From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexei Starovoitov Subject: Re: linux-next: build failure after merge of the net-next tree Date: Fri, 12 Jan 2018 08:43:25 -0800 Message-ID: <20180112164324.oiifyfdioeohl3lt@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> <20180112155609.utnakkerdbtbj7ne@ast-mbp.dhcp.thefacebook.com> <94b98645-581b-7824-f116-2467d1987347@iogearbox.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mail-pf0-f193.google.com ([209.85.192.193]:46897 "EHLO mail-pf0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934027AbeALQna (ORCPT ); Fri, 12 Jan 2018 11:43:30 -0500 Content-Disposition: inline In-Reply-To: <94b98645-581b-7824-f116-2467d1987347@iogearbox.net> Sender: linux-next-owner@vger.kernel.org List-ID: 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 On Fri, Jan 12, 2018 at 05:21:54PM +0100, Daniel Borkmann wrote: > On 01/12/2018 04:56 PM, Alexei Starovoitov wrote: > > 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. > > But if jit_subprogs() fails, then the err is propagated at the end of > the function (the 'return err' I mean). right. Also, since we do: fp->jit_requested = ebpf_jit_enabled(); and static inline bool ebpf_jit_enabled(void) { return bpf_jit_enable && bpf_jit_is_ebpf(); } and JIT_ALWAYS_ON depends on CONFIG_HAVE_EBPF_JIT we should be good.