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From:   Daniel Axtens <dja@axtens.net>
To:     Christophe Leroy <christophe.leroy@c-s.fr>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Nicholas Piggin <npiggin@gmail.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Alexander Potapenko <glider@google.com>,
        Dmitry Vyukov <dvyukov@google.com>
Cc:     linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        kasan-dev@googlegroups.com, linux-mm@kvack.org
Subject: Re: [PATCH v9 02/11] powerpc: prepare string/mem functions for KASAN
In-Reply-To: <45fb252fc1b27f2804109fa35ba2882ae29e6035.1551443453.git.christophe.leroy@c-s.fr>
References: <cover.1551443452.git.christophe.leroy@c-s.fr> <45fb252fc1b27f2804109fa35ba2882ae29e6035.1551443453.git.christophe.leroy@c-s.fr>
Date:   Mon, 04 Mar 2019 16:26:18 +1100
Message-ID: <87sgw31a85.fsf@dja-thinkpad.axtens.net>
MIME-Version: 1.0
Content-Type: text/plain
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Hi Christophe,
> diff --git a/arch/powerpc/include/asm/kasan.h b/arch/powerpc/include/asm/kasan.h
> new file mode 100644
> index 000000000000..c3161b8fc017
> --- /dev/null
> +++ b/arch/powerpc/include/asm/kasan.h
> @@ -0,0 +1,15 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef __ASM_KASAN_H
> +#define __ASM_KASAN_H
> +
> +#ifdef CONFIG_KASAN
> +#define _GLOBAL_KASAN(fn)	.weak fn ; _GLOBAL(__##fn) ; _GLOBAL(fn)
> +#define _GLOBAL_TOC_KASAN(fn)	.weak fn ; _GLOBAL_TOC(__##fn) ; _GLOBAL_TOC(fn)
> +#define EXPORT_SYMBOL_KASAN(fn)	EXPORT_SYMBOL(__##fn) ; EXPORT_SYMBOL(fn)

I'm having some trouble with this. I get warnings like this:

WARNING: EXPORT symbol "__memcpy" [vmlinux] version generation failed, symbol will not be versioned.

It seems to be related to the export line, as if I swap the exports to
do fn before __##fn I get:

WARNING: EXPORT symbol "memset" [vmlinux] version generation failed, symbol will not be versioned.

I have narrowed this down to combining 2 EXPORT_SYMBOL()s on one line.
This works - no warning:

EXPORT_SYMBOL(memset)
EXPORT_SYMBOL(__memset)

This throws a warning:

EXPORT_SYMBOL(memset) ; EXPORT_SYMBOL(__memset)

I notice in looking at the diff of preprocessed source we end up
invoking an asm macro that doesn't seem to have a full final argument, I
wonder if that's relevant...

-___EXPORT_SYMBOL __memset, __memset, ; ___EXPORT_SYMBOL memset, memset,
+___EXPORT_SYMBOL __memset, __memset,
+___EXPORT_SYMBOL memset, memset,

I also notice that nowhere else in the source do people have multiple
EXPORT_SYMBOLs on the same line, and other arches seem to just
unconditionally export both symbols on multiple lines.

I have no idea how this works for you - maybe it's affected by something 32bit.

How would you feel about this approach instead? I'm not tied to any of
the names or anything.

diff --git a/arch/powerpc/include/asm/ppc_asm.h b/arch/powerpc/include/asm/ppc_asm.h
index e0637730a8e7..7b6a91b448dd 100644
--- a/arch/powerpc/include/asm/ppc_asm.h
+++ b/arch/powerpc/include/asm/ppc_asm.h
@@ -214,6 +214,9 @@ name: \
 
 #define DOTSYM(a)      a
 
+#define PROVIDE_WEAK_ALIAS(strongname, weakname) \
+       .weak weakname ; .set weakname, strongname ;
+
 #else
 
 #define XGLUE(a,b) a##b
@@ -236,6 +239,10 @@ GLUE(.,name):
 
 #define DOTSYM(a)      GLUE(.,a)
 
+#define PROVIDE_WEAK_ALIAS(strongname, weakname) \
+       .weak weakname ; .set weakname, strongname ; \
+       .weak DOTSYM(weakname) ; .set DOTSYM(weakname), DOTSYM(strongname) ;
+
 #endif
 
 #else /* 32-bit */
@@ -251,6 +258,9 @@ GLUE(.,name):
 
 #define _GLOBAL_TOC(name) _GLOBAL(name)
 
+#define PROVIDE_WEAK_ALIAS(strongname, weakname) \
+       .weak weakname ; .set weakname, strongname ;
+
 #endif
 
 /*
--- a/arch/powerpc/lib/mem_64.S
+++ b/arch/powerpc/lib/mem_64.S
@@ -33,7 +33,8 @@ EXPORT_SYMBOL(__memset32)
 EXPORT_SYMBOL(__memset64)
 #endif
 
-_GLOBAL_KASAN(memset)
+PROVIDE_WEAK_ALIAS(__memset,memset)
+_GLOBAL(__memset)
        neg     r0,r3
        rlwimi  r4,r4,8,16,23
        andi.   r0,r0,7                 /* # bytes to be 8-byte aligned */
@@ -98,9 +99,11 @@ _GLOBAL_KASAN(memset)
 10:    bflr    31
        stb     r4,0(r6)
        blr
-EXPORT_SYMBOL_KASAN(memset)
+EXPORT_SYMBOL(memset)
+EXPORT_SYMBOL(__memset)
 
-_GLOBAL_TOC_KASAN(memmove)
+PROVIDE_WEAK_ALIAS(__memmove,memove)
+_GLOBAL_TOC(__memmove)
        cmplw   0,r3,r4
        bgt     backwards_memcpy
        b       memcpy
@@ -141,4 +144,5 @@ _GLOBAL(backwards_memcpy)
        beq     2b
        mtctr   r7
        b       1b
-EXPORT_SYMBOL_KASAN(memmove)
+EXPORT_SYMBOL(memmove)
+EXPORT_SYMBOL(__memmove)
diff --git a/arch/powerpc/lib/memcpy_64.S b/arch/powerpc/lib/memcpy_64.S
index 862b515b8868..7c1b09556cad 100644
--- a/arch/powerpc/lib/memcpy_64.S
+++ b/arch/powerpc/lib/memcpy_64.S
@@ -19,7 +19,8 @@
 #endif
 
        .align  7
-_GLOBAL_TOC_KASAN(memcpy)
+PROVIDE_WEAK_ALIAS(__memcpy,memcpy)
+_GLOBAL_TOC(__memcpy)
 BEGIN_FTR_SECTION
 #ifdef __LITTLE_ENDIAN__
        cmpdi   cr7,r5,0
@@ -230,4 +231,5 @@ END_FTR_SECTION_IFCLR(CPU_FTR_UNALIGNED_LD_STD)
 4:     ld      r3,-STACKFRAMESIZE+STK_REG(R31)(r1)     /* return dest pointer */
        blr
 #endif
-EXPORT_SYMBOL_KASAN(memcpy)
+EXPORT_SYMBOL(__memcpy)
+EXPORT_SYMBOL(memcpy)


Regards,
Daniel


> +#else
> +#define _GLOBAL_KASAN(fn)	_GLOBAL(fn)
> +#define _GLOBAL_TOC_KASAN(fn)	_GLOBAL_TOC(fn)
> +#define EXPORT_SYMBOL_KASAN(fn)	EXPORT_SYMBOL(fn)
> +#endif
> +
> +#endif
> diff --git a/arch/powerpc/include/asm/string.h b/arch/powerpc/include/asm/string.h
> index 1647de15a31e..9bf6dffb4090 100644
> --- a/arch/powerpc/include/asm/string.h
> +++ b/arch/powerpc/include/asm/string.h
> @@ -4,14 +4,17 @@
>  
>  #ifdef __KERNEL__
>  
> +#ifndef CONFIG_KASAN
>  #define __HAVE_ARCH_STRNCPY
>  #define __HAVE_ARCH_STRNCMP
> +#define __HAVE_ARCH_MEMCHR
> +#define __HAVE_ARCH_MEMCMP
> +#define __HAVE_ARCH_MEMSET16
> +#endif
> +
>  #define __HAVE_ARCH_MEMSET
>  #define __HAVE_ARCH_MEMCPY
>  #define __HAVE_ARCH_MEMMOVE
> -#define __HAVE_ARCH_MEMCMP
> -#define __HAVE_ARCH_MEMCHR
> -#define __HAVE_ARCH_MEMSET16
>  #define __HAVE_ARCH_MEMCPY_FLUSHCACHE
>  
>  extern char * strcpy(char *,const char *);
> @@ -27,7 +30,27 @@ extern int memcmp(const void *,const void *,__kernel_size_t);
>  extern void * memchr(const void *,int,__kernel_size_t);
>  extern void * memcpy_flushcache(void *,const void *,__kernel_size_t);
>  
> +void *__memset(void *s, int c, __kernel_size_t count);
> +void *__memcpy(void *to, const void *from, __kernel_size_t n);
> +void *__memmove(void *to, const void *from, __kernel_size_t n);
> +
> +#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)
> +
> +#ifndef __NO_FORTIFY
> +#define __NO_FORTIFY /* FORTIFY_SOURCE uses __builtin_memcpy, etc. */
> +#endif
> +
> +#endif
> +
>  #ifdef CONFIG_PPC64
> +#ifndef CONFIG_KASAN
>  #define __HAVE_ARCH_MEMSET32
>  #define __HAVE_ARCH_MEMSET64
>  
> @@ -49,8 +72,11 @@ static inline void *memset64(uint64_t *p, uint64_t v, __kernel_size_t n)
>  {
>  	return __memset64(p, v, n * 8);
>  }
> +#endif
>  #else
> +#ifndef CONFIG_KASAN
>  #define __HAVE_ARCH_STRLEN
> +#endif
>  
>  extern void *memset16(uint16_t *, uint16_t, __kernel_size_t);
>  #endif
> diff --git a/arch/powerpc/kernel/prom_init_check.sh b/arch/powerpc/kernel/prom_init_check.sh
> index 667df97d2595..181fd10008ef 100644
> --- a/arch/powerpc/kernel/prom_init_check.sh
> +++ b/arch/powerpc/kernel/prom_init_check.sh
> @@ -16,8 +16,16 @@
>  # If you really need to reference something from prom_init.o add
>  # it to the list below:
>  
> +grep "^CONFIG_KASAN=y$" .config >/dev/null
> +if [ $? -eq 0 ]
> +then
> +	MEM_FUNCS="__memcpy __memset"
> +else
> +	MEM_FUNCS="memcpy memset"
> +fi
> +
>  WHITELIST="add_reloc_offset __bss_start __bss_stop copy_and_flush
> -_end enter_prom memcpy memset reloc_offset __secondary_hold
> +_end enter_prom $MEM_FUNCS reloc_offset __secondary_hold
>  __secondary_hold_acknowledge __secondary_hold_spinloop __start
>  strcmp strcpy strlcpy strlen strncmp strstr kstrtobool logo_linux_clut224
>  reloc_got2 kernstart_addr memstart_addr linux_banner _stext
> diff --git a/arch/powerpc/lib/Makefile b/arch/powerpc/lib/Makefile
> index 79396e184bca..47a4de434c22 100644
> --- a/arch/powerpc/lib/Makefile
> +++ b/arch/powerpc/lib/Makefile
> @@ -8,9 +8,14 @@ ccflags-$(CONFIG_PPC64)	:= $(NO_MINIMAL_TOC)
>  CFLAGS_REMOVE_code-patching.o = $(CC_FLAGS_FTRACE)
>  CFLAGS_REMOVE_feature-fixups.o = $(CC_FLAGS_FTRACE)
>  
> -obj-y += string.o alloc.o code-patching.o feature-fixups.o
> +obj-y += alloc.o code-patching.o feature-fixups.o
>  
> -obj-$(CONFIG_PPC32)	+= div64.o copy_32.o crtsavres.o strlen_32.o
> +ifndef CONFIG_KASAN
> +obj-y	+=	string.o memcmp_$(BITS).o
> +obj-$(CONFIG_PPC32)	+= strlen_32.o
> +endif
> +
> +obj-$(CONFIG_PPC32)	+= div64.o copy_32.o crtsavres.o
>  
>  obj-$(CONFIG_FUNCTION_ERROR_INJECTION)	+= error-inject.o
>  
> @@ -34,7 +39,7 @@ obj64-$(CONFIG_KPROBES_SANITY_TEST)	+= test_emulate_step.o \
>  					   test_emulate_step_exec_instr.o
>  
>  obj-y			+= checksum_$(BITS).o checksum_wrappers.o \
> -			   string_$(BITS).o memcmp_$(BITS).o
> +			   string_$(BITS).o
>  
>  obj-y			+= sstep.o ldstfp.o quad.o
>  obj64-y			+= quad.o
> diff --git a/arch/powerpc/lib/copy_32.S b/arch/powerpc/lib/copy_32.S
> index ba66846fe973..fc4fa7246200 100644
> --- a/arch/powerpc/lib/copy_32.S
> +++ b/arch/powerpc/lib/copy_32.S
> @@ -14,6 +14,7 @@
>  #include <asm/ppc_asm.h>
>  #include <asm/export.h>
>  #include <asm/code-patching-asm.h>
> +#include <asm/kasan.h>
>  
>  #define COPY_16_BYTES		\
>  	lwz	r7,4(r4);	\
> @@ -68,6 +69,7 @@ CACHELINE_BYTES = L1_CACHE_BYTES
>  LG_CACHELINE_BYTES = L1_CACHE_SHIFT
>  CACHELINE_MASK = (L1_CACHE_BYTES-1)
>  
> +#ifndef CONFIG_KASAN
>  _GLOBAL(memset16)
>  	rlwinm.	r0 ,r5, 31, 1, 31
>  	addi	r6, r3, -4
> @@ -81,6 +83,7 @@ _GLOBAL(memset16)
>  	sth	r4, 4(r6)
>  	blr
>  EXPORT_SYMBOL(memset16)
> +#endif
>  
>  /*
>   * Use dcbz on the complete cache lines in the destination
> @@ -91,7 +94,7 @@ EXPORT_SYMBOL(memset16)
>   * We therefore skip the optimised bloc that uses dcbz. This jump is
>   * replaced by a nop once cache is active. This is done in machine_init()
>   */
> -_GLOBAL(memset)
> +_GLOBAL_KASAN(memset)
>  	cmplwi	0,r5,4
>  	blt	7f
>  
> @@ -150,7 +153,7 @@ _GLOBAL(memset)
>  9:	stbu	r4,1(r6)
>  	bdnz	9b
>  	blr
> -EXPORT_SYMBOL(memset)
> +EXPORT_SYMBOL_KASAN(memset)
>  
>  /*
>   * This version uses dcbz on the complete cache lines in the
> @@ -163,12 +166,12 @@ EXPORT_SYMBOL(memset)
>   * We therefore jump to generic_memcpy which doesn't use dcbz. This jump is
>   * replaced by a nop once cache is active. This is done in machine_init()
>   */
> -_GLOBAL(memmove)
> +_GLOBAL_KASAN(memmove)
>  	cmplw	0,r3,r4
>  	bgt	backwards_memcpy
>  	/* fall through */
>  
> -_GLOBAL(memcpy)
> +_GLOBAL_KASAN(memcpy)
>  1:	b	generic_memcpy
>  	patch_site	1b, patch__memcpy_nocache
>  
> @@ -242,8 +245,8 @@ _GLOBAL(memcpy)
>  	stbu	r0,1(r6)
>  	bdnz	40b
>  65:	blr
> -EXPORT_SYMBOL(memcpy)
> -EXPORT_SYMBOL(memmove)
> +EXPORT_SYMBOL_KASAN(memcpy)
> +EXPORT_SYMBOL_KASAN(memmove)
>  
>  generic_memcpy:
>  	srwi.	r7,r5,3
> diff --git a/arch/powerpc/lib/mem_64.S b/arch/powerpc/lib/mem_64.S
> index 3c3be02f33b7..7cd6cf6822a2 100644
> --- a/arch/powerpc/lib/mem_64.S
> +++ b/arch/powerpc/lib/mem_64.S
> @@ -12,7 +12,9 @@
>  #include <asm/errno.h>
>  #include <asm/ppc_asm.h>
>  #include <asm/export.h>
> +#include <asm/kasan.h>
>  
> +#ifndef CONFIG_KASAN
>  _GLOBAL(__memset16)
>  	rlwimi	r4,r4,16,0,15
>  	/* fall through */
> @@ -29,8 +31,9 @@ _GLOBAL(__memset64)
>  EXPORT_SYMBOL(__memset16)
>  EXPORT_SYMBOL(__memset32)
>  EXPORT_SYMBOL(__memset64)
> +#endif
>  
> -_GLOBAL(memset)
> +_GLOBAL_KASAN(memset)
>  	neg	r0,r3
>  	rlwimi	r4,r4,8,16,23
>  	andi.	r0,r0,7			/* # bytes to be 8-byte aligned */
> @@ -95,9 +98,9 @@ _GLOBAL(memset)
>  10:	bflr	31
>  	stb	r4,0(r6)
>  	blr
> -EXPORT_SYMBOL(memset)
> +EXPORT_SYMBOL_KASAN(memset)
>  
> -_GLOBAL_TOC(memmove)
> +_GLOBAL_TOC_KASAN(memmove)
>  	cmplw	0,r3,r4
>  	bgt	backwards_memcpy
>  	b	memcpy
> @@ -138,4 +141,4 @@ _GLOBAL(backwards_memcpy)
>  	beq	2b
>  	mtctr	r7
>  	b	1b
> -EXPORT_SYMBOL(memmove)
> +EXPORT_SYMBOL_KASAN(memmove)
> diff --git a/arch/powerpc/lib/memcpy_64.S b/arch/powerpc/lib/memcpy_64.S
> index 273ea67e60a1..862b515b8868 100644
> --- a/arch/powerpc/lib/memcpy_64.S
> +++ b/arch/powerpc/lib/memcpy_64.S
> @@ -11,6 +11,7 @@
>  #include <asm/export.h>
>  #include <asm/asm-compat.h>
>  #include <asm/feature-fixups.h>
> +#include <asm/kasan.h>
>  
>  #ifndef SELFTEST_CASE
>  /* For big-endian, 0 == most CPUs, 1 == POWER6, 2 == Cell */
> @@ -18,7 +19,7 @@
>  #endif
>  
>  	.align	7
> -_GLOBAL_TOC(memcpy)
> +_GLOBAL_TOC_KASAN(memcpy)
>  BEGIN_FTR_SECTION
>  #ifdef __LITTLE_ENDIAN__
>  	cmpdi	cr7,r5,0
> @@ -229,4 +230,4 @@ END_FTR_SECTION_IFCLR(CPU_FTR_UNALIGNED_LD_STD)
>  4:	ld	r3,-STACKFRAMESIZE+STK_REG(R31)(r1)	/* return dest pointer */
>  	blr
>  #endif
> -EXPORT_SYMBOL(memcpy)
> +EXPORT_SYMBOL_KASAN(memcpy)
> -- 
> 2.13.3