On Tue, Jan 14, 2020 at 02:56:38PM +0100, Martin Liška wrote:
> On 1/14/20 1:59 PM, Jakub Jelinek wrote:
> > On Tue, Jan 14, 2020 at 01:57:47PM +0100, Martin Liška wrote:
> > > > seems to be what they emit on x86_64. Now, wonder what they do on other
> > > > targets
> > >
> > > Other targets are not supported :P
> > >
> > > > , and how does it play with all the other options that add stuff
> > > > to the start of functions, e.g. -fcf-protection=full (where it needs to
> > > > really start with endbr64 instruction)
> > >
> > > Using the options one will get:
> > >
> > > _Z4savev: # @_Z4savev
> > > .cfi_startproc
> > > .long 846595819 # 0x327606eb
> > > .long .L__unnamed_2-_Z4savev
> > > # %bb.0:
> > > endbr64
> > >
> > > So endbr64 is placed after the RTTI record.
> >
> > Which is wrong, this will then fail on CET hardware.
>
> Sure, which is a minor limitation. FCF is supposed to be production
> security feature while UBSAN is more for a testing playground.
But then the compiler should just fail if you mix the two, rather than
emitting something that doesn't work at all.
Or better fix the design, so that it can grok an endbr64 together with
the following jump as another magic.
Jakub
