7882 Add /dev/full , the always-full memory device
Reviewed by: Adam Stevko <adam.stevko@gmail.com>
Reviewed by: Toomas Soome <tsoome@me.com>

*** 23,32 ****
--- 23,33 ----
   * Use is subject to license terms.
   */
  
  /*
   * Copyright (c) 2015, Joyent, Inc.  All rights reserved.
+  * Copyright (c) 2017 James S Blachly, MD <james.blachly@gmail.com>
   */
  
  #ifndef _SYS_MEM_H
  #define _SYS_MEM_H
  
*** 43,52 ****
--- 44,54 ----
  #define M_MEM           0       /* /dev/mem - physical main memory */
  #define M_KMEM          1       /* /dev/kmem - virtual kernel memory */
  #define M_NULL          2       /* /dev/null - EOF & Rathole */
  #define M_ALLKMEM       3       /* /dev/allkmem - virtual kernel memory & I/O */
  #define M_ZERO          12      /* /dev/zero - source of private memory */
+ #define M_FULL          13      /* /dev/full - write always ret ENOSPC */
  
  /*
   * Private ioctl for libkvm: translate virtual address to physical address.
   */
  #define MEM_VTOP                (('M' << 8) | 0x01)