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 <[email protected]>
Tested-by: Linus Walleij <[email protected]>
Reviewed-by: Catalin Marinas <[email protected]>
Signed-off-by: Catalin Marinas <[email protected]>

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

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/

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

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))

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

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

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);
 

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)
 

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;

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 {

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();

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)

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)

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)

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