Re: [PATCH v3 12/14] efi/riscv: libstub: mark when compiling libstub

Andrew Jones
2023-01-04T15:26:48Z

On Fri, Dec 02, 2022 at 05:37:16PM +0100, Ard Biesheuvel wrote:
> On Thu, 1 Dec 2022 at 23:39, Heiko Stübner <heiko@sntech.de> wrote:
> >
> > Hi Ard,
> >
> > Am Donnerstag, 1. Dezember 2022, 21:57:00 CET schrieb Ard Biesheuvel:
> > > On Thu, 1 Dec 2022 at 20:35, Andrew Jones <ajones@ventanamicro.com> wrote:
> > > >
> > > > On Wed, Nov 30, 2022 at 11:56:12PM +0100, Heiko Stuebner wrote:
> > > > > From: Heiko Stuebner <heiko.stuebner@vrull.eu>
> > > > >
> > > > > We may want to runtime-optimize some core functions (str*, mem*),
> > > > > but not have this leak into libstub and cause build issues.
> > > > > Instead libstub, for the short while it's running, should just use
> > > > > the generic implementation.
> > > > >
> > > > > So, to be able to determine whether functions, that are used both in
> > > > > libstub and the main kernel, are getting compiled as part of libstub or
> > > > > not, add a compile-flag we can check via #ifdef.
> > > > >
> > > > > Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
> > > > > Signed-off-by: Heiko Stuebner <heiko.stuebner@vrull.eu>
> > >
> > > I think it would be better to update arch/riscv/kernel/image-vars.h so
> > > that only these generic implementations are exposed to the stub in the
> > > first place.
> >
>
> Actually, all references to string and memory functions are going away
> from the stub. This is already in -next.
>
> EFI now has zboot support, which means you can create a EFI bootable
> kernel image that carries the actual kernel in compressed form rather
> than as a hybrid EFI/bare metal image.

While chatting about EFI stub string functions again in the context of [1]
we recalled this comment that states the references should be going away
anyway. I'm just replying here with interested parties on CC to try and
bring it back to the forefront.

[1] https://lore.kernel.org/all/20221216162141.1701255-5-alexghiti@rivosinc.com/

Thanks,
drew