1 files changed, 18 insertions, 131 deletions

diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c
index 418b2bba1521..325455d16dbc 100644
--- a/arch/arm64/kernel/kaslr.c
+++ b/arch/arm64/kernel/kaslr.c
@@ -13,7 +13,6 @@
 #include <linux/pgtable.h>
 #include <linux/random.h>
 
-#include <asm/cacheflush.h>
 #include <asm/fixmap.h>
 #include <asm/kernel-pgtable.h>
 #include <asm/memory.h>
@@ -21,128 +20,45 @@
 #include <asm/sections.h>
 #include <asm/setup.h>
 
-enum kaslr_status {
-	KASLR_ENABLED,
-	KASLR_DISABLED_CMDLINE,
-	KASLR_DISABLED_NO_SEED,
-	KASLR_DISABLED_FDT_REMAP,
-};
-
-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)
+static int __init kaslr_init(void)
 {
-	void *fdt;
-	u64 seed, offset, mask, module_range;
-	unsigned long raw;
+	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;
-	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;
+		pr_info("KASLR disabled on command line\n");
 		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;
+	if (!kaslr_offset()) {
+		pr_warn("KASLR disabled due to lack of seed\n");
 		return 0;
 	}
 
+	pr_info("KASLR enabled\n");
+
 	/*
-	 * 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
+	 * 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.
 	 */
-	mask = ((1UL << (VA_BITS_MIN - 2)) - 1) & ~(SZ_2M - 1);
-	offset = BIT(VA_BITS_MIN - 3) + (seed & mask);
+	BUILD_BUG_ON((IS_ENABLED(CONFIG_KASAN_GENERIC) ||
+	              IS_ENABLED(CONFIG_KASAN_SW_TAGS)) &&
+		     !IS_ENABLED(CONFIG_KASAN_VMALLOC));
 
-	/* 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;
+	seed = get_random_u32();
 
 	if (IS_ENABLED(CONFIG_RANDOMIZE_MODULE_REGION_FULL)) {
 		/*
@@ -154,8 +70,7 @@ u64 __init kaslr_early_init(void)
 		 * resolved normally.)
 		 */
 		module_range = SZ_2G - (u64)(_end - _stext);
-		module_alloc_base = max((u64)_end + offset - SZ_2G,
-					(u64)MODULES_VADDR);
+		module_alloc_base = max((u64)_end - SZ_2G, (u64)MODULES_VADDR);
 	} else {
 		/*
 		 * Randomize the module region by setting module_alloc_base to
@@ -167,40 +82,12 @@ u64 __init kaslr_early_init(void)
 		 * when ARM64_MODULE_PLTS is enabled.
 		 */
 		module_range = MODULES_VSIZE - (u64)(_etext - _stext);
-		module_alloc_base = (u64)_etext + offset - MODULES_VSIZE;
 	}
 
 	/* 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;
-}
-
-static int __init kaslr_init(void)
-{
-	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;
-	}
-
 	return 0;
 }
-core_initcall(kaslr_init)
+subsys_initcall(kaslr_init)