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 B44DEC47089 for ; Mon, 28 Nov 2022 01:58:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229777AbiK1B6F (ORCPT ); Sun, 27 Nov 2022 20:58:05 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55686 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229504AbiK1B6D (ORCPT ); Sun, 27 Nov 2022 20:58:03 -0500 Received: from mail-pf1-x42a.google.com (mail-pf1-x42a.google.com [IPv6:2607:f8b0:4864:20::42a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 96E535588; Sun, 27 Nov 2022 17:58:02 -0800 (PST) Received: by mail-pf1-x42a.google.com with SMTP id a16so8668390pfg.4; Sun, 27 Nov 2022 17:58:02 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=Qe5hs8FVwx45grj4bepS5YGWgIaIZzpvoky/dPKEgAk=; b=TpscOfhnmXx5pu5TdPhBFc7zRC07xeXebnx+Y9ppmhZYFRHkldn7qCe6ojvHTNGJU5 yfZ7a6rAKyzM8l7JTHp78PAiMDBaKEImvd0GA8o6MpXL0KeLnoofdor7TKoUGqrDeja3 r49Fy2JPrJgz7U/hjsabD6BCnoo2AQPT2GZ1NAZhu3jxsM5endb1hglbbJ0qGhYYM7bX e5803Ljb5Bc5BfiXqGccsVhBt8Y4VCS0mguJkq/odVAnUtzgI98Ie1YfixHOEUPgINjB 1T8qW/hDnDEdIhI5Lw1KMSl39i8klSdYMYCBmpZ1zX6pFJ0DaP0hGP+VUFFYrSdt0Z94 5VgQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=Qe5hs8FVwx45grj4bepS5YGWgIaIZzpvoky/dPKEgAk=; b=eN5b64gW4TKo3rfoTUTClnwxFTX14p/55DWS616YQILse13lgjtmF3Gs76/DuGxOSr 7PocdpsyQT2hle+g6IGwV9fBKviNANs6k15vn71/tnTPPi7S1SSecNSq5yfeIKULrsfs 3MOtNGqiHQ9Qr6jaeiT9Ei3Nmyf66AHw6QwLSsw/WNReE/sRITN+1GQHpJ1bhbBy8r4f W+H5jP46ufO1dX7Y/B/GGG24B2l/cJZfxnM5urkkfb1kHlpT/M7s7FdAOytY/ZoxVG8/ i7Ej+KSzvhKX6MA8Wj+6UDKKRAmZ4B8sNt2ea0y4hxz844YvWYYAzA9ducBivfNpJhy7 3QJg== X-Gm-Message-State: ANoB5pmA4gA4LydD2QNN6kxbFQgV6wmanh5IkUTt53jLqygVOGovIKR/ QqVU/0W+uMPeQCLPzboSZwA= X-Google-Smtp-Source: AA0mqf6LnCWalB/CHpLF1Wy9qOn4snB2bh4yLi18Y4L4ZAcXtWAV8uvGpIw9WL/CvXIIWkiMytzgmw== X-Received: by 2002:a63:902:0:b0:46e:9bb2:f0f7 with SMTP id 2-20020a630902000000b0046e9bb2f0f7mr26810278pgj.203.1669600681853; Sun, 27 Nov 2022 17:58:01 -0800 (PST) Received: from MacBook-Pro-5.local ([2620:10d:c090:500::7:8561]) by smtp.gmail.com with ESMTPSA id w9-20020a170902904900b00187033cac81sm7452217plz.145.2022.11.27.17.57.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 27 Nov 2022 17:58:01 -0800 (PST) Date: Sun, 27 Nov 2022 17:57:58 -0800 From: Alexei Starovoitov To: Yang Jihong Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, song@kernel.org, yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@google.com, haoluo@google.com, jolsa@kernel.org, illusionist.neo@gmail.com, linux@armlinux.org.uk, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, mykolal@fb.com, shuah@kernel.org, benjamin.tissoires@redhat.com, memxor@gmail.com, colin.i.king@gmail.com, asavkov@redhat.com, delyank@fb.com, bpf@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH bpf-next v3 1/4] bpf: Adapt 32-bit return value kfunc for 32-bit ARM when zext extension Message-ID: <20221128015758.aekybr3qlahfopwq@MacBook-Pro-5.local> References: <20221126094530.226629-1-yangjihong1@huawei.com> <20221126094530.226629-2-yangjihong1@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221126094530.226629-2-yangjihong1@huawei.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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() ? Before producing any patches please understand the logic fully. Your commit log "insn_def_regno should return dst_reg for BPF_JMP type of BPF_PSEUDO_KFUNC_CALL." Makes no sense to me, since dst_reg is unused in JMP insn. There is no concept of a src or dst register in a JMP insn. 32-bit x86 supports calling kfuncs. See emit_kfunc_call(). And we don't have this "verifier bug. zext_dst is set" issue there, right? But what you're saying in the commit log: "if data width of kfunc return value is 32 bits" should have been applicable to x86-32 as well. So please start with a test that demonstrates the issue on x86-32 and then we can discuss the way to fix it. The patch 2 sort-of makes sense. For patch 3 pls add new test funcs to bpf_testmod. We will move all of them from net/bpf/test_run.c to bpf_testmod eventually.