xref: /openbmc/qemu/linux-user/mmap.c (revision 4f8f199fa569492bb07efee02489f521629d275d)
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  #include <sys/shm.h>
21  #include "trace.h"
22  #include "exec/log.h"
23  #include "qemu.h"
24  #include "user-internals.h"
25  #include "user-mmap.h"
26  #include "target_mman.h"
27  #include "qemu/interval-tree.h"
28  
29  #ifdef TARGET_ARM
30  #include "target/arm/cpu-features.h"
31  #endif
32  
33  static pthread_mutex_t mmap_mutex = PTHREAD_MUTEX_INITIALIZER;
34  static __thread int 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      assert(mmap_lock_count > 0);
46      if (--mmap_lock_count == 0) {
47          pthread_mutex_unlock(&mmap_mutex);
48      }
49  }
50  
51  bool have_mmap_lock(void)
52  {
53      return mmap_lock_count > 0 ? true : false;
54  }
55  
56  /* Grab lock to make sure things are in a consistent state after fork().  */
57  void mmap_fork_start(void)
58  {
59      if (mmap_lock_count)
60          abort();
61      pthread_mutex_lock(&mmap_mutex);
62  }
63  
64  void mmap_fork_end(int child)
65  {
66      if (child) {
67          pthread_mutex_init(&mmap_mutex, NULL);
68      } else {
69          pthread_mutex_unlock(&mmap_mutex);
70      }
71  }
72  
73  /* Protected by mmap_lock. */
74  static IntervalTreeRoot shm_regions;
75  
76  static void shm_region_add(abi_ptr start, abi_ptr last)
77  {
78      IntervalTreeNode *i = g_new0(IntervalTreeNode, 1);
79  
80      i->start = start;
81      i->last = last;
82      interval_tree_insert(i, &shm_regions);
83  }
84  
85  static abi_ptr shm_region_find(abi_ptr start)
86  {
87      IntervalTreeNode *i;
88  
89      for (i = interval_tree_iter_first(&shm_regions, start, start); i;
90           i = interval_tree_iter_next(i, start, start)) {
91          if (i->start == start) {
92              return i->last;
93          }
94      }
95      return 0;
96  }
97  
98  static void shm_region_rm_complete(abi_ptr start, abi_ptr last)
99  {
100      IntervalTreeNode *i, *n;
101  
102      for (i = interval_tree_iter_first(&shm_regions, start, last); i; i = n) {
103          n = interval_tree_iter_next(i, start, last);
104          if (i->start >= start && i->last <= last) {
105              interval_tree_remove(i, &shm_regions);
106              g_free(i);
107          }
108      }
109  }
110  
111  /*
112   * Validate target prot bitmask.
113   * Return the prot bitmask for the host in *HOST_PROT.
114   * Return 0 if the target prot bitmask is invalid, otherwise
115   * the internal qemu page_flags (which will include PAGE_VALID).
116   */
117  static int validate_prot_to_pageflags(int prot)
118  {
119      int valid = PROT_READ | PROT_WRITE | PROT_EXEC | TARGET_PROT_SEM;
120      int page_flags = (prot & PAGE_BITS) | PAGE_VALID;
121  
122  #ifdef TARGET_AARCH64
123      {
124          ARMCPU *cpu = ARM_CPU(thread_cpu);
125  
126          /*
127           * The PROT_BTI bit is only accepted if the cpu supports the feature.
128           * Since this is the unusual case, don't bother checking unless
129           * the bit has been requested.  If set and valid, record the bit
130           * within QEMU's page_flags.
131           */
132          if ((prot & TARGET_PROT_BTI) && cpu_isar_feature(aa64_bti, cpu)) {
133              valid |= TARGET_PROT_BTI;
134              page_flags |= PAGE_BTI;
135          }
136          /* Similarly for the PROT_MTE bit. */
137          if ((prot & TARGET_PROT_MTE) && cpu_isar_feature(aa64_mte, cpu)) {
138              valid |= TARGET_PROT_MTE;
139              page_flags |= PAGE_MTE;
140          }
141      }
142  #elif defined(TARGET_HPPA)
143      valid |= PROT_GROWSDOWN | PROT_GROWSUP;
144  #endif
145  
146      return prot & ~valid ? 0 : page_flags;
147  }
148  
149  /*
150   * For the host, we need not pass anything except read/write/exec.
151   * While PROT_SEM is allowed by all hosts, it is also ignored, so
152   * don't bother transforming guest bit to host bit.  Any other
153   * target-specific prot bits will not be understood by the host
154   * and will need to be encoded into page_flags for qemu emulation.
155   *
156   * Pages that are executable by the guest will never be executed
157   * by the host, but the host will need to be able to read them.
158   */
159  static int target_to_host_prot(int prot)
160  {
161      return (prot & (PROT_READ | PROT_WRITE)) |
162             (prot & PROT_EXEC ? PROT_READ : 0);
163  }
164  
165  /* NOTE: all the constants are the HOST ones, but addresses are target. */
166  int target_mprotect(abi_ulong start, abi_ulong len, int target_prot)
167  {
168      int host_page_size = qemu_real_host_page_size();
169      abi_ulong starts[3];
170      abi_ulong lens[3];
171      int prots[3];
172      abi_ulong host_start, host_last, last;
173      int prot1, ret, page_flags, nranges;
174  
175      trace_target_mprotect(start, len, target_prot);
176  
177      if ((start & ~TARGET_PAGE_MASK) != 0) {
178          return -TARGET_EINVAL;
179      }
180      page_flags = validate_prot_to_pageflags(target_prot);
181      if (!page_flags) {
182          return -TARGET_EINVAL;
183      }
184      if (len == 0) {
185          return 0;
186      }
187      len = TARGET_PAGE_ALIGN(len);
188      if (!guest_range_valid_untagged(start, len)) {
189          return -TARGET_ENOMEM;
190      }
191  
192      last = start + len - 1;
193      host_start = start & -host_page_size;
194      host_last = ROUND_UP(last, host_page_size) - 1;
195      nranges = 0;
196  
197      mmap_lock();
198  
199      if (host_last - host_start < host_page_size) {
200          /* Single host page contains all guest pages: sum the prot. */
201          prot1 = target_prot;
202          for (abi_ulong a = host_start; a < start; a += TARGET_PAGE_SIZE) {
203              prot1 |= page_get_flags(a);
204          }
205          for (abi_ulong a = last; a < host_last; a += TARGET_PAGE_SIZE) {
206              prot1 |= page_get_flags(a + 1);
207          }
208          starts[nranges] = host_start;
209          lens[nranges] = host_page_size;
210          prots[nranges] = prot1;
211          nranges++;
212      } else {
213          if (host_start < start) {
214              /* Host page contains more than one guest page: sum the prot. */
215              prot1 = target_prot;
216              for (abi_ulong a = host_start; a < start; a += TARGET_PAGE_SIZE) {
217                  prot1 |= page_get_flags(a);
218              }
219              /* If the resulting sum differs, create a new range. */
220              if (prot1 != target_prot) {
221                  starts[nranges] = host_start;
222                  lens[nranges] = host_page_size;
223                  prots[nranges] = prot1;
224                  nranges++;
225                  host_start += host_page_size;
226              }
227          }
228  
229          if (last < host_last) {
230              /* Host page contains more than one guest page: sum the prot. */
231              prot1 = target_prot;
232              for (abi_ulong a = last; a < host_last; a += TARGET_PAGE_SIZE) {
233                  prot1 |= page_get_flags(a + 1);
234              }
235              /* If the resulting sum differs, create a new range. */
236              if (prot1 != target_prot) {
237                  host_last -= host_page_size;
238                  starts[nranges] = host_last + 1;
239                  lens[nranges] = host_page_size;
240                  prots[nranges] = prot1;
241                  nranges++;
242              }
243          }
244  
245          /* Create a range for the middle, if any remains. */
246          if (host_start < host_last) {
247              starts[nranges] = host_start;
248              lens[nranges] = host_last - host_start + 1;
249              prots[nranges] = target_prot;
250              nranges++;
251          }
252      }
253  
254      for (int i = 0; i < nranges; ++i) {
255          ret = mprotect(g2h_untagged(starts[i]), lens[i],
256                         target_to_host_prot(prots[i]));
257          if (ret != 0) {
258              goto error;
259          }
260      }
261  
262      page_set_flags(start, last, page_flags);
263      ret = 0;
264  
265   error:
266      mmap_unlock();
267      return ret;
268  }
269  
270  /*
271   * Perform munmap on behalf of the target, with host parameters.
272   * If reserved_va, we must replace the memory reservation.
273   */
274  static int do_munmap(void *addr, size_t len)
275  {
276      if (reserved_va) {
277          void *ptr = mmap(addr, len, PROT_NONE,
278                           MAP_FIXED | MAP_ANONYMOUS
279                           | MAP_PRIVATE | MAP_NORESERVE, -1, 0);
280          return ptr == addr ? 0 : -1;
281      }
282      return munmap(addr, len);
283  }
284  
285  /*
286   * Map an incomplete host page.
287   *
288   * Here be dragons.  This case will not work if there is an existing
289   * overlapping host page, which is file mapped, and for which the mapping
290   * is beyond the end of the file.  In that case, we will see SIGBUS when
291   * trying to write a portion of this page.
292   *
293   * FIXME: Work around this with a temporary signal handler and longjmp.
294   */
295  static bool mmap_frag(abi_ulong real_start, abi_ulong start, abi_ulong last,
296                        int prot, int flags, int fd, off_t offset)
297  {
298      int host_page_size = qemu_real_host_page_size();
299      abi_ulong real_last;
300      void *host_start;
301      int prot_old, prot_new;
302      int host_prot_old, host_prot_new;
303  
304      if (!(flags & MAP_ANONYMOUS)
305          && (flags & MAP_TYPE) == MAP_SHARED
306          && (prot & PROT_WRITE)) {
307          /*
308           * msync() won't work with the partial page, so we return an
309           * error if write is possible while it is a shared mapping.
310           */
311          errno = EINVAL;
312          return false;
313      }
314  
315      real_last = real_start + host_page_size - 1;
316      host_start = g2h_untagged(real_start);
317  
318      /* Get the protection of the target pages outside the mapping. */
319      prot_old = 0;
320      for (abi_ulong a = real_start; a < start; a += TARGET_PAGE_SIZE) {
321          prot_old |= page_get_flags(a);
322      }
323      for (abi_ulong a = real_last; a > last; a -= TARGET_PAGE_SIZE) {
324          prot_old |= page_get_flags(a);
325      }
326  
327      if (prot_old == 0) {
328          /*
329           * Since !(prot_old & PAGE_VALID), there were no guest pages
330           * outside of the fragment we need to map.  Allocate a new host
331           * page to cover, discarding whatever else may have been present.
332           */
333          void *p = mmap(host_start, host_page_size,
334                         target_to_host_prot(prot),
335                         flags | MAP_ANONYMOUS, -1, 0);
336          if (p != host_start) {
337              if (p != MAP_FAILED) {
338                  do_munmap(p, host_page_size);
339                  errno = EEXIST;
340              }
341              return false;
342          }
343          prot_old = prot;
344      }
345      prot_new = prot | prot_old;
346  
347      host_prot_old = target_to_host_prot(prot_old);
348      host_prot_new = target_to_host_prot(prot_new);
349  
350      /* Adjust protection to be able to write. */
351      if (!(host_prot_old & PROT_WRITE)) {
352          host_prot_old |= PROT_WRITE;
353          mprotect(host_start, host_page_size, host_prot_old);
354      }
355  
356      /* Read or zero the new guest pages. */
357      if (flags & MAP_ANONYMOUS) {
358          memset(g2h_untagged(start), 0, last - start + 1);
359      } else {
360          if (pread(fd, g2h_untagged(start), last - start + 1, offset) == -1) {
361              return false;
362          }
363      }
364  
365      /* Put final protection */
366      if (host_prot_new != host_prot_old) {
367          mprotect(host_start, host_page_size, host_prot_new);
368      }
369      return true;
370  }
371  
372  abi_ulong task_unmapped_base;
373  abi_ulong elf_et_dyn_base;
374  abi_ulong mmap_next_start;
375  
376  /*
377   * Subroutine of mmap_find_vma, used when we have pre-allocated
378   * a chunk of guest address space.
379   */
380  static abi_ulong mmap_find_vma_reserved(abi_ulong start, abi_ulong size,
381                                          abi_ulong align)
382  {
383      target_ulong ret;
384  
385      ret = page_find_range_empty(start, reserved_va, size, align);
386      if (ret == -1 && start > mmap_min_addr) {
387          /* Restart at the beginning of the address space. */
388          ret = page_find_range_empty(mmap_min_addr, start - 1, size, align);
389      }
390  
391      return ret;
392  }
393  
394  /*
395   * Find and reserve a free memory area of size 'size'. The search
396   * starts at 'start'.
397   * It must be called with mmap_lock() held.
398   * Return -1 if error.
399   */
400  abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size, abi_ulong align)
401  {
402      int host_page_size = qemu_real_host_page_size();
403      void *ptr, *prev;
404      abi_ulong addr;
405      int wrapped, repeat;
406  
407      align = MAX(align, host_page_size);
408  
409      /* If 'start' == 0, then a default start address is used. */
410      if (start == 0) {
411          start = mmap_next_start;
412      } else {
413          start &= -host_page_size;
414      }
415      start = ROUND_UP(start, align);
416      size = ROUND_UP(size, host_page_size);
417  
418      if (reserved_va) {
419          return mmap_find_vma_reserved(start, size, align);
420      }
421  
422      addr = start;
423      wrapped = repeat = 0;
424      prev = 0;
425  
426      for (;; prev = ptr) {
427          /*
428           * Reserve needed memory area to avoid a race.
429           * It should be discarded using:
430           *  - mmap() with MAP_FIXED flag
431           *  - mremap() with MREMAP_FIXED flag
432           *  - shmat() with SHM_REMAP flag
433           */
434          ptr = mmap(g2h_untagged(addr), size, PROT_NONE,
435                     MAP_ANONYMOUS | MAP_PRIVATE | MAP_NORESERVE, -1, 0);
436  
437          /* ENOMEM, if host address space has no memory */
438          if (ptr == MAP_FAILED) {
439              return (abi_ulong)-1;
440          }
441  
442          /*
443           * Count the number of sequential returns of the same address.
444           * This is used to modify the search algorithm below.
445           */
446          repeat = (ptr == prev ? repeat + 1 : 0);
447  
448          if (h2g_valid(ptr + size - 1)) {
449              addr = h2g(ptr);
450  
451              if ((addr & (align - 1)) == 0) {
452                  /* Success.  */
453                  if (start == mmap_next_start && addr >= task_unmapped_base) {
454                      mmap_next_start = addr + size;
455                  }
456                  return addr;
457              }
458  
459              /* The address is not properly aligned for the target.  */
460              switch (repeat) {
461              case 0:
462                  /*
463                   * Assume the result that the kernel gave us is the
464                   * first with enough free space, so start again at the
465                   * next higher target page.
466                   */
467                  addr = ROUND_UP(addr, align);
468                  break;
469              case 1:
470                  /*
471                   * Sometimes the kernel decides to perform the allocation
472                   * at the top end of memory instead.
473                   */
474                  addr &= -align;
475                  break;
476              case 2:
477                  /* Start over at low memory.  */
478                  addr = 0;
479                  break;
480              default:
481                  /* Fail.  This unaligned block must the last.  */
482                  addr = -1;
483                  break;
484              }
485          } else {
486              /*
487               * Since the result the kernel gave didn't fit, start
488               * again at low memory.  If any repetition, fail.
489               */
490              addr = (repeat ? -1 : 0);
491          }
492  
493          /* Unmap and try again.  */
494          munmap(ptr, size);
495  
496          /* ENOMEM if we checked the whole of the target address space.  */
497          if (addr == (abi_ulong)-1) {
498              return (abi_ulong)-1;
499          } else if (addr == 0) {
500              if (wrapped) {
501                  return (abi_ulong)-1;
502              }
503              wrapped = 1;
504              /*
505               * Don't actually use 0 when wrapping, instead indicate
506               * that we'd truly like an allocation in low memory.
507               */
508              addr = (mmap_min_addr > TARGET_PAGE_SIZE
509                       ? TARGET_PAGE_ALIGN(mmap_min_addr)
510                       : TARGET_PAGE_SIZE);
511          } else if (wrapped && addr >= start) {
512              return (abi_ulong)-1;
513          }
514      }
515  }
516  
517  /*
518   * Record a successful mmap within the user-exec interval tree.
519   */
520  static abi_long mmap_end(abi_ulong start, abi_ulong last,
521                           abi_ulong passthrough_start,
522                           abi_ulong passthrough_last,
523                           int flags, int page_flags)
524  {
525      if (flags & MAP_ANONYMOUS) {
526          page_flags |= PAGE_ANON;
527      }
528      page_flags |= PAGE_RESET;
529      if (passthrough_start > passthrough_last) {
530          page_set_flags(start, last, page_flags);
531      } else {
532          if (start < passthrough_start) {
533              page_set_flags(start, passthrough_start - 1, page_flags);
534          }
535          page_set_flags(passthrough_start, passthrough_last,
536                         page_flags | PAGE_PASSTHROUGH);
537          if (passthrough_last < last) {
538              page_set_flags(passthrough_last + 1, last, page_flags);
539          }
540      }
541      shm_region_rm_complete(start, last);
542      trace_target_mmap_complete(start);
543      if (qemu_loglevel_mask(CPU_LOG_PAGE)) {
544          FILE *f = qemu_log_trylock();
545          if (f) {
546              fprintf(f, "page layout changed following mmap\n");
547              page_dump(f);
548              qemu_log_unlock(f);
549          }
550      }
551      return start;
552  }
553  
554  /*
555   * Special case host page size == target page size,
556   * where there are no edge conditions.
557   */
558  static abi_long mmap_h_eq_g(abi_ulong start, abi_ulong len,
559                              int host_prot, int flags, int page_flags,
560                              int fd, off_t offset)
561  {
562      void *p, *want_p = g2h_untagged(start);
563      abi_ulong last;
564  
565      p = mmap(want_p, len, host_prot, flags, fd, offset);
566      if (p == MAP_FAILED) {
567          return -1;
568      }
569      /* If the host kernel does not support MAP_FIXED_NOREPLACE, emulate. */
570      if ((flags & MAP_FIXED_NOREPLACE) && p != want_p) {
571          do_munmap(p, len);
572          errno = EEXIST;
573          return -1;
574      }
575  
576      start = h2g(p);
577      last = start + len - 1;
578      return mmap_end(start, last, start, last, flags, page_flags);
579  }
580  
581  /*
582   * Special case host page size < target page size.
583   *
584   * The two special cases are increased guest alignment, and mapping
585   * past the end of a file.
586   *
587   * When mapping files into a memory area larger than the file,
588   * accesses to pages beyond the file size will cause a SIGBUS.
589   *
590   * For example, if mmaping a file of 100 bytes on a host with 4K
591   * pages emulating a target with 8K pages, the target expects to
592   * be able to access the first 8K. But the host will trap us on
593   * any access beyond 4K.
594   *
595   * When emulating a target with a larger page-size than the hosts,
596   * we may need to truncate file maps at EOF and add extra anonymous
597   * pages up to the targets page boundary.
598   *
599   * This workaround only works for files that do not change.
600   * If the file is later extended (e.g. ftruncate), the SIGBUS
601   * vanishes and the proper behaviour is that changes within the
602   * anon page should be reflected in the file.
603   *
604   * However, this case is rather common with executable images,
605   * so the workaround is important for even trivial tests, whereas
606   * the mmap of of a file being extended is less common.
607   */
608  static abi_long mmap_h_lt_g(abi_ulong start, abi_ulong len, int host_prot,
609                              int mmap_flags, int page_flags, int fd,
610                              off_t offset, int host_page_size)
611  {
612      void *p, *want_p = g2h_untagged(start);
613      off_t fileend_adj = 0;
614      int flags = mmap_flags;
615      abi_ulong last, pass_last;
616  
617      if (!(flags & MAP_ANONYMOUS)) {
618          struct stat sb;
619  
620          if (fstat(fd, &sb) == -1) {
621              return -1;
622          }
623          if (offset >= sb.st_size) {
624              /*
625               * The entire map is beyond the end of the file.
626               * Transform it to an anonymous mapping.
627               */
628              flags |= MAP_ANONYMOUS;
629              fd = -1;
630              offset = 0;
631          } else if (offset + len > sb.st_size) {
632              /*
633               * A portion of the map is beyond the end of the file.
634               * Truncate the file portion of the allocation.
635               */
636              fileend_adj = offset + len - sb.st_size;
637          }
638      }
639  
640      if (flags & (MAP_FIXED | MAP_FIXED_NOREPLACE)) {
641          if (fileend_adj) {
642              p = mmap(want_p, len, host_prot, flags | MAP_ANONYMOUS, -1, 0);
643          } else {
644              p = mmap(want_p, len, host_prot, flags, fd, offset);
645          }
646          if (p != want_p) {
647              if (p != MAP_FAILED) {
648                  /* Host does not support MAP_FIXED_NOREPLACE: emulate. */
649                  do_munmap(p, len);
650                  errno = EEXIST;
651              }
652              return -1;
653          }
654  
655          if (fileend_adj) {
656              void *t = mmap(p, len - fileend_adj, host_prot,
657                             (flags & ~MAP_FIXED_NOREPLACE) | MAP_FIXED,
658                             fd, offset);
659  
660              if (t == MAP_FAILED) {
661                  int save_errno = errno;
662  
663                  /*
664                   * We failed a map over the top of the successful anonymous
665                   * mapping above. The only failure mode is running out of VMAs,
666                   * and there's nothing that we can do to detect that earlier.
667                   * If we have replaced an existing mapping with MAP_FIXED,
668                   * then we cannot properly recover.  It's a coin toss whether
669                   * it would be better to exit or continue here.
670                   */
671                  if (!(flags & MAP_FIXED_NOREPLACE) &&
672                      !page_check_range_empty(start, start + len - 1)) {
673                      qemu_log("QEMU target_mmap late failure: %s",
674                               strerror(save_errno));
675                  }
676  
677                  do_munmap(want_p, len);
678                  errno = save_errno;
679                  return -1;
680              }
681          }
682      } else {
683          size_t host_len, part_len;
684  
685          /*
686           * Take care to align the host memory.  Perform a larger anonymous
687           * allocation and extract the aligned portion.  Remap the file on
688           * top of that.
689           */
690          host_len = len + TARGET_PAGE_SIZE - host_page_size;
691          p = mmap(want_p, host_len, host_prot, flags | MAP_ANONYMOUS, -1, 0);
692          if (p == MAP_FAILED) {
693              return -1;
694          }
695  
696          part_len = (uintptr_t)p & (TARGET_PAGE_SIZE - 1);
697          if (part_len) {
698              part_len = TARGET_PAGE_SIZE - part_len;
699              do_munmap(p, part_len);
700              p += part_len;
701              host_len -= part_len;
702          }
703          if (len < host_len) {
704              do_munmap(p + len, host_len - len);
705          }
706  
707          if (!(flags & MAP_ANONYMOUS)) {
708              void *t = mmap(p, len - fileend_adj, host_prot,
709                             flags | MAP_FIXED, fd, offset);
710  
711              if (t == MAP_FAILED) {
712                  int save_errno = errno;
713                  do_munmap(p, len);
714                  errno = save_errno;
715                  return -1;
716              }
717          }
718  
719          start = h2g(p);
720      }
721  
722      last = start + len - 1;
723      if (fileend_adj) {
724          pass_last = ROUND_UP(last - fileend_adj, host_page_size) - 1;
725      } else {
726          pass_last = last;
727      }
728      return mmap_end(start, last, start, pass_last, mmap_flags, page_flags);
729  }
730  
731  /*
732   * Special case host page size > target page size.
733   *
734   * The two special cases are address and file offsets that are valid
735   * for the guest that cannot be directly represented by the host.
736   */
737  static abi_long mmap_h_gt_g(abi_ulong start, abi_ulong len,
738                              int target_prot, int host_prot,
739                              int flags, int page_flags, int fd,
740                              off_t offset, int host_page_size)
741  {
742      void *p, *want_p = g2h_untagged(start);
743      off_t host_offset = offset & -host_page_size;
744      abi_ulong last, real_start, real_last;
745      bool misaligned_offset = false;
746      size_t host_len;
747  
748      if (!(flags & (MAP_FIXED | MAP_FIXED_NOREPLACE))) {
749          /*
750           * Adjust the offset to something representable on the host.
751           */
752          host_len = len + offset - host_offset;
753          p = mmap(want_p, host_len, host_prot, flags, fd, host_offset);
754          if (p == MAP_FAILED) {
755              return -1;
756          }
757  
758          /* Update start to the file position at offset. */
759          p += offset - host_offset;
760  
761          start = h2g(p);
762          last = start + len - 1;
763          return mmap_end(start, last, start, last, flags, page_flags);
764      }
765  
766      if (!(flags & MAP_ANONYMOUS)) {
767          misaligned_offset = (start ^ offset) & (host_page_size - 1);
768  
769          /*
770           * The fallback for misalignment is a private mapping + read.
771           * This carries none of semantics required of MAP_SHARED.
772           */
773          if (misaligned_offset && (flags & MAP_TYPE) != MAP_PRIVATE) {
774              errno = EINVAL;
775              return -1;
776          }
777      }
778  
779      last = start + len - 1;
780      real_start = start & -host_page_size;
781      real_last = ROUND_UP(last, host_page_size) - 1;
782  
783      /*
784       * Handle the start and end of the mapping.
785       */
786      if (real_start < start) {
787          abi_ulong real_page_last = real_start + host_page_size - 1;
788          if (last <= real_page_last) {
789              /* Entire allocation a subset of one host page. */
790              if (!mmap_frag(real_start, start, last, target_prot,
791                             flags, fd, offset)) {
792                  return -1;
793              }
794              return mmap_end(start, last, -1, 0, flags, page_flags);
795          }
796  
797          if (!mmap_frag(real_start, start, real_page_last, target_prot,
798                         flags, fd, offset)) {
799              return -1;
800          }
801          real_start = real_page_last + 1;
802      }
803  
804      if (last < real_last) {
805          abi_ulong real_page_start = real_last - host_page_size + 1;
806          if (!mmap_frag(real_page_start, real_page_start, last,
807                         target_prot, flags, fd,
808                         offset + real_page_start - start)) {
809              return -1;
810          }
811          real_last = real_page_start - 1;
812      }
813  
814      if (real_start > real_last) {
815          return mmap_end(start, last, -1, 0, flags, page_flags);
816      }
817  
818      /*
819       * Handle the middle of the mapping.
820       */
821  
822      host_len = real_last - real_start + 1;
823      want_p += real_start - start;
824  
825      if (flags & MAP_ANONYMOUS) {
826          p = mmap(want_p, host_len, host_prot, flags, -1, 0);
827      } else if (!misaligned_offset) {
828          p = mmap(want_p, host_len, host_prot, flags, fd,
829                   offset + real_start - start);
830      } else {
831          p = mmap(want_p, host_len, host_prot | PROT_WRITE,
832                   flags | MAP_ANONYMOUS, -1, 0);
833      }
834      if (p != want_p) {
835          if (p != MAP_FAILED) {
836              do_munmap(p, host_len);
837              errno = EEXIST;
838          }
839          return -1;
840      }
841  
842      if (misaligned_offset) {
843          /* TODO: The read could be short. */
844          if (pread(fd, p, host_len, offset + real_start - start) != host_len) {
845              do_munmap(p, host_len);
846              return -1;
847          }
848          if (!(host_prot & PROT_WRITE)) {
849              mprotect(p, host_len, host_prot);
850          }
851      }
852  
853      return mmap_end(start, last, -1, 0, flags, page_flags);
854  }
855  
856  static abi_long target_mmap__locked(abi_ulong start, abi_ulong len,
857                                      int target_prot, int flags, int page_flags,
858                                      int fd, off_t offset)
859  {
860      int host_page_size = qemu_real_host_page_size();
861      int host_prot;
862  
863      /*
864       * For reserved_va, we are in full control of the allocation.
865       * Find a suitable hole and convert to MAP_FIXED.
866       */
867      if (reserved_va) {
868          if (flags & MAP_FIXED_NOREPLACE) {
869              /* Validate that the chosen range is empty. */
870              if (!page_check_range_empty(start, start + len - 1)) {
871                  errno = EEXIST;
872                  return -1;
873              }
874              flags = (flags & ~MAP_FIXED_NOREPLACE) | MAP_FIXED;
875          } else if (!(flags & MAP_FIXED)) {
876              abi_ulong real_start = start & -host_page_size;
877              off_t host_offset = offset & -host_page_size;
878              size_t real_len = len + offset - host_offset;
879              abi_ulong align = MAX(host_page_size, TARGET_PAGE_SIZE);
880  
881              start = mmap_find_vma(real_start, real_len, align);
882              if (start == (abi_ulong)-1) {
883                  errno = ENOMEM;
884                  return -1;
885              }
886              start += offset - host_offset;
887              flags |= MAP_FIXED;
888          }
889      }
890  
891      host_prot = target_to_host_prot(target_prot);
892  
893      if (host_page_size == TARGET_PAGE_SIZE) {
894          return mmap_h_eq_g(start, len, host_prot, flags,
895                             page_flags, fd, offset);
896      } else if (host_page_size < TARGET_PAGE_SIZE) {
897          return mmap_h_lt_g(start, len, host_prot, flags,
898                             page_flags, fd, offset, host_page_size);
899      } else {
900          return mmap_h_gt_g(start, len, target_prot, host_prot, flags,
901                             page_flags, fd, offset, host_page_size);
902      }
903  }
904  
905  /* NOTE: all the constants are the HOST ones */
906  abi_long target_mmap(abi_ulong start, abi_ulong len, int target_prot,
907                       int flags, int fd, off_t offset)
908  {
909      abi_long ret;
910      int page_flags;
911  
912      trace_target_mmap(start, len, target_prot, flags, fd, offset);
913  
914      if (!len) {
915          errno = EINVAL;
916          return -1;
917      }
918  
919      page_flags = validate_prot_to_pageflags(target_prot);
920      if (!page_flags) {
921          errno = EINVAL;
922          return -1;
923      }
924  
925      /* Also check for overflows... */
926      len = TARGET_PAGE_ALIGN(len);
927      if (!len || len != (size_t)len) {
928          errno = ENOMEM;
929          return -1;
930      }
931  
932      if (offset & ~TARGET_PAGE_MASK) {
933          errno = EINVAL;
934          return -1;
935      }
936      if (flags & (MAP_FIXED | MAP_FIXED_NOREPLACE)) {
937          if (start & ~TARGET_PAGE_MASK) {
938              errno = EINVAL;
939              return -1;
940          }
941          if (!guest_range_valid_untagged(start, len)) {
942              errno = ENOMEM;
943              return -1;
944          }
945      }
946  
947      mmap_lock();
948  
949      ret = target_mmap__locked(start, len, target_prot, flags,
950                                page_flags, fd, offset);
951  
952      mmap_unlock();
953  
954      /*
955       * If we're mapping shared memory, ensure we generate code for parallel
956       * execution and flush old translations.  This will work up to the level
957       * supported by the host -- anything that requires EXCP_ATOMIC will not
958       * be atomic with respect to an external process.
959       */
960      if (ret != -1 && (flags & MAP_TYPE) != MAP_PRIVATE) {
961          CPUState *cpu = thread_cpu;
962          if (!(cpu->tcg_cflags & CF_PARALLEL)) {
963              cpu->tcg_cflags |= CF_PARALLEL;
964              tb_flush(cpu);
965          }
966      }
967  
968      return ret;
969  }
970  
971  static int mmap_reserve_or_unmap(abi_ulong start, abi_ulong len)
972  {
973      int host_page_size = qemu_real_host_page_size();
974      abi_ulong real_start;
975      abi_ulong real_last;
976      abi_ulong real_len;
977      abi_ulong last;
978      abi_ulong a;
979      void *host_start;
980      int prot;
981  
982      last = start + len - 1;
983      real_start = start & -host_page_size;
984      real_last = ROUND_UP(last, host_page_size) - 1;
985  
986      /*
987       * If guest pages remain on the first or last host pages,
988       * adjust the deallocation to retain those guest pages.
989       * The single page special case is required for the last page,
990       * lest real_start overflow to zero.
991       */
992      if (real_last - real_start < host_page_size) {
993          prot = 0;
994          for (a = real_start; a < start; a += TARGET_PAGE_SIZE) {
995              prot |= page_get_flags(a);
996          }
997          for (a = last; a < real_last; a += TARGET_PAGE_SIZE) {
998              prot |= page_get_flags(a + 1);
999          }
1000          if (prot != 0) {
1001              return 0;
1002          }
1003      } else {
1004          for (prot = 0, a = real_start; a < start; a += TARGET_PAGE_SIZE) {
1005              prot |= page_get_flags(a);
1006          }
1007          if (prot != 0) {
1008              real_start += host_page_size;
1009          }
1010  
1011          for (prot = 0, a = last; a < real_last; a += TARGET_PAGE_SIZE) {
1012              prot |= page_get_flags(a + 1);
1013          }
1014          if (prot != 0) {
1015              real_last -= host_page_size;
1016          }
1017  
1018          if (real_last < real_start) {
1019              return 0;
1020          }
1021      }
1022  
1023      real_len = real_last - real_start + 1;
1024      host_start = g2h_untagged(real_start);
1025  
1026      return do_munmap(host_start, real_len);
1027  }
1028  
1029  int target_munmap(abi_ulong start, abi_ulong len)
1030  {
1031      int ret;
1032  
1033      trace_target_munmap(start, len);
1034  
1035      if (start & ~TARGET_PAGE_MASK) {
1036          errno = EINVAL;
1037          return -1;
1038      }
1039      len = TARGET_PAGE_ALIGN(len);
1040      if (len == 0 || !guest_range_valid_untagged(start, len)) {
1041          errno = EINVAL;
1042          return -1;
1043      }
1044  
1045      mmap_lock();
1046      ret = mmap_reserve_or_unmap(start, len);
1047      if (likely(ret == 0)) {
1048          page_set_flags(start, start + len - 1, 0);
1049          shm_region_rm_complete(start, start + len - 1);
1050      }
1051      mmap_unlock();
1052  
1053      return ret;
1054  }
1055  
1056  abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
1057                         abi_ulong new_size, unsigned long flags,
1058                         abi_ulong new_addr)
1059  {
1060      int prot;
1061      void *host_addr;
1062  
1063      if (!guest_range_valid_untagged(old_addr, old_size) ||
1064          ((flags & MREMAP_FIXED) &&
1065           !guest_range_valid_untagged(new_addr, new_size)) ||
1066          ((flags & MREMAP_MAYMOVE) == 0 &&
1067           !guest_range_valid_untagged(old_addr, new_size))) {
1068          errno = ENOMEM;
1069          return -1;
1070      }
1071  
1072      mmap_lock();
1073  
1074      if (flags & MREMAP_FIXED) {
1075          host_addr = mremap(g2h_untagged(old_addr), old_size, new_size,
1076                             flags, g2h_untagged(new_addr));
1077  
1078          if (reserved_va && host_addr != MAP_FAILED) {
1079              /*
1080               * If new and old addresses overlap then the above mremap will
1081               * already have failed with EINVAL.
1082               */
1083              mmap_reserve_or_unmap(old_addr, old_size);
1084          }
1085      } else if (flags & MREMAP_MAYMOVE) {
1086          abi_ulong mmap_start;
1087  
1088          mmap_start = mmap_find_vma(0, new_size, TARGET_PAGE_SIZE);
1089  
1090          if (mmap_start == -1) {
1091              errno = ENOMEM;
1092              host_addr = MAP_FAILED;
1093          } else {
1094              host_addr = mremap(g2h_untagged(old_addr), old_size, new_size,
1095                                 flags | MREMAP_FIXED,
1096                                 g2h_untagged(mmap_start));
1097              if (reserved_va) {
1098                  mmap_reserve_or_unmap(old_addr, old_size);
1099              }
1100          }
1101      } else {
1102          int page_flags = 0;
1103          if (reserved_va && old_size < new_size) {
1104              abi_ulong addr;
1105              for (addr = old_addr + old_size;
1106                   addr < old_addr + new_size;
1107                   addr++) {
1108                  page_flags |= page_get_flags(addr);
1109              }
1110          }
1111          if (page_flags == 0) {
1112              host_addr = mremap(g2h_untagged(old_addr),
1113                                 old_size, new_size, flags);
1114  
1115              if (host_addr != MAP_FAILED) {
1116                  /* Check if address fits target address space */
1117                  if (!guest_range_valid_untagged(h2g(host_addr), new_size)) {
1118                      /* Revert mremap() changes */
1119                      host_addr = mremap(g2h_untagged(old_addr),
1120                                         new_size, old_size, flags);
1121                      errno = ENOMEM;
1122                      host_addr = MAP_FAILED;
1123                  } else if (reserved_va && old_size > new_size) {
1124                      mmap_reserve_or_unmap(old_addr + old_size,
1125                                            old_size - new_size);
1126                  }
1127              }
1128          } else {
1129              errno = ENOMEM;
1130              host_addr = MAP_FAILED;
1131          }
1132      }
1133  
1134      if (host_addr == MAP_FAILED) {
1135          new_addr = -1;
1136      } else {
1137          new_addr = h2g(host_addr);
1138          prot = page_get_flags(old_addr);
1139          page_set_flags(old_addr, old_addr + old_size - 1, 0);
1140          shm_region_rm_complete(old_addr, old_addr + old_size - 1);
1141          page_set_flags(new_addr, new_addr + new_size - 1,
1142                         prot | PAGE_VALID | PAGE_RESET);
1143          shm_region_rm_complete(new_addr, new_addr + new_size - 1);
1144      }
1145      mmap_unlock();
1146      return new_addr;
1147  }
1148  
1149  abi_long target_madvise(abi_ulong start, abi_ulong len_in, int advice)
1150  {
1151      abi_ulong len;
1152      int ret = 0;
1153  
1154      if (start & ~TARGET_PAGE_MASK) {
1155          return -TARGET_EINVAL;
1156      }
1157      if (len_in == 0) {
1158          return 0;
1159      }
1160      len = TARGET_PAGE_ALIGN(len_in);
1161      if (len == 0 || !guest_range_valid_untagged(start, len)) {
1162          return -TARGET_EINVAL;
1163      }
1164  
1165      /* Translate for some architectures which have different MADV_xxx values */
1166      switch (advice) {
1167      case TARGET_MADV_DONTNEED:      /* alpha */
1168          advice = MADV_DONTNEED;
1169          break;
1170      case TARGET_MADV_WIPEONFORK:    /* parisc */
1171          advice = MADV_WIPEONFORK;
1172          break;
1173      case TARGET_MADV_KEEPONFORK:    /* parisc */
1174          advice = MADV_KEEPONFORK;
1175          break;
1176      /* we do not care about the other MADV_xxx values yet */
1177      }
1178  
1179      /*
1180       * Most advice values are hints, so ignoring and returning success is ok.
1181       *
1182       * However, some advice values such as MADV_DONTNEED, MADV_WIPEONFORK and
1183       * MADV_KEEPONFORK are not hints and need to be emulated.
1184       *
1185       * A straight passthrough for those may not be safe because qemu sometimes
1186       * turns private file-backed mappings into anonymous mappings.
1187       * If all guest pages have PAGE_PASSTHROUGH set, mappings have the
1188       * same semantics for the host as for the guest.
1189       *
1190       * We pass through MADV_WIPEONFORK and MADV_KEEPONFORK if possible and
1191       * return failure if not.
1192       *
1193       * MADV_DONTNEED is passed through as well, if possible.
1194       * If passthrough isn't possible, we nevertheless (wrongly!) return
1195       * success, which is broken but some userspace programs fail to work
1196       * otherwise. Completely implementing such emulation is quite complicated
1197       * though.
1198       */
1199      mmap_lock();
1200      switch (advice) {
1201      case MADV_WIPEONFORK:
1202      case MADV_KEEPONFORK:
1203          ret = -EINVAL;
1204          /* fall through */
1205      case MADV_DONTNEED:
1206          if (page_check_range(start, len, PAGE_PASSTHROUGH)) {
1207              ret = get_errno(madvise(g2h_untagged(start), len, advice));
1208              if ((advice == MADV_DONTNEED) && (ret == 0)) {
1209                  page_reset_target_data(start, start + len - 1);
1210              }
1211          }
1212      }
1213      mmap_unlock();
1214  
1215      return ret;
1216  }
1217  
1218  #ifndef TARGET_FORCE_SHMLBA
1219  /*
1220   * For most architectures, SHMLBA is the same as the page size;
1221   * some architectures have larger values, in which case they should
1222   * define TARGET_FORCE_SHMLBA and provide a target_shmlba() function.
1223   * This corresponds to the kernel arch code defining __ARCH_FORCE_SHMLBA
1224   * and defining its own value for SHMLBA.
1225   *
1226   * The kernel also permits SHMLBA to be set by the architecture to a
1227   * value larger than the page size without setting __ARCH_FORCE_SHMLBA;
1228   * this means that addresses are rounded to the large size if
1229   * SHM_RND is set but addresses not aligned to that size are not rejected
1230   * as long as they are at least page-aligned. Since the only architecture
1231   * which uses this is ia64 this code doesn't provide for that oddity.
1232   */
1233  static inline abi_ulong target_shmlba(CPUArchState *cpu_env)
1234  {
1235      return TARGET_PAGE_SIZE;
1236  }
1237  #endif
1238  
1239  #if defined(__arm__) || defined(__mips__) || defined(__sparc__)
1240  #define HOST_FORCE_SHMLBA 1
1241  #else
1242  #define HOST_FORCE_SHMLBA 0
1243  #endif
1244  
1245  abi_ulong target_shmat(CPUArchState *cpu_env, int shmid,
1246                         abi_ulong shmaddr, int shmflg)
1247  {
1248      CPUState *cpu = env_cpu(cpu_env);
1249      struct shmid_ds shm_info;
1250      int ret;
1251      int h_pagesize;
1252      int t_shmlba, h_shmlba, m_shmlba;
1253      size_t t_len, h_len, m_len;
1254  
1255      /* shmat pointers are always untagged */
1256  
1257      /*
1258       * Because we can't use host shmat() unless the address is sufficiently
1259       * aligned for the host, we'll need to check both.
1260       * TODO: Could be fixed with softmmu.
1261       */
1262      t_shmlba = target_shmlba(cpu_env);
1263      h_pagesize = qemu_real_host_page_size();
1264      h_shmlba = (HOST_FORCE_SHMLBA ? SHMLBA : h_pagesize);
1265      m_shmlba = MAX(t_shmlba, h_shmlba);
1266  
1267      if (shmaddr) {
1268          if (shmaddr & (m_shmlba - 1)) {
1269              if (shmflg & SHM_RND) {
1270                  /*
1271                   * The guest is allowing the kernel to round the address.
1272                   * Assume that the guest is ok with us rounding to the
1273                   * host required alignment too.  Anyway if we don't, we'll
1274                   * get an error from the kernel.
1275                   */
1276                  shmaddr &= ~(m_shmlba - 1);
1277                  if (shmaddr == 0 && (shmflg & SHM_REMAP)) {
1278                      return -TARGET_EINVAL;
1279                  }
1280              } else {
1281                  int require = TARGET_PAGE_SIZE;
1282  #ifdef TARGET_FORCE_SHMLBA
1283                  require = t_shmlba;
1284  #endif
1285                  /*
1286                   * Include host required alignment, as otherwise we cannot
1287                   * use host shmat at all.
1288                   */
1289                  require = MAX(require, h_shmlba);
1290                  if (shmaddr & (require - 1)) {
1291                      return -TARGET_EINVAL;
1292                  }
1293              }
1294          }
1295      } else {
1296          if (shmflg & SHM_REMAP) {
1297              return -TARGET_EINVAL;
1298          }
1299      }
1300      /* All rounding now manually concluded. */
1301      shmflg &= ~SHM_RND;
1302  
1303      /* Find out the length of the shared memory segment. */
1304      ret = get_errno(shmctl(shmid, IPC_STAT, &shm_info));
1305      if (is_error(ret)) {
1306          /* can't get length, bail out */
1307          return ret;
1308      }
1309      t_len = TARGET_PAGE_ALIGN(shm_info.shm_segsz);
1310      h_len = ROUND_UP(shm_info.shm_segsz, h_pagesize);
1311      m_len = MAX(t_len, h_len);
1312  
1313      if (!guest_range_valid_untagged(shmaddr, m_len)) {
1314          return -TARGET_EINVAL;
1315      }
1316  
1317      WITH_MMAP_LOCK_GUARD() {
1318          bool mapped = false;
1319          void *want, *test;
1320          abi_ulong last;
1321  
1322          if (!shmaddr) {
1323              shmaddr = mmap_find_vma(0, m_len, m_shmlba);
1324              if (shmaddr == -1) {
1325                  return -TARGET_ENOMEM;
1326              }
1327              mapped = !reserved_va;
1328          } else if (shmflg & SHM_REMAP) {
1329              /*
1330               * If host page size > target page size, the host shmat may map
1331               * more memory than the guest expects.  Reject a mapping that
1332               * would replace memory in the unexpected gap.
1333               * TODO: Could be fixed with softmmu.
1334               */
1335              if (t_len < h_len &&
1336                  !page_check_range_empty(shmaddr + t_len,
1337                                          shmaddr + h_len - 1)) {
1338                  return -TARGET_EINVAL;
1339              }
1340          } else {
1341              if (!page_check_range_empty(shmaddr, shmaddr + m_len - 1)) {
1342                  return -TARGET_EINVAL;
1343              }
1344          }
1345  
1346          /* All placement is now complete. */
1347          want = (void *)g2h_untagged(shmaddr);
1348  
1349          /*
1350           * Map anonymous pages across the entire range, then remap with
1351           * the shared memory.  This is required for a number of corner
1352           * cases for which host and guest page sizes differ.
1353           */
1354          if (h_len != t_len) {
1355              int mmap_p = PROT_READ | (shmflg & SHM_RDONLY ? 0 : PROT_WRITE);
1356              int mmap_f = MAP_PRIVATE | MAP_ANONYMOUS
1357                         | (reserved_va || mapped || (shmflg & SHM_REMAP)
1358                            ? MAP_FIXED : MAP_FIXED_NOREPLACE);
1359  
1360              test = mmap(want, m_len, mmap_p, mmap_f, -1, 0);
1361              if (unlikely(test != want)) {
1362                  /* shmat returns EINVAL not EEXIST like mmap. */
1363                  ret = (test == MAP_FAILED && errno != EEXIST
1364                         ? get_errno(-1) : -TARGET_EINVAL);
1365                  if (mapped) {
1366                      do_munmap(want, m_len);
1367                  }
1368                  return ret;
1369              }
1370              mapped = true;
1371          }
1372  
1373          if (reserved_va || mapped) {
1374              shmflg |= SHM_REMAP;
1375          }
1376          test = shmat(shmid, want, shmflg);
1377          if (test == MAP_FAILED) {
1378              ret = get_errno(-1);
1379              if (mapped) {
1380                  do_munmap(want, m_len);
1381              }
1382              return ret;
1383          }
1384          assert(test == want);
1385  
1386          last = shmaddr + m_len - 1;
1387          page_set_flags(shmaddr, last,
1388                         PAGE_VALID | PAGE_RESET | PAGE_READ |
1389                         (shmflg & SHM_RDONLY ? 0 : PAGE_WRITE) |
1390                         (shmflg & SHM_EXEC ? PAGE_EXEC : 0));
1391  
1392          shm_region_rm_complete(shmaddr, last);
1393          shm_region_add(shmaddr, last);
1394      }
1395  
1396      /*
1397       * We're mapping shared memory, so ensure we generate code for parallel
1398       * execution and flush old translations.  This will work up to the level
1399       * supported by the host -- anything that requires EXCP_ATOMIC will not
1400       * be atomic with respect to an external process.
1401       */
1402      if (!(cpu->tcg_cflags & CF_PARALLEL)) {
1403          cpu->tcg_cflags |= CF_PARALLEL;
1404          tb_flush(cpu);
1405      }
1406  
1407      if (qemu_loglevel_mask(CPU_LOG_PAGE)) {
1408          FILE *f = qemu_log_trylock();
1409          if (f) {
1410              fprintf(f, "page layout changed following shmat\n");
1411              page_dump(f);
1412              qemu_log_unlock(f);
1413          }
1414      }
1415      return shmaddr;
1416  }
1417  
1418  abi_long target_shmdt(abi_ulong shmaddr)
1419  {
1420      abi_long rv;
1421  
1422      /* shmdt pointers are always untagged */
1423  
1424      WITH_MMAP_LOCK_GUARD() {
1425          abi_ulong last = shm_region_find(shmaddr);
1426          if (last == 0) {
1427              return -TARGET_EINVAL;
1428          }
1429  
1430          rv = get_errno(shmdt(g2h_untagged(shmaddr)));
1431          if (rv == 0) {
1432              abi_ulong size = last - shmaddr + 1;
1433  
1434              page_set_flags(shmaddr, last, 0);
1435              shm_region_rm_complete(shmaddr, last);
1436              mmap_reserve_or_unmap(shmaddr, size);
1437          }
1438      }
1439      return rv;
1440  }
1441