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 /* NOTE: all the constants are the HOST ones, but addresses are target. */
  33 int target_mprotect(abi_ulong start, abi_ulong len, int prot)
  34 {
  35     abi_ulong end, host_start, host_end, addr;
  36     int prot1, ret;
  37
  38 #ifdef DEBUG_MMAP
  39     printf("mprotect: start=0x" TARGET_FMT_lx
  40            "len=0x" TARGET_FMT_lx " prot=%c%c%c\n", start, len,
  41            prot & PROT_READ ? 'r' : '-',
  42            prot & PROT_WRITE ? 'w' : '-',
  43            prot & PROT_EXEC ? 'x' : '-');
  44 #endif
  45
  46     if ((start & ~TARGET_PAGE_MASK) != 0)
  47         return -EINVAL;
  48     len = TARGET_PAGE_ALIGN(len);
  49     end = start + len;
  50     if (end < start)
  51         return -EINVAL;
  52     if (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC))
  53         return -EINVAL;
  54     if (len == 0)
  55         return 0;
  56
  57     host_start = start & qemu_host_page_mask;
  58     host_end = HOST_PAGE_ALIGN(end);
  59     if (start > host_start) {
  60         /* handle host page containing start */
  61         prot1 = prot;
  62         for(addr = host_start; addr < start; addr += TARGET_PAGE_SIZE) {
  63             prot1 |= page_get_flags(addr);
  64         }
  65         if (host_end == host_start + qemu_host_page_size) {
  66             for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
  67                 prot1 |= page_get_flags(addr);
  68             }
  69             end = host_end;
  70         }
  71         ret = mprotect(g2h(host_start), qemu_host_page_size, prot1 & PAGE_BITS);
  72         if (ret != 0)
  73             return ret;
  74         host_start += qemu_host_page_size;
  75     }
  76     if (end < host_end) {
  77         prot1 = prot;
  78         for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
  79             prot1 |= page_get_flags(addr);
  80         }
  81         ret = mprotect(g2h(host_end - qemu_host_page_size), qemu_host_page_size,
  82                        prot1 & PAGE_BITS);
  83         if (ret != 0)
  84             return ret;
  85         host_end -= qemu_host_page_size;
  86     }
  87
  88     /* handle the pages in the middle */
  89     if (host_start < host_end) {
  90         ret = mprotect(g2h(host_start), host_end - host_start, prot);
  91         if (ret != 0)
  92             return ret;
  93     }
  94     page_set_flags(start, start + len, prot | PAGE_VALID);
  95     return 0;
  96 }
  97
  98 /* map an incomplete host page */
  99 static int mmap_frag(abi_ulong real_start,
 100                      abi_ulong start, abi_ulong end,
 101                      int prot, int flags, int fd, abi_ulong offset)
 102 {
 103     abi_ulong real_end, ret, addr;
 104     void *host_start;
 105     int prot1, prot_new;
 106
 107     real_end = real_start + qemu_host_page_size;
 108     host_start = g2h(real_start);
 109
 110     /* get the protection of the target pages outside the mapping */
 111     prot1 = 0;
 112     for(addr = real_start; addr < real_end; addr++) {
 113         if (addr < start || addr >= end)
 114             prot1 |= page_get_flags(addr);
 115     }
 116
 117     if (prot1 == 0) {
 118         /* no page was there, so we allocate one */
 119         ret = (long)mmap(host_start, qemu_host_page_size, prot,
 120                          flags | MAP_ANONYMOUS, -1, 0);
 121         if (ret == -1)
 122             return ret;
 123         prot1 = prot;
 124     }
 125     prot1 &= PAGE_BITS;
 126
 127     prot_new = prot | prot1;
 128     if (!(flags & MAP_ANONYMOUS)) {
 129         /* msync() won't work here, so we return an error if write is
 130            possible while it is a shared mapping */
 131         if ((flags & MAP_TYPE) == MAP_SHARED &&
 132             (prot & PROT_WRITE))
 133             return -EINVAL;
 134
 135         /* adjust protection to be able to read */
 136         if (!(prot1 & PROT_WRITE))
 137             mprotect(host_start, qemu_host_page_size, prot1 | PROT_WRITE);
 138
 139         /* read the corresponding file data */
 140         pread(fd, g2h(start), end - start, offset);
 141
 142         /* put final protection */
 143         if (prot_new != (prot1 | PROT_WRITE))
 144             mprotect(host_start, qemu_host_page_size, prot_new);
 145     } else {
 146         /* just update the protection */
 147         if (prot_new != prot1) {
 148             mprotect(host_start, qemu_host_page_size, prot_new);
 149         }
 150     }
 151     return 0;
 152 }
 153
 154 /* NOTE: all the constants are the HOST ones */
 155 abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,
 156                      int flags, int fd, abi_ulong offset)
 157 {
 158     abi_ulong ret, end, real_start, real_end, retaddr, host_offset, host_len;
 159     unsigned long host_start;
 160 #if defined(__alpha__) || defined(__sparc__) || defined(__x86_64__) || \
 161         defined(__ia64) || defined(__mips__)
 162     static abi_ulong last_start = 0x40000000;
 163 #elif defined(__CYGWIN__)
 164     /* Cygwin doesn't have a whole lot of address space.  */
 165     static abi_ulong last_start = 0x18000000;
 166 #endif
 167
 168 #ifdef DEBUG_MMAP
 169     {
 170         printf("mmap: start=0x" TARGET_FMT_lx
 171                " len=0x" TARGET_FMT_lx " prot=%c%c%c flags=",
 172                start, len,
 173                prot & PROT_READ ? 'r' : '-',
 174                prot & PROT_WRITE ? 'w' : '-',
 175                prot & PROT_EXEC ? 'x' : '-');
 176         if (flags & MAP_FIXED)
 177             printf("MAP_FIXED ");
 178         if (flags & MAP_ANONYMOUS)
 179             printf("MAP_ANON ");
 180         switch(flags & MAP_TYPE) {
 181         case MAP_PRIVATE:
 182             printf("MAP_PRIVATE ");
 183             break;
 184         case MAP_SHARED:
 185             printf("MAP_SHARED ");
 186             break;
 187         default:
 188             printf("[MAP_TYPE=0x%x] ", flags & MAP_TYPE);
 189             break;
 190         }
 191         printf("fd=%d offset=" TARGET_FMT_lx "\n", fd, offset);
 192     }
 193 #endif
 194
 195     if (offset & ~TARGET_PAGE_MASK) {
 196         errno = EINVAL;
 197         return -1;
 198     }
 199
 200     len = TARGET_PAGE_ALIGN(len);
 201     if (len == 0)
 202         return start;
 203     real_start = start & qemu_host_page_mask;
 204
 205     if (!(flags & MAP_FIXED)) {
 206 #if defined(__alpha__) || defined(__sparc__) || defined(__x86_64__) || \
 207     defined(__ia64) || defined(__mips__) || defined(__CYGWIN__)
 208         /* tell the kernel to search at the same place as i386 */
 209         if (real_start == 0) {
 210             real_start = last_start;
 211             last_start += HOST_PAGE_ALIGN(len);
 212         }
 213 #endif
 214             host_offset = offset & qemu_host_page_mask;
 215             host_len = len + offset - host_offset;
 216
 217         if (qemu_host_page_size > qemu_real_host_page_size) {
 218             /*
 219              * The guest expects to see mmapped areas aligned to it's pagesize.
 220              * If the host's real page size is smaller than the guest's, we need
 221              * to fixup the maps. It is done by allocating a larger area,
 222              * displacing the map (if needed) and finally chopping off the spare
 223              * room at the edges.
 224              */
 225
 226             /*
 227              * We assume qemu_host_page_size is always the same as
 228              * TARGET_PAGE_SIZE, see exec.c. qemu_real_host_page_size is the
 229              * hosts real page size.
 230              */
 231             abi_ulong host_end;
 232             unsigned long host_aligned_start;
 233
 234             host_len = HOST_PAGE_ALIGN(host_len + qemu_host_page_size
 235                                        - qemu_real_host_page_size);
 236             host_start = (unsigned long) mmap(real_start ?
 237                                               g2h(real_start) : NULL,
 238                                               host_len, prot, flags,
 239                                               fd, host_offset);
 240             if (host_start == -1)
 241                 return -1;
 242
 243             host_end = host_start + host_len;
 244
 245             /* Find start and end, aligned to the targets pagesize with-in the
 246                large mmaped area.  */
 247             host_aligned_start = TARGET_PAGE_ALIGN(host_start);
 248             if (!(flags & MAP_ANONYMOUS))
 249                 host_aligned_start += offset - host_offset;
 250
 251             start = h2g(host_aligned_start);
 252             end = start + TARGET_PAGE_ALIGN(len);
 253
 254             /* Chop off the leftovers, if any.  */
 255             if (host_aligned_start > host_start)
 256                 munmap((void *)host_start, host_aligned_start - host_start);
 257             if (end < host_end)
 258                 munmap((void *)g2h(end), host_end - end);
 259
 260             goto the_end1;
 261         } else {
 262             /* if not fixed, no need to do anything */
 263             host_start = (long)mmap(real_start ? g2h(real_start) : NULL,
 264                                     host_len, prot, flags, fd, host_offset);
 265             if (host_start == -1)
 266                 return -1;
 267             /* update start so that it points to the file position at 'offset' */
 268             if (!(flags & MAP_ANONYMOUS))
 269                 host_start += offset - host_offset;
 270             start = h2g(host_start);
 271             goto the_end1;
 272         }
 273     }
 274
 275     if (start & ~TARGET_PAGE_MASK) {
 276         errno = EINVAL;
 277         return -1;
 278     }
 279     end = start + len;
 280     real_end = HOST_PAGE_ALIGN(end);
 281
 282     /* worst case: we cannot map the file because the offset is not
 283        aligned, so we read it */
 284     if (!(flags & MAP_ANONYMOUS) &&
 285         (offset & ~qemu_host_page_mask) != (start & ~qemu_host_page_mask)) {
 286         /* msync() won't work here, so we return an error if write is
 287            possible while it is a shared mapping */
 288         if ((flags & MAP_TYPE) == MAP_SHARED &&
 289             (prot & PROT_WRITE)) {
 290             errno = EINVAL;
 291             return -1;
 292         }
 293         retaddr = target_mmap(start, len, prot | PROT_WRITE,
 294                               MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS,
 295                               -1, 0);
 296         if (retaddr == -1)
 297             return -1;
 298         pread(fd, g2h(start), len, offset);
 299         if (!(prot & PROT_WRITE)) {
 300             ret = target_mprotect(start, len, prot);
 301             if (ret != 0)
 302                 return ret;
 303         }
 304         goto the_end;
 305     }
 306
 307     /* handle the start of the mapping */
 308     if (start > real_start) {
 309         if (real_end == real_start + qemu_host_page_size) {
 310             /* one single host page */
 311             ret = mmap_frag(real_start, start, end,
 312                             prot, flags, fd, offset);
 313             if (ret == -1)
 314                 return ret;
 315             goto the_end1;
 316         }
 317         ret = mmap_frag(real_start, start, real_start + qemu_host_page_size,
 318                         prot, flags, fd, offset);
 319         if (ret == -1)
 320             return ret;
 321         real_start += qemu_host_page_size;
 322     }
 323     /* handle the end of the mapping */
 324     if (end < real_end) {
 325         ret = mmap_frag(real_end - qemu_host_page_size,
 326                         real_end - qemu_host_page_size, real_end,
 327                         prot, flags, fd,
 328                         offset + real_end - qemu_host_page_size - start);
 329         if (ret == -1)
 330             return -1;
 331         real_end -= qemu_host_page_size;
 332     }
 333
 334     /* map the middle (easier) */
 335     if (real_start < real_end) {
 336         unsigned long offset1;
 337         if (flags & MAP_ANONYMOUS)
 338           offset1 = 0;
 339         else
 340           offset1 = offset + real_start - start;
 341         ret = (long)mmap(g2h(real_start), real_end - real_start,
 342                          prot, flags, fd, offset1);
 343         if (ret == -1)
 344             return -1;
 345     }
 346  the_end1:
 347     page_set_flags(start, start + len, prot | PAGE_VALID);
 348  the_end:
 349 #ifdef DEBUG_MMAP
 350     printf("ret=0x%llx\n", start);
 351     page_dump(stdout);
 352     printf("\n");
 353 #endif
 354     return start;
 355 }
 356
 357 int target_munmap(abi_ulong start, abi_ulong len)
 358 {
 359     abi_ulong end, real_start, real_end, addr;
 360     int prot, ret;
 361
 362 #ifdef DEBUG_MMAP
 363     printf("munmap: start=0x%lx len=0x%lx\n", start, len);
 364 #endif
 365     if (start & ~TARGET_PAGE_MASK)
 366         return -EINVAL;
 367     len = TARGET_PAGE_ALIGN(len);
 368     if (len == 0)
 369         return -EINVAL;
 370     end = start + len;
 371     real_start = start & qemu_host_page_mask;
 372     real_end = HOST_PAGE_ALIGN(end);
 373
 374     if (start > real_start) {
 375         /* handle host page containing start */
 376         prot = 0;
 377         for(addr = real_start; addr < start; addr += TARGET_PAGE_SIZE) {
 378             prot |= page_get_flags(addr);
 379         }
 380         if (real_end == real_start + qemu_host_page_size) {
 381             for(addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
 382                 prot |= page_get_flags(addr);
 383             }
 384             end = real_end;
 385         }
 386         if (prot != 0)
 387             real_start += qemu_host_page_size;
 388     }
 389     if (end < real_end) {
 390         prot = 0;
 391         for(addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
 392             prot |= page_get_flags(addr);
 393         }
 394         if (prot != 0)
 395             real_end -= qemu_host_page_size;
 396     }
 397
 398     /* unmap what we can */
 399     if (real_start < real_end) {
 400         ret = munmap(g2h(real_start), real_end - real_start);
 401         if (ret != 0)
 402             return ret;
 403     }
 404
 405     page_set_flags(start, start + len, 0);
 406     return 0;
 407 }
 408
 409 /* XXX: currently, we only handle MAP_ANONYMOUS and not MAP_FIXED
 410    blocks which have been allocated starting on a host page */
 411 abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
 412                        abi_ulong new_size, unsigned long flags,
 413                        abi_ulong new_addr)
 414 {
 415     int prot;
 416     unsigned long host_addr;
 417
 418     /* XXX: use 5 args syscall */
 419     host_addr = (long)mremap(g2h(old_addr), old_size, new_size, flags);
 420     if (host_addr == -1)
 421         return -1;
 422     new_addr = h2g(host_addr);
 423     prot = page_get_flags(old_addr);
 424     page_set_flags(old_addr, old_addr + old_size, 0);
 425     page_set_flags(new_addr, new_addr + new_size, prot | PAGE_VALID);
 426     return new_addr;
 427 }
 428
 429 int target_msync(abi_ulong start, abi_ulong len, int flags)
 430 {
 431     abi_ulong end;
 432
 433     if (start & ~TARGET_PAGE_MASK)
 434         return -EINVAL;
 435     len = TARGET_PAGE_ALIGN(len);
 436     end = start + len;
 437     if (end < start)
 438         return -EINVAL;
 439     if (end == start)
 440         return 0;
 441
 442     start &= qemu_host_page_mask;
 443     return msync(g2h(start), end - start, flags);
 444 }
 445