21 #include <stdarg.h>
  22 #include <string.h>
  23 #include <unistd.h>
  24 #include <errno.h>
  25 #include <sys/mman.h>
  26
  27 #include "qemu.h"
  28 #include "qemu-common.h"
  29 #include "bsd-mman.h"
  30
  31 //#define DEBUG_MMAP
  32
  33 #if defined(CONFIG_USE_NPTL)
  34 pthread_mutex_t mmap_mutex;
  35 static int __thread mmap_lock_count;
  36
  37 void mmap_lock(void)
  38 {
  39     if (mmap_lock_count++ == 0) {
  40         pthread_mutex_lock(&mmap_mutex);
  41     }
  42 }
  43
  44 void mmap_unlock(void)
  45 {
  46     if (--mmap_lock_count == 0) {
  47         pthread_mutex_unlock(&mmap_mutex);
  48     }
  49 }
  50
  51 /* Grab lock to make sure things are in a consistent state after fork().  */
  52 void mmap_fork_start(void)
  53 {
  54     if (mmap_lock_count)
  55         abort();
  56     pthread_mutex_lock(&mmap_mutex);
  57 }
  58
  59 void mmap_fork_end(int child)
  60 {
  61     if (child)
  62         pthread_mutex_init(&mmap_mutex, NULL);
  63     else
  64         pthread_mutex_unlock(&mmap_mutex);
  65 }
  66 #else
  67 /* We aren't threadsafe to start with, so no need to worry about locking.  */
  68 void mmap_lock(void)
  69 {
  70 }
  71
  72 void mmap_unlock(void)
  73 {
  74 }
  75 #endif
  76
  77 /* NOTE: all the constants are the HOST ones, but addresses are target. */
  78 int target_mprotect(abi_ulong start, abi_ulong len, int prot)
  79 {
  80     abi_ulong end, host_start, host_end, addr;
  81     int prot1, ret;
  82
  83 #ifdef DEBUG_MMAP
  84     printf("mprotect: start=0x" TARGET_FMT_lx
  85            " len=0x" TARGET_FMT_lx " prot=%c%c%c\n", start, len,
  86            prot & PROT_READ ? 'r' : '-',
  87            prot & PROT_WRITE ? 'w' : '-',
  88            prot & PROT_EXEC ? 'x' : '-');
  89 #endif
  90
  91     if ((start & ~TARGET_PAGE_MASK) != 0)
  92         return -EINVAL;
  93     len = TARGET_PAGE_ALIGN(len);
  94     end = start + len;
  95     if (end < start)
  96         return -EINVAL;
  97     prot &= PROT_READ | PROT_WRITE | PROT_EXEC;
  98     if (len == 0)
  99         return 0;
 100
 101     mmap_lock();
 102     host_start = start & qemu_host_page_mask;
 103     host_end = HOST_PAGE_ALIGN(end);
 104     if (start > host_start) {
 105         /* handle host page containing start */
 106         prot1 = prot;
 107         for(addr = host_start; addr < start; addr += TARGET_PAGE_SIZE) {
 108             prot1 |= page_get_flags(addr);
 109         }
 110         if (host_end == host_start + qemu_host_page_size) {
 111             for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
 112                 prot1 |= page_get_flags(addr);
 113             }
 114             end = host_end;
 115         }
 116         ret = mprotect(g2h(host_start), qemu_host_page_size, prot1 & PAGE_BITS);
 117         if (ret != 0)
 118             goto error;
 119         host_start += qemu_host_page_size;
 120     }
 121     if (end < host_end) {
 122         prot1 = prot;
 123         for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
 124             prot1 |= page_get_flags(addr);
 125         }
 126         ret = mprotect(g2h(host_end - qemu_host_page_size), qemu_host_page_size,
 127                        prot1 & PAGE_BITS);
 128         if (ret != 0)
 129             goto error;
 130         host_end -= qemu_host_page_size;
 131     }
 132
 133     /* handle the pages in the middle */
 134     if (host_start < host_end) {
 135         ret = mprotect(g2h(host_start), host_end - host_start, prot);
 136         if (ret != 0)
 137             goto error;
 138     }
 139     page_set_flags(start, start + len, prot | PAGE_VALID);
 140     mmap_unlock();
 141     return 0;
 142 error:
 143     mmap_unlock();
 144     return ret;
 145 }
 146
 147 /* map an incomplete host page */
 148 static int mmap_frag(abi_ulong real_start,
 149                      abi_ulong start, abi_ulong end,
 150                      int prot, int flags, int fd, abi_ulong offset)
 151 {
 152     abi_ulong real_end, addr;
 153     void *host_start;
 154     int prot1, prot_new;
 155
 156     real_end = real_start + qemu_host_page_size;
 157     host_start = g2h(real_start);
 158
 159     /* get the protection of the target pages outside the mapping */
 160     prot1 = 0;
 161     for(addr = real_start; addr < real_end; addr++) {
 162         if (addr < start || addr >= end)
 163             prot1 |= page_get_flags(addr);
 164     }
 165
 166     if (prot1 == 0) {
 167         /* no page was there, so we allocate one */
 168         void *p = mmap(host_start, qemu_host_page_size, prot,
 169                        flags | MAP_ANON, -1, 0);
 170         if (p == MAP_FAILED)
 171             return -1;
 172         prot1 = prot;
 173     }
 174     prot1 &= PAGE_BITS;
 175
 176     prot_new = prot | prot1;
 177     if (!(flags & MAP_ANON)) {
 178         /* msync() won't work here, so we return an error if write is
 179            possible while it is a shared mapping */
 180         if ((flags & TARGET_BSD_MAP_FLAGMASK) == MAP_SHARED &&
 181             (prot & PROT_WRITE))
 182             return -1;
 183
 184         /* adjust protection to be able to read */
 185         if (!(prot1 & PROT_WRITE))
 186             mprotect(host_start, qemu_host_page_size, prot1 | PROT_WRITE);
 187
 188         /* read the corresponding file data */
 189         pread(fd, g2h(start), end - start, offset);
 190
 191         /* put final protection */
 192         if (prot_new != (prot1 | PROT_WRITE))
 193             mprotect(host_start, qemu_host_page_size, prot_new);
 194     } else {
 195         /* just update the protection */
 196         if (prot_new != prot1) {
 197             mprotect(host_start, qemu_host_page_size, prot_new);
 198         }
 199     }
 200     return 0;
 201 }
 202
 203 #if defined(__CYGWIN__)
 204 /* Cygwin doesn't have a whole lot of address space.  */
 205 static abi_ulong mmap_next_start = 0x18000000;
 206 #else
 207 static abi_ulong mmap_next_start = 0x40000000;
 208 #endif
 209
 210 unsigned long last_brk;
 211
 212 /* find a free memory area of size 'size'. The search starts at
 213    'start'. If 'start' == 0, then a default start address is used.
 214    Return -1 if error.
 215 */
 216 /* page_init() marks pages used by the host as reserved to be sure not
 217    to use them. */
 218 static abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size)
 219 {
 220     abi_ulong addr, addr1, addr_start;
 221     int prot;
 222     unsigned long new_brk;
 223
 224     new_brk = (unsigned long)sbrk(0);
 225     if (last_brk && last_brk < new_brk && last_brk == (target_ulong)last_brk) {
 226         /* This is a hack to catch the host allocating memory with brk().
 227            If it uses mmap then we loose.
 228            FIXME: We really want to avoid the host allocating memory in
 229            the first place, and maybe leave some slack to avoid switching
 230            to mmap.  */
 231         page_set_flags(last_brk & TARGET_PAGE_MASK,
 232                        TARGET_PAGE_ALIGN(new_brk),
 233                        PAGE_RESERVED);
 234     }
 235     last_brk = new_brk;
 236
 237     size = HOST_PAGE_ALIGN(size);
 238     start = start & qemu_host_page_mask;
 239     addr = start;
 240     if (addr == 0)
 241         addr = mmap_next_start;
 242     addr_start = addr;
 243     for(;;) {
 244         prot = 0;
 245         for(addr1 = addr; addr1 < (addr + size); addr1 += TARGET_PAGE_SIZE) {
 246             prot |= page_get_flags(addr1);
 247         }
 248         if (prot == 0)
 249             break;
 250         addr += qemu_host_page_size;
 251         /* we found nothing */
 252         if (addr == addr_start)
 253             return (abi_ulong)-1;
 254     }
 255     if (start == 0)
 256         mmap_next_start = addr + size;
 257     return addr;
 258 }
 259
 260 /* NOTE: all the constants are the HOST ones */
 261 abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,
 262                      int flags, int fd, abi_ulong offset)
 263 {
 264     abi_ulong ret, end, real_start, real_end, retaddr, host_offset, host_len;
 265     unsigned long host_start;
 266
 267     mmap_lock();
 268 #ifdef DEBUG_MMAP
 269     {
 270         printf("mmap: start=0x" TARGET_FMT_lx
 271                " len=0x" TARGET_FMT_lx " prot=%c%c%c flags=",
 272                start, len,
 273                prot & PROT_READ ? 'r' : '-',
 274                prot & PROT_WRITE ? 'w' : '-',
 275                prot & PROT_EXEC ? 'x' : '-');
 276         if (flags & MAP_FIXED)
 277             printf("MAP_FIXED ");
 278         if (flags & MAP_ANON)
 279             printf("MAP_ANON ");
 280         switch(flags & TARGET_BSD_MAP_FLAGMASK) {
 281         case MAP_PRIVATE:
 282             printf("MAP_PRIVATE ");
 283             break;
 284         case MAP_SHARED:
 285             printf("MAP_SHARED ");
 286             break;
 287         default:
 288             printf("[MAP_FLAGMASK=0x%x] ", flags & TARGET_BSD_MAP_FLAGMASK);
 289             break;
 290         }
 291         printf("fd=%d offset=" TARGET_FMT_lx "\n", fd, offset);
 292     }
 293 #endif
 294
 295     if (offset & ~TARGET_PAGE_MASK) {
 296         errno = EINVAL;
 297         goto fail;
 298     }
 299
 300     len = TARGET_PAGE_ALIGN(len);
 301     if (len == 0)
 302         goto the_end;
 303     real_start = start & qemu_host_page_mask;
 304
 305     if (!(flags & MAP_FIXED)) {
 306         abi_ulong mmap_start;
 307         void *p;
 308         host_offset = offset & qemu_host_page_mask;
 309         host_len = len + offset - host_offset;
 310         host_len = HOST_PAGE_ALIGN(host_len);
 311         mmap_start = mmap_find_vma(real_start, host_len);
 312         if (mmap_start == (abi_ulong)-1) {
 313             errno = ENOMEM;
 314             goto fail;
 315         }
 316         /* Note: we prefer to control the mapping address. It is
 317            especially important if qemu_host_page_size >
 318            qemu_real_host_page_size */
 319         p = mmap(g2h(mmap_start),
 320                  host_len, prot, flags | MAP_FIXED, fd, host_offset);
 321         if (p == MAP_FAILED)
 322             goto fail;
 323         /* update start so that it points to the file position at 'offset' */
 324         host_start = (unsigned long)p;
 325         if (!(flags & MAP_ANON))
 326             host_start += offset - host_offset;
 327         start = h2g(host_start);
 328     } else {
 329         int flg;
 330         target_ulong addr;
 331
 332         if (start & ~TARGET_PAGE_MASK) {
 333             errno = EINVAL;
 334             goto fail;
 335         }
 336         end = start + len;
 337         real_end = HOST_PAGE_ALIGN(end);
 338
 339         for(addr = real_start; addr < real_end; addr += TARGET_PAGE_SIZE) {
 340             flg = page_get_flags(addr);
 341             if (flg & PAGE_RESERVED) {
 342                 errno = ENXIO;
 343                 goto fail;
 344             }
 345         }
 346
 347         /* worst case: we cannot map the file because the offset is not
 348            aligned, so we read it */
 349         if (!(flags & MAP_ANON) &&
 350             (offset & ~qemu_host_page_mask) != (start & ~qemu_host_page_mask)) {
 351             /* msync() won't work here, so we return an error if write is
 352                possible while it is a shared mapping */
 353             if ((flags & TARGET_BSD_MAP_FLAGMASK) == MAP_SHARED &&
 354                 (prot & PROT_WRITE)) {
 355                 errno = EINVAL;
 356                 goto fail;
 357             }
 358             retaddr = target_mmap(start, len, prot | PROT_WRITE,
 359                                   MAP_FIXED | MAP_PRIVATE | MAP_ANON,
 360                                   -1, 0);
 361             if (retaddr == -1)
 362                 goto fail;
 363             pread(fd, g2h(start), len, offset);
 364             if (!(prot & PROT_WRITE)) {
 365                 ret = target_mprotect(start, len, prot);
 366                 if (ret != 0) {
 367                     start = ret;
 368                     goto the_end;
 369                 }
 370             }
 371             goto the_end;
 372         }
 373
 374         /* handle the start of the mapping */
 375         if (start > real_start) {
 376             if (real_end == real_start + qemu_host_page_size) {
 377                 /* one single host page */
 378                 ret = mmap_frag(real_start, start, end,
 379                                 prot, flags, fd, offset);
 380                 if (ret == -1)
 381                     goto fail;
 382                 goto the_end1;
 383             }
 384             ret = mmap_frag(real_start, start, real_start + qemu_host_page_size,
 385                             prot, flags, fd, offset);
 386             if (ret == -1)
 387                 goto fail;
 388             real_start += qemu_host_page_size;
 389         }
 390         /* handle the end of the mapping */
 391         if (end < real_end) {
 392             ret = mmap_frag(real_end - qemu_host_page_size,
 393                             real_end - qemu_host_page_size, real_end,
 394                             prot, flags, fd,
 395                             offset + real_end - qemu_host_page_size - start);
 396             if (ret == -1)
 397                 goto fail;
 398             real_end -= qemu_host_page_size;
 399         }
 400
 401         /* map the middle (easier) */
 402         if (real_start < real_end) {
 403             void *p;
 404             unsigned long offset1;
 405             if (flags & MAP_ANON)
 406                 offset1 = 0;
 407             else
 408                 offset1 = offset + real_start - start;
 409             p = mmap(g2h(real_start), real_end - real_start,
 410                      prot, flags, fd, offset1);
 411             if (p == MAP_FAILED)
 412                 goto fail;
 413         }
 414     }
 415  the_end1:
 416     page_set_flags(start, start + len, prot | PAGE_VALID);
 417  the_end:
 418 #ifdef DEBUG_MMAP
 419     printf("ret=0x" TARGET_FMT_lx "\n", start);
 420     page_dump(stdout);
 421     printf("\n");
 422 #endif
 423     mmap_unlock();
 424     return start;
 425 fail:
 426     mmap_unlock();
 427     return -1;
 428 }
 429
 430 int target_munmap(abi_ulong start, abi_ulong len)
 431 {
 432     abi_ulong end, real_start, real_end, addr;
 433     int prot, ret;
 434
 435 #ifdef DEBUG_MMAP
 436     printf("munmap: start=0x%lx len=0x%lx\n", start, len);
 437 #endif
 438     if (start & ~TARGET_PAGE_MASK)
 439         return -EINVAL;
 440     len = TARGET_PAGE_ALIGN(len);
 441     if (len == 0)
 442         return -EINVAL;
 443     mmap_lock();
 444     end = start + len;
 445     real_start = start & qemu_host_page_mask;
 446     real_end = HOST_PAGE_ALIGN(end);
 447
 448     if (start > real_start) {
 449         /* handle host page containing start */
 450         prot = 0;
 451         for(addr = real_start; addr < start; addr += TARGET_PAGE_SIZE) {
 452             prot |= page_get_flags(addr);
 453         }
 454         if (real_end == real_start + qemu_host_page_size) {
 455             for(addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
 456                 prot |= page_get_flags(addr);
 457             }
 458             end = real_end;
 459         }
 460         if (prot != 0)
 461             real_start += qemu_host_page_size;
 462     }
 463     if (end < real_end) {
 464         prot = 0;
 465         for(addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
 466             prot |= page_get_flags(addr);
 467         }
 468         if (prot != 0)
 469             real_end -= qemu_host_page_size;
 470     }
 471
 472     ret = 0;
 473     /* unmap what we can */
 474     if (real_start < real_end) {
 475         ret = munmap(g2h(real_start), real_end - real_start);
 476     }
 477
 478     if (ret == 0)
 479         page_set_flags(start, start + len, 0);
 480     mmap_unlock();
 481     return ret;
 482 }
 483
 484 int target_msync(abi_ulong start, abi_ulong len, int flags)
 485 {
 486     abi_ulong end;
 487
 488     if (start & ~TARGET_PAGE_MASK)
 489         return -EINVAL;
 490     len = TARGET_PAGE_ALIGN(len);
 491     end = start + len;
 492     if (end < start)
 493         return -EINVAL;
 494     if (end == start)
 495         return 0;
 496
 497     start &= qemu_host_page_mask;
 498     return msync(g2h(start), end - start, flags);
 499 }