This is the mail archive of the gcc@gcc.gnu.org mailing list for the GCC project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: Should CET be enabled by default in GCC8


On Wed, Apr 18, 2018 at 3:34 AM, Jakub Jelinek <jakub@redhat.com> wrote:
> On Wed, Apr 18, 2018 at 12:30:03PM +0200, Richard Biener wrote:
>> On Wed, 18 Apr 2018, Uros Bizjak wrote:
>>
>> > Hello!
>> >
>> > Currently, CET is enabled by default for linux if target supports
>> > multi-byte NOPs and if assembler supports CET insn. Effectively, with
>> > newer binutils, CET support is an opt-out feature.
>> >
>> > I don't think this should be the case, and I propose to consider CET
>> > as an opt-in feature. Multi-byte NOPs have non-zero cost (at least
>> > they increase the binary). If someone wants to enable the feature, it
>> > can be done in less surprising way to --enable-cet during configure
>> > time.
>> >
>> > I'd like to hear the opinion of RMs, if CET should remain to be an
>> > opt-out feature by default?
>>
>> My personal opinion is that CET should be opt-in (I explicitely
>> disable it for SUSE).  I'm not sure if it doesn't go the way MPX
>
> I agree it should be opt-in, have said that in the past already.
> In Fedora it will not make a difference, as the whole distro is
> built with -mcet -fcf-protection on i?86/x86_64.
>

I submitted a patch to add -mnop to enable multi-byte NOP code
generation which can be used with -fcf-protection to implement
indirect branch and return address tracking without -mcet:

https://gcc.gnu.org/ml/gcc-patches/2018-04/msg00868.html

-- 
H.J.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]