rand(3): Fix up sranddev(3) a bit better.

In case we can't read /dev/random for the seed, try kern.random. If that
fails, use the getpid()/gettimeofday() xor. For the latter, remove the
usage of an uninitialized variable.

We should probably just abort() when kern.random can't be read.

Discussed-with: dillon

lib/libc/stdlib/rand.c

@@ -35,6 +35,7 @@
 #include "namespace.h"
 #include <sys/time.h>          /* for sranddev() */
 #include <sys/types.h>
+#include <sys/sysctl.h>
 #include <fcntl.h>             /* for sranddev() */
 #include <stdlib.h>
 #include <unistd.h>            /* for sranddev() */
@@ -115,12 +116,18 @@ sranddev(void)
 		_close(fd);
 	}
 
+	if (!done) {
+		size_t len = sizeof(next);
+
+		if (sysctlbyname("kern.random", &next, &len, NULL, 0) == 0)
+			done = 1;
+	}
+
 	if (!done) {
 		struct timeval tv;
-		unsigned long junk;	/* XXX left uninitialized on purpose */
 
 		gettimeofday(&tv, NULL);
-		srand((getpid() << 16) ^ tv.tv_sec ^ tv.tv_usec ^ junk);
+		srand((getpid() << 16) ^ tv.tv_sec ^ tv.tv_usec);
 	}
 }