1 files changed, 18 insertions, 181 deletions

diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c
index cfa2cfde3019..c9503ed45a6c 100644
--- a/arch/arm64/kernel/kaslr.c
+++ b/arch/arm64/kernel/kaslr.c
@@ -4,201 +4,38 @@
  */
 
 #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/cacheflush.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>
 
-enum kaslr_status {
-	KASLR_ENABLED,
-	KASLR_DISABLED_CMDLINE,
-	KASLR_DISABLED_NO_SEED,
-	KASLR_DISABLED_FDT_REMAP,
-};
+bool __ro_after_init __kaslr_is_enabled = false;
 
-static enum kaslr_status __initdata kaslr_status;
-u64 __ro_after_init module_alloc_base;
-u16 __initdata memstart_offset_seed;
-
-static __init u64 get_kaslr_seed(void *fdt)
-{
-	int node, len;
-	fdt64_t *prop;
-	u64 ret;
-
-	node = fdt_path_offset(fdt, "/chosen");
-	if (node < 0)
-		return 0;
-
-	prop = fdt_getprop_w(fdt, node, "kaslr-seed", &len);
-	if (!prop || len != sizeof(u64))
-		return 0;
-
-	ret = fdt64_to_cpu(*prop);
-	*prop = 0;
-	return ret;
-}
-
-struct arm64_ftr_override kaslr_feature_override __initdata;
-
-/*
- * This routine will be executed with the kernel mapped at its default virtual
- * address, and if it returns successfully, the kernel will be remapped, and
- * start_kernel() will be executed from a randomized virtual offset. The
- * relocation will result in all absolute references (e.g., static variables
- * containing function pointers) to be reinitialized, and zero-initialized
- * .bss variables will be reset to 0.
- */
-u64 __init kaslr_early_init(void)
+void __init kaslr_init(void)
 {
-	void *fdt;
-	u64 seed, offset, mask, module_range;
-	unsigned long raw;
-
-	/*
-	 * 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;
-	dcache_clean_inval_poc((unsigned long)&module_alloc_base,
-			    (unsigned long)&module_alloc_base +
-				    sizeof(module_alloc_base));
-
-	/*
-	 * Try to map the FDT early. If this fails, we simply bail,
-	 * and proceed with KASLR disabled. We will make another
-	 * attempt at mapping the FDT in setup_machine()
-	 */
-	fdt = get_early_fdt_ptr();
-	if (!fdt) {
-		kaslr_status = KASLR_DISABLED_FDT_REMAP;
-		return 0;
-	}
-
-	/*
-	 * Retrieve (and wipe) the seed from the FDT
-	 */
-	seed = get_kaslr_seed(fdt);
-
-	/*
-	 * Check if 'nokaslr' appears on the command line, and
-	 * return 0 if that is the case.
-	 */
-	if (kaslr_feature_override.val & kaslr_feature_override.mask & 0xf) {
-		kaslr_status = KASLR_DISABLED_CMDLINE;
-		return 0;
-	}
-
-	/*
-	 * Mix in any entropy obtainable architecturally if enabled
-	 * and supported.
-	 */
-
-	if (arch_get_random_seed_long_early(&raw))
-		seed ^= raw;
-
-	if (!seed) {
-		kaslr_status = KASLR_DISABLED_NO_SEED;
-		return 0;
+	if (kaslr_disabled_cmdline()) {
+		pr_info("KASLR disabled on command line\n");
+		return;
 	}
 
 	/*
-	 * OK, so we are proceeding with KASLR enabled. Calculate a suitable
-	 * kernel image offset from the seed. Let's place the kernel in the
-	 * middle half of the VMALLOC area (VA_BITS_MIN - 2), and stay clear of
-	 * the lower and upper quarters to avoid colliding with other
-	 * allocations.
-	 * Even if we could randomize at page granularity for 16k and 64k pages,
-	 * let's always round to 2 MB so we don't interfere with the ability to
-	 * map using contiguous PTEs
+	 * 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.
 	 */
-	mask = ((1UL << (VA_BITS_MIN - 2)) - 1) & ~(SZ_2M - 1);
-	offset = BIT(VA_BITS_MIN - 3) + (seed & mask);
-
-	/* use the top 16 bits to randomize the linear region */
-	memstart_offset_seed = seed >> 48;
-
-	if (!IS_ENABLED(CONFIG_KASAN_VMALLOC) &&
-	    (IS_ENABLED(CONFIG_KASAN_GENERIC) ||
-	     IS_ENABLED(CONFIG_KASAN_SW_TAGS)))
-		/*
-		 * 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 is shadowed by KASAN zero pages. So keep modules
-		 * out of the vmalloc region if KASAN is enabled without
-		 * KASAN_VMALLOC, and put the kernel well within 4 GB of the
-		 * module region.
-		 */
-		return offset % SZ_2G;
-
-	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 + offset - 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.
-		 */
-		module_range = MODULES_VSIZE - (u64)(_etext - _stext);
-		module_alloc_base = (u64)_etext + offset - MODULES_VSIZE;
+	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;
-
-	dcache_clean_inval_poc((unsigned long)&module_alloc_base,
-			    (unsigned long)&module_alloc_base +
-				    sizeof(module_alloc_base));
-	dcache_clean_inval_poc((unsigned long)&memstart_offset_seed,
-			    (unsigned long)&memstart_offset_seed +
-				    sizeof(memstart_offset_seed));
-
-	return offset;
+	pr_info("KASLR enabled\n");
+	__kaslr_is_enabled = true;
 }
 
-static int __init kaslr_init(void)
+static int __init parse_nokaslr(char *unused)
 {
-	switch (kaslr_status) {
-	case KASLR_ENABLED:
-		pr_info("KASLR enabled\n");
-		break;
-	case KASLR_DISABLED_CMDLINE:
-		pr_info("KASLR disabled on command line\n");
-		break;
-	case KASLR_DISABLED_NO_SEED:
-		pr_warn("KASLR disabled due to lack of seed\n");
-		break;
-	case KASLR_DISABLED_FDT_REMAP:
-		pr_warn("KASLR disabled due to FDT remapping failure\n");
-		break;
-	}
-
+	/* nokaslr param handling is done by early cpufeature code */
 	return 0;
 }
-core_initcall(kaslr_init)
+early_param("nokaslr", parse_nokaslr);