Re: [PATCH] x86/ibt: Implement FineIBT

[Kees Cook]

On Tue, Oct 18, 2022 at 10:30:27PM +0200, Peter Zijlstra wrote:
> On Tue, Oct 18, 2022 at 01:17:28PM -0700, Joao Moreira wrote:
> > > 
> > > > Tangent: why are these nop instead of 0xcc? These bytes aren't
> > > > executed
> > > > ever are they?
> > > 
> > > Because that's what the compiler gets us through
> > > -fpatchable-function-entry.
> > 
> > Is it useful to get the compiler to emit 0xcc with
> > -fpatchable-function-entry under any circumstance? I can probably change
> > that quickly if needed/useful.
> 
> Having it emit 0xcc for the bytes in front of the symbol might be
> interesting. It would mean a few kernel changes, but nothing too hard.

The world is pretty different with endbr, but I still always need big
nop areas as giant "jump anywhere in here" targets. ;)

-- 
Kees Cook