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, 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         void *p = mmap(host_start, qemu_host_page_size, prot,
 120                        flags | MAP_ANONYMOUS, -1, 0);
 121         if (p == MAP_FAILED)
 122             return -1;
 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 #if defined(__CYGWIN__)
 155 /* Cygwin doesn't have a whole lot of address space.  */
 156 static abi_ulong mmap_next_start = 0x18000000;
 157 #else
 158 static abi_ulong mmap_next_start = 0x40000000;
 159 #endif
 160
 161 /* find a free memory area of size 'size'. The search starts at
 162    'start'. If 'start' == 0, then a default start address is used.
 163    Return -1 if error.
 164 */
 165 /* page_init() marks pages used by the host as reserved to be sure not
 166    to use them. */
 167 static abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size)
 168 {
 169     abi_ulong addr, addr1, addr_start;
 170     int prot;
 171
 172     size = HOST_PAGE_ALIGN(size);
 173     start = start & qemu_host_page_mask;
 174     addr = start;
 175     if (addr == 0)
 176         addr = mmap_next_start;
 177     addr_start = addr;
 178     for(;;) {
 179         prot = 0;
 180         for(addr1 = addr; addr1 < (addr + size); addr1 += TARGET_PAGE_SIZE) {
 181             prot |= page_get_flags(addr1);
 182         }
 183         if (prot == 0)
 184             break;
 185         addr += qemu_host_page_size;
 186         /* we found nothing */
 187         if (addr == addr_start)
 188             return (abi_ulong)-1;
 189     }
 190     if (start == 0)
 191         mmap_next_start = addr + size;
 192     return addr;
 193 }
 194
 195 /* NOTE: all the constants are the HOST ones */
 196 abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,
 197                      int flags, int fd, abi_ulong offset)
 198 {
 199     abi_ulong ret, end, real_start, real_end, retaddr, host_offset, host_len;
 200     unsigned long host_start;
 201
 202 #ifdef DEBUG_MMAP
 203     {
 204         printf("mmap: start=0x" TARGET_FMT_lx
 205                " len=0x" TARGET_FMT_lx " prot=%c%c%c flags=",
 206                start, len,
 207                prot & PROT_READ ? 'r' : '-',
 208                prot & PROT_WRITE ? 'w' : '-',
 209                prot & PROT_EXEC ? 'x' : '-');
 210         if (flags & MAP_FIXED)
 211             printf("MAP_FIXED ");
 212         if (flags & MAP_ANONYMOUS)
 213             printf("MAP_ANON ");
 214         switch(flags & MAP_TYPE) {
 215         case MAP_PRIVATE:
 216             printf("MAP_PRIVATE ");
 217             break;
 218         case MAP_SHARED:
 219             printf("MAP_SHARED ");
 220             break;
 221         default:
 222             printf("[MAP_TYPE=0x%x] ", flags & MAP_TYPE);
 223             break;
 224         }
 225         printf("fd=%d offset=" TARGET_FMT_lx "\n", fd, offset);
 226     }
 227 #endif
 228
 229     if (offset & ~TARGET_PAGE_MASK) {
 230         errno = EINVAL;
 231         return -1;
 232     }
 233
 234     len = TARGET_PAGE_ALIGN(len);
 235     if (len == 0)
 236         return start;
 237     real_start = start & qemu_host_page_mask;
 238
 239     if (!(flags & MAP_FIXED)) {
 240         abi_ulong mmap_start;
 241         void *p;
 242         host_offset = offset & qemu_host_page_mask;
 243         host_len = len + offset - host_offset;
 244         host_len = HOST_PAGE_ALIGN(host_len);
 245         mmap_start = mmap_find_vma(real_start, host_len);
 246         if (mmap_start == (abi_ulong)-1) {
 247             errno = ENOMEM;
 248             return -1;
 249         }
 250         /* Note: we prefer to control the mapping address. It is
 251            especially important if qemu_host_page_size >
 252            qemu_real_host_page_size */
 253         p = mmap(g2h(mmap_start),
 254                  host_len, prot, flags | MAP_FIXED, fd, host_offset);
 255         if (p == MAP_FAILED)
 256             return -1;
 257         /* update start so that it points to the file position at 'offset' */
 258         host_start = (unsigned long)p;
 259         if (!(flags & MAP_ANONYMOUS))
 260             host_start += offset - host_offset;
 261         start = h2g(host_start);
 262     } else {
 263         if (start & ~TARGET_PAGE_MASK) {
 264             errno = EINVAL;
 265             return -1;
 266         }
 267         end = start + len;
 268         real_end = HOST_PAGE_ALIGN(end);
 269
 270         /* worst case: we cannot map the file because the offset is not
 271            aligned, so we read it */
 272         if (!(flags & MAP_ANONYMOUS) &&
 273             (offset & ~qemu_host_page_mask) != (start & ~qemu_host_page_mask)) {
 274             /* msync() won't work here, so we return an error if write is
 275                possible while it is a shared mapping */
 276             if ((flags & MAP_TYPE) == MAP_SHARED &&
 277                 (prot & PROT_WRITE)) {
 278                 errno = EINVAL;
 279                 return -1;
 280             }
 281             retaddr = target_mmap(start, len, prot | PROT_WRITE,
 282                                   MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS,
 283                                   -1, 0);
 284             if (retaddr == -1)
 285                 return -1;
 286             pread(fd, g2h(start), len, offset);
 287             if (!(prot & PROT_WRITE)) {
 288                 ret = target_mprotect(start, len, prot);
 289                 if (ret != 0)
 290                     return ret;
 291             }
 292             goto the_end;
 293         }
 294
 295         /* handle the start of the mapping */
 296         if (start > real_start) {
 297             if (real_end == real_start + qemu_host_page_size) {
 298                 /* one single host page */
 299                 ret = mmap_frag(real_start, start, end,
 300                                 prot, flags, fd, offset);
 301                 if (ret == -1)
 302                     return ret;
 303                 goto the_end1;
 304             }
 305             ret = mmap_frag(real_start, start, real_start + qemu_host_page_size,
 306                             prot, flags, fd, offset);
 307             if (ret == -1)
 308                 return ret;
 309             real_start += qemu_host_page_size;
 310         }
 311         /* handle the end of the mapping */
 312         if (end < real_end) {
 313             ret = mmap_frag(real_end - qemu_host_page_size,
 314                             real_end - qemu_host_page_size, real_end,
 315                             prot, flags, fd,
 316                             offset + real_end - qemu_host_page_size - start);
 317             if (ret == -1)
 318                 return -1;
 319             real_end -= qemu_host_page_size;
 320         }
 321
 322         /* map the middle (easier) */
 323         if (real_start < real_end) {
 324             void *p;
 325             unsigned long offset1;
 326             if (flags & MAP_ANONYMOUS)
 327                 offset1 = 0;
 328             else
 329                 offset1 = offset + real_start - start;
 330             p = mmap(g2h(real_start), real_end - real_start,
 331                      prot, flags, fd, offset1);
 332             if (p == MAP_FAILED)
 333                 return -1;
 334         }
 335     }
 336  the_end1:
 337     page_set_flags(start, start + len, prot | PAGE_VALID);
 338  the_end:
 339 #ifdef DEBUG_MMAP
 340     printf("ret=0x%llx\n", start);
 341     page_dump(stdout);
 342     printf("\n");
 343 #endif
 344     return start;
 345 }
 346
 347 int target_munmap(abi_ulong start, abi_ulong len)
 348 {
 349     abi_ulong end, real_start, real_end, addr;
 350     int prot, ret;
 351
 352 #ifdef DEBUG_MMAP
 353     printf("munmap: start=0x%lx len=0x%lx\n", start, len);
 354 #endif
 355     if (start & ~TARGET_PAGE_MASK)
 356         return -EINVAL;
 357     len = TARGET_PAGE_ALIGN(len);
 358     if (len == 0)
 359         return -EINVAL;
 360     end = start + len;
 361     real_start = start & qemu_host_page_mask;
 362     real_end = HOST_PAGE_ALIGN(end);
 363
 364     if (start > real_start) {
 365         /* handle host page containing start */
 366         prot = 0;
 367         for(addr = real_start; addr < start; addr += TARGET_PAGE_SIZE) {
 368             prot |= page_get_flags(addr);
 369         }
 370         if (real_end == real_start + qemu_host_page_size) {
 371             for(addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
 372                 prot |= page_get_flags(addr);
 373             }
 374             end = real_end;
 375         }
 376         if (prot != 0)
 377             real_start += qemu_host_page_size;
 378     }
 379     if (end < real_end) {
 380         prot = 0;
 381         for(addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
 382             prot |= page_get_flags(addr);
 383         }
 384         if (prot != 0)
 385             real_end -= qemu_host_page_size;
 386     }
 387
 388     /* unmap what we can */
 389     if (real_start < real_end) {
 390         ret = munmap(g2h(real_start), real_end - real_start);
 391         if (ret != 0)
 392             return ret;
 393     }
 394
 395     page_set_flags(start, start + len, 0);
 396     return 0;
 397 }
 398
 399 /* XXX: currently, we only handle MAP_ANONYMOUS and not MAP_FIXED
 400    blocks which have been allocated starting on a host page */
 401 abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
 402                        abi_ulong new_size, unsigned long flags,
 403                        abi_ulong new_addr)
 404 {
 405     int prot;
 406     unsigned long host_addr;
 407
 408     /* XXX: use 5 args syscall */
 409     host_addr = (long)mremap(g2h(old_addr), old_size, new_size, flags);
 410     if (host_addr == -1)
 411         return -1;
 412     new_addr = h2g(host_addr);
 413     prot = page_get_flags(old_addr);
 414     page_set_flags(old_addr, old_addr + old_size, 0);
 415     page_set_flags(new_addr, new_addr + new_size, prot | PAGE_VALID);
 416     return new_addr;
 417 }
 418
 419 int target_msync(abi_ulong start, abi_ulong len, int flags)
 420 {
 421     abi_ulong end;
 422
 423     if (start & ~TARGET_PAGE_MASK)
 424         return -EINVAL;
 425     len = TARGET_PAGE_ALIGN(len);
 426     end = start + len;
 427     if (end < start)
 428         return -EINVAL;
 429     if (end == start)
 430         return 0;
 431
 432     start &= qemu_host_page_mask;
 433     return msync(g2h(start), end - start, flags);
 434 }
 435