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., 51 Franklin Street - Fifth Floor, Boston,
  19  *  MA 02110-1301, USA.
  20  */
  21 #include <stdlib.h>
  22 #include <stdio.h>
  23 #include <stdarg.h>
  24 #include <string.h>
  25 #include <unistd.h>
  26 #include <errno.h>
  27 #include <sys/mman.h>
  28 #include <linux/mman.h>
  29 #include <linux/unistd.h>
  30
  31 #include "qemu.h"
  32 #include "qemu-common.h"
  33
  34 //#define DEBUG_MMAP
  35
  36 #if defined(USE_NPTL)
  37 pthread_mutex_t mmap_mutex;
  38 static int __thread mmap_lock_count;
  39
  40 void mmap_lock(void)
  41 {
  42     if (mmap_lock_count++ == 0) {
  43         pthread_mutex_lock(&mmap_mutex);
  44     }
  45 }
  46
  47 void mmap_unlock(void)
  48 {
  49     if (--mmap_lock_count == 0) {
  50         pthread_mutex_unlock(&mmap_mutex);
  51     }
  52 }
  53
  54 /* Grab lock to make sure things are in a consistent state after fork().  */
  55 void mmap_fork_start(void)
  56 {
  57     if (mmap_lock_count)
  58         abort();
  59     pthread_mutex_lock(&mmap_mutex);
  60 }
  61
  62 void mmap_fork_end(int child)
  63 {
  64     if (child)
  65         pthread_mutex_init(&mmap_mutex, NULL);
  66     else
  67         pthread_mutex_unlock(&mmap_mutex);
  68 }
  69 #else
  70 /* We aren't threadsafe to start with, so no need to worry about locking.  */
  71 void mmap_lock(void)
  72 {
  73 }
  74
  75 void mmap_unlock(void)
  76 {
  77 }
  78 #endif
  79
  80 void *qemu_vmalloc(size_t size)
  81 {
  82     void *p;
  83     unsigned long addr;
  84     mmap_lock();
  85     /* Use map and mark the pages as used.  */
  86     p = mmap(NULL, size, PROT_READ | PROT_WRITE,
  87              MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
  88
  89     addr = (unsigned long)p;
  90     if (addr == (target_ulong) addr) {
  91         /* Allocated region overlaps guest address space.
  92            This may recurse.  */
  93         page_set_flags(addr & TARGET_PAGE_MASK, TARGET_PAGE_ALIGN(addr + size),
  94                        PAGE_RESERVED);
  95     }
  96
  97     mmap_unlock();
  98     return p;
  99 }
 100
 101 void *qemu_malloc(size_t size)
 102 {
 103     char * p;
 104     size += 16;
 105     p = qemu_vmalloc(size);
 106     *(size_t *)p = size;
 107     return p + 16;
 108 }
 109
 110 /* We use map, which is always zero initialized.  */
 111 void * qemu_mallocz(size_t size)
 112 {
 113     return qemu_malloc(size);
 114 }
 115
 116 void qemu_free(void *ptr)
 117 {
 118     /* FIXME: We should unmark the reserved pages here.  However this gets
 119        complicated when one target page spans multiple host pages, so we
 120        don't bother.  */
 121     size_t *p;
 122     p = (size_t *)((char *)ptr - 16);
 123     munmap(p, *p);
 124 }
 125
 126 void *qemu_realloc(void *ptr, size_t size)
 127 {
 128     size_t old_size, copy;
 129     void *new_ptr;
 130
 131     if (!ptr)
 132         return qemu_malloc(size);
 133     old_size = *(size_t *)((char *)ptr - 16);
 134     copy = old_size < size ? old_size : size;
 135     new_ptr = qemu_malloc(size);
 136     memcpy(new_ptr, ptr, copy);
 137     qemu_free(ptr);
 138     return new_ptr;
 139 }
 140
 141 /* NOTE: all the constants are the HOST ones, but addresses are target. */
 142 int target_mprotect(abi_ulong start, abi_ulong len, int prot)
 143 {
 144     abi_ulong end, host_start, host_end, addr;
 145     int prot1, ret;
 146
 147 #ifdef DEBUG_MMAP
 148     printf("mprotect: start=0x" TARGET_FMT_lx
 149            "len=0x" TARGET_FMT_lx " prot=%c%c%c\n", start, len,
 150            prot & PROT_READ ? 'r' : '-',
 151            prot & PROT_WRITE ? 'w' : '-',
 152            prot & PROT_EXEC ? 'x' : '-');
 153 #endif
 154
 155     if ((start & ~TARGET_PAGE_MASK) != 0)
 156         return -EINVAL;
 157     len = TARGET_PAGE_ALIGN(len);
 158     end = start + len;
 159     if (end < start)
 160         return -EINVAL;
 161     prot &= PROT_READ | PROT_WRITE | PROT_EXEC;
 162     if (len == 0)
 163         return 0;
 164
 165     mmap_lock();
 166     host_start = start & qemu_host_page_mask;
 167     host_end = HOST_PAGE_ALIGN(end);
 168     if (start > host_start) {
 169         /* handle host page containing start */
 170         prot1 = prot;
 171         for(addr = host_start; addr < start; addr += TARGET_PAGE_SIZE) {
 172             prot1 |= page_get_flags(addr);
 173         }
 174         if (host_end == host_start + qemu_host_page_size) {
 175             for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
 176                 prot1 |= page_get_flags(addr);
 177             }
 178             end = host_end;
 179         }
 180         ret = mprotect(g2h(host_start), qemu_host_page_size, prot1 & PAGE_BITS);
 181         if (ret != 0)
 182             goto error;
 183         host_start += qemu_host_page_size;
 184     }
 185     if (end < host_end) {
 186         prot1 = prot;
 187         for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
 188             prot1 |= page_get_flags(addr);
 189         }
 190         ret = mprotect(g2h(host_end - qemu_host_page_size), qemu_host_page_size,
 191                        prot1 & PAGE_BITS);
 192         if (ret != 0)
 193             goto error;
 194         host_end -= qemu_host_page_size;
 195     }
 196
 197     /* handle the pages in the middle */
 198     if (host_start < host_end) {
 199         ret = mprotect(g2h(host_start), host_end - host_start, prot);
 200         if (ret != 0)
 201             goto error;
 202     }
 203     page_set_flags(start, start + len, prot | PAGE_VALID);
 204     mmap_unlock();
 205     return 0;
 206 error:
 207     mmap_unlock();
 208     return ret;
 209 }
 210
 211 /* map an incomplete host page */
 212 static int mmap_frag(abi_ulong real_start,
 213                      abi_ulong start, abi_ulong end,
 214                      int prot, int flags, int fd, abi_ulong offset)
 215 {
 216     abi_ulong real_end, addr;
 217     void *host_start;
 218     int prot1, prot_new;
 219
 220     real_end = real_start + qemu_host_page_size;
 221     host_start = g2h(real_start);
 222
 223     /* get the protection of the target pages outside the mapping */
 224     prot1 = 0;
 225     for(addr = real_start; addr < real_end; addr++) {
 226         if (addr < start || addr >= end)
 227             prot1 |= page_get_flags(addr);
 228     }
 229
 230     if (prot1 == 0) {
 231         /* no page was there, so we allocate one */
 232         void *p = mmap(host_start, qemu_host_page_size, prot,
 233                        flags | MAP_ANONYMOUS, -1, 0);
 234         if (p == MAP_FAILED)
 235             return -1;
 236         prot1 = prot;
 237     }
 238     prot1 &= PAGE_BITS;
 239
 240     prot_new = prot | prot1;
 241     if (!(flags & MAP_ANONYMOUS)) {
 242         /* msync() won't work here, so we return an error if write is
 243            possible while it is a shared mapping */
 244         if ((flags & MAP_TYPE) == MAP_SHARED &&
 245             (prot & PROT_WRITE))
 246             return -EINVAL;
 247
 248         /* adjust protection to be able to read */
 249         if (!(prot1 & PROT_WRITE))
 250             mprotect(host_start, qemu_host_page_size, prot1 | PROT_WRITE);
 251
 252         /* read the corresponding file data */
 253         pread(fd, g2h(start), end - start, offset);
 254
 255         /* put final protection */
 256         if (prot_new != (prot1 | PROT_WRITE))
 257             mprotect(host_start, qemu_host_page_size, prot_new);
 258     } else {
 259         /* just update the protection */
 260         if (prot_new != prot1) {
 261             mprotect(host_start, qemu_host_page_size, prot_new);
 262         }
 263     }
 264     return 0;
 265 }
 266
 267 #if defined(__CYGWIN__)
 268 /* Cygwin doesn't have a whole lot of address space.  */
 269 static abi_ulong mmap_next_start = 0x18000000;
 270 #else
 271 static abi_ulong mmap_next_start = 0x40000000;
 272 #endif
 273
 274 unsigned long last_brk;
 275
 276 /* find a free memory area of size 'size'. The search starts at
 277    'start'. If 'start' == 0, then a default start address is used.
 278    Return -1 if error.
 279 */
 280 /* page_init() marks pages used by the host as reserved to be sure not
 281    to use them. */
 282 static abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size)
 283 {
 284     abi_ulong addr, addr1, addr_start;
 285     int prot;
 286     unsigned long new_brk;
 287
 288     new_brk = (unsigned long)sbrk(0);
 289     if (last_brk && last_brk < new_brk && last_brk == (target_ulong)last_brk) {
 290         /* This is a hack to catch the host allocating memory with brk().
 291            If it uses mmap then we loose.
 292            FIXME: We really want to avoid the host allocating memory in
 293            the first place, and maybe leave some slack to avoid switching
 294            to mmap.  */
 295         page_set_flags(last_brk & TARGET_PAGE_MASK,
 296                        TARGET_PAGE_ALIGN(new_brk),
 297                        PAGE_RESERVED);
 298     }
 299     last_brk = new_brk;
 300
 301     size = HOST_PAGE_ALIGN(size);
 302     start = start & qemu_host_page_mask;
 303     addr = start;
 304     if (addr == 0)
 305         addr = mmap_next_start;
 306     addr_start = addr;
 307     for(;;) {
 308         prot = 0;
 309         for(addr1 = addr; addr1 < (addr + size); addr1 += TARGET_PAGE_SIZE) {
 310             prot |= page_get_flags(addr1);
 311         }
 312         if (prot == 0)
 313             break;
 314         addr += qemu_host_page_size;
 315         /* we found nothing */
 316         if (addr == addr_start)
 317             return (abi_ulong)-1;
 318     }
 319     if (start == 0)
 320         mmap_next_start = addr + size;
 321     return addr;
 322 }
 323
 324 /* NOTE: all the constants are the HOST ones */
 325 abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,
 326                      int flags, int fd, abi_ulong offset)
 327 {
 328     abi_ulong ret, end, real_start, real_end, retaddr, host_offset, host_len;
 329     unsigned long host_start;
 330
 331     mmap_lock();
 332 #ifdef DEBUG_MMAP
 333     {
 334         printf("mmap: start=0x" TARGET_FMT_lx
 335                " len=0x" TARGET_FMT_lx " prot=%c%c%c flags=",
 336                start, len,
 337                prot & PROT_READ ? 'r' : '-',
 338                prot & PROT_WRITE ? 'w' : '-',
 339                prot & PROT_EXEC ? 'x' : '-');
 340         if (flags & MAP_FIXED)
 341             printf("MAP_FIXED ");
 342         if (flags & MAP_ANONYMOUS)
 343             printf("MAP_ANON ");
 344         switch(flags & MAP_TYPE) {
 345         case MAP_PRIVATE:
 346             printf("MAP_PRIVATE ");
 347             break;
 348         case MAP_SHARED:
 349             printf("MAP_SHARED ");
 350             break;
 351         default:
 352             printf("[MAP_TYPE=0x%x] ", flags & MAP_TYPE);
 353             break;
 354         }
 355         printf("fd=%d offset=" TARGET_FMT_lx "\n", fd, offset);
 356     }
 357 #endif
 358
 359     if (offset & ~TARGET_PAGE_MASK) {
 360         errno = EINVAL;
 361         goto fail;
 362     }
 363
 364     len = TARGET_PAGE_ALIGN(len);
 365     if (len == 0)
 366         goto the_end;
 367     real_start = start & qemu_host_page_mask;
 368
 369     if (!(flags & MAP_FIXED)) {
 370         abi_ulong mmap_start;
 371         void *p;
 372         host_offset = offset & qemu_host_page_mask;
 373         host_len = len + offset - host_offset;
 374         host_len = HOST_PAGE_ALIGN(host_len);
 375         mmap_start = mmap_find_vma(real_start, host_len);
 376         if (mmap_start == (abi_ulong)-1) {
 377             errno = ENOMEM;
 378             goto fail;
 379         }
 380         /* Note: we prefer to control the mapping address. It is
 381            especially important if qemu_host_page_size >
 382            qemu_real_host_page_size */
 383         p = mmap(g2h(mmap_start),
 384                  host_len, prot, flags | MAP_FIXED, fd, host_offset);
 385         if (p == MAP_FAILED)
 386             goto fail;
 387         /* update start so that it points to the file position at 'offset' */
 388         host_start = (unsigned long)p;
 389         if (!(flags & MAP_ANONYMOUS))
 390             host_start += offset - host_offset;
 391         start = h2g(host_start);
 392     } else {
 393         int flg;
 394         target_ulong addr;
 395
 396         if (start & ~TARGET_PAGE_MASK) {
 397             errno = EINVAL;
 398             goto fail;
 399         }
 400         end = start + len;
 401         real_end = HOST_PAGE_ALIGN(end);
 402
 403         /*
 404          * Test if requested memory area fits target address space
 405          * It can fail only on 64-bit host with 32-bit target.
 406          * On any other target/host host mmap() handles this error correctly.
 407          */
 408         if ((unsigned long)start + len - 1 > (abi_ulong) -1) {
 409             errno = EINVAL;
 410             goto fail;
 411         }
 412
 413         for(addr = real_start; addr < real_end; addr += TARGET_PAGE_SIZE) {
 414             flg = page_get_flags(addr);
 415             if (flg & PAGE_RESERVED) {
 416                 errno = ENXIO;
 417                 goto fail;
 418             }
 419         }
 420
 421         /* worst case: we cannot map the file because the offset is not
 422            aligned, so we read it */
 423         if (!(flags & MAP_ANONYMOUS) &&
 424             (offset & ~qemu_host_page_mask) != (start & ~qemu_host_page_mask)) {
 425             /* msync() won't work here, so we return an error if write is
 426                possible while it is a shared mapping */
 427             if ((flags & MAP_TYPE) == MAP_SHARED &&
 428                 (prot & PROT_WRITE)) {
 429                 errno = EINVAL;
 430                 goto fail;
 431             }
 432             retaddr = target_mmap(start, len, prot | PROT_WRITE,
 433                                   MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS,
 434                                   -1, 0);
 435             if (retaddr == -1)
 436                 goto fail;
 437             pread(fd, g2h(start), len, offset);
 438             if (!(prot & PROT_WRITE)) {
 439                 ret = target_mprotect(start, len, prot);
 440                 if (ret != 0) {
 441                     start = ret;
 442                     goto the_end;
 443                 }
 444             }
 445             goto the_end;
 446         }
 447
 448         /* handle the start of the mapping */
 449         if (start > real_start) {
 450             if (real_end == real_start + qemu_host_page_size) {
 451                 /* one single host page */
 452                 ret = mmap_frag(real_start, start, end,
 453                                 prot, flags, fd, offset);
 454                 if (ret == -1)
 455                     goto fail;
 456                 goto the_end1;
 457             }
 458             ret = mmap_frag(real_start, start, real_start + qemu_host_page_size,
 459                             prot, flags, fd, offset);
 460             if (ret == -1)
 461                 goto fail;
 462             real_start += qemu_host_page_size;
 463         }
 464         /* handle the end of the mapping */
 465         if (end < real_end) {
 466             ret = mmap_frag(real_end - qemu_host_page_size,
 467                             real_end - qemu_host_page_size, real_end,
 468                             prot, flags, fd,
 469                             offset + real_end - qemu_host_page_size - start);
 470             if (ret == -1)
 471                 goto fail;
 472             real_end -= qemu_host_page_size;
 473         }
 474
 475         /* map the middle (easier) */
 476         if (real_start < real_end) {
 477             void *p;
 478             unsigned long offset1;
 479             if (flags & MAP_ANONYMOUS)
 480                 offset1 = 0;
 481             else
 482                 offset1 = offset + real_start - start;
 483             p = mmap(g2h(real_start), real_end - real_start,
 484                      prot, flags, fd, offset1);
 485             if (p == MAP_FAILED)
 486                 goto fail;
 487         }
 488     }
 489  the_end1:
 490     page_set_flags(start, start + len, prot | PAGE_VALID);
 491  the_end:
 492 #ifdef DEBUG_MMAP
 493     printf("ret=0x" TARGET_FMT_lx "\n", start);
 494     page_dump(stdout);
 495     printf("\n");
 496 #endif
 497     mmap_unlock();
 498     return start;
 499 fail:
 500     mmap_unlock();
 501     return -1;
 502 }
 503
 504 int target_munmap(abi_ulong start, abi_ulong len)
 505 {
 506     abi_ulong end, real_start, real_end, addr;
 507     int prot, ret;
 508
 509 #ifdef DEBUG_MMAP
 510     printf("munmap: start=0x%lx len=0x%lx\n", start, len);
 511 #endif
 512     if (start & ~TARGET_PAGE_MASK)
 513         return -EINVAL;
 514     len = TARGET_PAGE_ALIGN(len);
 515     if (len == 0)
 516         return -EINVAL;
 517     mmap_lock();
 518     end = start + len;
 519     real_start = start & qemu_host_page_mask;
 520     real_end = HOST_PAGE_ALIGN(end);
 521
 522     if (start > real_start) {
 523         /* handle host page containing start */
 524         prot = 0;
 525         for(addr = real_start; addr < start; addr += TARGET_PAGE_SIZE) {
 526             prot |= page_get_flags(addr);
 527         }
 528         if (real_end == real_start + qemu_host_page_size) {
 529             for(addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
 530                 prot |= page_get_flags(addr);
 531             }
 532             end = real_end;
 533         }
 534         if (prot != 0)
 535             real_start += qemu_host_page_size;
 536     }
 537     if (end < real_end) {
 538         prot = 0;
 539         for(addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
 540             prot |= page_get_flags(addr);
 541         }
 542         if (prot != 0)
 543             real_end -= qemu_host_page_size;
 544     }
 545
 546     ret = 0;
 547     /* unmap what we can */
 548     if (real_start < real_end) {
 549         ret = munmap(g2h(real_start), real_end - real_start);
 550     }
 551
 552     if (ret == 0)
 553         page_set_flags(start, start + len, 0);
 554     mmap_unlock();
 555     return ret;
 556 }
 557
 558 abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
 559                        abi_ulong new_size, unsigned long flags,
 560                        abi_ulong new_addr)
 561 {
 562     int prot;
 563     void *host_addr;
 564
 565     mmap_lock();
 566
 567     if (flags & MREMAP_FIXED)
 568         host_addr = (void *) syscall(__NR_mremap, g2h(old_addr),
 569                                      old_size, new_size,
 570                                      flags,
 571                                      new_addr);
 572     else if (flags & MREMAP_MAYMOVE) {
 573         abi_ulong mmap_start;
 574
 575         mmap_start = mmap_find_vma(0, new_size);
 576
 577         if (mmap_start == -1) {
 578             errno = ENOMEM;
 579             host_addr = MAP_FAILED;
 580         } else
 581             host_addr = (void *) syscall(__NR_mremap, g2h(old_addr),
 582                                          old_size, new_size,
 583                                          flags | MREMAP_FIXED,
 584                                          g2h(mmap_start));
 585     } else {
 586         host_addr = mremap(g2h(old_addr), old_size, new_size, flags);
 587         /* Check if address fits target address space */
 588         if ((unsigned long)host_addr + new_size > (abi_ulong)-1) {
 589             /* Revert mremap() changes */
 590             host_addr = mremap(g2h(old_addr), new_size, old_size, flags);
 591             errno = ENOMEM;
 592             host_addr = MAP_FAILED;
 593         }
 594     }
 595
 596     if (host_addr == MAP_FAILED) {
 597         new_addr = -1;
 598     } else {
 599         new_addr = h2g(host_addr);
 600         prot = page_get_flags(old_addr);
 601         page_set_flags(old_addr, old_addr + old_size, 0);
 602         page_set_flags(new_addr, new_addr + new_size, prot | PAGE_VALID);
 603     }
 604     mmap_unlock();
 605     return new_addr;
 606 }
 607
 608 int target_msync(abi_ulong start, abi_ulong len, int flags)
 609 {
 610     abi_ulong end;
 611
 612     if (start & ~TARGET_PAGE_MASK)
 613         return -EINVAL;
 614     len = TARGET_PAGE_ALIGN(len);
 615     end = start + len;
 616     if (end < start)
 617         return -EINVAL;
 618     if (end == start)
 619         return 0;
 620
 621     start &= qemu_host_page_mask;
 622     return msync(g2h(start), end - start, flags);
 623 }