sync code with last improvements from OpenBSD

xserver/os/busfault.c

@@ -0,0 +1,152 @@
+/*
+ * 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;
+}