On Wed, 24 Jun 2020 at 17:45, Kees Cook <keescook@xxxxxxxxxxxx> wrote: > > On Wed, Jun 24, 2020 at 05:31:06PM +0200, Ard Biesheuvel wrote: > > On Wed, 24 Jun 2020 at 17:21, Kees Cook <keescook@xxxxxxxxxxxx> wrote: > > > > > > On Wed, Jun 24, 2020 at 12:46:32PM +0200, Ard Biesheuvel wrote: > > > > I'm not sure if there is a point to having PAC and/or BTI in the EFI > > > > stub, given that it runs under the control of the firmware, with its > > > > memory mappings and PAC configuration etc. > > > > > > Is BTI being ignored when the firmware runs? > > > > Given that it requires the 'guarded' attribute to be set in the page > > tables, and the fact that the UEFI spec does not require it for > > executables that it invokes, nor describes any means of annotating > > such executables as having been built with BTI annotations, I think we > > can safely assume that the EFI stub will execute with BTI disabled in > > the foreseeable future. > > yaaaaaay. *sigh* How long until EFI catches up? > > That said, BTI shouldn't _hurt_, right? If EFI ever decides to enable > it, we'll be ready? > Sure. Although I anticipate that we'll need to set some flag in the PE/COFF header to enable it, and so any BTI opcodes we emit without that will never take effect in practice.
