arm64: add KASAN support

This patch adds arch specific code for kernel address sanitizer
(see Documentation/kasan.txt).

1/8 of kernel addresses reserved for shadow memory. There was no
big enough hole for this, so virtual addresses for shadow were
stolen from vmalloc area.

At early boot stage the whole shadow region populated with just
one physical page (kasan_zero_page). Later, this page reused
as readonly zero shadow for some memory that KASan currently
don't track (vmalloc).
After mapping the physical memory, pages for shadow memory are
allocated and mapped.

Functions like memset/memmove/memcpy do a lot of memory accesses.
If bad pointer passed to one of these function it is important
to catch this. Compiler's instrumentation cannot do this since
these functions are written in assembly.
KASan replaces memory functions with manually instrumented variants.
Original functions declared as weak symbols so strong definitions
in mm/kasan/kasan.c could replace them. Original functions have aliases
with '__' prefix in name, so we could call non-instrumented variant
if needed.
Some files built without kasan instrumentation (e.g. mm/slub.c).
Original mem* function replaced (via #define) with prefixed variants
to disable memory access checks for such files.

Signed-off-by: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Tested-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

16 files changed, 277 insertions, 5 deletions

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 1b35bdbd5d74..2782c1189208 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -48,6 +48,7 @@ config ARM64
 	select HAVE_ARCH_AUDITSYSCALL
 	select HAVE_ARCH_BITREVERSE
 	select HAVE_ARCH_JUMP_LABEL
+	select HAVE_ARCH_KASAN if SPARSEMEM_VMEMMAP
 	select HAVE_ARCH_KGDB
 	select HAVE_ARCH_SECCOMP_FILTER
 	select HAVE_ARCH_TRACEHOOK
diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index f9914d7c1bb0..f41c6761ec36 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -55,6 +55,13 @@ else
 TEXT_OFFSET := 0x00080000
 endif
 
+# KASAN_SHADOW_OFFSET = VA_START + (1 << (VA_BITS - 3)) - (1 << 61)
+# in 32-bit arithmetic
+KASAN_SHADOW_OFFSET := $(shell printf "0x%08x00000000\n" $$(( \
+			(0xffffffff & (-1 << ($(CONFIG_ARM64_VA_BITS) - 32))) \
+			+ (1 << ($(CONFIG_ARM64_VA_BITS) - 32 - 3)) \
+			- (1 << (64 - 32 - 3)) )) )
+
 export	TEXT_OFFSET GZFLAGS
 
 core-y		+= arch/arm64/kernel/ arch/arm64/mm/
diff --git a/arch/arm64/include/asm/kasan.h b/arch/arm64/include/asm/kasan.h
new file mode 100644
index 000000000000..71dfe14acdca
--- /dev/null
+++ b/arch/arm64/include/asm/kasan.h
@@ -0,0 +1,36 @@
+#ifndef __ASM_KASAN_H
+#define __ASM_KASAN_H
+
+#ifndef __ASSEMBLY__
+
+#ifdef CONFIG_KASAN
+
+#include <asm/memory.h>
+
+/*
+ * KASAN_SHADOW_START: beginning of the kernel virtual addresses.
+ * KASAN_SHADOW_END: KASAN_SHADOW_START + 1/8 of kernel virtual addresses.
+ */
+#define KASAN_SHADOW_START      (VA_START)
+#define KASAN_SHADOW_END        (KASAN_SHADOW_START + (1UL << (VA_BITS - 3)))
+
+/*
+ * This value is used to map an address to the corresponding shadow
+ * address by the following formula:
+ *     shadow_addr = (address >> 3) + KASAN_SHADOW_OFFSET;
+ *
+ * (1 << 61) shadow addresses - [KASAN_SHADOW_OFFSET,KASAN_SHADOW_END]
+ * cover all 64-bits of virtual addresses. So KASAN_SHADOW_OFFSET
+ * should satisfy the following equation:
+ *      KASAN_SHADOW_OFFSET = KASAN_SHADOW_END - (1ULL << 61)
+ */
+#define KASAN_SHADOW_OFFSET     (KASAN_SHADOW_END - (1ULL << (64 - 3)))
+
+void kasan_init(void);
+
+#else
+static inline void kasan_init(void) { }
+#endif
+
+#endif
+#endif
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 3f481ef42c07..e3b515fbf0c2 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -41,7 +41,14 @@
  *	fixed mappings and modules
  */
 #define VMEMMAP_SIZE		ALIGN((1UL << (VA_BITS - PAGE_SHIFT)) * sizeof(struct page), PUD_SIZE)
+
+#ifndef CONFIG_KASAN
 #define VMALLOC_START		(VA_START)
+#else
+#include <asm/kasan.h>
+#define VMALLOC_START		(KASAN_SHADOW_END + SZ_64K)
+#endif
+
 #define VMALLOC_END		(PAGE_OFFSET - PUD_SIZE - VMEMMAP_SIZE - SZ_64K)
 
 #define vmemmap			((struct page *)(VMALLOC_END + SZ_64K))
diff --git a/arch/arm64/include/asm/string.h b/arch/arm64/include/asm/string.h
index 64d2d4884a9d..2eb714c4639f 100644
--- a/arch/arm64/include/asm/string.h
+++ b/arch/arm64/include/asm/string.h
@@ -36,17 +36,33 @@ extern __kernel_size_t strnlen(const char *, __kernel_size_t);
 
 #define __HAVE_ARCH_MEMCPY
 extern void *memcpy(void *, const void *, __kernel_size_t);
+extern void *__memcpy(void *, const void *, __kernel_size_t);
 
 #define __HAVE_ARCH_MEMMOVE
 extern void *memmove(void *, const void *, __kernel_size_t);
+extern void *__memmove(void *, const void *, __kernel_size_t);
 
 #define __HAVE_ARCH_MEMCHR
 extern void *memchr(const void *, int, __kernel_size_t);
 
 #define __HAVE_ARCH_MEMSET
 extern void *memset(void *, int, __kernel_size_t);
+extern void *__memset(void *, int, __kernel_size_t);
 
 #define __HAVE_ARCH_MEMCMP
 extern int memcmp(const void *, const void *, size_t);
 
+
+#if defined(CONFIG_KASAN) && !defined(__SANITIZE_ADDRESS__)
+
+/*
+ * For files that are not instrumented (e.g. mm/slub.c) we
+ * should use not instrumented version of mem* functions.
+ */
+
+#define memcpy(dst, src, len) __memcpy(dst, src, len)
+#define memmove(dst, src, len) __memmove(dst, src, len)
+#define memset(s, c, n) __memset(s, c, n)
+#endif
+
 #endif
diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index 7b17f6245f1e..1b6bda2ff102 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -7,6 +7,8 @@ AFLAGS_head.o		:= -DTEXT_OFFSET=$(TEXT_OFFSET)
 CFLAGS_efi-stub.o 	:= -DTEXT_OFFSET=$(TEXT_OFFSET)
 CFLAGS_armv8_deprecated.o := -I$(src)
 
+KASAN_SANITIZE_efi-stub.o	:= n
+
 CFLAGS_REMOVE_ftrace.o = -pg
 CFLAGS_REMOVE_insn.o = -pg
 CFLAGS_REMOVE_return_address.o = -pg
diff --git a/arch/arm64/kernel/arm64ksyms.c b/arch/arm64/kernel/arm64ksyms.c
index a85843ddbde8..3b6d8cc9dfe0 100644
--- a/arch/arm64/kernel/arm64ksyms.c
+++ b/arch/arm64/kernel/arm64ksyms.c
@@ -51,6 +51,9 @@ EXPORT_SYMBOL(strnlen);
 EXPORT_SYMBOL(memset);
 EXPORT_SYMBOL(memcpy);
 EXPORT_SYMBOL(memmove);
+EXPORT_SYMBOL(__memset);
+EXPORT_SYMBOL(__memcpy);
+EXPORT_SYMBOL(__memmove);
 EXPORT_SYMBOL(memchr);
 EXPORT_SYMBOL(memcmp);
 
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 28a81e948df9..2a8c1d5b3fae 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -444,6 +444,9 @@ __mmap_switched:
 	str_l	x21, __fdt_pointer, x5		// Save FDT pointer
 	str_l	x24, memstart_addr, x6		// Save PHYS_OFFSET
 	mov	x29, #0
+#ifdef CONFIG_KASAN
+	bl	kasan_early_init
+#endif
 	b	start_kernel
 ENDPROC(__mmap_switched)
 
diff --git a/arch/arm64/kernel/image.h b/arch/arm64/kernel/image.h
index e083af0dd546..6eb8fee93321 100644
--- a/arch/arm64/kernel/image.h
+++ b/arch/arm64/kernel/image.h
@@ -80,6 +80,12 @@ __efistub_strcmp		= __pi_strcmp;
 __efistub_strncmp		= __pi_strncmp;
 __efistub___flush_dcache_area	= __pi___flush_dcache_area;
 
+#ifdef CONFIG_KASAN
+__efistub___memcpy		= __pi_memcpy;
+__efistub___memmove		= __pi_memmove;
+__efistub___memset		= __pi_memset;
+#endif
+
 __efistub__text			= _text;
 __efistub__end			= _end;
 __efistub__edata		= _edata;
diff --git a/arch/arm64/kernel/module.c b/arch/arm64/kernel/module.c
index 876eb8df50bf..f4bc779e62e8 100644
--- a/arch/arm64/kernel/module.c
+++ b/arch/arm64/kernel/module.c
@@ -21,6 +21,7 @@
 #include <linux/bitops.h>
 #include <linux/elf.h>
 #include <linux/gfp.h>
+#include <linux/kasan.h>
 #include <linux/kernel.h>
 #include <linux/mm.h>
 #include <linux/moduleloader.h>
@@ -34,9 +35,18 @@
 
 void *module_alloc(unsigned long size)
 {
-	return __vmalloc_node_range(size, 1, MODULES_VADDR, MODULES_END,
-				    GFP_KERNEL, PAGE_KERNEL_EXEC, 0,
-				    NUMA_NO_NODE, __builtin_return_address(0));
+	void *p;
+
+	p = __vmalloc_node_range(size, MODULE_ALIGN, MODULES_VADDR, MODULES_END,
+				GFP_KERNEL, PAGE_KERNEL_EXEC, 0,
+				NUMA_NO_NODE, __builtin_return_address(0));
+
+	if (p && (kasan_module_alloc(p, size) < 0)) {
+		vfree(p);
+		return NULL;
+	}
+
+	return p;
 }
 
 enum aarch64_reloc_op {
diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index 6bab21f84a9f..79df79a2ea61 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -54,6 +54,7 @@
 #include <asm/elf.h>
 #include <asm/cpufeature.h>
 #include <asm/cpu_ops.h>
+#include <asm/kasan.h>
 #include <asm/sections.h>
 #include <asm/setup.h>
 #include <asm/smp_plat.h>
@@ -434,6 +435,9 @@ void __init setup_arch(char **cmdline_p)
 
 	paging_init();
 	relocate_initrd();
+
+	kasan_init();
+
 	request_standard_resources();
 
 	early_ioremap_reset();
diff --git a/arch/arm64/lib/memcpy.S b/arch/arm64/lib/memcpy.S
index 36a6a62cf263..67613937711f 100644
--- a/arch/arm64/lib/memcpy.S
+++ b/arch/arm64/lib/memcpy.S
@@ -68,7 +68,10 @@
 	stp \ptr, \regB, [\regC], \val
 	.endm
 
+	.weak memcpy
+ENTRY(__memcpy)
 ENTRY(memcpy)
 #include "copy_template.S"
 	ret
 ENDPIPROC(memcpy)
+ENDPROC(__memcpy)
diff --git a/arch/arm64/lib/memmove.S b/arch/arm64/lib/memmove.S
index 68e2f2035e23..a5a4459013b1 100644
--- a/arch/arm64/lib/memmove.S
+++ b/arch/arm64/lib/memmove.S
@@ -57,12 +57,14 @@ C_h	.req	x12
 D_l	.req	x13
 D_h	.req	x14
 
+	.weak memmove
+ENTRY(__memmove)
 ENTRY(memmove)
 	cmp	dstin, src
-	b.lo	memcpy
+	b.lo	__memcpy
 	add	tmp1, src, count
 	cmp	dstin, tmp1
-	b.hs	memcpy		/* No overlap.  */
+	b.hs	__memcpy		/* No overlap.  */
 
 	add	dst, dstin, count
 	add	src, src, count
@@ -195,3 +197,4 @@ ENTRY(memmove)
 	b.ne	.Ltail63
 	ret
 ENDPIPROC(memmove)
+ENDPROC(__memmove)
diff --git a/arch/arm64/lib/memset.S b/arch/arm64/lib/memset.S
index 29f405f08792..f2670a9f218c 100644
--- a/arch/arm64/lib/memset.S
+++ b/arch/arm64/lib/memset.S
@@ -54,6 +54,8 @@ dst		.req	x8
 tmp3w		.req	w9
 tmp3		.req	x9
 
+	.weak memset
+ENTRY(__memset)
 ENTRY(memset)
 	mov	dst, dstin	/* Preserve return value.  */
 	and	A_lw, val, #255
@@ -214,3 +216,4 @@ ENTRY(memset)
 	b.ne	.Ltail_maybe_long
 	ret
 ENDPIPROC(memset)
+ENDPROC(__memset)
diff --git a/arch/arm64/mm/Makefile b/arch/arm64/mm/Makefile
index 773d37a14039..57f57fde5722 100644
--- a/arch/arm64/mm/Makefile
+++ b/arch/arm64/mm/Makefile
@@ -4,3 +4,6 @@ obj-y				:= dma-mapping.o extable.o fault.o init.o \
 				   context.o proc.o pageattr.o
 obj-$(CONFIG_HUGETLB_PAGE)	+= hugetlbpage.o
 obj-$(CONFIG_ARM64_PTDUMP)	+= dump.o
+
+obj-$(CONFIG_KASAN)		+= kasan_init.o
+KASAN_SANITIZE_kasan_init.o	:= n
diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
new file mode 100644
index 000000000000..b6a92f5dd568
--- /dev/null
+++ b/arch/arm64/mm/kasan_init.c
@@ -0,0 +1,165 @@
+/*
+ * This file contains kasan initialization code for ARM64.
+ *
+ * Copyright (c) 2015 Samsung Electronics Co., Ltd.
+ * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+
+#define pr_fmt(fmt) "kasan: " fmt
+#include <linux/kasan.h>
+#include <linux/kernel.h>
+#include <linux/memblock.h>
+#include <linux/start_kernel.h>
+
+#include <asm/page.h>
+#include <asm/pgalloc.h>
+#include <asm/pgtable.h>
+#include <asm/tlbflush.h>
+
+static pgd_t tmp_pg_dir[PTRS_PER_PGD] __initdata __aligned(PGD_SIZE);
+
+static void __init kasan_early_pte_populate(pmd_t *pmd, unsigned long addr,
+					unsigned long end)
+{
+	pte_t *pte;
+	unsigned long next;
+
+	if (pmd_none(*pmd))
+		pmd_populate_kernel(&init_mm, pmd, kasan_zero_pte);
+
+	pte = pte_offset_kernel(pmd, addr);
+	do {
+		next = addr + PAGE_SIZE;
+		set_pte(pte, pfn_pte(virt_to_pfn(kasan_zero_page),
+					PAGE_KERNEL));
+	} while (pte++, addr = next, addr != end && pte_none(*pte));
+}
+
+static void __init kasan_early_pmd_populate(pud_t *pud,
+					unsigned long addr,
+					unsigned long end)
+{
+	pmd_t *pmd;
+	unsigned long next;
+
+	if (pud_none(*pud))
+		pud_populate(&init_mm, pud, kasan_zero_pmd);
+
+	pmd = pmd_offset(pud, addr);
+	do {
+		next = pmd_addr_end(addr, end);
+		kasan_early_pte_populate(pmd, addr, next);
+	} while (pmd++, addr = next, addr != end && pmd_none(*pmd));
+}
+
+static void __init kasan_early_pud_populate(pgd_t *pgd,
+					unsigned long addr,
+					unsigned long end)
+{
+	pud_t *pud;
+	unsigned long next;
+
+	if (pgd_none(*pgd))
+		pgd_populate(&init_mm, pgd, kasan_zero_pud);
+
+	pud = pud_offset(pgd, addr);
+	do {
+		next = pud_addr_end(addr, end);
+		kasan_early_pmd_populate(pud, addr, next);
+	} while (pud++, addr = next, addr != end && pud_none(*pud));
+}
+
+static void __init kasan_map_early_shadow(void)
+{
+	unsigned long addr = KASAN_SHADOW_START;
+	unsigned long end = KASAN_SHADOW_END;
+	unsigned long next;
+	pgd_t *pgd;
+
+	pgd = pgd_offset_k(addr);
+	do {
+		next = pgd_addr_end(addr, end);
+		kasan_early_pud_populate(pgd, addr, next);
+	} while (pgd++, addr = next, addr != end);
+}
+
+void __init kasan_early_init(void)
+{
+	BUILD_BUG_ON(KASAN_SHADOW_OFFSET != KASAN_SHADOW_END - (1UL << 61));
+	BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_START, PGDIR_SIZE));
+	BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, PGDIR_SIZE));
+	kasan_map_early_shadow();
+}
+
+static void __init clear_pgds(unsigned long start,
+			unsigned long end)
+{
+	/*
+	 * Remove references to kasan page tables from
+	 * swapper_pg_dir. pgd_clear() can't be used
+	 * here because it's nop on 2,3-level pagetable setups
+	 */
+	for (; start < end; start += PGDIR_SIZE)
+		set_pgd(pgd_offset_k(start), __pgd(0));
+}
+
+static void __init cpu_set_ttbr1(unsigned long ttbr1)
+{
+	asm(
+	"	msr	ttbr1_el1, %0\n"
+	"	isb"
+	:
+	: "r" (ttbr1));
+}
+
+void __init kasan_init(void)
+{
+	struct memblock_region *reg;
+
+	/*
+	 * We are going to perform proper setup of shadow memory.
+	 * At first we should unmap early shadow (clear_pgds() call bellow).
+	 * However, instrumented code couldn't execute without shadow memory.
+	 * tmp_pg_dir used to keep early shadow mapped until full shadow
+	 * setup will be finished.
+	 */
+	memcpy(tmp_pg_dir, swapper_pg_dir, sizeof(tmp_pg_dir));
+	cpu_set_ttbr1(__pa(tmp_pg_dir));
+	flush_tlb_all();
+
+	clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);
+
+	kasan_populate_zero_shadow((void *)KASAN_SHADOW_START,
+			kasan_mem_to_shadow((void *)MODULES_VADDR));
+
+	for_each_memblock(memory, reg) {
+		void *start = (void *)__phys_to_virt(reg->base);
+		void *end = (void *)__phys_to_virt(reg->base + reg->size);
+
+		if (start >= end)
+			break;
+
+		/*
+		 * end + 1 here is intentional. We check several shadow bytes in
+		 * advance to slightly speed up fastpath. In some rare cases
+		 * we could cross boundary of mapped shadow, so we just map
+		 * some more here.
+		 */
+		vmemmap_populate((unsigned long)kasan_mem_to_shadow(start),
+				(unsigned long)kasan_mem_to_shadow(end) + 1,
+				pfn_to_nid(virt_to_pfn(start)));
+	}
+
+	memset(kasan_zero_page, 0, PAGE_SIZE);
+	cpu_set_ttbr1(__pa(swapper_pg_dir));
+	flush_tlb_all();
+
+	/* At this point kasan is fully initialized. Enable error messages */
+	init_task.kasan_depth = 0;
+	pr_info("KernelAddressSanitizer initialized\n");
+}