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kasan: show gcc version requirements in Kconfig and Documentation

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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: Joe Perches <joe@perches.com>
Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Joe Perches 2015-05-05 16:23:38 -07:00 committed by Linus Torvalds
parent 09789e5de1
commit 01e76903f6
2 changed files with 11 additions and 5 deletions
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8
Documentation/kasan.txt
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@ -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

8
lib/Kconfig.kasan
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@ -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