linux-kernel - Re: [PATCH 1/2] stackleak: Update for arm64

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Message-ID: <20180222165834.GC18421@arm.com>
Date:   Thu, 22 Feb 2018 16:58:34 +0000
From:   Will Deacon <will.deacon@....com>
To:     Laura Abbott <labbott@...hat.com>
Cc:     Alexander Popov <alex.popov@...ux.com>,
        Kees Cook <keescook@...omium.org>,
        Mark Rutland <mark.rutland@....com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kernel-hardening@...ts.openwall.com, richard.sandiford@....com
Subject: Re: [PATCH 1/2] stackleak: Update for arm64

Hi Laura,

On Tue, Feb 20, 2018 at 05:13:02PM -0800, Laura Abbott wrote:
> 
> arm64 has another layer of indirection in the RTL.
> Account for this in the plugin.
> 
> Signed-off-by: Laura Abbott <labbott@...hat.com>
> ---
>  scripts/gcc-plugins/stackleak_plugin.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/scripts/gcc-plugins/stackleak_plugin.c b/scripts/gcc-plugins/stackleak_plugin.c
> index 6fc991c98d8b..7dfaa027423f 100644
> --- a/scripts/gcc-plugins/stackleak_plugin.c
> +++ b/scripts/gcc-plugins/stackleak_plugin.c
> @@ -244,6 +244,11 @@ static unsigned int stackleak_final_execute(void)
>  		 * that insn.
>  		 */
>  		body = PATTERN(insn);
> +		/* arm64 is different */
> +		if (GET_CODE(body) == PARALLEL) {
> +			body = XEXP(body, 0);
> +			body = XEXP(body, 0);
> +		}

Like most kernel developers, I don't know the first thing about GCC internals
so I asked our GCC team and Richard (CC'd) reckons this should be:

	if (GET_CODE(body) == PARALLEL)
		body = XVECEXP(body, 0, 0);

instead of the hunk above. Can you give that a go instead, please?

Cheers,

Will