From mboxrd@z Thu Jan 1 00:00:00 1970 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964799AbeALP4Q (ORCPT + 1 other); Fri, 12 Jan 2018 10:56:16 -0500 Received: from mail-pf0-f195.google.com ([209.85.192.195]:40001 "EHLO mail-pf0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933975AbeALP4O (ORCPT ); Fri, 12 Jan 2018 10:56:14 -0500 X-Google-Smtp-Source: ACJfBos8ssK04AzQuXOXXsjtJYoykKyTVHJzDdVxvtt3KE6ZeWzHXSHbJYmt9bWreWqlRY7Iv4KlOg== Date: Fri, 12 Jan 2018 07:56:10 -0800 From: Alexei Starovoitov To: Daniel Borkmann Cc: David Miller , sfr@canb.auug.org.au, netdev@vger.kernel.org, ast@kernel.org, linux-next@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: linux-next: build failure after merge of the net-next tree Message-ID: <20180112155609.utnakkerdbtbj7ne@ast-mbp.dhcp.thefacebook.com> References: <20180111115355.29c2f905@canb.auug.org.au> <20180111015853.2pmxtqlrsyxelqf6@ast-mbp> <20180111.221145.643386077098131140.davem@davemloft.net> <20180112042148.jsxb26fodw3fgneb@ast-mbp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170421 (1.8.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: On Fri, Jan 12, 2018 at 11:45:42AM +0100, Daniel Borkmann wrote: > On 01/12/2018 05:21 AM, Alexei Starovoitov wrote: > > On Thu, Jan 11, 2018 at 10:11:45PM -0500, David Miller wrote: > >> From: Alexei Starovoitov > >> Date: Wed, 10 Jan 2018 17:58:54 -0800 > >> > >>> On Thu, Jan 11, 2018 at 11:53:55AM +1100, Stephen Rothwell wrote: > >>>> Hi all, > >>>> > >>>> After merging the net-next tree, today's linux-next build (x86_64 > >>>> allmodconfig) failed like this: > >>>> > >>>> kernel/bpf/verifier.o: In function `bpf_check': > >>>> verifier.c:(.text+0xd86e): undefined reference to `bpf_patch_call_args' > >>>> > >>>> Caused by commit > >>>> > >>>> 1ea47e01ad6e ("bpf: add support for bpf_call to interpreter") > >>>> > >>>> interacting with commit > >>>> > >>>> 290af86629b2 ("bpf: introduce BPF_JIT_ALWAYS_ON config") > >>>> > >>>> from the bpf and net trees. > >>>> > >>>> I have just reverted commit 290af86629b2 for today. A better solution > >>>> would be nice (lie fixing this in a merge between the net-next and net > >>>> trees). > >>> > >>> that's due to 'endif' from 290af86629b2 needs to be moved above > >>> bpf_patch_call_args() definition. > >> > >> That doesn't fix it, because then you'd need to expose > >> interpreters_args as well and obviously that can't be right. > >> > >> Instead, we should never call bpf_patch_call_args() when JIT always on > >> is enabled. So if we fail to JIT the subprogs we should fail > >> immediately. > > > > right, as I was trying to say one extra hunk would be needed for net-next. > > I was reading this patch: > > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > > index a2b211262c25..ca80559c4ec3 100644 > > --- a/kernel/bpf/verifier.c > > +++ b/kernel/bpf/verifier.c > > @@ -5267,7 +5267,11 @@ static int fixup_call_args(struct bpf_verifier_env *env) > > depth = get_callee_stack_depth(env, insn, i); > > if (depth < 0) > > return depth; > > +#ifdef CONFIG_BPF_JIT_ALWAYS_ON > > + return -ENOTSUPP; > > +#else > > bpf_patch_call_args(insn, depth); > > +#endif > > } > > return 0; > > > > but below should be fine too. > > Will test it asap. > > > >> This is the net --> net-next merge resolution I am about to use to fix > >> this: > >> > >> ... > >> +static int fixup_call_args(struct bpf_verifier_env *env) > >> +{ > >> + struct bpf_prog *prog = env->prog; > >> + struct bpf_insn *insn = prog->insnsi; > >> - int i, depth; > >> ++ int i, depth, err; > >> + > >> - if (env->prog->jit_requested) > >> - if (jit_subprogs(env) == 0) > >> ++ err = 0; > > Looks fine to me. The only thing I was wondering was whether we should > set err = -ENOTSUPP here above, but actually that is unnecessary. Say, > if for some reason we would missed to set prog->jit_requested bit under > CONFIG_BPF_JIT_ALWAYS_ON, we would return 0 here even if we would have > calls in the prog. But that also means for bpf_prog_load() that right > after bpf_check() returned, we would go into bpf_prog_select_runtime() > since prog->bpf_func is still NULL at that point, and bpf_int_jit_compile() > from there wouldn't do anything either since prog->jit_requested was > not set in the first place, therefore we return with -ENOTSUPP from > there. So the resolution looks fine to me, we can leave it as is. jit_subprogs() can fail, so err = -ENOTSUPP is necessary.