LXR linux/arch/x86/mm/setup

   1#include <linux/spinlock.h>
   2#include <linux/errno.h>
   3#include <linux/init.h>
   4
   5#include <asm/pgtable.h>
   6#include <asm/proto.h>
   7
   8static int disable_nx;
   9
  10/*
  11 * noexec = on|off
  12 *
  13 * Control non-executable mappings for processes.
  14 *
  15 * on      Enable
  16 * off     Disable
  17 */
  18static int __init noexec_setup(char *str)
  19{
  20        if (!str)
  21                return -EINVAL;
  22        if (!strncmp(str, "on", 2)) {
  23                disable_nx = 0;
  24        } else if (!strncmp(str, "off", 3)) {
  25                disable_nx = 1;
  26        }
  27        x86_configure_nx();
  28        return 0;
  29}
  30early_param("noexec", noexec_setup);
  31
  32void x86_configure_nx(void)
  33{
  34        if (cpu_has_nx && !disable_nx)
  35                __supported_pte_mask |= _PAGE_NX;
  36        else
  37                __supported_pte_mask &= ~_PAGE_NX;
  38}
  39
  40void __init x86_report_nx(void)
  41{
  42        if (!cpu_has_nx) {
  43                printk(KERN_NOTICE "Notice: NX (Execute Disable) protection "
  44                       "missing in CPU!\n");
  45        } else {
  46#if defined(CONFIG_X86_64) || defined(CONFIG_X86_PAE)
  47                if (disable_nx) {
  48                        printk(KERN_INFO "NX (Execute Disable) protection: "
  49                               "disabled by kernel command line option\n");
  50                } else {
  51                        printk(KERN_INFO "NX (Execute Disable) protection: "
  52                               "active\n");
  53                }
  54#else
  55                /* 32bit non-PAE kernel, NX cannot be used */
  56                printk(KERN_NOTICE "Notice: NX (Execute Disable) protection "
  57                       "cannot be enabled: non-PAE kernel!\n");
  58#endif
  59        }
  60}
  61