1 files changed, 19 insertions, 69 deletions

diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c
index 325455d16dbc..1da3e25f9d9e 100644
--- a/arch/arm64/kernel/kaslr.c
+++ b/arch/arm64/kernel/kaslr.c
@@ -4,90 +4,40 @@
  */
 
 #include <linux/cache.h>
-#include <linux/crc32.h>
 #include <linux/init.h>
-#include <linux/libfdt.h>
-#include <linux/mm_types.h>
-#include <linux/sched.h>
-#include <linux/types.h>
-#include <linux/pgtable.h>
-#include <linux/random.h>
+#include <linux/printk.h>
 
-#include <asm/fixmap.h>
-#include <asm/kernel-pgtable.h>
+#include <asm/cpufeature.h>
 #include <asm/memory.h>
-#include <asm/mmu.h>
-#include <asm/sections.h>
-#include <asm/setup.h>
 
-u64 __ro_after_init module_alloc_base;
 u16 __initdata memstart_offset_seed;
 
-struct arm64_ftr_override kaslr_feature_override __initdata;
+bool __ro_after_init __kaslr_is_enabled = false;
 
-static int __init kaslr_init(void)
+void __init kaslr_init(void)
 {
-	u64 module_range;
-	u32 seed;
-
-	/*
-	 * Set a reasonable default for module_alloc_base in case
-	 * we end up running with module randomization disabled.
-	 */
-	module_alloc_base = (u64)_etext - MODULES_VSIZE;
-
-	if (kaslr_feature_override.val & kaslr_feature_override.mask & 0xf) {
+	if (kaslr_disabled_cmdline()) {
 		pr_info("KASLR disabled on command line\n");
-		return 0;
+		return;
 	}
 
-	if (!kaslr_offset()) {
-		pr_warn("KASLR disabled due to lack of seed\n");
-		return 0;
-	}
-
-	pr_info("KASLR enabled\n");
-
 	/*
-	 * KASAN without KASAN_VMALLOC does not expect the module region to
-	 * intersect the vmalloc region, since shadow memory is allocated for
-	 * each module at load time, whereas the vmalloc region will already be
-	 * shadowed by KASAN zero pages.
+	 * The KASLR offset modulo MIN_KIMG_ALIGN is taken from the physical
+	 * placement of the image rather than from the seed, so a displacement
+	 * of less than MIN_KIMG_ALIGN means that no seed was provided.
 	 */
-	BUILD_BUG_ON((IS_ENABLED(CONFIG_KASAN_GENERIC) ||
-	              IS_ENABLED(CONFIG_KASAN_SW_TAGS)) &&
-		     !IS_ENABLED(CONFIG_KASAN_VMALLOC));
-
-	seed = get_random_u32();
-
-	if (IS_ENABLED(CONFIG_RANDOMIZE_MODULE_REGION_FULL)) {
-		/*
-		 * Randomize the module region over a 2 GB window covering the
-		 * kernel. This reduces the risk of modules leaking information
-		 * about the address of the kernel itself, but results in
-		 * branches between modules and the core kernel that are
-		 * resolved via PLTs. (Branches between modules will be
-		 * resolved normally.)
-		 */
-		module_range = SZ_2G - (u64)(_end - _stext);
-		module_alloc_base = max((u64)_end - SZ_2G, (u64)MODULES_VADDR);
-	} else {
-		/*
-		 * Randomize the module region by setting module_alloc_base to
-		 * a PAGE_SIZE multiple in the range [_etext - MODULES_VSIZE,
-		 * _stext) . This guarantees that the resulting region still
-		 * covers [_stext, _etext], and that all relative branches can
-		 * be resolved without veneers unless this region is exhausted
-		 * and we fall back to a larger 2GB window in module_alloc()
-		 * when ARM64_MODULE_PLTS is enabled.
-		 */
-		module_range = MODULES_VSIZE - (u64)(_etext - _stext);
+	if (kaslr_offset() < MIN_KIMG_ALIGN) {
+		pr_warn("KASLR disabled due to lack of seed\n");
+		return;
 	}
 
-	/* use the lower 21 bits to randomize the base of the module region */
-	module_alloc_base += (module_range * (seed & ((1 << 21) - 1))) >> 21;
-	module_alloc_base &= PAGE_MASK;
+	pr_info("KASLR enabled\n");
+	__kaslr_is_enabled = true;
+}
 
+static int __init parse_nokaslr(char *unused)
+{
+	/* nokaslr param handling is done by early cpufeature code */
 	return 0;
 }
-subsys_initcall(kaslr_init)
+early_param("nokaslr", parse_nokaslr);