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
   7int nx_enabled;
   8
   9#if defined(CONFIG_X86_64) || defined(CONFIG_X86_PAE)
  10static int disable_nx __cpuinitdata;
  11
  12/*
  13 * noexec = on|off
  14 *
  15 * Control non-executable mappings for processes.
  16 *
  17 * on      Enable
  18 * off     Disable
  19 */
  20static int __init noexec_setup(char *str)
  21{
  22        if (!str)
  23                return -EINVAL;
  24        if (!strncmp(str, "on", 2)) {
  25                __supported_pte_mask |= _PAGE_NX;
  26                disable_nx = 0;
  27        } else if (!strncmp(str, "off", 3)) {
  28                disable_nx = 1;
  29                __supported_pte_mask &= ~_PAGE_NX;
  30        }
  31        return 0;
  32}
  33early_param("noexec", noexec_setup);
  34#endif
  35
  36#ifdef CONFIG_X86_PAE
  37void __init set_nx(void)
  38{
  39        unsigned int v[4], l, h;
  40
  41        if (cpu_has_pae && (cpuid_eax(0x80000000) > 0x80000001)) {
  42                cpuid(0x80000001, &v[0], &v[1], &v[2], &v[3]);
  43
  44                if ((v[3] & (1 << 20)) && !disable_nx) {
  45                        rdmsr(MSR_EFER, l, h);
  46                        l |= EFER_NX;
  47                        wrmsr(MSR_EFER, l, h);
  48                        nx_enabled = 1;
  49                        __supported_pte_mask |= _PAGE_NX;
  50                }
  51        }
  52}
  53#else
  54void set_nx(void)
  55{
  56}
  57#endif
  58
  59#ifdef CONFIG_X86_64
  60void __cpuinit check_efer(void)
  61{
  62        unsigned long efer;
  63
  64        rdmsrl(MSR_EFER, efer);
  65        if (!(efer & EFER_NX) || disable_nx)
  66                __supported_pte_mask &= ~_PAGE_NX;
  67}
  68#endif
  69
  70