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Date: Fri, 12 Aug 2016 10:17:23 -0500
From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@kernel.org>,
        "H . Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
        Andy Lutomirski <luto@amacapital.net>,
        Linus Torvalds <torvalds@linux-foundation.org>,
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        Frederic Weisbecker <fweisbec@gmail.com>,
        Byungchul Park <byungchul.park@lge.com>,
        Nilay Vaish <nilayvaish@gmail.com>
Subject: Re: [PATCH v3 51/51] x86/mm: convert arch_within_stack_frames() to
 use the new unwinder
Message-ID: <20160812151723.b754g7btabokhvr5@treble>
References: <cover.1471011425.git.jpoimboe@redhat.com>
 <e5636723b781d151e7983c88c6a07c03315e2714.1471011425.git.jpoimboe@redhat.com>
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On Fri, Aug 12, 2016 at 09:29:10AM -0500, Josh Poimboeuf wrote:
> Convert arch_within_stack_frames() to use the new unwinder.
> 
> Boot tested with CONFIG_HARDENED_USERCOPY.
> 
> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
> ---
>  arch/x86/lib/usercopy.c | 25 +++++++++++++++++++------
>  1 file changed, 19 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/lib/usercopy.c b/arch/x86/lib/usercopy.c
> index 96ce151..9d0913c 100644
> --- a/arch/x86/lib/usercopy.c
> +++ b/arch/x86/lib/usercopy.c
> @@ -50,12 +50,21 @@ int arch_within_stack_frames(const void * const stack,
>  			     const void * const stackend,
>  			     const void *obj, unsigned long len)
>  {
> -	const void *frame = NULL;
> -	const void *oldframe;
> +	struct unwind_state state;
> +	const void *frame, *oldframe;
> +
> +	unwind_start(&state, current, NULL, NULL);
> +
> +	if (!unwind_next_frame(&state))
> +		return 0;
> +
> +	oldframe = unwind_get_stack_ptr(&state);

Actually, I think this isn't quite right.  Now that the function isn't
inlined, this needs to unwind another frame to be equivalent to current
behavior.

-- 
Josh