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 disable_nx is set, clear NX on all new mappings going forward. */
  36         if (disable_nx)
  37                 __supported_pte_mask &= ~_PAGE_NX;
  38 }
  39
  40 void __init x86_report_nx(void)
  41 {
  42         if (!boot_cpu_has(X86_FEATURE_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 }