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, see <http://www.gnu.org/licenses/>.
  18  */
  19 #include "qemu/osdep.h"
  20
  21 #include "qemu.h"
  22 #include "qemu-common.h"
  23 #include "translate-all.h"
  24
  25 //#define DEBUG_MMAP
  26
  27 static pthread_mutex_t mmap_mutex = PTHREAD_MUTEX_INITIALIZER;
  28 static __thread int mmap_lock_count;
  29
  30 void mmap_lock(void)
  31 {
  32     if (mmap_lock_count++ == 0) {
  33         pthread_mutex_lock(&mmap_mutex);
  34     }
  35 }
  36
  37 void mmap_unlock(void)
  38 {
  39     if (--mmap_lock_count == 0) {
  40         pthread_mutex_unlock(&mmap_mutex);
  41     }
  42 }
  43
  44 bool have_mmap_lock(void)
  45 {
  46     return mmap_lock_count > 0 ? true : false;
  47 }
  48
  49 /* Grab lock to make sure things are in a consistent state after fork().  */
  50 void mmap_fork_start(void)
  51 {
  52     if (mmap_lock_count)
  53         abort();
  54     pthread_mutex_lock(&mmap_mutex);
  55 }
  56
  57 void mmap_fork_end(int child)
  58 {
  59     if (child)
  60         pthread_mutex_init(&mmap_mutex, NULL);
  61     else
  62         pthread_mutex_unlock(&mmap_mutex);
  63 }
  64
  65 /* NOTE: all the constants are the HOST ones, but addresses are target. */
  66 int target_mprotect(abi_ulong start, abi_ulong len, int prot)
  67 {
  68     abi_ulong end, host_start, host_end, addr;
  69     int prot1, ret;
  70
  71 #ifdef DEBUG_MMAP
  72     printf("mprotect: start=0x" TARGET_ABI_FMT_lx
  73            "len=0x" TARGET_ABI_FMT_lx " prot=%c%c%c\n", start, len,
  74            prot & PROT_READ ? 'r' : '-',
  75            prot & PROT_WRITE ? 'w' : '-',
  76            prot & PROT_EXEC ? 'x' : '-');
  77 #endif
  78
  79     if ((start & ~TARGET_PAGE_MASK) != 0)
  80         return -TARGET_EINVAL;
  81     len = TARGET_PAGE_ALIGN(len);
  82     end = start + len;
  83     if (!guest_range_valid(start, len)) {
  84         return -TARGET_ENOMEM;
  85     }
  86     prot &= PROT_READ | PROT_WRITE | PROT_EXEC;
  87     if (len == 0)
  88         return 0;
  89
  90     mmap_lock();
  91     host_start = start & qemu_host_page_mask;
  92     host_end = HOST_PAGE_ALIGN(end);
  93     if (start > host_start) {
  94         /* handle host page containing start */
  95         prot1 = prot;
  96         for(addr = host_start; addr < start; addr += TARGET_PAGE_SIZE) {
  97             prot1 |= page_get_flags(addr);
  98         }
  99         if (host_end == host_start + qemu_host_page_size) {
 100             for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
 101                 prot1 |= page_get_flags(addr);
 102             }
 103             end = host_end;
 104         }
 105         ret = mprotect(g2h(host_start), qemu_host_page_size, prot1 & PAGE_BITS);
 106         if (ret != 0)
 107             goto error;
 108         host_start += qemu_host_page_size;
 109     }
 110     if (end < host_end) {
 111         prot1 = prot;
 112         for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
 113             prot1 |= page_get_flags(addr);
 114         }
 115         ret = mprotect(g2h(host_end - qemu_host_page_size), qemu_host_page_size,
 116                        prot1 & PAGE_BITS);
 117         if (ret != 0)
 118             goto error;
 119         host_end -= qemu_host_page_size;
 120     }
 121
 122     /* handle the pages in the middle */
 123     if (host_start < host_end) {
 124         ret = mprotect(g2h(host_start), host_end - host_start, prot);
 125         if (ret != 0)
 126             goto error;
 127     }
 128     page_set_flags(start, start + len, prot | PAGE_VALID);
 129     mmap_unlock();
 130     return 0;
 131 error:
 132     mmap_unlock();
 133     return ret;
 134 }
 135
 136 /* map an incomplete host page */
 137 static int mmap_frag(abi_ulong real_start,
 138                      abi_ulong start, abi_ulong end,
 139                      int prot, int flags, int fd, abi_ulong offset)
 140 {
 141     abi_ulong real_end, addr;
 142     void *host_start;
 143     int prot1, prot_new;
 144
 145     real_end = real_start + qemu_host_page_size;
 146     host_start = g2h(real_start);
 147
 148     /* get the protection of the target pages outside the mapping */
 149     prot1 = 0;
 150     for(addr = real_start; addr < real_end; addr++) {
 151         if (addr < start || addr >= end)
 152             prot1 |= page_get_flags(addr);
 153     }
 154
 155     if (prot1 == 0) {
 156         /* no page was there, so we allocate one */
 157         void *p = mmap(host_start, qemu_host_page_size, prot,
 158                        flags | MAP_ANONYMOUS, -1, 0);
 159         if (p == MAP_FAILED)
 160             return -1;
 161         prot1 = prot;
 162     }
 163     prot1 &= PAGE_BITS;
 164
 165     prot_new = prot | prot1;
 166     if (!(flags & MAP_ANONYMOUS)) {
 167         /* msync() won't work here, so we return an error if write is
 168            possible while it is a shared mapping */
 169         if ((flags & MAP_TYPE) == MAP_SHARED &&
 170             (prot & PROT_WRITE))
 171             return -1;
 172
 173         /* adjust protection to be able to read */
 174         if (!(prot1 & PROT_WRITE))
 175             mprotect(host_start, qemu_host_page_size, prot1 | PROT_WRITE);
 176
 177         /* read the corresponding file data */
 178         if (pread(fd, g2h(start), end - start, offset) == -1)
 179             return -1;
 180
 181         /* put final protection */
 182         if (prot_new != (prot1 | PROT_WRITE))
 183             mprotect(host_start, qemu_host_page_size, prot_new);
 184     } else {
 185         if (prot_new != prot1) {
 186             mprotect(host_start, qemu_host_page_size, prot_new);
 187         }
 188         if (prot_new & PROT_WRITE) {
 189             memset(g2h(start), 0, end - start);
 190         }
 191     }
 192     return 0;
 193 }
 194
 195 #if HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 64
 196 # define TASK_UNMAPPED_BASE  (1ul << 38)
 197 #else
 198 # define TASK_UNMAPPED_BASE  0x40000000
 199 #endif
 200 abi_ulong mmap_next_start = TASK_UNMAPPED_BASE;
 201
 202 unsigned long last_brk;
 203
 204 /* Subroutine of mmap_find_vma, used when we have pre-allocated a chunk
 205    of guest address space.  */
 206 static abi_ulong mmap_find_vma_reserved(abi_ulong start, abi_ulong size)
 207 {
 208     abi_ulong addr;
 209     abi_ulong end_addr;
 210     int prot;
 211     int looped = 0;
 212
 213     if (size > reserved_va) {
 214         return (abi_ulong)-1;
 215     }
 216
 217     size = HOST_PAGE_ALIGN(size);
 218     end_addr = start + size;
 219     if (end_addr > reserved_va) {
 220         end_addr = reserved_va;
 221     }
 222     addr = end_addr - qemu_host_page_size;
 223
 224     while (1) {
 225         if (addr > end_addr) {
 226             if (looped) {
 227                 return (abi_ulong)-1;
 228             }
 229             end_addr = reserved_va;
 230             addr = end_addr - qemu_host_page_size;
 231             looped = 1;
 232             continue;
 233         }
 234         prot = page_get_flags(addr);
 235         if (prot) {
 236             end_addr = addr;
 237         }
 238         if (addr && addr + size == end_addr) {
 239             break;
 240         }
 241         addr -= qemu_host_page_size;
 242     }
 243
 244     if (start == mmap_next_start) {
 245         mmap_next_start = addr;
 246     }
 247
 248     return addr;
 249 }
 250
 251 /*
 252  * Find and reserve a free memory area of size 'size'. The search
 253  * starts at 'start'.
 254  * It must be called with mmap_lock() held.
 255  * Return -1 if error.
 256  */
 257 abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size)
 258 {
 259     void *ptr, *prev;
 260     abi_ulong addr;
 261     int wrapped, repeat;
 262
 263     /* If 'start' == 0, then a default start address is used. */
 264     if (start == 0) {
 265         start = mmap_next_start;
 266     } else {
 267         start &= qemu_host_page_mask;
 268     }
 269
 270     size = HOST_PAGE_ALIGN(size);
 271
 272     if (reserved_va) {
 273         return mmap_find_vma_reserved(start, size);
 274     }
 275
 276     addr = start;
 277     wrapped = repeat = 0;
 278     prev = 0;
 279
 280     for (;; prev = ptr) {
 281         /*
 282          * Reserve needed memory area to avoid a race.
 283          * It should be discarded using:
 284          *  - mmap() with MAP_FIXED flag
 285          *  - mremap() with MREMAP_FIXED flag
 286          *  - shmat() with SHM_REMAP flag
 287          */
 288         ptr = mmap(g2h(addr), size, PROT_NONE,
 289                    MAP_ANONYMOUS|MAP_PRIVATE|MAP_NORESERVE, -1, 0);
 290
 291         /* ENOMEM, if host address space has no memory */
 292         if (ptr == MAP_FAILED) {
 293             return (abi_ulong)-1;
 294         }
 295
 296         /* Count the number of sequential returns of the same address.
 297            This is used to modify the search algorithm below.  */
 298         repeat = (ptr == prev ? repeat + 1 : 0);
 299
 300         if (h2g_valid(ptr + size - 1)) {
 301             addr = h2g(ptr);
 302
 303             if ((addr & ~TARGET_PAGE_MASK) == 0) {
 304                 /* Success.  */
 305                 if (start == mmap_next_start && addr >= TASK_UNMAPPED_BASE) {
 306                     mmap_next_start = addr + size;
 307                 }
 308                 return addr;
 309             }
 310
 311             /* The address is not properly aligned for the target.  */
 312             switch (repeat) {
 313             case 0:
 314                 /* Assume the result that the kernel gave us is the
 315                    first with enough free space, so start again at the
 316                    next higher target page.  */
 317                 addr = TARGET_PAGE_ALIGN(addr);
 318                 break;
 319             case 1:
 320                 /* Sometimes the kernel decides to perform the allocation
 321                    at the top end of memory instead.  */
 322                 addr &= TARGET_PAGE_MASK;
 323                 break;
 324             case 2:
 325                 /* Start over at low memory.  */
 326                 addr = 0;
 327                 break;
 328             default:
 329                 /* Fail.  This unaligned block must the last.  */
 330                 addr = -1;
 331                 break;
 332             }
 333         } else {
 334             /* Since the result the kernel gave didn't fit, start
 335                again at low memory.  If any repetition, fail.  */
 336             addr = (repeat ? -1 : 0);
 337         }
 338
 339         /* Unmap and try again.  */
 340         munmap(ptr, size);
 341
 342         /* ENOMEM if we checked the whole of the target address space.  */
 343         if (addr == (abi_ulong)-1) {
 344             return (abi_ulong)-1;
 345         } else if (addr == 0) {
 346             if (wrapped) {
 347                 return (abi_ulong)-1;
 348             }
 349             wrapped = 1;
 350             /* Don't actually use 0 when wrapping, instead indicate
 351                that we'd truly like an allocation in low memory.  */
 352             addr = (mmap_min_addr > TARGET_PAGE_SIZE
 353                      ? TARGET_PAGE_ALIGN(mmap_min_addr)
 354                      : TARGET_PAGE_SIZE);
 355         } else if (wrapped && addr >= start) {
 356             return (abi_ulong)-1;
 357         }
 358     }
 359 }
 360
 361 /* NOTE: all the constants are the HOST ones */
 362 abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,
 363                      int flags, int fd, abi_ulong offset)
 364 {
 365     abi_ulong ret, end, real_start, real_end, retaddr, host_offset, host_len;
 366
 367     mmap_lock();
 368 #ifdef DEBUG_MMAP
 369     {
 370         printf("mmap: start=0x" TARGET_ABI_FMT_lx
 371                " len=0x" TARGET_ABI_FMT_lx " prot=%c%c%c flags=",
 372                start, len,
 373                prot & PROT_READ ? 'r' : '-',
 374                prot & PROT_WRITE ? 'w' : '-',
 375                prot & PROT_EXEC ? 'x' : '-');
 376         if (flags & MAP_FIXED)
 377             printf("MAP_FIXED ");
 378         if (flags & MAP_ANONYMOUS)
 379             printf("MAP_ANON ");
 380         switch(flags & MAP_TYPE) {
 381         case MAP_PRIVATE:
 382             printf("MAP_PRIVATE ");
 383             break;
 384         case MAP_SHARED:
 385             printf("MAP_SHARED ");
 386             break;
 387         default:
 388             printf("[MAP_TYPE=0x%x] ", flags & MAP_TYPE);
 389             break;
 390         }
 391         printf("fd=%d offset=" TARGET_ABI_FMT_lx "\n", fd, offset);
 392     }
 393 #endif
 394
 395     if (offset & ~TARGET_PAGE_MASK) {
 396         errno = EINVAL;
 397         goto fail;
 398     }
 399
 400     len = TARGET_PAGE_ALIGN(len);
 401     if (len == 0)
 402         goto the_end;
 403     real_start = start & qemu_host_page_mask;
 404     host_offset = offset & qemu_host_page_mask;
 405
 406     /* If the user is asking for the kernel to find a location, do that
 407        before we truncate the length for mapping files below.  */
 408     if (!(flags & MAP_FIXED)) {
 409         host_len = len + offset - host_offset;
 410         host_len = HOST_PAGE_ALIGN(host_len);
 411         start = mmap_find_vma(real_start, host_len);
 412         if (start == (abi_ulong)-1) {
 413             errno = ENOMEM;
 414             goto fail;
 415         }
 416     }
 417
 418     /* When mapping files into a memory area larger than the file, accesses
 419        to pages beyond the file size will cause a SIGBUS.
 420
 421        For example, if mmaping a file of 100 bytes on a host with 4K pages
 422        emulating a target with 8K pages, the target expects to be able to
 423        access the first 8K. But the host will trap us on any access beyond
 424        4K.
 425
 426        When emulating a target with a larger page-size than the hosts, we
 427        may need to truncate file maps at EOF and add extra anonymous pages
 428        up to the targets page boundary.  */
 429
 430     if ((qemu_real_host_page_size < qemu_host_page_size) &&
 431         !(flags & MAP_ANONYMOUS)) {
 432         struct stat sb;
 433
 434        if (fstat (fd, &sb) == -1)
 435            goto fail;
 436
 437        /* Are we trying to create a map beyond EOF?.  */
 438        if (offset + len > sb.st_size) {
 439            /* If so, truncate the file map at eof aligned with
 440               the hosts real pagesize. Additional anonymous maps
 441               will be created beyond EOF.  */
 442            len = REAL_HOST_PAGE_ALIGN(sb.st_size - offset);
 443        }
 444     }
 445
 446     if (!(flags & MAP_FIXED)) {
 447         unsigned long host_start;
 448         void *p;
 449
 450         host_len = len + offset - host_offset;
 451         host_len = HOST_PAGE_ALIGN(host_len);
 452
 453         /* Note: we prefer to control the mapping address. It is
 454            especially important if qemu_host_page_size >
 455            qemu_real_host_page_size */
 456         p = mmap(g2h(start), host_len, prot,
 457                  flags | MAP_FIXED | MAP_ANONYMOUS, -1, 0);
 458         if (p == MAP_FAILED)
 459             goto fail;
 460         /* update start so that it points to the file position at 'offset' */
 461         host_start = (unsigned long)p;
 462         if (!(flags & MAP_ANONYMOUS)) {
 463             p = mmap(g2h(start), len, prot,
 464                      flags | MAP_FIXED, fd, host_offset);
 465             if (p == MAP_FAILED) {
 466                 munmap(g2h(start), host_len);
 467                 goto fail;
 468             }
 469             host_start += offset - host_offset;
 470         }
 471         start = h2g(host_start);
 472     } else {
 473         if (start & ~TARGET_PAGE_MASK) {
 474             errno = EINVAL;
 475             goto fail;
 476         }
 477         end = start + len;
 478         real_end = HOST_PAGE_ALIGN(end);
 479
 480         /*
 481          * Test if requested memory area fits target address space
 482          * It can fail only on 64-bit host with 32-bit target.
 483          * On any other target/host host mmap() handles this error correctly.
 484          */
 485         if (!guest_range_valid(start, len)) {
 486             errno = ENOMEM;
 487             goto fail;
 488         }
 489
 490         /* worst case: we cannot map the file because the offset is not
 491            aligned, so we read it */
 492         if (!(flags & MAP_ANONYMOUS) &&
 493             (offset & ~qemu_host_page_mask) != (start & ~qemu_host_page_mask)) {
 494             /* msync() won't work here, so we return an error if write is
 495                possible while it is a shared mapping */
 496             if ((flags & MAP_TYPE) == MAP_SHARED &&
 497                 (prot & PROT_WRITE)) {
 498                 errno = EINVAL;
 499                 goto fail;
 500             }
 501             retaddr = target_mmap(start, len, prot | PROT_WRITE,
 502                                   MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS,
 503                                   -1, 0);
 504             if (retaddr == -1)
 505                 goto fail;
 506             if (pread(fd, g2h(start), len, offset) == -1)
 507                 goto fail;
 508             if (!(prot & PROT_WRITE)) {
 509                 ret = target_mprotect(start, len, prot);
 510                 assert(ret == 0);
 511             }
 512             goto the_end;
 513         }
 514
 515         /* handle the start of the mapping */
 516         if (start > real_start) {
 517             if (real_end == real_start + qemu_host_page_size) {
 518                 /* one single host page */
 519                 ret = mmap_frag(real_start, start, end,
 520                                 prot, flags, fd, offset);
 521                 if (ret == -1)
 522                     goto fail;
 523                 goto the_end1;
 524             }
 525             ret = mmap_frag(real_start, start, real_start + qemu_host_page_size,
 526                             prot, flags, fd, offset);
 527             if (ret == -1)
 528                 goto fail;
 529             real_start += qemu_host_page_size;
 530         }
 531         /* handle the end of the mapping */
 532         if (end < real_end) {
 533             ret = mmap_frag(real_end - qemu_host_page_size,
 534                             real_end - qemu_host_page_size, end,
 535                             prot, flags, fd,
 536                             offset + real_end - qemu_host_page_size - start);
 537             if (ret == -1)
 538                 goto fail;
 539             real_end -= qemu_host_page_size;
 540         }
 541
 542         /* map the middle (easier) */
 543         if (real_start < real_end) {
 544             void *p;
 545             unsigned long offset1;
 546             if (flags & MAP_ANONYMOUS)
 547                 offset1 = 0;
 548             else
 549                 offset1 = offset + real_start - start;
 550             p = mmap(g2h(real_start), real_end - real_start,
 551                      prot, flags, fd, offset1);
 552             if (p == MAP_FAILED)
 553                 goto fail;
 554         }
 555     }
 556  the_end1:
 557     page_set_flags(start, start + len, prot | PAGE_VALID);
 558  the_end:
 559 #ifdef DEBUG_MMAP
 560     printf("ret=0x" TARGET_ABI_FMT_lx "\n", start);
 561     page_dump(stdout);
 562     printf("\n");
 563 #endif
 564     tb_invalidate_phys_range(start, start + len);
 565     mmap_unlock();
 566     return start;
 567 fail:
 568     mmap_unlock();
 569     return -1;
 570 }
 571
 572 static void mmap_reserve(abi_ulong start, abi_ulong size)
 573 {
 574     abi_ulong real_start;
 575     abi_ulong real_end;
 576     abi_ulong addr;
 577     abi_ulong end;
 578     int prot;
 579
 580     real_start = start & qemu_host_page_mask;
 581     real_end = HOST_PAGE_ALIGN(start + size);
 582     end = start + size;
 583     if (start > real_start) {
 584         /* handle host page containing start */
 585         prot = 0;
 586         for (addr = real_start; addr < start; addr += TARGET_PAGE_SIZE) {
 587             prot |= page_get_flags(addr);
 588         }
 589         if (real_end == real_start + qemu_host_page_size) {
 590             for (addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
 591                 prot |= page_get_flags(addr);
 592             }
 593             end = real_end;
 594         }
 595         if (prot != 0)
 596             real_start += qemu_host_page_size;
 597     }
 598     if (end < real_end) {
 599         prot = 0;
 600         for (addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
 601             prot |= page_get_flags(addr);
 602         }
 603         if (prot != 0)
 604             real_end -= qemu_host_page_size;
 605     }
 606     if (real_start != real_end) {
 607         mmap(g2h(real_start), real_end - real_start, PROT_NONE,
 608                  MAP_FIXED | MAP_ANONYMOUS | MAP_PRIVATE | MAP_NORESERVE,
 609                  -1, 0);
 610     }
 611 }
 612
 613 int target_munmap(abi_ulong start, abi_ulong len)
 614 {
 615     abi_ulong end, real_start, real_end, addr;
 616     int prot, ret;
 617
 618 #ifdef DEBUG_MMAP
 619     printf("munmap: start=0x" TARGET_ABI_FMT_lx " len=0x"
 620            TARGET_ABI_FMT_lx "\n",
 621            start, len);
 622 #endif
 623     if (start & ~TARGET_PAGE_MASK)
 624         return -TARGET_EINVAL;
 625     len = TARGET_PAGE_ALIGN(len);
 626     if (len == 0 || !guest_range_valid(start, len)) {
 627         return -TARGET_EINVAL;
 628     }
 629
 630     mmap_lock();
 631     end = start + len;
 632     real_start = start & qemu_host_page_mask;
 633     real_end = HOST_PAGE_ALIGN(end);
 634
 635     if (start > real_start) {
 636         /* handle host page containing start */
 637         prot = 0;
 638         for(addr = real_start; addr < start; addr += TARGET_PAGE_SIZE) {
 639             prot |= page_get_flags(addr);
 640         }
 641         if (real_end == real_start + qemu_host_page_size) {
 642             for(addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
 643                 prot |= page_get_flags(addr);
 644             }
 645             end = real_end;
 646         }
 647         if (prot != 0)
 648             real_start += qemu_host_page_size;
 649     }
 650     if (end < real_end) {
 651         prot = 0;
 652         for(addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
 653             prot |= page_get_flags(addr);
 654         }
 655         if (prot != 0)
 656             real_end -= qemu_host_page_size;
 657     }
 658
 659     ret = 0;
 660     /* unmap what we can */
 661     if (real_start < real_end) {
 662         if (reserved_va) {
 663             mmap_reserve(real_start, real_end - real_start);
 664         } else {
 665             ret = munmap(g2h(real_start), real_end - real_start);
 666         }
 667     }
 668
 669     if (ret == 0) {
 670         page_set_flags(start, start + len, 0);
 671         tb_invalidate_phys_range(start, start + len);
 672     }
 673     mmap_unlock();
 674     return ret;
 675 }
 676
 677 abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
 678                        abi_ulong new_size, unsigned long flags,
 679                        abi_ulong new_addr)
 680 {
 681     int prot;
 682     void *host_addr;
 683
 684     if (!guest_range_valid(old_addr, old_size) ||
 685         ((flags & MREMAP_FIXED) &&
 686          !guest_range_valid(new_addr, new_size))) {
 687         errno = ENOMEM;
 688         return -1;
 689     }
 690
 691     mmap_lock();
 692
 693     if (flags & MREMAP_FIXED) {
 694         host_addr = mremap(g2h(old_addr), old_size, new_size,
 695                            flags, g2h(new_addr));
 696
 697         if (reserved_va && host_addr != MAP_FAILED) {
 698             /* If new and old addresses overlap then the above mremap will
 699                already have failed with EINVAL.  */
 700             mmap_reserve(old_addr, old_size);
 701         }
 702     } else if (flags & MREMAP_MAYMOVE) {
 703         abi_ulong mmap_start;
 704
 705         mmap_start = mmap_find_vma(0, new_size);
 706
 707         if (mmap_start == -1) {
 708             errno = ENOMEM;
 709             host_addr = MAP_FAILED;
 710         } else {
 711             host_addr = mremap(g2h(old_addr), old_size, new_size,
 712                                flags | MREMAP_FIXED, g2h(mmap_start));
 713             if (reserved_va) {
 714                 mmap_reserve(old_addr, old_size);
 715             }
 716         }
 717     } else {
 718         int prot = 0;
 719         if (reserved_va && old_size < new_size) {
 720             abi_ulong addr;
 721             for (addr = old_addr + old_size;
 722                  addr < old_addr + new_size;
 723                  addr++) {
 724                 prot |= page_get_flags(addr);
 725             }
 726         }
 727         if (prot == 0) {
 728             host_addr = mremap(g2h(old_addr), old_size, new_size, flags);
 729             if (host_addr != MAP_FAILED && reserved_va && old_size > new_size) {
 730                 mmap_reserve(old_addr + old_size, new_size - old_size);
 731             }
 732         } else {
 733             errno = ENOMEM;
 734             host_addr = MAP_FAILED;
 735         }
 736         /* Check if address fits target address space */
 737         if ((unsigned long)host_addr + new_size > (abi_ulong)-1) {
 738             /* Revert mremap() changes */
 739             host_addr = mremap(g2h(old_addr), new_size, old_size, flags);
 740             errno = ENOMEM;
 741             host_addr = MAP_FAILED;
 742         }
 743     }
 744
 745     if (host_addr == MAP_FAILED) {
 746         new_addr = -1;
 747     } else {
 748         new_addr = h2g(host_addr);
 749         prot = page_get_flags(old_addr);
 750         page_set_flags(old_addr, old_addr + old_size, 0);
 751         page_set_flags(new_addr, new_addr + new_size, prot | PAGE_VALID);
 752     }
 753     tb_invalidate_phys_range(new_addr, new_addr + new_size);
 754     mmap_unlock();
 755     return new_addr;
 756 }