. new kernel call sysctl for generic unprivileged system operations;

now used for printing diagnostic messages through the kernel message
   buffer. this lets processes print diagnostics without sending messages
   to tty and log directly, simplifying the message protocol a lot and
   reducing difficulties with deadlocks and other situations in which
   diagnostics are blackholed (e.g. grants don't work). this makes
   DIAGNOSTICS(_S), ASYN_DIAGNOSTICS and DIAG_REPL obsolete, although tty
   and log still accept the codes for 'old' binaries. This also simplifies
   diagnostics in several servers and drivers - only tty needs its own
   kputc() now.
 . simplifications in vfs, and some effort to get the vnode references
   right (consistent) even during shutdown. m_mounted_on is now NULL
   for root filesystems (!) (the original and new root), a less awkward
   special case than 'm_mounted_on == m_root_node'. root now has exactly
   one reference, to root, if no files are open, just like all other
   filesystems. m_driver_e is unused.

kernel/table.c

@@ -83,9 +83,9 @@ PUBLIC char *t_stack[TOT_STACK_SPACE / sizeof(char *)];
  */
 #define FS_C SYS_KILL, SYS_VIRCOPY, SYS_SAFECOPYFROM, SYS_SAFECOPYTO, \
     SYS_VIRVCOPY, SYS_UMAP, SYS_GETINFO, SYS_EXIT, SYS_TIMES, SYS_SETALARM, \
-    SYS_PRIVCTL, SYS_TRACE , SYS_SETGRANT, SYS_PROFBUF
+    SYS_PRIVCTL, SYS_TRACE , SYS_SETGRANT, SYS_PROFBUF, SYS_SYSCTL
 #define DRV_C	FS_C, SYS_SEGCTL, SYS_IRQCTL, SYS_INT86, SYS_DEVIO, \
-	SYS_SDEVIO, SYS_VDEVIO, SYS_SETGRANT, SYS_PROFBUF
+	SYS_SDEVIO, SYS_VDEVIO, SYS_SETGRANT, SYS_PROFBUF, SYS_SYSCTL
 
 PRIVATE int
   fs_c[] = { FS_C },