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Subject[RFC PATCH v3 13/13] kasan: introduce inline instrumentation
Date
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 | 5 +++++
lib/Kconfig.kasan | 24 ++++++++++++++++++++++++
mm/kasan/report.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 74 insertions(+)

diff --git a/Makefile b/Makefile
index 6cefe5e..fe7c534 100644
--- a/Makefile
+++ b/Makefile
@@ -773,6 +773,11 @@ KBUILD_CFLAGS += $(call cc-option, -fno-inline-functions-called-once)
endif

ifdef CONFIG_KASAN
+ifdef CONFIG_KASAN_INLINE
+CFLAGS_KASAN += $(call cc-option, -fasan-shadow-offset=$(CONFIG_KASAN_SHADOW_OFFSET)) \
+ $(call cc-option, --param asan-instrumentation-with-call-threshold=10000)
+endif
+
ifeq ($(CFLAGS_KASAN),)
$(warning Cannot use CONFIG_KASAN: \
-fsanitize=kernel-address not supported by compiler)
diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
index faddb0e..c4ac040 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 usefull 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/report.c b/mm/kasan/report.c
index c42f6ba..a9262f8 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -212,3 +212,48 @@ void kasan_report_user_access(struct access_info *info)
"=================================\n");
spin_unlock_irqrestore(&report_lock, flags);
}
+
+#define CALL_KASAN_REPORT(__addr, __size, __is_write) \
+ struct access_info info; \
+ info.access_addr = __addr; \
+ info.access_size = __size; \
+ info.is_write = __is_write; \
+ info.ip = _RET_IP_; \
+ kasan_report_error(&info)
+
+#define DEFINE_ASAN_REPORT_LOAD(size) \
+void __asan_report_recover_load##size(unsigned long addr) \
+{ \
+ CALL_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) \
+{ \
+ CALL_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)
+{
+ CALL_KASAN_REPORT(addr, size, false);
+}
+EXPORT_SYMBOL(__asan_report_recover_load_n);
+
+void __asan_report_recover_store_n(unsigned long addr, size_t size)
+{
+ CALL_KASAN_REPORT(addr, size, true);
+}
+EXPORT_SYMBOL(__asan_report_recover_store_n);
--
2.1.1


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