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Re: RFC: stack/heap collision vulnerability and mitigation with GCC
- From: Uros Bizjak <ubizjak at gmail dot com>
- To: Florian Weimer <fweimer at redhat dot com>
- Cc: Richard Biener <richard dot guenther at gmail dot com>, Jakub Jelinek <jakub at redhat dot com>, Jeff Law <law at redhat dot com>, Jan Hubicka <jh at suse dot cz>, Eric Botcazou <ebotcazou at adacore dot com>, gcc-patches <gcc-patches at gcc dot gnu dot org>
- Date: Tue, 20 Jun 2017 14:20:40 +0200
- Subject: Re: RFC: stack/heap collision vulnerability and mitigation with GCC
- Authentication-results: sourceware.org; auth=none
- References: <bef46e40-8004-0f80-4928-ad0795eb76ba@redhat.com> <20170619172932.GV2123@tucnak> <6b026ac5-7b68-f93b-e005-17288163f442@redhat.com> <20170619175149.GY2123@tucnak> <CAFULd4Z98CnqziqTg4GKE8uomepdzkpSeMQ40n1kF=cpA973PA@mail.gmail.com> <CAFiYyc1vAukq31r0CjEpfETAk6MTUVpFuhTapftP6179Q5FL=A@mail.gmail.com> <CAFULd4YPYze+ngEq74JW75=jibk6YVL-JvvKD4z-4aF1TZN_=Q@mail.gmail.com> <09134f33-7f93-752d-c069-f86819191dd4@redhat.com> <CAFULd4YsYwN1saXYySMnNy4r=f6R1wbe0K4pOMmHM75HYJ5dQg@mail.gmail.com>
On Tue, Jun 20, 2017 at 2:17 PM, Uros Bizjak <ubizjak@gmail.com> wrote:
> On Tue, Jun 20, 2017 at 2:13 PM, Florian Weimer <fweimer@redhat.com> wrote:
>> On 06/20/2017 01:10 PM, Uros Bizjak wrote:
>>
>>> 74,99% a.out a.out [.] test_or
>>> 12,50% a.out a.out [.] test_movb
>>> 12,50% a.out a.out [.] test_movl
>>
>> Could you try notl/notb/negl/negb as well, please?
>
> These all have the same (long) runtime as test_or.
Perhaps we can use "testb $0, %0"? It doesn't write to the memory, but
otherwise has the same runtime as movb/movl.
Uros.