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 X-Spam-Level: X-Spam-Status: No, score=-9.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E8FA2C31E51 for ; Sat, 15 Jun 2019 19:12:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BCF202080A for ; Sat, 15 Jun 2019 19:12:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1560625961; bh=Yb/LI51bMPBAEudcbaRa07Porw7qvfR07aKDvocFxnQ=; h=From:To:CC:Subject:Date:In-Reply-To:References:List-ID:From; b=0gaVen4H9kjj/X3qx2zpeOhthlf1TfBa00sDDaaU6QNn0sVOwwtHUXCSSekOIEedC RspsjvdarHSrwI7yunxIzZJALk1pINqqG+jQ/BBg2wGBG10ddqkZG+VDmb0FlRcnQM lS9Xggr4iMPpDed/zGjou3wjsh43MIFZu+8ArN3g= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726993AbfFOTMh convert rfc822-to-8bit (ORCPT ); Sat, 15 Jun 2019 15:12:37 -0400 Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:41184 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726772AbfFOTMg (ORCPT ); Sat, 15 Jun 2019 15:12:36 -0400 Received: from pps.filterd (m0109334.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x5FJCVg1011065 for ; Sat, 15 Jun 2019 12:12:35 -0700 Received: from maileast.thefacebook.com ([163.114.130.16]) by mx0a-00082601.pphosted.com with ESMTP id 2t4yykgscb-4 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Sat, 15 Jun 2019 12:12:35 -0700 Received: from mx-out.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:83::6) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1713.5; Sat, 15 Jun 2019 12:12:32 -0700 Received: by devbig007.ftw2.facebook.com (Postfix, from userid 572438) id 4444F760AA7; Sat, 15 Jun 2019 12:12:32 -0700 (PDT) Smtp-Origin-Hostprefix: devbig From: Alexei Starovoitov Smtp-Origin-Hostname: devbig007.ftw2.facebook.com To: CC: , , , Smtp-Origin-Cluster: ftw2c04 Subject: [PATCH v3 bpf-next 3/9] bpf: extend is_branch_taken to registers Date: Sat, 15 Jun 2019 12:12:19 -0700 Message-ID: <20190615191225.2409862-4-ast@kernel.org> X-Mailer: git-send-email 2.20.0 In-Reply-To: <20190615191225.2409862-1-ast@kernel.org> References: <20190615191225.2409862-1-ast@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT X-FB-Internal: Safe Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-06-15_11:,, signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 priorityscore=1501 malwarescore=0 suspectscore=1 phishscore=0 bulkscore=0 spamscore=0 clxscore=1034 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=594 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1906150182 X-FB-Internal: deliver Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org This patch extends is_branch_taken() logic from JMP+K instructions to JMP+X instructions. Conditional branches are often done when src and dst registers contain known scalars. In such case the verifier can follow the branch that is going to be taken when program executes. That speeds up the verification and is essential feature to support bounded loops. Signed-off-by: Alexei Starovoitov Acked-by: Andrii Nakryiko --- kernel/bpf/verifier.c | 34 +++++++++++++++++++--------------- 1 file changed, 19 insertions(+), 15 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 6c13d86569a6..8d3a4ef1d969 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -5266,9 +5266,10 @@ static int check_cond_jmp_op(struct bpf_verifier_env *env, struct bpf_verifier_state *this_branch = env->cur_state; struct bpf_verifier_state *other_branch; struct bpf_reg_state *regs = this_branch->frame[this_branch->curframe]->regs; - struct bpf_reg_state *dst_reg, *other_branch_regs; + struct bpf_reg_state *dst_reg, *other_branch_regs, *src_reg = NULL; u8 opcode = BPF_OP(insn->code); bool is_jmp32; + int pred = -1; int err; /* Only conditional jumps are expected to reach here. */ @@ -5293,6 +5294,7 @@ static int check_cond_jmp_op(struct bpf_verifier_env *env, insn->src_reg); return -EACCES; } + src_reg = ®s[insn->src_reg]; } else { if (insn->src_reg != BPF_REG_0) { verbose(env, "BPF_JMP/JMP32 uses reserved fields\n"); @@ -5308,20 +5310,22 @@ static int check_cond_jmp_op(struct bpf_verifier_env *env, dst_reg = ®s[insn->dst_reg]; is_jmp32 = BPF_CLASS(insn->code) == BPF_JMP32; - if (BPF_SRC(insn->code) == BPF_K) { - int pred = is_branch_taken(dst_reg, insn->imm, opcode, - is_jmp32); - - if (pred == 1) { - /* only follow the goto, ignore fall-through */ - *insn_idx += insn->off; - return 0; - } else if (pred == 0) { - /* only follow fall-through branch, since - * that's where the program will go - */ - return 0; - } + if (BPF_SRC(insn->code) == BPF_K) + pred = is_branch_taken(dst_reg, insn->imm, + opcode, is_jmp32); + else if (src_reg->type == SCALAR_VALUE && + tnum_is_const(src_reg->var_off)) + pred = is_branch_taken(dst_reg, src_reg->var_off.value, + opcode, is_jmp32); + if (pred == 1) { + /* only follow the goto, ignore fall-through */ + *insn_idx += insn->off; + return 0; + } else if (pred == 0) { + /* only follow fall-through branch, since + * that's where the program will go + */ + return 0; } other_branch = push_stack(env, *insn_idx + insn->off + 1, *insn_idx, -- 2.20.0