arch/x86/mm/setup_nx.c

   1 #include <linux/spinlock.h>
   2 #include <linux/errno.h>
   3 #include <linux/init.h>
   4
   5 #include <asm/pgtable.h>
   6
   7 int nx_enabled;
   8
   9 #if defined(CONFIG_X86_64) || defined(CONFIG_X86_PAE)
  10 static 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  */
  20 static 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 }
  33 early_param("noexec", noexec_setup);
  34 #endif
  35
  36 #ifdef CONFIG_X86_PAE
  37 void __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
  54 void set_nx(void)
  55 {
  56 }
  57 #endif
  58
  59 #ifdef CONFIG_X86_64
  60 void __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