linux-kernel - Re: [PATCH 2/3] tools/objtool: add kasan_check

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Message-ID: <20190528171942.GV2623@hirez.programming.kicks-ass.net>
Date:   Tue, 28 May 2019 19:19:42 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Marco Elver <elver@...gle.com>
Cc:     aryabinin@...tuozzo.com, dvyukov@...gle.com, glider@...gle.com,
        andreyknvl@...gle.com, corbet@....net, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, hpa@...or.com, x86@...nel.org,
        arnd@...db.de, jpoimboe@...hat.com, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        kasan-dev@...glegroups.com
Subject: Re: [PATCH 2/3] tools/objtool: add kasan_check_* to uaccess whitelist

On Tue, May 28, 2019 at 06:32:57PM +0200, Marco Elver wrote:
> This is a pre-requisite for enabling bitops instrumentation. Some bitops
> may safely be used with instrumentation in uaccess regions.
> 
> For example, on x86, `test_bit` is used to test a CPU-feature in a
> uaccess region:   arch/x86/ia32/ia32_signal.c:361

That one can easily be moved out of the uaccess region. Any else?

> Signed-off-by: Marco Elver <elver@...gle.com>
> ---
>  tools/objtool/check.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/tools/objtool/check.c b/tools/objtool/check.c
> index 172f99195726..eff0e5209402 100644
> --- a/tools/objtool/check.c
> +++ b/tools/objtool/check.c
> @@ -443,6 +443,8 @@ static void add_ignores(struct objtool_file *file)
>  static const char *uaccess_safe_builtin[] = {
>  	/* KASAN */
>  	"kasan_report",
> +	"kasan_check_read",
> +	"kasan_check_write",
>  	"check_memory_region",
>  	/* KASAN out-of-line */
>  	"__asan_loadN_noabort",
> -- 
> 2.22.0.rc1.257.g3120a18244-goog
>