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Commit 01e76903 authored by Joe Perches's avatar Joe Perches Committed by Linus Torvalds
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>
parent 09789e5d

Documentation/kasan.txt

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

bugs.





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

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

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

kernel be built with the SLUB allocator.

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

and choose between CONFIG_KASAN_OUTLINE and CONFIG_KASAN_INLINE. Outline/inline

is compiler instrumentation types. The former produces smaller binary the

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

latter.

of 5.0 or later.





Currently KASAN works only with the SLUB memory allocator.

Currently KASAN works only with the SLUB memory allocator.

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

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

lib/Kconfig.kasan

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

	help

	  Enables kernel address sanitizer - runtime memory debugger,

	  Enables kernel address sanitizer - runtime memory debugger,

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

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

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

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

	  of available memory and brings about ~x3 performance slowdown.

	  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,

	  For better error detection enable CONFIG_STACKTRACE,

	  and add slub_debug=U to boot cmdline.

	  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

	  memory accesses. This is faster than outline (in some workloads

	  it gives about x2 boost over outline instrumentation), but

	  it gives about x2 boost over outline instrumentation), but

	  make kernel's .text size much bigger.

	  make kernel's .text size much bigger.

	  This requires a gcc version of 5.0 or later.





endchoice

endchoice