linux-kernel - Re: [PATCH 1/3] crypto: X25519 low-level primitives for ppc64le.

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Date: Thu, 16 May 2024 14:48:12 -0500
From: Segher Boessenkool <segher@...nel.crashing.org>
To: Michael Ellerman <mpe@...erman.id.au>
Cc: Andy Polyakov <appro@...ptogams.org>, Danny Tsen <dtsen@...ux.ibm.com>,
        linux-crypto@...r.kernel.org, herbert@...dor.apana.org.au,
        dtsen@...ibm.com, nayna@...ux.ibm.com, linux-kernel@...r.kernel.org,
        ltcgcw@...ux.vnet.ibm.com, leitao@...ian.org,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 1/3] crypto: X25519 low-level primitives for ppc64le.

Hi!

On Thu, May 16, 2024 at 10:06:58PM +1000, Michael Ellerman wrote:
> Andy Polyakov <appro@...ptogams.org> writes:
> >>> +.abiversion	2
> >>
> >> I'd prefer that was left to the compiler flags.
> >
> > Problem is that it's the compiler that is responsible for providing this
> > directive in the intermediate .s prior invoking the assembler. And there
> > is no assembler flag to pass through -Wa.
> 
> Hmm, right. But none of our existing .S files include .abiversion
> directives.
> 
> We build .S files with gcc, passing -mabi=elfv2, but it seems to have no
> effect.

Yup.  You coulds include some header file, maybe?  Since you run the
assembler code through the C preprocessor anyway, for some weird reason :-)

> But the actual code follows ELFv2, because we wrote it that way, and I
> guess the linker doesn't look at the actual ABI version of the .o ?

It isn't a version.  It is an actual different ABI.

GNU LD allows linking together whatever, yes.

> Is .abiversion documented anywhere? I can't see it in the manual.

Yeah me neither.  https://sourceware.org/bugzilla/enter_bug.cgi ?
A commandline flag (to GAS) would seem best?


Segher