IABSD.fr/xenocara/xserver/os/busfault.c

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• Author : matthieu
  Date : 2017-12-08 15:01:59
  Hash : 1a66cad3
  Message : Update to xserver 1.19.5. Tested by bru@, jsg@ and others

• xserver/os/busfault.c

• /*
   * Copyright © 2013 Keith Packard
   *
   * Permission to use, copy, modify, distribute, and sell this software and its
   * documentation for any purpose is hereby granted without fee, provided that
   * the above copyright notice appear in all copies and that both that copyright
   * notice and this permission notice appear in supporting documentation, and
   * that the name of the copyright holders not be used in advertising or
   * publicity pertaining to distribution of the software without specific,
   * written prior permission.  The copyright holders make no representations
   * about the suitability of this software for any purpose.  It is provided "as
   * is" without express or implied warranty.
   *
   * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
   * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
   * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
   * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
   * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
   * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
   * OF THIS SOFTWARE.
   */
  
  #ifdef HAVE_DIX_CONFIG_H
  #include <dix-config.h>
  #endif
  
  #include <X11/Xos.h>
  #include <X11/Xdefs.h>
  #include "misc.h"
  #include <busfault.h>
  #include <list.h>
  #include <stddef.h>
  #include <stdlib.h>
  #include <stdint.h>
  #include <sys/mman.h>
  #include <signal.h>
  
  struct busfault {
      struct xorg_list    list;
  
      void                *addr;
      size_t              size;
  
      Bool                valid;
  
      busfault_notify_ptr notify;
      void                *context;
  };
  
  static Bool             busfaulted;
  static struct xorg_list busfaults;
  
  struct busfault *
  busfault_register_mmap(void *addr, size_t size, busfault_notify_ptr notify, void *context)
  {
      struct busfault     *busfault;
  
      busfault = calloc(1, sizeof (struct busfault));
      if (!busfault)
          return NULL;
  
      busfault->addr = addr;
      busfault->size = size;
      busfault->notify = notify;
      busfault->context = context;
      busfault->valid = TRUE;
  
      xorg_list_add(&busfault->list, &busfaults);
      return busfault;
  }
  
  void
  busfault_unregister(struct busfault *busfault)
  {
      xorg_list_del(&busfault->list);
      free(busfault);
  }
  
  void
  busfault_check(void)
  {
      struct busfault     *busfault, *tmp;
  
      if (!busfaulted)
          return;
  
      busfaulted = FALSE;
  
      xorg_list_for_each_entry_safe(busfault, tmp, &busfaults, list) {
          if (!busfault->valid)
              (*busfault->notify)(busfault->context);
      }
  }
  
  static void (*previous_busfault_sigaction)(int sig, siginfo_t *info, void *param);
  
  static void
  busfault_sigaction(int sig, siginfo_t *info, void *param)
  {
      void                *fault = info->si_addr;
      struct busfault     *iter, *busfault = NULL;
      void                *new_addr;
  
      /* Locate the faulting address in our list of shared segments
       */
      xorg_list_for_each_entry(iter, &busfaults, list) {
  	if ((char *) iter->addr <= (char *) fault && (char *) fault < (char *) iter->addr + iter->size) {
  	    busfault = iter;
  	    break;
  	}
      }
      if (!busfault)
          goto panic;
  
      if (!busfault->valid)
          goto panic;
  
      busfault->valid = FALSE;
      busfaulted = TRUE;
  
      /* The client truncated the file; unmap the shared file, map
       * /dev/zero over that area and keep going
       */
  
      new_addr = mmap(busfault->addr, busfault->size, PROT_READ|PROT_WRITE,
                      MAP_ANON|MAP_PRIVATE|MAP_FIXED, -1, 0);
  
      if (new_addr == MAP_FAILED)
          goto panic;
  
      return;
  panic:
      if (previous_busfault_sigaction)
          (*previous_busfault_sigaction)(sig, info, param);
      else
          FatalError("bus error\n");
  }
  
  Bool
  busfault_init(void)
  {
      struct sigaction    act, old_act;
  
      act.sa_sigaction = busfault_sigaction;
      act.sa_flags = SA_SIGINFO;
      sigemptyset(&act.sa_mask);
      if (sigaction(SIGBUS, &act, &old_act) < 0)
          return FALSE;
      previous_busfault_sigaction = old_act.sa_sigaction;
      xorg_list_init(&busfaults);
      return TRUE;
  }