LXR linux/arch/x86/mm/setup

   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
  10static 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 */
  20static 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}
  32early_param("noexec", noexec_setup);
  33
  34void 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
  42void __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}
  63