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SubjectRe: [RFC PATCH v4 13/13] kasan: introduce inline instrumentation
On Mon, Oct 6, 2014 at 7:54 PM, Andrey Ryabinin <a.ryabinin@samsung.com> wrote:
> This patch only demonstration how easy this could be achieved.
> GCC doesn't support this feature yet. Two patches required for this:
> https://gcc.gnu.org/ml/gcc-patches/2014-09/msg00452.html
> https://gcc.gnu.org/ml/gcc-patches/2014-09/msg00605.html
>
> In inline instrumentation mode compiler directly inserts code
> checking shadow memory instead of __asan_load/__asan_store
> calls.
> This is usually faster than outline. In some workloads inline is
> 2 times faster than outline instrumentation.
>
> The downside of inline instrumentation is bloated kernel's .text size:
>
> size noasan/vmlinux
> text data bss dec hex filename
> 11759720 1566560 946176 14272456 d9c7c8 noasan/vmlinux
>
> size outline/vmlinux
> text data bss dec hex filename
> 16553474 1602592 950272 19106338 1238a22 outline/vmlinux
>
> size inline/vmlinux
> text data bss dec hex filename
> 32064759 1598688 946176 34609623 21019d7 inline/vmlinux
>
> Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
> ---
> Makefile | 6 +++++-
> lib/Kconfig.kasan | 24 ++++++++++++++++++++++++
> mm/kasan/kasan.c | 14 +-------------
> mm/kasan/kasan.h | 22 ++++++++++++++++++++++
> mm/kasan/report.c | 37 +++++++++++++++++++++++++++++++++++++
> 5 files changed, 89 insertions(+), 14 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index 6f8be78..01cfa71 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -758,7 +758,11 @@ KBUILD_CFLAGS += $(call cc-option, -fno-inline-functions-called-once)
> endif
>
> ifdef CONFIG_KASAN
> - ifeq ($(CFLAGS_KASAN),)
> +ifdef CONFIG_KASAN_INLINE
> +CFLAGS_KASAN += $(call cc-option, -fasan-shadow-offset=$(CONFIG_KASAN_SHADOW_OFFSET)) \
> + $(call cc-option, --param asan-instrumentation-with-call-threshold=10000)
> +endif
> + ifeq ($(strip $(CFLAGS_KASAN)),)
> $(warning Cannot use CONFIG_KASAN: \
> -fsanitize=kernel-address not supported by compiler)
> endif
> diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
> index 94293c8..ec5d680 100644
> --- a/lib/Kconfig.kasan
> +++ b/lib/Kconfig.kasan
> @@ -27,4 +27,28 @@ config TEST_KASAN
> out of bounds accesses, use after free. It is useful for testing
> kernel debugging features like kernel address sanitizer.
>
> +choice
> + prompt "Instrumentation type"
> + depends on KASAN
> + default KASAN_INLINE if X86_64
> +
> +config KASAN_OUTLINE
> + bool "Outline instrumentation"
> + help
> + Before every memory access compiler insert function call
> + __asan_load*/__asan_store*. These functions performs check
> + of shadow memory. This is slower than inline instrumentation,
> + however it doesn't bloat size of kernel's .text section so
> + much as inline does.
> +
> +config KASAN_INLINE
> + bool "Inline instrumentation"
> + help
> + Compiler directly inserts code checking shadow memory before
> + memory accesses. This is faster than outline (in some workloads
> + it gives about x2 boost over outline instrumentation), but
> + make kernel's .text size much bigger.
> +
> +endchoice
> +
> endif
> diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
> index d4552a2..6e34fdb 100644
> --- a/mm/kasan/kasan.c
> +++ b/mm/kasan/kasan.c
> @@ -32,11 +32,6 @@
> #include "kasan.h"
> #include "../slab.h"
>
> -static inline bool kasan_enabled(void)
> -{
> - return !current->kasan_depth;
> -}
> -
> /*
> * Poisons the shadow memory for 'size' bytes starting from 'addr'.
> * Memory addresses should be aligned to KASAN_SHADOW_SCALE_SIZE.
> @@ -250,14 +245,7 @@ static __always_inline void check_memory_region(unsigned long addr,
> if (likely(!memory_is_poisoned(addr, size)))
> return;
>
> - if (likely(!kasan_enabled()))
> - return;
> -
> - info.access_addr = addr;
> - info.access_size = size;
> - info.is_write = write;
> - info.ip = _RET_IP_;
> - kasan_report_error(&info);
> + kasan_report(addr, size, write);
> }
>
> void kasan_alloc_pages(struct page *page, unsigned int order)
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index b70a3d1..049349b 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -29,4 +29,26 @@ static inline unsigned long kasan_shadow_to_mem(unsigned long shadow_addr)
> return (shadow_addr - KASAN_SHADOW_OFFSET) << KASAN_SHADOW_SCALE_SHIFT;
> }
>
> +static inline bool kasan_enabled(void)
> +{
> + return !current->kasan_depth;
> +}
> +
> +static __always_inline void kasan_report(unsigned long addr,
> + size_t size,
> + bool is_write)
> +{
> + struct access_info info;
> +
> + if (likely(!kasan_enabled()))
> + return;

/\/\/\/\/\

that's smart

> + info.access_addr = addr;
> + info.access_size = size;
> + info.is_write = is_write;
> + info.ip = _RET_IP_;
> + kasan_report_error(&info);
> +}
> +
> +
> #endif
> diff --git a/mm/kasan/report.c b/mm/kasan/report.c
> index 03ce28e..39ec639 100644
> --- a/mm/kasan/report.c
> +++ b/mm/kasan/report.c
> @@ -199,3 +199,40 @@ void kasan_report_user_access(struct access_info *info)
> "=================================\n");
> spin_unlock_irqrestore(&report_lock, flags);
> }
> +
> +#define DEFINE_ASAN_REPORT_LOAD(size) \
> +void __asan_report_recover_load##size(unsigned long addr) \
> +{ \
> + kasan_report(addr, size, false); \
> +} \
> +EXPORT_SYMBOL(__asan_report_recover_load##size)
> +
> +#define DEFINE_ASAN_REPORT_STORE(size) \
> +void __asan_report_recover_store##size(unsigned long addr) \
> +{ \
> + kasan_report(addr, size, true); \
> +} \
> +EXPORT_SYMBOL(__asan_report_recover_store##size)
> +
> +DEFINE_ASAN_REPORT_LOAD(1);
> +DEFINE_ASAN_REPORT_LOAD(2);
> +DEFINE_ASAN_REPORT_LOAD(4);
> +DEFINE_ASAN_REPORT_LOAD(8);
> +DEFINE_ASAN_REPORT_LOAD(16);
> +DEFINE_ASAN_REPORT_STORE(1);
> +DEFINE_ASAN_REPORT_STORE(2);
> +DEFINE_ASAN_REPORT_STORE(4);
> +DEFINE_ASAN_REPORT_STORE(8);
> +DEFINE_ASAN_REPORT_STORE(16);
> +
> +void __asan_report_recover_load_n(unsigned long addr, size_t size)
> +{
> + kasan_report(addr, size, false);
> +}
> +EXPORT_SYMBOL(__asan_report_recover_load_n);
> +
> +void __asan_report_recover_store_n(unsigned long addr, size_t size)
> +{
> + kasan_report(addr, size, true);
> +}
> +EXPORT_SYMBOL(__asan_report_recover_store_n);
> --
> 2.1.2
>

looks good to me


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