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 #include <asm/proto.h>
   7 #include <asm/cpufeature.h>
   8
   9 static 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  */
  19 static 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 }
  31 early_param("noexec", noexec_setup);
  32
  33 void 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
  41 void __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 }