kern_memio - fix check for zerodev to fix memory mappings

* Change iszerodev() to check against a saaved cdev_t returned by
  the make_dev creating /dev/zero instead of relying on some
  major/minor magic.

* This fixes a problem when running mono, which caused a segfault
  on memset().

Reported-By: Hasso Tepper
Reported-By: Matthew Dillon

diff --git a/sys/kern/kern_memio.c b/sys/kern/kern_memio.c
index 7f8bb47..7ea25aa 100644 (file)
--- a/sys/kern/kern_memio.c
+++ b/sys/kern/kern_memio.c
@@ -90,6 +90,7 @@ static struct dev_ops mem_ops = {
 
 static int rand_bolt;
 static caddr_t zbuf;
+static cdev_t  zerodev = NULL;
 
 MALLOC_DEFINE(M_MEMDESC, "memdesc", "memory range descriptors");
 static int mem_ioctl (cdev_t, u_long, caddr_t, int, struct ucred *);
@@ -548,8 +549,7 @@ mmpoll(struct dev_poll_args *ap)
 int
 iszerodev(cdev_t dev)
 {
-       return ((major(dev) == mem_ops.head.maj)
-         && minor(dev) == 12);
+       return (zerodev != NULL);
 }
 
 static void
@@ -565,7 +565,7 @@ mem_drvinit(void *unused)
        make_dev(&mem_ops, 2, UID_ROOT, GID_WHEEL, 0666, "null");
        make_dev(&mem_ops, 3, UID_ROOT, GID_WHEEL, 0644, "random");
        make_dev(&mem_ops, 4, UID_ROOT, GID_WHEEL, 0644, "urandom");
-       make_dev(&mem_ops, 12, UID_ROOT, GID_WHEEL, 0666, "zero");
+       zerodev = make_dev(&mem_ops, 12, UID_ROOT, GID_WHEEL, 0666, "zero");
        make_dev(&mem_ops, 14, UID_ROOT, GID_WHEEL, 0600, "io");
 }