[PATCH] Deprecate numerical sysctl

Deprecate the numerical sysctl name space. People can use /proc/sys
instead.

The numeric name space was never well maintained and especially
in distribution kernels is not very consistent (everybody has their
own extensions, conflicting with others). It's also a great
source of rejects when merging patches.  The name-based /proc/sys
is a much better interface for this, which people should use instead.

Discussion of this on l-k found no advocate for it, so it seems to not
be very popular anyways.

This patch deprecates numerical name space accesses to make it possible
to remove them in the future. The only exception is kernel.version,
which is used by glibc (this one has to be maintained forever)

include/linux/sysctl.h

@@ -6,16 +6,10 @@
  ****************************************************************
  ****************************************************************
  **
- **  WARNING:  
  **  The values in this file are exported to user space via 
- **  the sysctl() binary interface.  Do *NOT* change the 
- **  numbering of any existing values here, and do not change
- **  any numbers within any one set of values.  If you have
- **  to redefine an existing interface, use a new number for it.
- **  The kernel will then return ENOTDIR to any application using
- **  the old binary interface.
- **
- **  --sct
+ **  the sysctl() binary interface.  However this interface
+ **  is unstable and deprecated and will be removed in the future. 
+ **  For a stable interface use /proc/sys.
  **
  ****************************************************************
  ****************************************************************

kernel/sysctl.c

@@ -852,7 +852,16 @@ asmlinkage long sys_sysctl(struct __sysctl_args __user *args)
 
 	if (copy_from_user(&tmp, args, sizeof(tmp)))
 		return -EFAULT;
-		
+	
+	if (tmp.nlen != 2 || tmp.name[0] != CTL_KERN ||
+	    tmp.name[1] != KERN_VERSION) { 
+		int i;
+		printk(KERN_INFO "%s: numerical sysctl ", current->comm); 
+		for (i = 0; i < tmp.nlen; i++) 
+			printk("%d ", tmp.name[i]); 
+		printk("is obsolete.\n");
+	} 
+
 	lock_kernel();
 	error = do_sysctl(tmp.name, tmp.nlen, tmp.oldval, tmp.oldlenp,
 			  tmp.newval, tmp.newlen);