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
  28 #include "qemu.h"
  29
  30 //#define DEBUG_MMAP
  31
  32 #if defined(USE_NPTL)
  33 pthread_mutex_t mmap_mutex;
  34 static int __thread mmap_lock_count;
  35
  36 void mmap_lock(void)
  37 {
  38     if (mmap_lock_count++ == 0) {
  39         pthread_mutex_lock(&mmap_mutex);
  40     }
  41 }
  42
  43 void mmap_unlock(void)
  44 {
  45     if (--mmap_lock_count == 0) {
  46         pthread_mutex_unlock(&mmap_mutex);
  47     }
  48 }
  49 #else
  50 /* We aren't threadsafe to start with, so no need to worry about locking.  */
  51 void mmap_lock(void)
  52 {
  53 }
  54
  55 void mmap_unlock(void)
  56 {
  57 }
  58 #endif
  59
  60 /* NOTE: all the constants are the HOST ones, but addresses are target. */
  61 int target_mprotect(abi_ulong start, abi_ulong len, int prot)
  62 {
  63     abi_ulong end, host_start, host_end, addr;
  64     int prot1, ret;
  65
  66 #ifdef DEBUG_MMAP
  67     printf("mprotect: start=0x" TARGET_FMT_lx
  68            "len=0x" TARGET_FMT_lx " prot=%c%c%c\n", start, len,
  69            prot & PROT_READ ? 'r' : '-',
  70            prot & PROT_WRITE ? 'w' : '-',
  71            prot & PROT_EXEC ? 'x' : '-');
  72 #endif
  73
  74     if ((start & ~TARGET_PAGE_MASK) != 0)
  75         return -EINVAL;
  76     len = TARGET_PAGE_ALIGN(len);
  77     end = start + len;
  78     if (end < start)
  79         return -EINVAL;
  80     prot &= PROT_READ | PROT_WRITE | PROT_EXEC;
  81     if (len == 0)
  82         return 0;
  83
  84     mmap_lock();
  85     host_start = start & qemu_host_page_mask;
  86     host_end = HOST_PAGE_ALIGN(end);
  87     if (start > host_start) {
  88         /* handle host page containing start */
  89         prot1 = prot;
  90         for(addr = host_start; addr < start; addr += TARGET_PAGE_SIZE) {
  91             prot1 |= page_get_flags(addr);
  92         }
  93         if (host_end == host_start + qemu_host_page_size) {
  94             for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
  95                 prot1 |= page_get_flags(addr);
  96             }
  97             end = host_end;
  98         }
  99         ret = mprotect(g2h(host_start), qemu_host_page_size, prot1 & PAGE_BITS);
 100         if (ret != 0)
 101             goto error;
 102         host_start += qemu_host_page_size;
 103     }
 104     if (end < host_end) {
 105         prot1 = prot;
 106         for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
 107             prot1 |= page_get_flags(addr);
 108         }
 109         ret = mprotect(g2h(host_end - qemu_host_page_size), qemu_host_page_size,
 110                        prot1 & PAGE_BITS);
 111         if (ret != 0)
 112             goto error;
 113         host_end -= qemu_host_page_size;
 114     }
 115
 116     /* handle the pages in the middle */
 117     if (host_start < host_end) {
 118         ret = mprotect(g2h(host_start), host_end - host_start, prot);
 119         if (ret != 0)
 120             goto error;
 121     }
 122     page_set_flags(start, start + len, prot | PAGE_VALID);
 123     mmap_unlock();
 124     return 0;
 125 error:
 126     mmap_unlock();
 127     return ret;
 128 }
 129
 130 /* map an incomplete host page */
 131 static int mmap_frag(abi_ulong real_start,
 132                      abi_ulong start, abi_ulong end,
 133                      int prot, int flags, int fd, abi_ulong offset)
 134 {
 135     abi_ulong real_end, addr;
 136     void *host_start;
 137     int prot1, prot_new;
 138
 139     real_end = real_start + qemu_host_page_size;
 140     host_start = g2h(real_start);
 141
 142     /* get the protection of the target pages outside the mapping */
 143     prot1 = 0;
 144     for(addr = real_start; addr < real_end; addr++) {
 145         if (addr < start || addr >= end)
 146             prot1 |= page_get_flags(addr);
 147     }
 148
 149     if (prot1 == 0) {
 150         /* no page was there, so we allocate one */
 151         void *p = mmap(host_start, qemu_host_page_size, prot,
 152                        flags | MAP_ANONYMOUS, -1, 0);
 153         if (p == MAP_FAILED)
 154             return -1;
 155         prot1 = prot;
 156     }
 157     prot1 &= PAGE_BITS;
 158
 159     prot_new = prot | prot1;
 160     if (!(flags & MAP_ANONYMOUS)) {
 161         /* msync() won't work here, so we return an error if write is
 162            possible while it is a shared mapping */
 163         if ((flags & MAP_TYPE) == MAP_SHARED &&
 164             (prot & PROT_WRITE))
 165             return -EINVAL;
 166
 167         /* adjust protection to be able to read */
 168         if (!(prot1 & PROT_WRITE))
 169             mprotect(host_start, qemu_host_page_size, prot1 | PROT_WRITE);
 170
 171         /* read the corresponding file data */
 172         pread(fd, g2h(start), end - start, offset);
 173
 174         /* put final protection */
 175         if (prot_new != (prot1 | PROT_WRITE))
 176             mprotect(host_start, qemu_host_page_size, prot_new);
 177     } else {
 178         /* just update the protection */
 179         if (prot_new != prot1) {
 180             mprotect(host_start, qemu_host_page_size, prot_new);
 181         }
 182     }
 183     return 0;
 184 }
 185
 186 #if defined(__CYGWIN__)
 187 /* Cygwin doesn't have a whole lot of address space.  */
 188 static abi_ulong mmap_next_start = 0x18000000;
 189 #else
 190 static abi_ulong mmap_next_start = 0x40000000;
 191 #endif
 192
 193 unsigned long last_brk;
 194
 195 /* find a free memory area of size 'size'. The search starts at
 196    'start'. If 'start' == 0, then a default start address is used.
 197    Return -1 if error.
 198 */
 199 /* page_init() marks pages used by the host as reserved to be sure not
 200    to use them. */
 201 static abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size)
 202 {
 203     abi_ulong addr, addr1, addr_start;
 204     int prot;
 205     unsigned long new_brk;
 206
 207     new_brk = (unsigned long)sbrk(0);
 208     if (last_brk && last_brk < new_brk && last_brk == (target_ulong)last_brk) {
 209         /* This is a hack to catch the host allocating memory with brk().
 210            If it uses mmap then we loose.
 211            FIXME: We really want to avoid the host allocating memory in
 212            the first place, and maybe leave some slack to avoid switching
 213            to mmap.  */
 214         page_set_flags(last_brk & TARGET_PAGE_MASK,
 215                        TARGET_PAGE_ALIGN(new_brk),
 216                        PAGE_RESERVED);
 217     }
 218     last_brk = new_brk;
 219
 220     size = HOST_PAGE_ALIGN(size);
 221     start = start & qemu_host_page_mask;
 222     addr = start;
 223     if (addr == 0)
 224         addr = mmap_next_start;
 225     addr_start = addr;
 226     for(;;) {
 227         prot = 0;
 228         for(addr1 = addr; addr1 < (addr + size); addr1 += TARGET_PAGE_SIZE) {
 229             prot |= page_get_flags(addr1);
 230         }
 231         if (prot == 0)
 232             break;
 233         addr += qemu_host_page_size;
 234         /* we found nothing */
 235         if (addr == addr_start)
 236             return (abi_ulong)-1;
 237     }
 238     if (start == 0)
 239         mmap_next_start = addr + size;
 240     return addr;
 241 }
 242
 243 /* NOTE: all the constants are the HOST ones */
 244 abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,
 245                      int flags, int fd, abi_ulong offset)
 246 {
 247     abi_ulong ret, end, real_start, real_end, retaddr, host_offset, host_len;
 248     unsigned long host_start;
 249
 250     mmap_lock();
 251 #ifdef DEBUG_MMAP
 252     {
 253         printf("mmap: start=0x" TARGET_FMT_lx
 254                " len=0x" TARGET_FMT_lx " prot=%c%c%c flags=",
 255                start, len,
 256                prot & PROT_READ ? 'r' : '-',
 257                prot & PROT_WRITE ? 'w' : '-',
 258                prot & PROT_EXEC ? 'x' : '-');
 259         if (flags & MAP_FIXED)
 260             printf("MAP_FIXED ");
 261         if (flags & MAP_ANONYMOUS)
 262             printf("MAP_ANON ");
 263         switch(flags & MAP_TYPE) {
 264         case MAP_PRIVATE:
 265             printf("MAP_PRIVATE ");
 266             break;
 267         case MAP_SHARED:
 268             printf("MAP_SHARED ");
 269             break;
 270         default:
 271             printf("[MAP_TYPE=0x%x] ", flags & MAP_TYPE);
 272             break;
 273         }
 274         printf("fd=%d offset=" TARGET_FMT_lx "\n", fd, offset);
 275     }
 276 #endif
 277
 278     if (offset & ~TARGET_PAGE_MASK) {
 279         errno = EINVAL;
 280         goto fail;
 281     }
 282
 283     len = TARGET_PAGE_ALIGN(len);
 284     if (len == 0)
 285         goto the_end;
 286     real_start = start & qemu_host_page_mask;
 287
 288     if (!(flags & MAP_FIXED)) {
 289         abi_ulong mmap_start;
 290         void *p;
 291         host_offset = offset & qemu_host_page_mask;
 292         host_len = len + offset - host_offset;
 293         host_len = HOST_PAGE_ALIGN(host_len);
 294         mmap_start = mmap_find_vma(real_start, host_len);
 295         if (mmap_start == (abi_ulong)-1) {
 296             errno = ENOMEM;
 297             goto fail;
 298         }
 299         /* Note: we prefer to control the mapping address. It is
 300            especially important if qemu_host_page_size >
 301            qemu_real_host_page_size */
 302         p = mmap(g2h(mmap_start),
 303                  host_len, prot, flags | MAP_FIXED, fd, host_offset);
 304         if (p == MAP_FAILED)
 305             goto fail;
 306         /* update start so that it points to the file position at 'offset' */
 307         host_start = (unsigned long)p;
 308         if (!(flags & MAP_ANONYMOUS))
 309             host_start += offset - host_offset;
 310         start = h2g(host_start);
 311     } else {
 312         int flg;
 313         target_ulong addr;
 314
 315         if (start & ~TARGET_PAGE_MASK) {
 316             errno = EINVAL;
 317             goto fail;
 318         }
 319         end = start + len;
 320         real_end = HOST_PAGE_ALIGN(end);
 321
 322         for(addr = real_start; addr < real_end; addr += TARGET_PAGE_SIZE) {
 323             flg = page_get_flags(addr);
 324             if (flg & PAGE_RESERVED) {
 325                 errno = ENXIO;
 326                 goto fail;
 327             }
 328         }
 329
 330         /* worst case: we cannot map the file because the offset is not
 331            aligned, so we read it */
 332         if (!(flags & MAP_ANONYMOUS) &&
 333             (offset & ~qemu_host_page_mask) != (start & ~qemu_host_page_mask)) {
 334             /* msync() won't work here, so we return an error if write is
 335                possible while it is a shared mapping */
 336             if ((flags & MAP_TYPE) == MAP_SHARED &&
 337                 (prot & PROT_WRITE)) {
 338                 errno = EINVAL;
 339                 goto fail;
 340             }
 341             retaddr = target_mmap(start, len, prot | PROT_WRITE,
 342                                   MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS,
 343                                   -1, 0);
 344             if (retaddr == -1)
 345                 goto fail;
 346             pread(fd, g2h(start), len, offset);
 347             if (!(prot & PROT_WRITE)) {
 348                 ret = target_mprotect(start, len, prot);
 349                 if (ret != 0) {
 350                     start = ret;
 351                     goto the_end;
 352                 }
 353             }
 354             goto the_end;
 355         }
 356
 357         /* handle the start of the mapping */
 358         if (start > real_start) {
 359             if (real_end == real_start + qemu_host_page_size) {
 360                 /* one single host page */
 361                 ret = mmap_frag(real_start, start, end,
 362                                 prot, flags, fd, offset);
 363                 if (ret == -1)
 364                     goto fail;
 365                 goto the_end1;
 366             }
 367             ret = mmap_frag(real_start, start, real_start + qemu_host_page_size,
 368                             prot, flags, fd, offset);
 369             if (ret == -1)
 370                 goto fail;
 371             real_start += qemu_host_page_size;
 372         }
 373         /* handle the end of the mapping */
 374         if (end < real_end) {
 375             ret = mmap_frag(real_end - qemu_host_page_size,
 376                             real_end - qemu_host_page_size, real_end,
 377                             prot, flags, fd,
 378                             offset + real_end - qemu_host_page_size - start);
 379             if (ret == -1)
 380                 goto fail;
 381             real_end -= qemu_host_page_size;
 382         }
 383
 384         /* map the middle (easier) */
 385         if (real_start < real_end) {
 386             void *p;
 387             unsigned long offset1;
 388             if (flags & MAP_ANONYMOUS)
 389                 offset1 = 0;
 390             else
 391                 offset1 = offset + real_start - start;
 392             p = mmap(g2h(real_start), real_end - real_start,
 393                      prot, flags, fd, offset1);
 394             if (p == MAP_FAILED)
 395                 goto fail;
 396         }
 397     }
 398  the_end1:
 399     page_set_flags(start, start + len, prot | PAGE_VALID);
 400  the_end:
 401 #ifdef DEBUG_MMAP
 402     printf("ret=0x" TARGET_FMT_lx "\n", start);
 403     page_dump(stdout);
 404     printf("\n");
 405 #endif
 406     mmap_unlock();
 407     return start;
 408 fail:
 409     mmap_unlock();
 410     return -1;
 411 }
 412
 413 int target_munmap(abi_ulong start, abi_ulong len)
 414 {
 415     abi_ulong end, real_start, real_end, addr;
 416     int prot, ret;
 417
 418 #ifdef DEBUG_MMAP
 419     printf("munmap: start=0x%lx len=0x%lx\n", start, len);
 420 #endif
 421     if (start & ~TARGET_PAGE_MASK)
 422         return -EINVAL;
 423     len = TARGET_PAGE_ALIGN(len);
 424     if (len == 0)
 425         return -EINVAL;
 426     mmap_lock();
 427     end = start + len;
 428     real_start = start & qemu_host_page_mask;
 429     real_end = HOST_PAGE_ALIGN(end);
 430
 431     if (start > real_start) {
 432         /* handle host page containing start */
 433         prot = 0;
 434         for(addr = real_start; addr < start; addr += TARGET_PAGE_SIZE) {
 435             prot |= page_get_flags(addr);
 436         }
 437         if (real_end == real_start + qemu_host_page_size) {
 438             for(addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
 439                 prot |= page_get_flags(addr);
 440             }
 441             end = real_end;
 442         }
 443         if (prot != 0)
 444             real_start += qemu_host_page_size;
 445     }
 446     if (end < real_end) {
 447         prot = 0;
 448         for(addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
 449             prot |= page_get_flags(addr);
 450         }
 451         if (prot != 0)
 452             real_end -= qemu_host_page_size;
 453     }
 454
 455     ret = 0;
 456     /* unmap what we can */
 457     if (real_start < real_end) {
 458         ret = munmap(g2h(real_start), real_end - real_start);
 459     }
 460
 461     if (ret == 0)
 462         page_set_flags(start, start + len, 0);
 463     mmap_unlock();
 464     return ret;
 465 }
 466
 467 /* XXX: currently, we only handle MAP_ANONYMOUS and not MAP_FIXED
 468    blocks which have been allocated starting on a host page */
 469 abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
 470                        abi_ulong new_size, unsigned long flags,
 471                        abi_ulong new_addr)
 472 {
 473     int prot;
 474     unsigned long host_addr;
 475
 476     mmap_lock();
 477     /* XXX: use 5 args syscall */
 478     host_addr = (long)mremap(g2h(old_addr), old_size, new_size, flags);
 479     if (host_addr == -1) {
 480         new_addr = -1;
 481     } else {
 482         new_addr = h2g(host_addr);
 483         prot = page_get_flags(old_addr);
 484         page_set_flags(old_addr, old_addr + old_size, 0);
 485         page_set_flags(new_addr, new_addr + new_size, prot | PAGE_VALID);
 486     }
 487     mmap_unlock();
 488     return new_addr;
 489 }
 490
 491 int target_msync(abi_ulong start, abi_ulong len, int flags)
 492 {
 493     abi_ulong end;
 494
 495     if (start & ~TARGET_PAGE_MASK)
 496         return -EINVAL;
 497     len = TARGET_PAGE_ALIGN(len);
 498     end = start + len;
 499     if (end < start)
 500         return -EINVAL;
 501     if (end == start)
 502         return 0;
 503
 504     start &= qemu_host_page_mask;
 505     return msync(g2h(start), end - start, flags);
 506 }