root/arch/x86/mm/setup_nx.c

DEFINITIONS

1. noexec_setup
2. x86_configure_nx
3. x86_report_nx

   1 // SPDX-License-Identifier: GPL-2.0
   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 #include <asm/cpufeature.h>
   9 
  10 static int disable_nx;
  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                 disable_nx = 0;
  26         } else if (!strncmp(str, "off", 3)) {
  27                 disable_nx = 1;
  28         }
  29         x86_configure_nx();
  30         return 0;
  31 }
  32 early_param("noexec", noexec_setup);
  33 
  34 void x86_configure_nx(void)
  35 {
  36         if (boot_cpu_has(X86_FEATURE_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 (!boot_cpu_has(X86_FEATURE_NX)) {
  45                 printk(KERN_NOTICE "Notice: NX (Execute Disable) protection "
  46                        "missing in CPU!\n");
  47         } else {
  48 #if defined(CONFIG_X86_64) || defined(CONFIG_X86_PAE)
  49                 if (disable_nx) {
  50                         printk(KERN_INFO "NX (Execute Disable) protection: "
  51                                "disabled by kernel command line option\n");
  52                 } else {
  53                         printk(KERN_INFO "NX (Execute Disable) protection: "
  54                                "active\n");
  55                 }
  56 #else
  57                 /* 32bit non-PAE kernel, NX cannot be used */
  58                 printk(KERN_NOTICE "Notice: NX (Execute Disable) protection "
  59                        "cannot be enabled: non-PAE kernel!\n");
  60 #endif
  61         }
  62 }