On Thu, Feb 22, 2018 at 9:32 AM, H.J. Lu <hjl.to...@gmail.com> wrote: > On Thu, Feb 22, 2018 at 9:10 AM, Jeff Law <l...@redhat.com> wrote: >> On 02/22/2018 07:38 AM, Jan Hubicka wrote: >>>>>> >>>>>> Hi Jan, >>>>>> >>>>>> https://gcc.gnu.org/ml/gcc-patches/2018-01/msg02233.html >>>>>> >>>>>> Is OK for trunk? >>>>> >>>>> I see that using register makes the problem go away and pushing address >>>>> to stack >>>>> seemed bit odd anyway. However how does this work on other types of thunk? >>>> >>>> Kernel only uses -mindirect-branch=thunk-extern. I am working on a >>>> proposal >>>> to use -mindirect-branch=thunk-extern in user space to support CET in a >>>> single >>>> binary. So at the end of the day, only >>>> -mindirect-branch=thunk-extern will be used. >>> >>> OK, so it is about the fact that we do not really want to support all >>> -mindirect-branch options in the future? If we don't want to support the >>> correctly, >>> I wonder why we are including them at all. Shall we at least output >>> warning/sorry >>> when user tries other thunk type with stack unwinding enabled? >>> (does Kernel use it?) >> A few notes. >> >> 1. It's not even clear at this time that retpolining user space binaries >> makes any sense at all. SO before doing anything to make this easier >> I'd like to see a justification for why it's really needed. > > Hi Jeff, > > Which part were commenting? My patch to add TARGET_INDIRECT_BRANCH_REGISTER > or removing -mindirect-branch choices?
Is my patch OK for trunk? >> 2. On the other hand, the existing thunk options do make it easier to >> test independent of hte kernel. ie, I can turn on inline thunks by >> default and test things in user space (ie, do thunks generally work >> properly). > > It sounds reasonable. > Thanks. -- H.J.
