From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E965DC352A1 for ; Sat, 3 Dec 2022 16:41:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229815AbiLCQlA (ORCPT ); Sat, 3 Dec 2022 11:41:00 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43022 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229448AbiLCQk4 (ORCPT ); Sat, 3 Dec 2022 11:40:56 -0500 Received: from mail-ed1-x52a.google.com (mail-ed1-x52a.google.com [IPv6:2a00:1450:4864:20::52a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1EBC01FCD2; Sat, 3 Dec 2022 08:40:54 -0800 (PST) Received: by mail-ed1-x52a.google.com with SMTP id l11so10293964edb.4; Sat, 03 Dec 2022 08:40:54 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=LQ8xubanzd9+YmlzrGLsTJHNMcl91Ughdo9/l+FSuMM=; b=hiY3HcrHTc3T2Oy7z7Tj94uZbex9hv4uZ8RdWdocPqJJ3JrlvPjas0gykuLomSXAbO IWOmQSX4LMYYWtTZ1CacLVMD7c84cCa7h4ylhirAXzjVmWxRgNQsCKGfBemrqbIsHrgL DwHiR0sJJgpwnLiwFD+vQOEP8MwvxxAhvw/9MIL/sNtwLlPEcAuAhHckHERutyU5PuVB RLxLScIOFmKMwRCoTjNoJKP4mxXCbIcaTyON0/pTw1MfzNKjPN3UlrPTODnDs0aSagCb hVK2lX+vulXKUVwDflC5uLOZ4fNe58A0OgzpHbcHwiebSknNt5MsDGclTYvdPFw/YfOt 0tKA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=LQ8xubanzd9+YmlzrGLsTJHNMcl91Ughdo9/l+FSuMM=; b=YnYu0/NrdZXjLrXXpFoX96B6MwYLYJijXkGUD9jYs+oYuMR56h5qMJ4wNyC3hHKFKZ 6/wR91i7rlcZhoY2beiGJ+/SvxF8vck7fiX6QVGsVW/YcsDXhE9Zr4K6xH1XEbhLFC2v tdakiEE0jHQmsg3x/CqgevCQ30Qx16Yglwgj+w/e/lBoTUsMDxHIiTeg1Au+VJidXaKY QmqRqPIeSHVmzPFxSLMjUjsVIeG3CORjNMw5uyz94KCvSMLCnUdf4I5fyy0pqR1MejUX W01SD8CbTSyY55HvxtWuvaV/LXLvViIQCIQ5Ctz2ROpLnrUmbDha+s4WCUW6gDd7aiMl iOLw== X-Gm-Message-State: ANoB5pkcA0psZLvGNXCG/HEOCBo1B5YcY6EVQDC7RY5xTWt2QVeYYrK2 KiYBaZNKUzY890haOSPWZTA63jOyxjAZDd+HYhE= X-Google-Smtp-Source: AA0mqf4Fw05PxBvulQnp1D6VoFF5JChDHkFZuOW2NiyjEVA5vYEc30GGZtqJod+PxyqLMHFYYJGccX0aEIHnfwS1zzg= X-Received: by 2002:a05:6402:5289:b0:462:70ee:fdb8 with SMTP id en9-20020a056402528900b0046270eefdb8mr33646016edb.66.1670085651954; Sat, 03 Dec 2022 08:40:51 -0800 (PST) MIME-Version: 1.0 References: <20221126094530.226629-1-yangjihong1@huawei.com> <20221126094530.226629-2-yangjihong1@huawei.com> <20221128015758.aekybr3qlahfopwq@MacBook-Pro-5.local> <8cb54255-4dce-6d50-d6f0-ac9af0e56f37@huawei.com> In-Reply-To: <8cb54255-4dce-6d50-d6f0-ac9af0e56f37@huawei.com> From: Alexei Starovoitov Date: Sat, 3 Dec 2022 08:40:40 -0800 Message-ID: Subject: Re: [PATCH bpf-next v3 1/4] bpf: Adapt 32-bit return value kfunc for 32-bit ARM when zext extension To: Yang Jihong Cc: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Shubham Bansal , Russell King , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Mykola Lysenko , Shuah Khan , Benjamin Tissoires , Kumar Kartikeya Dwivedi , colin.i.king@gmail.com, Artem Savkov , Delyan Kratunov , bpf , linux-arm-kernel , LKML , Network Development , "open list:KERNEL SELFTEST FRAMEWORK" Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 2, 2022 at 6:58 PM Yang Jihong wrote: > > > > On 2022/11/29 0:41, Alexei Starovoitov wrote: > > On Mon, Nov 28, 2022 at 4:40 AM Yang Jihong wrote: > >> > >> > >> > >> On 2022/11/28 9:57, Alexei Starovoitov wrote: > >>> On Sat, Nov 26, 2022 at 05:45:27PM +0800, Yang Jihong wrote: > >>>> For ARM32 architecture, if data width of kfunc return value is 32 bits, > >>>> need to do explicit zero extension for high 32-bit, insn_def_regno should > >>>> return dst_reg for BPF_JMP type of BPF_PSEUDO_KFUNC_CALL. Otherwise, > >>>> opt_subreg_zext_lo32_rnd_hi32 returns -EFAULT, resulting in BPF failure. > >>>> > >>>> Signed-off-by: Yang Jihong > >>>> --- > >>>> kernel/bpf/verifier.c | 44 ++++++++++++++++++++++++++++++++++++++++--- > >>>> 1 file changed, 41 insertions(+), 3 deletions(-) > >>>> > >>>> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > >>>> index 264b3dc714cc..193ea927aa69 100644 > >>>> --- a/kernel/bpf/verifier.c > >>>> +++ b/kernel/bpf/verifier.c > >>>> @@ -1927,6 +1927,21 @@ find_kfunc_desc(const struct bpf_prog *prog, u32 func_id, u16 offset) > >>>> sizeof(tab->descs[0]), kfunc_desc_cmp_by_id_off); > >>>> } > >>>> > >>>> +static int kfunc_desc_cmp_by_imm(const void *a, const void *b); > >>>> + > >>>> +static const struct bpf_kfunc_desc * > >>>> +find_kfunc_desc_by_imm(const struct bpf_prog *prog, s32 imm) > >>>> +{ > >>>> + struct bpf_kfunc_desc desc = { > >>>> + .imm = imm, > >>>> + }; > >>>> + struct bpf_kfunc_desc_tab *tab; > >>>> + > >>>> + tab = prog->aux->kfunc_tab; > >>>> + return bsearch(&desc, tab->descs, tab->nr_descs, > >>>> + sizeof(tab->descs[0]), kfunc_desc_cmp_by_imm); > >>>> +} > >>>> + > >>>> static struct btf *__find_kfunc_desc_btf(struct bpf_verifier_env *env, > >>>> s16 offset) > >>>> { > >>>> @@ -2342,6 +2357,13 @@ static bool is_reg64(struct bpf_verifier_env *env, struct bpf_insn *insn, > >>>> */ > >>>> if (insn->src_reg == BPF_PSEUDO_CALL) > >>>> return false; > >>>> + > >>>> + /* Kfunc call will reach here because of insn_has_def32, > >>>> + * conservatively return TRUE. > >>>> + */ > >>>> + if (insn->src_reg == BPF_PSEUDO_KFUNC_CALL) > >>>> + return true; > >>>> + > >>>> /* Helper call will reach here because of arg type > >>>> * check, conservatively return TRUE. > >>>> */ > >>>> @@ -2405,10 +2427,26 @@ static bool is_reg64(struct bpf_verifier_env *env, struct bpf_insn *insn, > >>>> } > >>>> > >>>> /* Return the regno defined by the insn, or -1. */ > >>>> -static int insn_def_regno(const struct bpf_insn *insn) > >>>> +static int insn_def_regno(struct bpf_verifier_env *env, const struct bpf_insn *insn) > >>>> { > >>>> switch (BPF_CLASS(insn->code)) { > >>>> case BPF_JMP: > >>>> + if (insn->src_reg == BPF_PSEUDO_KFUNC_CALL) { > >>>> + const struct bpf_kfunc_desc *desc; > >>>> + > >>>> + /* The value of desc cannot be NULL */ > >>>> + desc = find_kfunc_desc_by_imm(env->prog, insn->imm); > >>>> + > >>>> + /* A kfunc can return void. > >>>> + * The btf type of the kfunc's return value needs > >>>> + * to be checked against "void" first > >>>> + */ > >>>> + if (desc->func_model.ret_size == 0) > >>>> + return -1; > >>>> + else > >>>> + return insn->dst_reg; > >>>> + } > >>>> + fallthrough; > >>> > >>> I cannot make any sense of this patch. > >>> insn->dst_reg above is 0. > >>> The kfunc call doesn't define a register from insn_def_regno() pov. > >>> > >>> Are you hacking insn_def_regno() to return 0 so that > >>> if (WARN_ON(load_reg == -1)) { > >>> verbose(env, "verifier bug. zext_dst is set, but no reg is defined\n"); > >>> return -EFAULT; > >>> } > >>> in opt_subreg_zext_lo32_rnd_hi32() doesn't trigger ? > >>> > >>> But this verifier message should have been a hint that you need > >>> to analyze why zext_dst is set on this kfunc call. > >>> Maybe it shouldn't ? > >>> Did you analyze the logic of mark_btf_func_reg_size() ? > >> make r0 zext is not caused by mark_btf_func_reg_size. > >> > >> This problem occurs when running the kfunc_call_test_ref_btf_id test > >> case in the 32-bit ARM environment. > > > > Why is it not failing on x86-32 ? > Use the latest mainline kernel code to test on the x86_32 machine. The > test also fails: > > # ./test_progs -t kfunc_call/kfunc_call_test_ref_btf_id > Failed to load bpf_testmod.ko into the kernel: -8 > WARNING! Selftests relying on bpf_testmod.ko will be skipped. > libbpf: prog 'kfunc_call_test_ref_btf_id': BPF program load failed: > Bad address > libbpf: prog 'kfunc_call_test_ref_btf_id': -- BEGIN PROG LOAD LOG -- > processed 25 insns (limit 1000000) max_states_per_insn 0 total_states > 2 peak_states 2 mark_read 1 > -- END PROG LOAD LOG -- > libbpf: prog 'kfunc_call_test_ref_btf_id': failed to load: -14 > libbpf: failed to load object 'kfunc_call_test' > libbpf: failed to load BPF skeleton 'kfunc_call_test': -14 > verify_success:FAIL:skel unexpected error: -14 > > Therefore, this problem also exists on x86_32: > "verifier bug. zext_dst is set, but no reg is defined" The kernel returns -14 == EFAULT. That's a completely different issue.