arch/x86/mm/setup_nx.c

   1 #include <linux/sched.h>
   2 #include <linux/spinlock.h>
   3 #include <linux/errno.h>
   4 #include <linux/init.h>
   5
   6 #include <asm/pgtable.h>
   7 #include <asm/proto.h>
   8
   9 static int disable_nx __cpuinitdata;
  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                 exec_shield = 0;
  28         }
  29         x86_configure_nx();
  30         return 0;
  31 }
  32 early_param("noexec", noexec_setup);
  33
  34 void __cpuinit x86_configure_nx(void)
  35 {
  36         if (cpu_has_nx && !disable_nx)
  37                 __supported_pte_mask |= _PAGE_NX;
  38         else
  39                 __supported_pte_mask &= ~_PAGE_NX;
  40 }
  41
  42 void __init x86_report_nx(void)
  43 {
  44         if (!cpu_has_nx) {
  45                 if (exec_shield)
  46                         printk(KERN_INFO "Using x86 segment limits to approximate NX protection\n");
  47                 else
  48
  49                 printk(KERN_NOTICE "Notice: NX (Execute Disable) protection "
  50                        "missing in CPU!\n");
  51         } else {
  52 #if defined(CONFIG_X86_64) || defined(CONFIG_X86_PAE)
  53                 if (disable_nx) {
  54                         printk(KERN_INFO "NX (Execute Disable) protection: "
  55                                "disabled by kernel command line option\n");
  56                 } else {
  57                         printk(KERN_INFO "NX (Execute Disable) protection: "
  58                                "active\n");
  59                 }
  60 #else
  61                 /* 32bit non-PAE kernel, NX cannot be used */
  62                 printk(KERN_NOTICE "Notice: NX (Execute Disable) protection "
  63                        "cannot be enabled: non-PAE kernel!\n");
  64 #endif
  65         }
  66 }