document how malloc(0) blobbies are stored, and their character

src/lib/libc/stdlib/malloc.3

@@ -34,7 +34,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.\"	$OpenBSD: malloc.3,v 1.23 2001/11/05 21:31:21 millert Exp $
+.\"	$OpenBSD: malloc.3,v 1.24 2001/12/05 09:49:39 deraadt Exp $
 .\"
 .Dd August 27, 1996
 .Dt MALLOC 3
@@ -81,6 +81,11 @@ or larger, the memory returned will be page-aligned.
 Allocation of a zero size object returns a pointer to a zero size object.
 This zero size object is access protected, so any access to it will
 generate an exception (SIGSEGV).
+Many zero-sized objects can be placed consecutively in shared
+protected pages.
+The minimum size of the protection on each object is suitably aligned and
+sized as previously stated, but the protection may extend further depending
+on where in a protected zone the object lands.
 .Pp
 The
 .Fn calloc