From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751450AbcFVF3h (ORCPT ); Wed, 22 Jun 2016 01:29:37 -0400 Received: from ozlabs.org ([103.22.144.67]:50829 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750957AbcFVF3f (ORCPT ); Wed, 22 Jun 2016 01:29:35 -0400 Message-ID: <1466572831.19785.5.camel@ellerman.id.au> Subject: Re: [PATCH] ppc: Fix BPF JIT for ABIv2 From: Michael Ellerman To: "Naveen N. Rao" , Thadeu Lima de Souza Cascardo Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, netdev@vger.kernel.org, Matt Evans , Daniel Borkmann , Alexei Starovoitov , Denis Kirjanov , Paul Mackerras , "David S. Miller" , Ananth N Mavinakayanahalli Date: Wed, 22 Jun 2016 15:20:31 +1000 In-Reply-To: <20160621085807.GE8886@naverao1-tp.localdomain> References: <908d3552b5eb240b28f70aee7c4c86e2b600aa02.1465304785.git.naveen.n.rao@linux.vnet.ibm.com> <3rWKtT2tSrz9t2G@ozlabs.org> <20160617130042.GO3516@indiana.gru.redhat.com> <20160619174914.GC8886@naverao1-tp.localdomain> <20160620185620.GD3516@indiana.gru.redhat.com> <20160621085807.GE8886@naverao1-tp.localdomain> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.16.5-1ubuntu3.1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2016-06-21 at 14:28 +0530, Naveen N. Rao wrote: > On 2016/06/20 03:56PM, Thadeu Lima de Souza Cascardo wrote: > > On Sun, Jun 19, 2016 at 11:19:14PM +0530, Naveen N. Rao wrote: > > > On 2016/06/17 10:00AM, Thadeu Lima de Souza Cascardo wrote: > > > > > > > > Hi, Michael and Naveen. > > > > > > > > I noticed independently that there is a problem with BPF JIT and ABIv2, and > > > > worked out the patch below before I noticed Naveen's patchset and the latest > > > > changes in ppc tree for a better way to check for ABI versions. > > > > > > > > However, since the issue described below affect mainline and stable kernels, > > > > would you consider applying it before merging your two patchsets, so that we can > > > > more easily backport the fix? > > > > > > Hi Cascardo, > > > Given that this has been broken on ABIv2 since forever, I didn't bother > > > fixing it. But, I can see why this would be a good thing to have for > > > -stable and existing distros. However, while your patch below may fix > > > the crash you're seeing on ppc64le, it is not sufficient -- you'll need > > > changes in bpf_jit_asm.S as well. > > > > Hi, Naveen. > > > > Any tips on how to exercise possible issues there? Or what changes you think > > would be sufficient? > > The calling convention is different with ABIv2 and so we'll need changes > in bpf_slow_path_common() and sk_negative_common(). > > However, rather than enabling classic JIT for ppc64le, are we better off > just disabling it? > > --- a/arch/powerpc/Kconfig > +++ b/arch/powerpc/Kconfig > @@ -128,7 +128,7 @@ config PPC > select IRQ_FORCED_THREADING > select HAVE_RCU_TABLE_FREE if SMP > select HAVE_SYSCALL_TRACEPOINTS > - select HAVE_CBPF_JIT > + select HAVE_CBPF_JIT if CPU_BIG_ENDIAN > select HAVE_ARCH_JUMP_LABEL > select ARCH_HAVE_NMI_SAFE_CMPXCHG > select ARCH_HAS_GCOV_PROFILE_ALL > > > Michael, > Let me know your thoughts on whether you intend to take this patch or > Cascardo's patch for -stable before the eBPF patches. I can redo my > patches accordingly. Can one of you send me a proper version of this patch, with change log and sign-off etc. cheers