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Wed, 20 May 2020 19:23:53 -0700 (PDT) Received: from localhost ([124.170.14.63]) by smtp.gmail.com with ESMTPSA id 98sm3049301pjo.12.2020.05.20.19.23.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 20 May 2020 19:23:53 -0700 (PDT) Date: Thu, 21 May 2020 12:23:47 +1000 From: Nicholas Piggin Subject: Re: [PATCH v3] powerpc/64: Option to use ELF V2 ABI for big-endian kernels To: Michael Ellerman , Segher Boessenkool References: <20200429011959.1423180-1-npiggin@gmail.com> <87eerhagyd.fsf@mpe.ellerman.id.au> <20200518121917.GJ31009@gate.crashing.org> In-Reply-To: <20200518121917.GJ31009@gate.crashing.org> MIME-Version: 1.0 Message-Id: <1590021606.pn09h4pdi3.astroid@bobo.none> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Excerpts from Segher Boessenkool's message of May 18, 2020 10:19 pm: > Hi! >=20 > On Mon, May 18, 2020 at 04:35:22PM +1000, Michael Ellerman wrote: >> Nicholas Piggin writes: >> > Provide an option to build big-endian kernels using the ELF V2 ABI. Th= is works >> > on GCC and clang (since about 2014). it is is not officially supported= by the >> > GNU toolchain, but it can give big-endian kernels some useful advanta= ges of >> > the V2 ABI (e.g., less stack usage). >=20 >> This doesn't build with clang: >>=20 >> /tmp/aesp8-ppc-dad624.s: Assembler messages: >> /tmp/aesp8-ppc-dad624.s: Error: .size expression for aes_p8_set_encryp= t_key does not evaluate to a constant >=20 > What does this assembler code that clang doesn't swallow look like? Is > that valid code? Etc. The .size directive calculation is .text - .opd because the preprocessor=20 isn't passing -mabi=3Delfv2 which makes our _GLOBAL function entry macro=20 use the v1 convention. I guess I got the 64-bit vdso wrong as well, it=20 should remain in ELFv1. Thanks, Nick