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, write to the Free Software
  18  *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19  */
  20 #include <stdlib.h>
  21 #include <stdio.h>
  22 #include <stdarg.h>
  23 #include <string.h>
  24 #include <unistd.h>
  25 #include <errno.h>
  26 #include <sys/mman.h>
  27
  28 #include "qemu.h"
  29 #include "qemu-common.h"
  30 #include "bsd-mman.h"
  31
  32 //#define DEBUG_MMAP
  33
  34 #if defined(USE_NPTL)
  35 pthread_mutex_t mmap_mutex;
  36 static int __thread mmap_lock_count;
  37
  38 void mmap_lock(void)
  39 {
  40     if (mmap_lock_count++ == 0) {
  41         pthread_mutex_lock(&mmap_mutex);
  42     }
  43 }
  44
  45 void mmap_unlock(void)
  46 {
  47     if (--mmap_lock_count == 0) {
  48         pthread_mutex_unlock(&mmap_mutex);
  49     }
  50 }
  51
  52 /* Grab lock to make sure things are in a consistent state after fork().  */
  53 void mmap_fork_start(void)
  54 {
  55     if (mmap_lock_count)
  56         abort();
  57     pthread_mutex_lock(&mmap_mutex);
  58 }
  59
  60 void mmap_fork_end(int child)
  61 {
  62     if (child)
  63         pthread_mutex_init(&mmap_mutex, NULL);
  64     else
  65         pthread_mutex_unlock(&mmap_mutex);
  66 }
  67 #else
  68 /* We aren't threadsafe to start with, so no need to worry about locking.  */
  69 void mmap_lock(void)
  70 {
  71 }
  72
  73 void mmap_unlock(void)
  74 {
  75 }
  76 #endif
  77
  78 void *qemu_vmalloc(size_t size)
  79 {
  80     void *p;
  81     unsigned long addr;
  82     mmap_lock();
  83     /* Use map and mark the pages as used.  */
  84     p = mmap(NULL, size, PROT_READ | PROT_WRITE,
  85              MAP_PRIVATE | MAP_ANON, -1, 0);
  86
  87     addr = (unsigned long)p;
  88     if (addr == (target_ulong) addr) {
  89         /* Allocated region overlaps guest address space.
  90            This may recurse.  */
  91         page_set_flags(addr & TARGET_PAGE_MASK, TARGET_PAGE_ALIGN(addr + size),
  92                        PAGE_RESERVED);
  93     }
  94
  95     mmap_unlock();
  96     return p;
  97 }
  98
  99 void *qemu_malloc(size_t size)
 100 {
 101     char * p;
 102     size += 16;
 103     p = qemu_vmalloc(size);
 104     *(size_t *)p = size;
 105     return p + 16;
 106 }
 107
 108 /* We use map, which is always zero initialized.  */
 109 void * qemu_mallocz(size_t size)
 110 {
 111     return qemu_malloc(size);
 112 }
 113
 114 void qemu_free(void *ptr)
 115 {
 116     /* FIXME: We should unmark the reserved pages here.  However this gets
 117        complicated when one target page spans multiple host pages, so we
 118        don't bother.  */
 119     size_t *p;
 120     p = (size_t *)((char *)ptr - 16);
 121     munmap(p, *p);
 122 }
 123
 124 /* NOTE: all the constants are the HOST ones, but addresses are target. */
 125 int target_mprotect(abi_ulong start, abi_ulong len, int prot)
 126 {
 127     abi_ulong end, host_start, host_end, addr;
 128     int prot1, ret;
 129
 130 #ifdef DEBUG_MMAP
 131     printf("mprotect: start=0x" TARGET_FMT_lx
 132            " len=0x" TARGET_FMT_lx " prot=%c%c%c\n", start, len,
 133            prot & PROT_READ ? 'r' : '-',
 134            prot & PROT_WRITE ? 'w' : '-',
 135            prot & PROT_EXEC ? 'x' : '-');
 136 #endif
 137
 138     if ((start & ~TARGET_PAGE_MASK) != 0)
 139         return -EINVAL;
 140     len = TARGET_PAGE_ALIGN(len);
 141     end = start + len;
 142     if (end < start)
 143         return -EINVAL;
 144     prot &= PROT_READ | PROT_WRITE | PROT_EXEC;
 145     if (len == 0)
 146         return 0;
 147
 148     mmap_lock();
 149     host_start = start & qemu_host_page_mask;
 150     host_end = HOST_PAGE_ALIGN(end);
 151     if (start > host_start) {
 152         /* handle host page containing start */
 153         prot1 = prot;
 154         for(addr = host_start; addr < start; addr += TARGET_PAGE_SIZE) {
 155             prot1 |= page_get_flags(addr);
 156         }
 157         if (host_end == host_start + qemu_host_page_size) {
 158             for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
 159                 prot1 |= page_get_flags(addr);
 160             }
 161             end = host_end;
 162         }
 163         ret = mprotect(g2h(host_start), qemu_host_page_size, prot1 & PAGE_BITS);
 164         if (ret != 0)
 165             goto error;
 166         host_start += qemu_host_page_size;
 167     }
 168     if (end < host_end) {
 169         prot1 = prot;
 170         for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
 171             prot1 |= page_get_flags(addr);
 172         }
 173         ret = mprotect(g2h(host_end - qemu_host_page_size), qemu_host_page_size,
 174                        prot1 & PAGE_BITS);
 175         if (ret != 0)
 176             goto error;
 177         host_end -= qemu_host_page_size;
 178     }
 179
 180     /* handle the pages in the middle */
 181     if (host_start < host_end) {
 182         ret = mprotect(g2h(host_start), host_end - host_start, prot);
 183         if (ret != 0)
 184             goto error;
 185     }
 186     page_set_flags(start, start + len, prot | PAGE_VALID);
 187     mmap_unlock();
 188     return 0;
 189 error:
 190     mmap_unlock();
 191     return ret;
 192 }
 193
 194 /* map an incomplete host page */
 195 static int mmap_frag(abi_ulong real_start,
 196                      abi_ulong start, abi_ulong end,
 197                      int prot, int flags, int fd, abi_ulong offset)
 198 {
 199     abi_ulong real_end, addr;
 200     void *host_start;
 201     int prot1, prot_new;
 202
 203     real_end = real_start + qemu_host_page_size;
 204     host_start = g2h(real_start);
 205
 206     /* get the protection of the target pages outside the mapping */
 207     prot1 = 0;
 208     for(addr = real_start; addr < real_end; addr++) {
 209         if (addr < start || addr >= end)
 210             prot1 |= page_get_flags(addr);
 211     }
 212
 213     if (prot1 == 0) {
 214         /* no page was there, so we allocate one */
 215         void *p = mmap(host_start, qemu_host_page_size, prot,
 216                        flags | MAP_ANON, -1, 0);
 217         if (p == MAP_FAILED)
 218             return -1;
 219         prot1 = prot;
 220     }
 221     prot1 &= PAGE_BITS;
 222
 223     prot_new = prot | prot1;
 224     if (!(flags & MAP_ANON)) {
 225         /* msync() won't work here, so we return an error if write is
 226            possible while it is a shared mapping */
 227         if ((flags & TARGET_BSD_MAP_FLAGMASK) == MAP_SHARED &&
 228             (prot & PROT_WRITE))
 229             return -EINVAL;
 230
 231         /* adjust protection to be able to read */
 232         if (!(prot1 & PROT_WRITE))
 233             mprotect(host_start, qemu_host_page_size, prot1 | PROT_WRITE);
 234
 235         /* read the corresponding file data */
 236         pread(fd, g2h(start), end - start, offset);
 237
 238         /* put final protection */
 239         if (prot_new != (prot1 | PROT_WRITE))
 240             mprotect(host_start, qemu_host_page_size, prot_new);
 241     } else {
 242         /* just update the protection */
 243         if (prot_new != prot1) {
 244             mprotect(host_start, qemu_host_page_size, prot_new);
 245         }
 246     }
 247     return 0;
 248 }
 249
 250 #if defined(__CYGWIN__)
 251 /* Cygwin doesn't have a whole lot of address space.  */
 252 static abi_ulong mmap_next_start = 0x18000000;
 253 #else
 254 static abi_ulong mmap_next_start = 0x40000000;
 255 #endif
 256
 257 unsigned long last_brk;
 258
 259 /* find a free memory area of size 'size'. The search starts at
 260    'start'. If 'start' == 0, then a default start address is used.
 261    Return -1 if error.
 262 */
 263 /* page_init() marks pages used by the host as reserved to be sure not
 264    to use them. */
 265 static abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size)
 266 {
 267     abi_ulong addr, addr1, addr_start;
 268     int prot;
 269     unsigned long new_brk;
 270
 271     new_brk = (unsigned long)sbrk(0);
 272     if (last_brk && last_brk < new_brk && last_brk == (target_ulong)last_brk) {
 273         /* This is a hack to catch the host allocating memory with brk().
 274            If it uses mmap then we loose.
 275            FIXME: We really want to avoid the host allocating memory in
 276            the first place, and maybe leave some slack to avoid switching
 277            to mmap.  */
 278         page_set_flags(last_brk & TARGET_PAGE_MASK,
 279                        TARGET_PAGE_ALIGN(new_brk),
 280                        PAGE_RESERVED);
 281     }
 282     last_brk = new_brk;
 283
 284     size = HOST_PAGE_ALIGN(size);
 285     start = start & qemu_host_page_mask;
 286     addr = start;
 287     if (addr == 0)
 288         addr = mmap_next_start;
 289     addr_start = addr;
 290     for(;;) {
 291         prot = 0;
 292         for(addr1 = addr; addr1 < (addr + size); addr1 += TARGET_PAGE_SIZE) {
 293             prot |= page_get_flags(addr1);
 294         }
 295         if (prot == 0)
 296             break;
 297         addr += qemu_host_page_size;
 298         /* we found nothing */
 299         if (addr == addr_start)
 300             return (abi_ulong)-1;
 301     }
 302     if (start == 0)
 303         mmap_next_start = addr + size;
 304     return addr;
 305 }
 306
 307 /* NOTE: all the constants are the HOST ones */
 308 abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,
 309                      int flags, int fd, abi_ulong offset)
 310 {
 311     abi_ulong ret, end, real_start, real_end, retaddr, host_offset, host_len;
 312     unsigned long host_start;
 313
 314     mmap_lock();
 315 #ifdef DEBUG_MMAP
 316     {
 317         printf("mmap: start=0x" TARGET_FMT_lx
 318                " len=0x" TARGET_FMT_lx " prot=%c%c%c flags=",
 319                start, len,
 320                prot & PROT_READ ? 'r' : '-',
 321                prot & PROT_WRITE ? 'w' : '-',
 322                prot & PROT_EXEC ? 'x' : '-');
 323         if (flags & MAP_FIXED)
 324             printf("MAP_FIXED ");
 325         if (flags & MAP_ANON)
 326             printf("MAP_ANON ");
 327         switch(flags & TARGET_BSD_MAP_FLAGMASK) {
 328         case MAP_PRIVATE:
 329             printf("MAP_PRIVATE ");
 330             break;
 331         case MAP_SHARED:
 332             printf("MAP_SHARED ");
 333             break;
 334         default:
 335             printf("[MAP_FLAGMASK=0x%x] ", flags & TARGET_BSD_MAP_FLAGMASK);
 336             break;
 337         }
 338         printf("fd=%d offset=" TARGET_FMT_lx "\n", fd, offset);
 339     }
 340 #endif
 341
 342     if (offset & ~TARGET_PAGE_MASK) {
 343         errno = EINVAL;
 344         goto fail;
 345     }
 346
 347     len = TARGET_PAGE_ALIGN(len);
 348     if (len == 0)
 349         goto the_end;
 350     real_start = start & qemu_host_page_mask;
 351
 352     if (!(flags & MAP_FIXED)) {
 353         abi_ulong mmap_start;
 354         void *p;
 355         host_offset = offset & qemu_host_page_mask;
 356         host_len = len + offset - host_offset;
 357         host_len = HOST_PAGE_ALIGN(host_len);
 358         mmap_start = mmap_find_vma(real_start, host_len);
 359         if (mmap_start == (abi_ulong)-1) {
 360             errno = ENOMEM;
 361             goto fail;
 362         }
 363         /* Note: we prefer to control the mapping address. It is
 364            especially important if qemu_host_page_size >
 365            qemu_real_host_page_size */
 366         p = mmap(g2h(mmap_start),
 367                  host_len, prot, flags | MAP_FIXED, fd, host_offset);
 368         if (p == MAP_FAILED)
 369             goto fail;
 370         /* update start so that it points to the file position at 'offset' */
 371         host_start = (unsigned long)p;
 372         if (!(flags & MAP_ANON))
 373             host_start += offset - host_offset;
 374         start = h2g(host_start);
 375     } else {
 376         int flg;
 377         target_ulong addr;
 378
 379         if (start & ~TARGET_PAGE_MASK) {
 380             errno = EINVAL;
 381             goto fail;
 382         }
 383         end = start + len;
 384         real_end = HOST_PAGE_ALIGN(end);
 385
 386         for(addr = real_start; addr < real_end; addr += TARGET_PAGE_SIZE) {
 387             flg = page_get_flags(addr);
 388             if (flg & PAGE_RESERVED) {
 389                 errno = ENXIO;
 390                 goto fail;
 391             }
 392         }
 393
 394         /* worst case: we cannot map the file because the offset is not
 395            aligned, so we read it */
 396         if (!(flags & MAP_ANON) &&
 397             (offset & ~qemu_host_page_mask) != (start & ~qemu_host_page_mask)) {
 398             /* msync() won't work here, so we return an error if write is
 399                possible while it is a shared mapping */
 400             if ((flags & TARGET_BSD_MAP_FLAGMASK) == MAP_SHARED &&
 401                 (prot & PROT_WRITE)) {
 402                 errno = EINVAL;
 403                 goto fail;
 404             }
 405             retaddr = target_mmap(start, len, prot | PROT_WRITE,
 406                                   MAP_FIXED | MAP_PRIVATE | MAP_ANON,
 407                                   -1, 0);
 408             if (retaddr == -1)
 409                 goto fail;
 410             pread(fd, g2h(start), len, offset);
 411             if (!(prot & PROT_WRITE)) {
 412                 ret = target_mprotect(start, len, prot);
 413                 if (ret != 0) {
 414                     start = ret;
 415                     goto the_end;
 416                 }
 417             }
 418             goto the_end;
 419         }
 420
 421         /* handle the start of the mapping */
 422         if (start > real_start) {
 423             if (real_end == real_start + qemu_host_page_size) {
 424                 /* one single host page */
 425                 ret = mmap_frag(real_start, start, end,
 426                                 prot, flags, fd, offset);
 427                 if (ret == -1)
 428                     goto fail;
 429                 goto the_end1;
 430             }
 431             ret = mmap_frag(real_start, start, real_start + qemu_host_page_size,
 432                             prot, flags, fd, offset);
 433             if (ret == -1)
 434                 goto fail;
 435             real_start += qemu_host_page_size;
 436         }
 437         /* handle the end of the mapping */
 438         if (end < real_end) {
 439             ret = mmap_frag(real_end - qemu_host_page_size,
 440                             real_end - qemu_host_page_size, real_end,
 441                             prot, flags, fd,
 442                             offset + real_end - qemu_host_page_size - start);
 443             if (ret == -1)
 444                 goto fail;
 445             real_end -= qemu_host_page_size;
 446         }
 447
 448         /* map the middle (easier) */
 449         if (real_start < real_end) {
 450             void *p;
 451             unsigned long offset1;
 452             if (flags & MAP_ANON)
 453                 offset1 = 0;
 454             else
 455                 offset1 = offset + real_start - start;
 456             p = mmap(g2h(real_start), real_end - real_start,
 457                      prot, flags, fd, offset1);
 458             if (p == MAP_FAILED)
 459                 goto fail;
 460         }
 461     }
 462  the_end1:
 463     page_set_flags(start, start + len, prot | PAGE_VALID);
 464  the_end:
 465 #ifdef DEBUG_MMAP
 466     printf("ret=0x" TARGET_FMT_lx "\n", start);
 467     page_dump(stdout);
 468     printf("\n");
 469 #endif
 470     mmap_unlock();
 471     return start;
 472 fail:
 473     mmap_unlock();
 474     return -1;
 475 }
 476
 477 int target_munmap(abi_ulong start, abi_ulong len)
 478 {
 479     abi_ulong end, real_start, real_end, addr;
 480     int prot, ret;
 481
 482 #ifdef DEBUG_MMAP
 483     printf("munmap: start=0x%lx len=0x%lx\n", start, len);
 484 #endif
 485     if (start & ~TARGET_PAGE_MASK)
 486         return -EINVAL;
 487     len = TARGET_PAGE_ALIGN(len);
 488     if (len == 0)
 489         return -EINVAL;
 490     mmap_lock();
 491     end = start + len;
 492     real_start = start & qemu_host_page_mask;
 493     real_end = HOST_PAGE_ALIGN(end);
 494
 495     if (start > real_start) {
 496         /* handle host page containing start */
 497         prot = 0;
 498         for(addr = real_start; addr < start; addr += TARGET_PAGE_SIZE) {
 499             prot |= page_get_flags(addr);
 500         }
 501         if (real_end == real_start + qemu_host_page_size) {
 502             for(addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
 503                 prot |= page_get_flags(addr);
 504             }
 505             end = real_end;
 506         }
 507         if (prot != 0)
 508             real_start += qemu_host_page_size;
 509     }
 510     if (end < real_end) {
 511         prot = 0;
 512         for(addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
 513             prot |= page_get_flags(addr);
 514         }
 515         if (prot != 0)
 516             real_end -= qemu_host_page_size;
 517     }
 518
 519     ret = 0;
 520     /* unmap what we can */
 521     if (real_start < real_end) {
 522         ret = munmap(g2h(real_start), real_end - real_start);
 523     }
 524
 525     if (ret == 0)
 526         page_set_flags(start, start + len, 0);
 527     mmap_unlock();
 528     return ret;
 529 }
 530
 531 int target_msync(abi_ulong start, abi_ulong len, int flags)
 532 {
 533     abi_ulong end;
 534
 535     if (start & ~TARGET_PAGE_MASK)
 536         return -EINVAL;
 537     len = TARGET_PAGE_ALIGN(len);
 538     end = start + len;
 539     if (end < start)
 540         return -EINVAL;
 541     if (end == start)
 542         return 0;
 543
 544     start &= qemu_host_page_mask;
 545     return msync(g2h(start), end - start, flags);
 546 }