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Subject[PATCH] 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.

Signed-off-by: Joe Perches <>

(dropping Ingo from cc's)

On Thu, 2015-04-16 at 23:59 -0400, Sasha Levin wrote:
> On 04/16/2015 11:21 PM, Steven Rostedt wrote:
> > I have no idea what event caused the issue :-/
> 4.9.2+ is needed for KASan.

Perhaps the documentation and Kconfig entries could
describe that a bit better.

Documentation/kasan.txt | 6 +++---
lib/Kconfig.kasan | 6 ++++--
2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/Documentation/kasan.txt b/Documentation/kasan.txt
index 092fc10..3038b4b 100644
--- a/Documentation/kasan.txt
+++ b/Documentation/kasan.txt
@@ -9,7 +9,7 @@ a fast and comprehensive solution for finding use-after-free and out-of-bounds

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.

Currently KASan is supported only for x86_64 architecture and requires that the
kernel be built with the SLUB allocator.
@@ -23,8 +23,8 @@ 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 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
diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
index 4fecaedc..1e1c23e 100644
--- a/lib/Kconfig.kasan
+++ b/lib/Kconfig.kasan
@@ -10,8 +10,9 @@ config KASAN
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. It 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 +41,7 @@ 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.


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