2 * mmap support for qemu
4 * Copyright (c) 2003 Fabrice Bellard
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.
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.
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/>.
25 #include <sys/types.h>
28 #include <linux/mman.h>
29 #include <linux/unistd.h>
32 #include "qemu-common.h"
36 #if defined(CONFIG_USE_NPTL)
37 static pthread_mutex_t mmap_mutex = PTHREAD_MUTEX_INITIALIZER;
38 static __thread int mmap_lock_count;
42 if (mmap_lock_count++ == 0) {
43 pthread_mutex_lock(&mmap_mutex);
47 void mmap_unlock(void)
49 if (--mmap_lock_count == 0) {
50 pthread_mutex_unlock(&mmap_mutex);
54 /* Grab lock to make sure things are in a consistent state after fork(). */
55 void mmap_fork_start(void)
59 pthread_mutex_lock(&mmap_mutex);
62 void mmap_fork_end(int child)
65 pthread_mutex_init(&mmap_mutex, NULL);
67 pthread_mutex_unlock(&mmap_mutex);
70 /* We aren't threadsafe to start with, so no need to worry about locking. */
75 void mmap_unlock(void)
80 /* NOTE: all the constants are the HOST ones, but addresses are target. */
81 int target_mprotect(abi_ulong start, abi_ulong len, int prot)
83 abi_ulong end, host_start, host_end, addr;
87 printf("mprotect: start=0x" TARGET_ABI_FMT_lx
88 "len=0x" TARGET_ABI_FMT_lx " prot=%c%c%c\n", start, len,
89 prot & PROT_READ ? 'r' : '-',
90 prot & PROT_WRITE ? 'w' : '-',
91 prot & PROT_EXEC ? 'x' : '-');
94 if ((start & ~TARGET_PAGE_MASK) != 0)
96 len = TARGET_PAGE_ALIGN(len);
100 prot &= PROT_READ | PROT_WRITE | PROT_EXEC;
105 host_start = start & qemu_host_page_mask;
106 host_end = HOST_PAGE_ALIGN(end);
107 if (start > host_start) {
108 /* handle host page containing start */
110 for(addr = host_start; addr < start; addr += TARGET_PAGE_SIZE) {
111 prot1 |= page_get_flags(addr);
113 if (host_end == host_start + qemu_host_page_size) {
114 for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
115 prot1 |= page_get_flags(addr);
119 ret = mprotect(g2h(host_start), qemu_host_page_size, prot1 & PAGE_BITS);
122 host_start += qemu_host_page_size;
124 if (end < host_end) {
126 for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
127 prot1 |= page_get_flags(addr);
129 ret = mprotect(g2h(host_end - qemu_host_page_size), qemu_host_page_size,
133 host_end -= qemu_host_page_size;
136 /* handle the pages in the middle */
137 if (host_start < host_end) {
138 ret = mprotect(g2h(host_start), host_end - host_start, prot);
142 page_set_flags(start, start + len, prot | PAGE_VALID);
150 /* map an incomplete host page */
151 static int mmap_frag(abi_ulong real_start,
152 abi_ulong start, abi_ulong end,
153 int prot, int flags, int fd, abi_ulong offset)
155 abi_ulong real_end, addr;
159 real_end = real_start + qemu_host_page_size;
160 host_start = g2h(real_start);
162 /* get the protection of the target pages outside the mapping */
164 for(addr = real_start; addr < real_end; addr++) {
165 if (addr < start || addr >= end)
166 prot1 |= page_get_flags(addr);
170 /* no page was there, so we allocate one */
171 void *p = mmap(host_start, qemu_host_page_size, prot,
172 flags | MAP_ANONYMOUS, -1, 0);
179 prot_new = prot | prot1;
180 if (!(flags & MAP_ANONYMOUS)) {
181 /* msync() won't work here, so we return an error if write is
182 possible while it is a shared mapping */
183 if ((flags & MAP_TYPE) == MAP_SHARED &&
187 /* adjust protection to be able to read */
188 if (!(prot1 & PROT_WRITE))
189 mprotect(host_start, qemu_host_page_size, prot1 | PROT_WRITE);
191 /* read the corresponding file data */
192 if (pread(fd, g2h(start), end - start, offset) == -1)
195 /* put final protection */
196 if (prot_new != (prot1 | PROT_WRITE))
197 mprotect(host_start, qemu_host_page_size, prot_new);
199 /* just update the protection */
200 if (prot_new != prot1) {
201 mprotect(host_start, qemu_host_page_size, prot_new);
207 #if HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 64
208 # define TASK_UNMAPPED_BASE (1ul << 38)
209 #elif defined(__CYGWIN__)
210 /* Cygwin doesn't have a whole lot of address space. */
211 # define TASK_UNMAPPED_BASE 0x18000000
213 # define TASK_UNMAPPED_BASE 0x40000000
215 static abi_ulong mmap_next_start = TASK_UNMAPPED_BASE;
217 unsigned long last_brk;
219 /* Subroutine of mmap_find_vma, used when we have pre-allocated a chunk
220 of guest address space. */
221 static abi_ulong mmap_find_vma_reserved(abi_ulong start, abi_ulong size)
228 if (size > RESERVED_VA) {
229 return (abi_ulong)-1;
233 for (addr = start; last_addr + size != addr; addr += qemu_host_page_size) {
234 if (last_addr + size >= RESERVED_VA
235 || (abi_ulong)(last_addr + size) < last_addr) {
237 return (abi_ulong)-1;
239 last_addr = qemu_host_page_size;
244 prot = page_get_flags(addr);
246 last_addr = addr + qemu_host_page_size;
249 mmap_next_start = addr;
254 * Find and reserve a free memory area of size 'size'. The search
256 * It must be called with mmap_lock() held.
257 * Return -1 if error.
259 abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size)
265 /* If 'start' == 0, then a default start address is used. */
267 start = mmap_next_start;
269 start &= qemu_host_page_mask;
272 size = HOST_PAGE_ALIGN(size);
275 return mmap_find_vma_reserved(start, size);
279 wrapped = repeat = 0;
282 for (;; prev = ptr) {
284 * Reserve needed memory area to avoid a race.
285 * It should be discarded using:
286 * - mmap() with MAP_FIXED flag
287 * - mremap() with MREMAP_FIXED flag
288 * - shmat() with SHM_REMAP flag
290 ptr = mmap(g2h(addr), size, PROT_NONE,
291 MAP_ANONYMOUS|MAP_PRIVATE|MAP_NORESERVE, -1, 0);
293 /* ENOMEM, if host address space has no memory */
294 if (ptr == MAP_FAILED) {
295 return (abi_ulong)-1;
298 /* Count the number of sequential returns of the same address.
299 This is used to modify the search algorithm below. */
300 repeat = (ptr == prev ? repeat + 1 : 0);
302 if (h2g_valid(ptr + size - 1)) {
305 if ((addr & ~TARGET_PAGE_MASK) == 0) {
307 if (start == mmap_next_start && addr >= TASK_UNMAPPED_BASE) {
308 mmap_next_start = addr + size;
313 /* The address is not properly aligned for the target. */
316 /* Assume the result that the kernel gave us is the
317 first with enough free space, so start again at the
318 next higher target page. */
319 addr = TARGET_PAGE_ALIGN(addr);
322 /* Sometimes the kernel decides to perform the allocation
323 at the top end of memory instead. */
324 addr &= TARGET_PAGE_MASK;
327 /* Start over at low memory. */
331 /* Fail. This unaligned block must the last. */
336 /* Since the result the kernel gave didn't fit, start
337 again at low memory. If any repetition, fail. */
338 addr = (repeat ? -1 : 0);
341 /* Unmap and try again. */
344 /* ENOMEM if we checked the whole of the target address space. */
345 if (addr == (abi_ulong)-1) {
346 return (abi_ulong)-1;
347 } else if (addr == 0) {
349 return (abi_ulong)-1;
352 /* Don't actually use 0 when wrapping, instead indicate
353 that we'd truely like an allocation in low memory. */
354 addr = (mmap_min_addr > TARGET_PAGE_SIZE
355 ? TARGET_PAGE_ALIGN(mmap_min_addr)
357 } else if (wrapped && addr >= start) {
358 return (abi_ulong)-1;
363 /* NOTE: all the constants are the HOST ones */
364 abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,
365 int flags, int fd, abi_ulong offset)
367 abi_ulong ret, end, real_start, real_end, retaddr, host_offset, host_len;
368 unsigned long host_start;
373 printf("mmap: start=0x" TARGET_ABI_FMT_lx
374 " len=0x" TARGET_ABI_FMT_lx " prot=%c%c%c flags=",
376 prot & PROT_READ ? 'r' : '-',
377 prot & PROT_WRITE ? 'w' : '-',
378 prot & PROT_EXEC ? 'x' : '-');
379 if (flags & MAP_FIXED)
380 printf("MAP_FIXED ");
381 if (flags & MAP_ANONYMOUS)
383 switch(flags & MAP_TYPE) {
385 printf("MAP_PRIVATE ");
388 printf("MAP_SHARED ");
391 printf("[MAP_TYPE=0x%x] ", flags & MAP_TYPE);
394 printf("fd=%d offset=" TARGET_ABI_FMT_lx "\n", fd, offset);
398 if (offset & ~TARGET_PAGE_MASK) {
403 len = TARGET_PAGE_ALIGN(len);
406 real_start = start & qemu_host_page_mask;
408 /* When mapping files into a memory area larger than the file, accesses
409 to pages beyond the file size will cause a SIGBUS.
411 For example, if mmaping a file of 100 bytes on a host with 4K pages
412 emulating a target with 8K pages, the target expects to be able to
413 access the first 8K. But the host will trap us on any access beyond
416 When emulating a target with a larger page-size than the hosts, we
417 may need to truncate file maps at EOF and add extra anonymous pages
418 up to the targets page boundary. */
420 if ((qemu_real_host_page_size < TARGET_PAGE_SIZE)
421 && !(flags & MAP_ANONYMOUS)) {
424 if (fstat (fd, &sb) == -1)
427 /* Are we trying to create a map beyond EOF?. */
428 if (offset + len > sb.st_size) {
429 /* If so, truncate the file map at eof aligned with
430 the hosts real pagesize. Additional anonymous maps
431 will be created beyond EOF. */
432 len = (sb.st_size - offset);
433 len += qemu_real_host_page_size - 1;
434 len &= ~(qemu_real_host_page_size - 1);
438 if (!(flags & MAP_FIXED)) {
439 abi_ulong mmap_start;
441 host_offset = offset & qemu_host_page_mask;
442 host_len = len + offset - host_offset;
443 host_len = HOST_PAGE_ALIGN(host_len);
444 mmap_start = mmap_find_vma(real_start, host_len);
445 if (mmap_start == (abi_ulong)-1) {
449 /* Note: we prefer to control the mapping address. It is
450 especially important if qemu_host_page_size >
451 qemu_real_host_page_size */
452 p = mmap(g2h(mmap_start),
453 host_len, prot, flags | MAP_FIXED | MAP_ANONYMOUS, -1, 0);
456 /* update start so that it points to the file position at 'offset' */
457 host_start = (unsigned long)p;
458 if (!(flags & MAP_ANONYMOUS)) {
459 p = mmap(g2h(mmap_start), len, prot,
460 flags | MAP_FIXED, fd, host_offset);
461 host_start += offset - host_offset;
463 start = h2g(host_start);
465 if (start & ~TARGET_PAGE_MASK) {
470 real_end = HOST_PAGE_ALIGN(end);
473 * Test if requested memory area fits target address space
474 * It can fail only on 64-bit host with 32-bit target.
475 * On any other target/host host mmap() handles this error correctly.
477 if ((unsigned long)start + len - 1 > (abi_ulong) -1) {
482 /* worst case: we cannot map the file because the offset is not
483 aligned, so we read it */
484 if (!(flags & MAP_ANONYMOUS) &&
485 (offset & ~qemu_host_page_mask) != (start & ~qemu_host_page_mask)) {
486 /* msync() won't work here, so we return an error if write is
487 possible while it is a shared mapping */
488 if ((flags & MAP_TYPE) == MAP_SHARED &&
489 (prot & PROT_WRITE)) {
493 retaddr = target_mmap(start, len, prot | PROT_WRITE,
494 MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS,
498 if (pread(fd, g2h(start), len, offset) == -1)
500 if (!(prot & PROT_WRITE)) {
501 ret = target_mprotect(start, len, prot);
510 /* handle the start of the mapping */
511 if (start > real_start) {
512 if (real_end == real_start + qemu_host_page_size) {
513 /* one single host page */
514 ret = mmap_frag(real_start, start, end,
515 prot, flags, fd, offset);
520 ret = mmap_frag(real_start, start, real_start + qemu_host_page_size,
521 prot, flags, fd, offset);
524 real_start += qemu_host_page_size;
526 /* handle the end of the mapping */
527 if (end < real_end) {
528 ret = mmap_frag(real_end - qemu_host_page_size,
529 real_end - qemu_host_page_size, real_end,
531 offset + real_end - qemu_host_page_size - start);
534 real_end -= qemu_host_page_size;
537 /* map the middle (easier) */
538 if (real_start < real_end) {
540 unsigned long offset1;
541 if (flags & MAP_ANONYMOUS)
544 offset1 = offset + real_start - start;
545 p = mmap(g2h(real_start), real_end - real_start,
546 prot, flags, fd, offset1);
552 page_set_flags(start, start + len, prot | PAGE_VALID);
555 printf("ret=0x" TARGET_ABI_FMT_lx "\n", start);
566 static void mmap_reserve(abi_ulong start, abi_ulong size)
568 abi_ulong real_start;
574 real_start = start & qemu_host_page_mask;
575 real_end = HOST_PAGE_ALIGN(start + size);
577 if (start > real_start) {
578 /* handle host page containing start */
580 for (addr = real_start; addr < start; addr += TARGET_PAGE_SIZE) {
581 prot |= page_get_flags(addr);
583 if (real_end == real_start + qemu_host_page_size) {
584 for (addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
585 prot |= page_get_flags(addr);
590 real_start += qemu_host_page_size;
592 if (end < real_end) {
594 for (addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
595 prot |= page_get_flags(addr);
598 real_end -= qemu_host_page_size;
600 if (real_start != real_end) {
601 mmap(g2h(real_start), real_end - real_start, PROT_NONE,
602 MAP_FIXED | MAP_ANONYMOUS | MAP_PRIVATE | MAP_NORESERVE,
607 int target_munmap(abi_ulong start, abi_ulong len)
609 abi_ulong end, real_start, real_end, addr;
613 printf("munmap: start=0x" TARGET_ABI_FMT_lx " len=0x"
614 TARGET_ABI_FMT_lx "\n",
617 if (start & ~TARGET_PAGE_MASK)
619 len = TARGET_PAGE_ALIGN(len);
624 real_start = start & qemu_host_page_mask;
625 real_end = HOST_PAGE_ALIGN(end);
627 if (start > real_start) {
628 /* handle host page containing start */
630 for(addr = real_start; addr < start; addr += TARGET_PAGE_SIZE) {
631 prot |= page_get_flags(addr);
633 if (real_end == real_start + qemu_host_page_size) {
634 for(addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
635 prot |= page_get_flags(addr);
640 real_start += qemu_host_page_size;
642 if (end < real_end) {
644 for(addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
645 prot |= page_get_flags(addr);
648 real_end -= qemu_host_page_size;
652 /* unmap what we can */
653 if (real_start < real_end) {
655 mmap_reserve(real_start, real_end - real_start);
657 ret = munmap(g2h(real_start), real_end - real_start);
662 page_set_flags(start, start + len, 0);
667 abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
668 abi_ulong new_size, unsigned long flags,
676 if (flags & MREMAP_FIXED) {
677 host_addr = (void *) syscall(__NR_mremap, g2h(old_addr),
682 if (RESERVED_VA && host_addr != MAP_FAILED) {
683 /* If new and old addresses overlap then the above mremap will
684 already have failed with EINVAL. */
685 mmap_reserve(old_addr, old_size);
687 } else if (flags & MREMAP_MAYMOVE) {
688 abi_ulong mmap_start;
690 mmap_start = mmap_find_vma(0, new_size);
692 if (mmap_start == -1) {
694 host_addr = MAP_FAILED;
696 host_addr = (void *) syscall(__NR_mremap, g2h(old_addr),
698 flags | MREMAP_FIXED,
701 mmap_reserve(old_addr, old_size);
706 if (RESERVED_VA && old_size < new_size) {
708 for (addr = old_addr + old_size;
709 addr < old_addr + new_size;
711 prot |= page_get_flags(addr);
715 host_addr = mremap(g2h(old_addr), old_size, new_size, flags);
716 if (host_addr != MAP_FAILED && RESERVED_VA && old_size > new_size) {
717 mmap_reserve(old_addr + old_size, new_size - old_size);
721 host_addr = MAP_FAILED;
723 /* Check if address fits target address space */
724 if ((unsigned long)host_addr + new_size > (abi_ulong)-1) {
725 /* Revert mremap() changes */
726 host_addr = mremap(g2h(old_addr), new_size, old_size, flags);
728 host_addr = MAP_FAILED;
732 if (host_addr == MAP_FAILED) {
735 new_addr = h2g(host_addr);
736 prot = page_get_flags(old_addr);
737 page_set_flags(old_addr, old_addr + old_size, 0);
738 page_set_flags(new_addr, new_addr + new_size, prot | PAGE_VALID);
744 int target_msync(abi_ulong start, abi_ulong len, int flags)
748 if (start & ~TARGET_PAGE_MASK)
750 len = TARGET_PAGE_ALIGN(len);
757 start &= qemu_host_page_mask;
758 return msync(g2h(start), end - start, flags);