From: Herbert Xu Subject: Re: [PATCH] lib/mpi: Fix umul_ppmm() for MIPS64r6 Date: Fri, 22 Dec 2017 18:08:08 +1100 Message-ID: <20171222070808.GB27149@gondor.apana.org.au> References: <20171205233135.1763-1-james.hogan@mips.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Ralf Baechle , "David S. Miller" , James Hogan , linux-mips@linux-mips.org, linux-crypto@vger.kernel.org To: James Hogan Return-path: Received: from [128.1.224.119] ([128.1.224.119]:45972 "EHLO ringil.hmeau.com" rhost-flags-FAIL-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1751104AbdLVHIZ (ORCPT ); Fri, 22 Dec 2017 02:08:25 -0500 Content-Disposition: inline In-Reply-To: <20171205233135.1763-1-james.hogan@mips.com> Sender: linux-crypto-owner@vger.kernel.org List-ID: On Tue, Dec 05, 2017 at 11:31:35PM +0000, James Hogan wrote: > From: James Hogan > > Current MIPS64r6 toolchains aren't able to generate efficient > DMULU/DMUHU based code for the C implementation of umul_ppmm(), which > performs an unsigned 64 x 64 bit multiply and returns the upper and > lower 64-bit halves of the 128-bit result. Instead it widens the 64-bit > inputs to 128-bits and emits a __multi3 intrinsic call to perform a 128 > x 128 multiply. This is both inefficient, and it results in a link error > since we don't include __multi3 in MIPS linux. > > For example commit 90a53e4432b1 ("cfg80211: implement regdb signature > checking") merged in v4.15-rc1 recently broke the 64r6_defconfig and > 64r6el_defconfig builds by indirectly selecting MPILIB. The same build > errors can be reproduced on older kernels by enabling e.g. CRYPTO_RSA: > > lib/mpi/generic_mpih-mul1.o: In function `mpihelp_mul_1': > lib/mpi/generic_mpih-mul1.c:50: undefined reference to `__multi3' > lib/mpi/generic_mpih-mul2.o: In function `mpihelp_addmul_1': > lib/mpi/generic_mpih-mul2.c:49: undefined reference to `__multi3' > lib/mpi/generic_mpih-mul3.o: In function `mpihelp_submul_1': > lib/mpi/generic_mpih-mul3.c:49: undefined reference to `__multi3' > lib/mpi/mpih-div.o In function `mpihelp_divrem': > lib/mpi/mpih-div.c:205: undefined reference to `__multi3' > lib/mpi/mpih-div.c:142: undefined reference to `__multi3' > > Therefore add an efficient MIPS64r6 implementation of umul_ppmm() using > inline assembly and the DMULU/DMUHU instructions, to prevent __multi3 > calls being emitted. > > Fixes: 7fd08ca58ae6 ("MIPS: Add build support for the MIPS R6 ISA") > Signed-off-by: James Hogan > Cc: Ralf Baechle > Cc: Herbert Xu > Cc: "David S. Miller" > Cc: linux-mips@linux-mips.org > Cc: linux-crypto@vger.kernel.org > --- > Please can somebody apply this fix for v4.15, as the MIPS 64r6_defconfig > and 64r6el_defconfig builds are broken without it. I can take this but I'd like to see an ack from someone on the MIPS side. Thanks, -- Email: Herbert Xu Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt