Re: [PATCH v8 02/11] powerpc: prepare string/mem functions for KASAN

From: Daniel Axtens
Date: Wed Feb 27 2019 - 01:55:04 EST

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Christophe Leroy <christophe.leroy@xxxxxx> writes:

> CONFIG_KASAN implements wrappers for memcpy() memmove() and memset()
> Those wrappers are doing the verification then call respectively
> __memcpy() __memmove() and __memset(). The arches are therefore
> expected to rename their optimised functions that way.
>
> For files on which KASAN is inhibited, #defines are used to allow
> them to directly call optimised versions of the functions without
> going through the KASAN wrappers.
>
> See commit 393f203f5fd5 ("x86_64: kasan: add interceptors for
> memset/memmove/memcpy functions") for details.
>
> Other string / mem functions do not (yet) have kasan wrappers,
> we therefore have to fallback to the generic versions when
> KASAN is active, otherwise KASAN checks will be skipped.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
> ---
> arch/powerpc/include/asm/kasan.h | 15 +++++++++++++++
> arch/powerpc/include/asm/string.h | 32 +++++++++++++++++++++++++++++---
> arch/powerpc/kernel/prom_init_check.sh | 10 +++++++++-
> arch/powerpc/lib/Makefile | 11 ++++++++---
> arch/powerpc/lib/copy_32.S | 15 +++++++++------
> arch/powerpc/lib/mem_64.S | 11 +++++++----
> arch/powerpc/lib/memcpy_64.S | 5 +++--
> 7 files changed, 80 insertions(+), 19 deletions(-)
> create mode 100644 arch/powerpc/include/asm/kasan.h
>
> 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)

[FWIW, and this shouldn't block your patch:] This doesn't seem to work
with the 64bit elf abi v1, as we have symbols and dot symbols - our
_GLOBAL* doesn't just create a symtab entry. I don't fully understand
the inner workings just yet, but Aneesh and Balbir have solutions that
use .set instead of creating two entries.

What I am also struggling with is why we export the __symbol
version. I know the x86 version does this, but I can't figure that out
either - why would a module need an uninstrumented copy?

Anyway, I am getting some issues such as:

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

I think Balbir and Aneesh avoided this by just not ever exporting the
__symbol versions, but perhaps that won't fly for the final version. It
looks like we can also avoid this by jumping through some extra hoops
and creating new weak symbols - I'll keep working on it and let you know
how I go.

As I said, I don't think this should necessarily block your patches -
it's just notes on ppc64 progress.

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

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