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Commit 9e838566 authored by Joe Perches's avatar Joe Perches Committed by Alex Shi
Browse files

kasan: show gcc version requirements in Kconfig and Documentation 



The documentation shows a need for gcc > 4.9.2, but it's really >=.  The
Kconfig entries don't show require versions so add them.  Correct a
latter/later typo too.  Also mention that gcc 5 required to catch out of
bounds accesses to global and stack variables.

Signed-off-by: default avatarJoe Perches <joe@perches.com>
Signed-off-by: default avatarAndrey Ryabinin <a.ryabinin@samsung.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit 01e76903f655a4d88c2e09d3182436c65f6e1213)
Signed-off-by: default avatarAlex Shi <alex.shi@linaro.org>
parent e83e29a0

Documentation/kasan.txt

+5 −3
Original line number Diff line number Diff line
@@ -9,7 +9,9 @@ a fast and comprehensive solution for finding use-after-free and out-of-bounds 
bugs.



KASan uses compile-time instrumentation for checking every memory access,

therefore you will need a certain version of GCC > 4.9.2

therefore you will need a gcc version of 4.9.2 or later. KASan could detect out

of bounds accesses to stack or global variables, but only if gcc 5.0 or later was

used to built the kernel.



Currently KASan is supported only for x86_64 architecture and requires that the

kernel be built with the SLUB allocator.
@@ -23,8 +25,8 @@ To enable KASAN configure kernel with: 


and choose between CONFIG_KASAN_OUTLINE and CONFIG_KASAN_INLINE. Outline/inline

is compiler instrumentation types. The former produces smaller binary the

latter is 1.1 - 2 times faster. Inline instrumentation requires GCC 5.0 or

latter.

latter is 1.1 - 2 times faster. Inline instrumentation requires a gcc version

of 5.0 or later.



Currently KASAN works only with the SLUB memory allocator.

For better bug detection and nicer report, enable CONFIG_STACKTRACE and put

lib/Kconfig.kasan

+6 −2
Original line number Diff line number Diff line
@@ -10,8 +10,11 @@ config KASAN 
	help

	  Enables kernel address sanitizer - runtime memory debugger,

	  designed to find out-of-bounds accesses and use-after-free bugs.

	  This is strictly debugging feature. It consumes about 1/8

	  of available memory and brings about ~x3 performance slowdown.

	  This is strictly a debugging feature and it requires a gcc version

	  of 4.9.2 or later. Detection of out of bounds accesses to stack or

	  global variables requires gcc 5.0 or later.

	  This feature consumes about 1/8 of available memory and brings about

	  ~x3 performance slowdown.

	  For better error detection enable CONFIG_STACKTRACE,

	  and add slub_debug=U to boot cmdline.
@@ -40,6 +43,7 @@ config KASAN_INLINE 
	  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.

	  This requires a gcc version of 5.0 or later.



endchoice