Message-ID: <1429245851.2850.76.camel@perches.com>
Subject: [PATCH] kasan: Show gcc version requirements in Kconfig and
 Documentation
From: Joe Perches <joe@perches.com>
To: Sasha Levin <sasha.levin@oracle.com>
Cc: Steven Rostedt <rostedt@goodmis.org>, linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Guilherme Cox <cox@computer.org>, Tony Luck <tony.luck@gmail.com>,
        Xie XiuQi <xiexiuqi@huawei.com>
Date: Thu, 16 Apr 2015 21:44:11 -0700
In-Reply-To: <5530852A.70202@oracle.com>
References: <20150403013802.220157513@goodmis.org>
	 <20150403014123.997385206@goodmis.org>	<552E661D.5060502@oracle.com>
	 <20150415100549.09cabb59@gandalf.local.home>	<552F0937.4010009@oracle.com>
	 <20150416232116.39cd9f74@grimm.local.home> <5530852A.70202@oracle.com>
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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.

Signed-off-by: Joe Perches <joe@perches.com>
---

(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
 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.
 
 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.
+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
 	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.  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.
 
 endchoice
 

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