From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Borkmann Subject: Re: linux-next: build failure after merge of the net-next tree Date: Fri, 12 Jan 2018 11:45:42 +0100 Message-ID: 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=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20180112042148.jsxb26fodw3fgneb@ast-mbp> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Alexei Starovoitov , David Miller Cc: sfr@canb.auug.org.au, netdev@vger.kernel.org, ast@kernel.org, linux-next@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-next.vger.kernel.org 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. >> ++ if (env->prog->jit_requested) { >> ++ err = jit_subprogs(env); >> ++ if (err == 0) >> + return 0; >> - >> ++ } >> ++#ifndef CONFIG_BPF_JIT_ALWAYS_ON >> + for (i = 0; i < prog->len; i++, insn++) { >> + if (insn->code != (BPF_JMP | BPF_CALL) || >> + insn->src_reg != BPF_PSEUDO_CALL) >> + continue; >> + depth = get_callee_stack_depth(env, insn, i); >> + if (depth < 0) >> + return depth; >> + bpf_patch_call_args(insn, depth); >> + } >> - return 0; >> ++ err = 0; >> ++#endif >> ++ return err; >> +} >> + >> /* fixup insn->imm field of bpf_call instructions >> * and inline eligible helpers as explicit sequence of BPF instructions >> *