[PATCH 2/5 v2] ARM: Replace memory functions for KASan

[Linus Walleij <linus.walleij@linaro.org>]

From: Andrey Ryabinin <aryabinin@virtuozzo.com>

Functions like memset()/memmove()/memcpy() do a lot of memory
accesses.

If a bad pointer is passed to one of these functions it is important
to catch this. Compiler instrumentation cannot do this since these
functions are written in assembly.

KASan replaces these memory functions with instrumented variants.

The original functions are declared as weak symbols so that
the strong definitions in mm/kasan/kasan.c can replace them.

The original functions have aliases with a '__' prefix in their
name, so we can call the non-instrumented variant if needed.

We must use __memcpy()/__memset() in place of memcpy()/memset()
when we copy .data to RAM and when we clear .bss, because
kasan_early_init cannot be called before the initialization of
.data and .bss.

For the kernel compression and EFI libstub we need to tag on
the -D__SANITIZE_ADDRESS__ CFLAG, which is unfortunate: this is
used only when building with KASan enabled.

When building with KASan, all mem*() functions such as memcpy()
etc are instrumented. However, code that disable KASan for an
entire directory with KASAN_SANITIZE := n in the Kconfig file will
run into problems if they try to use the mem*() functions, as the
define that guards the uninstrumented variants look like so:

  #if defined(CONFIG_KASAN) && !defined(__SANITIZE_ADDRESS__)
  (...)
  define memcpy(dst, src, len) __memcpy(dst, src, len)
  (...)

As you see, KASAN is enabled, but the compilation procedure
relies on the Makefile passing -fsanitize=kernel-address
to the compiler for each instrumented file so that in turn
__SANITIZE_ADDRESS__ gets set and these weakly defined functions
are usually replaced with instrumented KASan variants.

If KASAN is enabled but __SANITIZE_ADDRESS__ is not set,
i.e. -fsanitize is not passed, the idea is that these #defines
kick in and define e.g. memcpy() to __memcpy() - all good.

Uncompress and libstub uses memcpy(), disables KASan with
KASAN_SANITIZE := n so CONFIG_KASAN is defined, but not
__SANITIZE_ADDRESS__ and we get a compilation error unless
we patch in -D__SANITIZE_ADDRESS__ to these Makefiles.

Reported-by: Russell King - ARM Linux <linux@armlinux.org.uk>
Signed-off-by: Abbott Liu <liuwenliang@huawei.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
ChangeLog v1->v2:
- Move the hacks around __SANITIZE_ADDRESS__ into this file
- Edit the commit message
- Rebase on the other v2 patches
---
 arch/arm/boot/compressed/Makefile     |  2 ++
 arch/arm/include/asm/string.h         | 17 +++++++++++++++++
 arch/arm/kernel/head-common.S         |  4 ++--
 arch/arm/lib/memcpy.S                 |  3 +++
 arch/arm/lib/memmove.S                |  5 ++++-
 arch/arm/lib/memset.S                 |  3 +++
 drivers/firmware/efi/libstub/Makefile |  5 ++++-
 7 files changed, 35 insertions(+), 4 deletions(-)

diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
index abd6f3d5c2ba..9d0316876052 100644
--- a/arch/arm/boot/compressed/Makefile
+++ b/arch/arm/boot/compressed/Makefile
@@ -25,6 +25,8 @@ endif
 
 GCOV_PROFILE		:= n
 KASAN_SANITIZE		:= n
+# Make sure we get the uninstrumented __mem*() functions
+CFLAGS_KERNEL		:= -D__SANITIZE_ADDRESS__
 
 # Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
 KCOV_INSTRUMENT		:= n
diff --git a/arch/arm/include/asm/string.h b/arch/arm/include/asm/string.h
index 111a1d8a41dd..2e1dd7a0cf63 100644
--- a/arch/arm/include/asm/string.h
+++ b/arch/arm/include/asm/string.h
@@ -15,15 +15,18 @@ extern char * strchr(const char * s, int c);
 
 #define __HAVE_ARCH_MEMCPY
 extern void * memcpy(void *, const void *, __kernel_size_t);
+extern void *__memcpy(void *dest, const void *src, __kernel_size_t n);
 
 #define __HAVE_ARCH_MEMMOVE
 extern void * memmove(void *, const void *, __kernel_size_t);
+extern void *__memmove(void *dest, const void *src, __kernel_size_t n);
 
 #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 *s, int c, __kernel_size_t n);
 
 #define __HAVE_ARCH_MEMSET32
 extern void *__memset32(uint32_t *, uint32_t v, __kernel_size_t);
@@ -39,4 +42,18 @@ static inline void *memset64(uint64_t *p, uint64_t v, __kernel_size_t n)
 	return __memset64(p, v, n * 8, v >> 32);
 }
 
+
+
+#if defined(CONFIG_KASAN) && !defined(__SANITIZE_ADDRESS__)
+
+/*
+ * For files that are not instrumented (e.g. mm/slub.c) we
+ * must use non-instrumented versions of the 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/arm/kernel/head-common.S b/arch/arm/kernel/head-common.S
index 4a3982812a40..6840c7c60a85 100644
--- a/arch/arm/kernel/head-common.S
+++ b/arch/arm/kernel/head-common.S
@@ -95,7 +95,7 @@ __mmap_switched:
  THUMB(	ldmia	r4!, {r0, r1, r2, r3} )
  THUMB(	mov	sp, r3 )
 	sub	r2, r2, r1
-	bl	memcpy				@ copy .data to RAM
+	bl	__memcpy			@ copy .data to RAM
 #endif
 
    ARM(	ldmia	r4!, {r0, r1, sp} )
@@ -103,7 +103,7 @@ __mmap_switched:
  THUMB(	mov	sp, r3 )
 	sub	r2, r1, r0
 	mov	r1, #0
-	bl	memset				@ clear .bss
+	bl	__memset			@ clear .bss
 
 	ldmia	r4, {r0, r1, r2, r3}
 	str	r9, [r0]			@ Save processor ID
diff --git a/arch/arm/lib/memcpy.S b/arch/arm/lib/memcpy.S
index 09a333153dc6..ad4625d16e11 100644
--- a/arch/arm/lib/memcpy.S
+++ b/arch/arm/lib/memcpy.S
@@ -58,6 +58,8 @@
 
 /* Prototype: void *memcpy(void *dest, const void *src, size_t n); */
 
+.weak memcpy
+ENTRY(__memcpy)
 ENTRY(mmiocpy)
 ENTRY(memcpy)
 
@@ -65,3 +67,4 @@ ENTRY(memcpy)
 
 ENDPROC(memcpy)
 ENDPROC(mmiocpy)
+ENDPROC(__memcpy)
diff --git a/arch/arm/lib/memmove.S b/arch/arm/lib/memmove.S
index b50e5770fb44..fd123ea5a5a4 100644
--- a/arch/arm/lib/memmove.S
+++ b/arch/arm/lib/memmove.S
@@ -24,12 +24,14 @@
  * occurring in the opposite direction.
  */
 
+.weak memmove
+ENTRY(__memmove)
 ENTRY(memmove)
 	UNWIND(	.fnstart			)
 
 		subs	ip, r0, r1
 		cmphi	r2, ip
-		bls	memcpy
+		bls	__memcpy
 
 		stmfd	sp!, {r0, r4, lr}
 	UNWIND(	.fnend				)
@@ -222,3 +224,4 @@ ENTRY(memmove)
 18:		backward_copy_shift	push=24	pull=8
 
 ENDPROC(memmove)
+ENDPROC(__memmove)
diff --git a/arch/arm/lib/memset.S b/arch/arm/lib/memset.S
index 6ca4535c47fb..0e7ff0423f50 100644
--- a/arch/arm/lib/memset.S
+++ b/arch/arm/lib/memset.S
@@ -13,6 +13,8 @@
 	.text
 	.align	5
 
+.weak memset
+ENTRY(__memset)
 ENTRY(mmioset)
 ENTRY(memset)
 UNWIND( .fnstart         )
@@ -132,6 +134,7 @@ UNWIND( .fnstart            )
 UNWIND( .fnend   )
 ENDPROC(memset)
 ENDPROC(mmioset)
+ENDPROC(__memset)
 
 ENTRY(__memset32)
 UNWIND( .fnstart         )
diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index 094eabdecfe6..ea37c9c21273 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -19,9 +19,12 @@ cflags-$(CONFIG_X86)		+= -m$(BITS) -D__KERNEL__ -O2 \
 # disable the stackleak plugin
 cflags-$(CONFIG_ARM64)		:= $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \
 				   -fpie $(DISABLE_STACKLEAK_PLUGIN)
+# Define __SANITIZE_ADDRESS__ in order to get the weak __mem*() functions
+# when building with KASan.
 cflags-$(CONFIG_ARM)		:= $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \
 				   -fno-builtin -fpic \
-				   $(call cc-option,-mno-single-pic-base)
+				   $(call cc-option,-mno-single-pic-base) \
+				   -D__SANITIZE_ADDRESS__
 
 cflags-$(CONFIG_EFI_ARMSTUB)	+= -I$(srctree)/scripts/dtc/libfdt
 
-- 
2.25.1


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