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Subject: Re: [PATCH 1/2] stackleak: Update for arm64
To:     Will Deacon <will.deacon@arm.com>
Cc:     Alexander Popov <alex.popov@linux.com>,
        Kees Cook <keescook@chromium.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        kernel-hardening@lists.openwall.com, richard.sandiford@arm.com
References: <20180221011303.20392-1-labbott@redhat.com>
 <20180221011303.20392-2-labbott@redhat.com> <20180222165834.GC18421@arm.com>
From:   Laura Abbott <labbott@redhat.com>
Message-ID: <fdd74037-5b47-b4e1-e692-54534d518e88@redhat.com>
Date:   Thu, 22 Feb 2018 11:38:48 -0800
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On 02/22/2018 08:58 AM, Will Deacon wrote:
> 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@redhat.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
> 

Yep, seems to work fine and makes sense from my understanding of
gcc internals. I'll fix it up for the next version. Thanks for the
review!

Laura