os/busfault.c

   1 /*
   2  * Copyright © 2013 Keith Packard
   3  *
   4  * Permission to use, copy, modify, distribute, and sell this software and its
   5  * documentation for any purpose is hereby granted without fee, provided that
   6  * the above copyright notice appear in all copies and that both that copyright
   7  * notice and this permission notice appear in supporting documentation, and
   8  * that the name of the copyright holders not be used in advertising or
   9  * publicity pertaining to distribution of the software without specific,
  10  * written prior permission.  The copyright holders make no representations
  11  * about the suitability of this software for any purpose.  It is provided "as
  12  * is" without express or implied warranty.
  13  *
  14  * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
  15  * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
  16  * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
  17  * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
  18  * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
  19  * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
  20  * OF THIS SOFTWARE.
  21  */
  22
  23 #include <dix-config.h>
  24
  25 #include <X11/Xos.h>
  26 #include <X11/Xdefs.h>
  27
  28 #include "os/busfault.h"
  29
  30 #include "misc.h"
  31 #include <list.h>
  32 #include <stddef.h>
  33 #include <stdlib.h>
  34 #include <stdint.h>
  35 #include <sys/mman.h>
  36 #include <signal.h>
  37
  38 struct busfault {
  39     struct xorg_list    list;
  40
  41     void                *addr;
  42     size_t              size;
  43
  44     Bool                valid;
  45
  46     busfault_notify_ptr notify;
  47     void                *context;
  48 };
  49
  50 static Bool             busfaulted;
  51 static struct xorg_list busfaults;
  52
  53 struct busfault *
  54 busfault_register_mmap(void *addr, size_t size, busfault_notify_ptr notify, void *context)
  55 {
  56     struct busfault     *busfault;
  57
  58     busfault = calloc(1, sizeof (struct busfault));
  59     if (!busfault)
  60         return NULL;
  61
  62     busfault->addr = addr;
  63     busfault->size = size;
  64     busfault->notify = notify;
  65     busfault->context = context;
  66     busfault->valid = TRUE;
  67
  68     xorg_list_add(&busfault->list, &busfaults);
  69     return busfault;
  70 }
  71
  72 void
  73 busfault_unregister(struct busfault *busfault)
  74 {
  75     xorg_list_del(&busfault->list);
  76     free(busfault);
  77 }
  78
  79 void
  80 busfault_check(void)
  81 {
  82     struct busfault     *busfault, *tmp;
  83
  84     if (!busfaulted)
  85         return;
  86
  87     busfaulted = FALSE;
  88
  89     xorg_list_for_each_entry_safe(busfault, tmp, &busfaults, list) {
  90         if (!busfault->valid)
  91             (*busfault->notify)(busfault->context);
  92     }
  93 }
  94
  95 static void (*previous_busfault_sigaction)(int sig, siginfo_t *info, void *param);
  96
  97 static void
  98 busfault_sigaction(int sig, siginfo_t *info, void *param)
  99 {
 100     void                *fault = info->si_addr;
 101     struct busfault     *iter, *busfault = NULL;
 102     void                *new_addr;
 103
 104     /* Locate the faulting address in our list of shared segments
 105      */
 106     xorg_list_for_each_entry(iter, &busfaults, list) {
 107         if ((char *) iter->addr <= (char *) fault && (char *) fault < (char *) iter->addr + iter->size) {
 108             busfault = iter;
 109             break;
 110         }
 111     }
 112     if (!busfault)
 113         goto panic;
 114
 115     if (!busfault->valid)
 116         goto panic;
 117
 118     busfault->valid = FALSE;
 119     busfaulted = TRUE;
 120
 121     /* The client truncated the file; unmap the shared file, map
 122      * /dev/zero over that area and keep going
 123      */
 124
 125     new_addr = mmap(busfault->addr, busfault->size, PROT_READ|PROT_WRITE,
 126                     MAP_ANON|MAP_PRIVATE|MAP_FIXED, -1, 0);
 127
 128     if (new_addr == MAP_FAILED)
 129         goto panic;
 130
 131     return;
 132 panic:
 133     if (previous_busfault_sigaction)
 134         (*previous_busfault_sigaction)(sig, info, param);
 135     else
 136         FatalError("bus error\n");
 137 }
 138
 139 Bool
 140 busfault_init(void)
 141 {
 142     struct sigaction    act, old_act;
 143
 144     act.sa_sigaction = busfault_sigaction;
 145     act.sa_flags = SA_SIGINFO;
 146     sigemptyset(&act.sa_mask);
 147     if (sigaction(SIGBUS, &act, &old_act) < 0)
 148         return FALSE;
 149     previous_busfault_sigaction = old_act.sa_sigaction;
 150     xorg_list_init(&busfaults);
 151     return TRUE;
 152 }