arch/arm64/kernel/kaslr.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2016 Linaro Ltd <ard.biesheuvel@linaro.org>
   4  */
   5
   6 #include <linux/cache.h>
   7 #include <linux/init.h>
   8 #include <linux/printk.h>
   9
  10 #include <asm/cpufeature.h>
  11 #include <asm/memory.h>
  12
  13 u16 __initdata memstart_offset_seed;
  14
  15 bool __ro_after_init __kaslr_is_enabled = false;
  16
  17 void __init kaslr_init(void)
  18 {
  19         if (cpuid_feature_extract_unsigned_field(arm64_sw_feature_override.val &
  20                                                  arm64_sw_feature_override.mask,
  21                                                  ARM64_SW_FEATURE_OVERRIDE_NOKASLR)) {
  22                 pr_info("KASLR disabled on command line\n");
  23                 return;
  24         }
  25
  26         /*
  27          * The KASLR offset modulo MIN_KIMG_ALIGN is taken from the physical
  28          * placement of the image rather than from the seed, so a displacement
  29          * of less than MIN_KIMG_ALIGN means that no seed was provided.
  30          */
  31         if (kaslr_offset() < MIN_KIMG_ALIGN) {
  32                 pr_warn("KASLR disabled due to lack of seed\n");
  33                 return;
  34         }
  35
  36         pr_info("KASLR enabled\n");
  37         __kaslr_is_enabled = true;
  38 }