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#include <asm/cpufeature.h>
   8
   9static int disable_nx;
  10
  11/*
  12 * noexec = on|off
  13 *
  14 * Control non-executable mappings for processes.
  15 *
  16 * on      Enable
  17 * off     Disable
  18 */
  19static int __init noexec_setup(char *str)
  20{
  21        if (!str)
  22                return -EINVAL;
  23        if (!strncmp(str, "on", 2)) {
  24                disable_nx = 0;
  25        } else if (!strncmp(str, "off", 3)) {
  26                disable_nx = 1;
  27        }
  28        x86_configure_nx();
  29        return 0;
  30}
  31early_param("noexec", noexec_setup);
  32
  33void x86_configure_nx(void)
  34{
  35        if (boot_cpu_has(X86_FEATURE_NX) && !disable_nx)
  36                __supported_pte_mask |= _PAGE_NX;
  37        else
  38                __supported_pte_mask &= ~_PAGE_NX;
  39}
  40
  41void __init x86_report_nx(void)
  42{
  43        if (!boot_cpu_has(X86_FEATURE_NX)) {
  44                printk(KERN_NOTICE "Notice: NX (Execute Disable) protection "
  45                       "missing in CPU!\n");
  46        } else {
  47#if defined(CONFIG_X86_64) || defined(CONFIG_X86_PAE)
  48                if (disable_nx) {
  49                        printk(KERN_INFO "NX (Execute Disable) protection: "
  50                               "disabled by kernel command line option\n");
  51                } else {
  52                        printk(KERN_INFO "NX (Execute Disable) protection: "
  53                               "active\n");
  54                }
  55#else
  56                /* 32bit non-PAE kernel, NX cannot be used */
  57                printk(KERN_NOTICE "Notice: NX (Execute Disable) protection "
  58                       "cannot be enabled: non-PAE kernel!\n");
  59#endif
  60        }
  61}
  62