linux-user/mmap.c

   1 /*
   2  *  mmap support for qemu
   3  *
   4  *  Copyright (c) 2003 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 #include <linux/mman.h>
  28 #include <linux/unistd.h>
  29
  30 #include "qemu.h"
  31 #include "qemu-common.h"
  32
  33 //#define DEBUG_MMAP
  34
  35 #if defined(USE_NPTL)
  36 pthread_mutex_t mmap_mutex;
  37 static int __thread mmap_lock_count;
  38
  39 void mmap_lock(void)
  40 {
  41     if (mmap_lock_count++ == 0) {
  42         pthread_mutex_lock(&mmap_mutex);
  43     }
  44 }
  45
  46 void mmap_unlock(void)
  47 {
  48     if (--mmap_lock_count == 0) {
  49         pthread_mutex_unlock(&mmap_mutex);
  50     }
  51 }
  52
  53 /* Grab lock to make sure things are in a consistent state after fork().  */
  54 void mmap_fork_start(void)
  55 {
  56     if (mmap_lock_count)
  57         abort();
  58     pthread_mutex_lock(&mmap_mutex);
  59 }
  60
  61 void mmap_fork_end(int child)
  62 {
  63     if (child)
  64         pthread_mutex_init(&mmap_mutex, NULL);
  65     else
  66         pthread_mutex_unlock(&mmap_mutex);
  67 }
  68 #else
  69 /* We aren't threadsafe to start with, so no need to worry about locking.  */
  70 void mmap_lock(void)
  71 {
  72 }
  73
  74 void mmap_unlock(void)
  75 {
  76 }
  77 #endif
  78
  79 void *qemu_vmalloc(size_t size)
  80 {
  81     void *p;
  82     unsigned long addr;
  83     mmap_lock();
  84     /* Use map and mark the pages as used.  */
  85     p = mmap(NULL, size, PROT_READ | PROT_WRITE,
  86              MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
  87
  88     addr = (unsigned long)p;
  89     if (addr == (target_ulong) addr) {
  90         /* Allocated region overlaps guest address space.
  91            This may recurse.  */
  92         page_set_flags(addr & TARGET_PAGE_MASK, TARGET_PAGE_ALIGN(addr + size),
  93                        PAGE_RESERVED);
  94     }
  95
  96     mmap_unlock();
  97     return p;
  98 }
  99
 100 void *qemu_malloc(size_t size)
 101 {
 102     char * p;
 103     size += 16;
 104     p = qemu_vmalloc(size);
 105     *(size_t *)p = size;
 106     return p + 16;
 107 }
 108
 109 /* We use map, which is always zero initialized.  */
 110 void * qemu_mallocz(size_t size)
 111 {
 112     return qemu_malloc(size);
 113 }
 114
 115 void qemu_free(void *ptr)
 116 {
 117     /* FIXME: We should unmark the reserved pages here.  However this gets
 118        complicated when one target page spans multiple host pages, so we
 119        don't bother.  */
 120     size_t *p;
 121     p = (size_t *)((char *)ptr - 16);
 122     munmap(p, *p);
 123 }
 124
 125 /* NOTE: all the constants are the HOST ones, but addresses are target. */
 126 int target_mprotect(abi_ulong start, abi_ulong len, int prot)
 127 {
 128     abi_ulong end, host_start, host_end, addr;
 129     int prot1, ret;
 130
 131 #ifdef DEBUG_MMAP
 132     printf("mprotect: start=0x" TARGET_FMT_lx
 133            "len=0x" TARGET_FMT_lx " prot=%c%c%c\n", start, len,
 134            prot & PROT_READ ? 'r' : '-',
 135            prot & PROT_WRITE ? 'w' : '-',
 136            prot & PROT_EXEC ? 'x' : '-');
 137 #endif
 138
 139     if ((start & ~TARGET_PAGE_MASK) != 0)
 140         return -EINVAL;
 141     len = TARGET_PAGE_ALIGN(len);
 142     end = start + len;
 143     if (end < start)
 144         return -EINVAL;
 145     prot &= PROT_READ | PROT_WRITE | PROT_EXEC;
 146     if (len == 0)
 147         return 0;
 148
 149     mmap_lock();
 150     host_start = start & qemu_host_page_mask;
 151     host_end = HOST_PAGE_ALIGN(end);
 152     if (start > host_start) {
 153         /* handle host page containing start */
 154         prot1 = prot;
 155         for(addr = host_start; addr < start; addr += TARGET_PAGE_SIZE) {
 156             prot1 |= page_get_flags(addr);
 157         }
 158         if (host_end == host_start + qemu_host_page_size) {
 159             for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
 160                 prot1 |= page_get_flags(addr);
 161             }
 162             end = host_end;
 163         }
 164         ret = mprotect(g2h(host_start), qemu_host_page_size, prot1 & PAGE_BITS);
 165         if (ret != 0)
 166             goto error;
 167         host_start += qemu_host_page_size;
 168     }
 169     if (end < host_end) {
 170         prot1 = prot;
 171         for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
 172             prot1 |= page_get_flags(addr);
 173         }
 174         ret = mprotect(g2h(host_end - qemu_host_page_size), qemu_host_page_size,
 175                        prot1 & PAGE_BITS);
 176         if (ret != 0)
 177             goto error;
 178         host_end -= qemu_host_page_size;
 179     }
 180
 181     /* handle the pages in the middle */
 182     if (host_start < host_end) {
 183         ret = mprotect(g2h(host_start), host_end - host_start, prot);
 184         if (ret != 0)
 185             goto error;
 186     }
 187     page_set_flags(start, start + len, prot | PAGE_VALID);
 188     mmap_unlock();
 189     return 0;
 190 error:
 191     mmap_unlock();
 192     return ret;
 193 }
 194
 195 /* map an incomplete host page */
 196 static int mmap_frag(abi_ulong real_start,
 197                      abi_ulong start, abi_ulong end,
 198                      int prot, int flags, int fd, abi_ulong offset)
 199 {
 200     abi_ulong real_end, addr;
 201     void *host_start;
 202     int prot1, prot_new;
 203
 204     real_end = real_start + qemu_host_page_size;
 205     host_start = g2h(real_start);
 206
 207     /* get the protection of the target pages outside the mapping */
 208     prot1 = 0;
 209     for(addr = real_start; addr < real_end; addr++) {
 210         if (addr < start || addr >= end)
 211             prot1 |= page_get_flags(addr);
 212     }
 213
 214     if (prot1 == 0) {
 215         /* no page was there, so we allocate one */
 216         void *p = mmap(host_start, qemu_host_page_size, prot,
 217                        flags | MAP_ANONYMOUS, -1, 0);
 218         if (p == MAP_FAILED)
 219             return -1;
 220         prot1 = prot;
 221     }
 222     prot1 &= PAGE_BITS;
 223
 224     prot_new = prot | prot1;
 225     if (!(flags & MAP_ANONYMOUS)) {
 226         /* msync() won't work here, so we return an error if write is
 227            possible while it is a shared mapping */
 228         if ((flags & MAP_TYPE) == MAP_SHARED &&
 229             (prot & PROT_WRITE))
 230             return -EINVAL;
 231
 232         /* adjust protection to be able to read */
 233         if (!(prot1 & PROT_WRITE))
 234             mprotect(host_start, qemu_host_page_size, prot1 | PROT_WRITE);
 235
 236         /* read the corresponding file data */
 237         pread(fd, g2h(start), end - start, offset);
 238
 239         /* put final protection */
 240         if (prot_new != (prot1 | PROT_WRITE))
 241             mprotect(host_start, qemu_host_page_size, prot_new);
 242     } else {
 243         /* just update the protection */
 244         if (prot_new != prot1) {
 245             mprotect(host_start, qemu_host_page_size, prot_new);
 246         }
 247     }
 248     return 0;
 249 }
 250
 251 #if defined(__CYGWIN__)
 252 /* Cygwin doesn't have a whole lot of address space.  */
 253 static abi_ulong mmap_next_start = 0x18000000;
 254 #else
 255 static abi_ulong mmap_next_start = 0x40000000;
 256 #endif
 257
 258 unsigned long last_brk;
 259
 260 /* find a free memory area of size 'size'. The search starts at
 261    'start'. If 'start' == 0, then a default start address is used.
 262    Return -1 if error.
 263 */
 264 /* page_init() marks pages used by the host as reserved to be sure not
 265    to use them. */
 266 static abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size)
 267 {
 268     abi_ulong addr, addr1, addr_start;
 269     int prot;
 270     unsigned long new_brk;
 271
 272     new_brk = (unsigned long)sbrk(0);
 273     if (last_brk && last_brk < new_brk && last_brk == (target_ulong)last_brk) {
 274         /* This is a hack to catch the host allocating memory with brk().
 275            If it uses mmap then we loose.
 276            FIXME: We really want to avoid the host allocating memory in
 277            the first place, and maybe leave some slack to avoid switching
 278            to mmap.  */
 279         page_set_flags(last_brk & TARGET_PAGE_MASK,
 280                        TARGET_PAGE_ALIGN(new_brk),
 281                        PAGE_RESERVED);
 282     }
 283     last_brk = new_brk;
 284
 285     size = HOST_PAGE_ALIGN(size);
 286     start = start & qemu_host_page_mask;
 287     addr = start;
 288     if (addr == 0)
 289         addr = mmap_next_start;
 290     addr_start = addr;
 291     for(;;) {
 292         prot = 0;
 293         for(addr1 = addr; addr1 < (addr + size); addr1 += TARGET_PAGE_SIZE) {
 294             prot |= page_get_flags(addr1);
 295         }
 296         if (prot == 0)
 297             break;
 298         addr += qemu_host_page_size;
 299         /* we found nothing */
 300         if (addr == addr_start)
 301             return (abi_ulong)-1;
 302     }
 303     if (start == 0)
 304         mmap_next_start = addr + size;
 305     return addr;
 306 }
 307
 308 /* NOTE: all the constants are the HOST ones */
 309 abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,
 310                      int flags, int fd, abi_ulong offset)
 311 {
 312     abi_ulong ret, end, real_start, real_end, retaddr, host_offset, host_len;
 313     unsigned long host_start;
 314
 315     mmap_lock();
 316 #ifdef DEBUG_MMAP
 317     {
 318         printf("mmap: start=0x" TARGET_FMT_lx
 319                " len=0x" TARGET_FMT_lx " prot=%c%c%c flags=",
 320                start, len,
 321                prot & PROT_READ ? 'r' : '-',
 322                prot & PROT_WRITE ? 'w' : '-',
 323                prot & PROT_EXEC ? 'x' : '-');
 324         if (flags & MAP_FIXED)
 325             printf("MAP_FIXED ");
 326         if (flags & MAP_ANONYMOUS)
 327             printf("MAP_ANON ");
 328         switch(flags & MAP_TYPE) {
 329         case MAP_PRIVATE:
 330             printf("MAP_PRIVATE ");
 331             break;
 332         case MAP_SHARED:
 333             printf("MAP_SHARED ");
 334             break;
 335         default:
 336             printf("[MAP_TYPE=0x%x] ", flags & MAP_TYPE);
 337             break;
 338         }
 339         printf("fd=%d offset=" TARGET_FMT_lx "\n", fd, offset);
 340     }
 341 #endif
 342
 343     if (offset & ~TARGET_PAGE_MASK) {
 344         errno = EINVAL;
 345         goto fail;
 346     }
 347
 348     len = TARGET_PAGE_ALIGN(len);
 349     if (len == 0)
 350         goto the_end;
 351     real_start = start & qemu_host_page_mask;
 352
 353     if (!(flags & MAP_FIXED)) {
 354         abi_ulong mmap_start;
 355         void *p;
 356         host_offset = offset & qemu_host_page_mask;
 357         host_len = len + offset - host_offset;
 358         host_len = HOST_PAGE_ALIGN(host_len);
 359         mmap_start = mmap_find_vma(real_start, host_len);
 360         if (mmap_start == (abi_ulong)-1) {
 361             errno = ENOMEM;
 362             goto fail;
 363         }
 364         /* Note: we prefer to control the mapping address. It is
 365            especially important if qemu_host_page_size >
 366            qemu_real_host_page_size */
 367         p = mmap(g2h(mmap_start),
 368                  host_len, prot, flags | MAP_FIXED, fd, host_offset);
 369         if (p == MAP_FAILED)
 370             goto fail;
 371         /* update start so that it points to the file position at 'offset' */
 372         host_start = (unsigned long)p;
 373         if (!(flags & MAP_ANONYMOUS))
 374             host_start += offset - host_offset;
 375         start = h2g(host_start);
 376     } else {
 377         int flg;
 378         target_ulong addr;
 379
 380         if (start & ~TARGET_PAGE_MASK) {
 381             errno = EINVAL;
 382             goto fail;
 383         }
 384         end = start + len;
 385         real_end = HOST_PAGE_ALIGN(end);
 386
 387         /*
 388          * Test if requested memory area fits target address space
 389          * It can fail only on 64-bit host with 32-bit target.
 390          * On any other target/host host mmap() handles this error correctly.
 391          */
 392         if ((unsigned long)start + len - 1 > (abi_ulong) -1) {
 393             errno = EINVAL;
 394             goto fail;
 395         }
 396
 397         for(addr = real_start; addr < real_end; addr += TARGET_PAGE_SIZE) {
 398             flg = page_get_flags(addr);
 399             if (flg & PAGE_RESERVED) {
 400                 errno = ENXIO;
 401                 goto fail;
 402             }
 403         }
 404
 405         /* worst case: we cannot map the file because the offset is not
 406            aligned, so we read it */
 407         if (!(flags & MAP_ANONYMOUS) &&
 408             (offset & ~qemu_host_page_mask) != (start & ~qemu_host_page_mask)) {
 409             /* msync() won't work here, so we return an error if write is
 410                possible while it is a shared mapping */
 411             if ((flags & MAP_TYPE) == MAP_SHARED &&
 412                 (prot & PROT_WRITE)) {
 413                 errno = EINVAL;
 414                 goto fail;
 415             }
 416             retaddr = target_mmap(start, len, prot | PROT_WRITE,
 417                                   MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS,
 418                                   -1, 0);
 419             if (retaddr == -1)
 420                 goto fail;
 421             pread(fd, g2h(start), len, offset);
 422             if (!(prot & PROT_WRITE)) {
 423                 ret = target_mprotect(start, len, prot);
 424                 if (ret != 0) {
 425                     start = ret;
 426                     goto the_end;
 427                 }
 428             }
 429             goto the_end;
 430         }
 431
 432         /* handle the start of the mapping */
 433         if (start > real_start) {
 434             if (real_end == real_start + qemu_host_page_size) {
 435                 /* one single host page */
 436                 ret = mmap_frag(real_start, start, end,
 437                                 prot, flags, fd, offset);
 438                 if (ret == -1)
 439                     goto fail;
 440                 goto the_end1;
 441             }
 442             ret = mmap_frag(real_start, start, real_start + qemu_host_page_size,
 443                             prot, flags, fd, offset);
 444             if (ret == -1)
 445                 goto fail;
 446             real_start += qemu_host_page_size;
 447         }
 448         /* handle the end of the mapping */
 449         if (end < real_end) {
 450             ret = mmap_frag(real_end - qemu_host_page_size,
 451                             real_end - qemu_host_page_size, real_end,
 452                             prot, flags, fd,
 453                             offset + real_end - qemu_host_page_size - start);
 454             if (ret == -1)
 455                 goto fail;
 456             real_end -= qemu_host_page_size;
 457         }
 458
 459         /* map the middle (easier) */
 460         if (real_start < real_end) {
 461             void *p;
 462             unsigned long offset1;
 463             if (flags & MAP_ANONYMOUS)
 464                 offset1 = 0;
 465             else
 466                 offset1 = offset + real_start - start;
 467             p = mmap(g2h(real_start), real_end - real_start,
 468                      prot, flags, fd, offset1);
 469             if (p == MAP_FAILED)
 470                 goto fail;
 471         }
 472     }
 473  the_end1:
 474     page_set_flags(start, start + len, prot | PAGE_VALID);
 475  the_end:
 476 #ifdef DEBUG_MMAP
 477     printf("ret=0x" TARGET_FMT_lx "\n", start);
 478     page_dump(stdout);
 479     printf("\n");
 480 #endif
 481     mmap_unlock();
 482     return start;
 483 fail:
 484     mmap_unlock();
 485     return -1;
 486 }
 487
 488 int target_munmap(abi_ulong start, abi_ulong len)
 489 {
 490     abi_ulong end, real_start, real_end, addr;
 491     int prot, ret;
 492
 493 #ifdef DEBUG_MMAP
 494     printf("munmap: start=0x%lx len=0x%lx\n", start, len);
 495 #endif
 496     if (start & ~TARGET_PAGE_MASK)
 497         return -EINVAL;
 498     len = TARGET_PAGE_ALIGN(len);
 499     if (len == 0)
 500         return -EINVAL;
 501     mmap_lock();
 502     end = start + len;
 503     real_start = start & qemu_host_page_mask;
 504     real_end = HOST_PAGE_ALIGN(end);
 505
 506     if (start > real_start) {
 507         /* handle host page containing start */
 508         prot = 0;
 509         for(addr = real_start; addr < start; addr += TARGET_PAGE_SIZE) {
 510             prot |= page_get_flags(addr);
 511         }
 512         if (real_end == real_start + qemu_host_page_size) {
 513             for(addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
 514                 prot |= page_get_flags(addr);
 515             }
 516             end = real_end;
 517         }
 518         if (prot != 0)
 519             real_start += qemu_host_page_size;
 520     }
 521     if (end < real_end) {
 522         prot = 0;
 523         for(addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
 524             prot |= page_get_flags(addr);
 525         }
 526         if (prot != 0)
 527             real_end -= qemu_host_page_size;
 528     }
 529
 530     ret = 0;
 531     /* unmap what we can */
 532     if (real_start < real_end) {
 533         ret = munmap(g2h(real_start), real_end - real_start);
 534     }
 535
 536     if (ret == 0)
 537         page_set_flags(start, start + len, 0);
 538     mmap_unlock();
 539     return ret;
 540 }
 541
 542 abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
 543                        abi_ulong new_size, unsigned long flags,
 544                        abi_ulong new_addr)
 545 {
 546     int prot;
 547     void *host_addr;
 548
 549     mmap_lock();
 550
 551     if (flags & MREMAP_FIXED)
 552         host_addr = (void *) syscall(__NR_mremap, g2h(old_addr),
 553                                      old_size, new_size,
 554                                      flags,
 555                                      new_addr);
 556     else if (flags & MREMAP_MAYMOVE) {
 557         abi_ulong mmap_start;
 558
 559         mmap_start = mmap_find_vma(0, new_size);
 560
 561         if (mmap_start == -1) {
 562             errno = ENOMEM;
 563             host_addr = MAP_FAILED;
 564         } else
 565             host_addr = (void *) syscall(__NR_mremap, g2h(old_addr),
 566                                          old_size, new_size,
 567                                          flags | MREMAP_FIXED,
 568                                          g2h(mmap_start));
 569     } else {
 570         host_addr = mremap(g2h(old_addr), old_size, new_size, flags);
 571         /* Check if address fits target address space */
 572         if ((unsigned long)host_addr + new_size > (abi_ulong)-1) {
 573             /* Revert mremap() changes */
 574             host_addr = mremap(g2h(old_addr), new_size, old_size, flags);
 575             errno = ENOMEM;
 576             host_addr = MAP_FAILED;
 577         }
 578     }
 579
 580     if (host_addr == MAP_FAILED) {
 581         new_addr = -1;
 582     } else {
 583         new_addr = h2g(host_addr);
 584         prot = page_get_flags(old_addr);
 585         page_set_flags(old_addr, old_addr + old_size, 0);
 586         page_set_flags(new_addr, new_addr + new_size, prot | PAGE_VALID);
 587     }
 588     mmap_unlock();
 589     return new_addr;
 590 }
 591
 592 int target_msync(abi_ulong start, abi_ulong len, int flags)
 593 {
 594     abi_ulong end;
 595
 596     if (start & ~TARGET_PAGE_MASK)
 597         return -EINVAL;
 598     len = TARGET_PAGE_ALIGN(len);
 599     end = start + len;
 600     if (end < start)
 601         return -EINVAL;
 602     if (end == start)
 603         return 0;
 604
 605     start &= qemu_host_page_mask;
 606     return msync(g2h(start), end - start, flags);
 607 }