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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,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 AC8B4C2D0D1 for ; Sun, 29 Dec 2019 18:02:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 85783207FF for ; Sun, 29 Dec 2019 18:02:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1577642556; bh=OSw2OidlEAr8cvvBNF4Jmh30draQsb4AfRlRw2pxhbE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=aGlOIeA93peq4NZv1t03Ok0qAOy2tvvT4OhrCaj0qa/vJTJKTBYYKAEAjKj86wlps 0EVUH4duAIewVJJx3vRei+FF4BkAAzpc3TOWDHs89rMRvPx8XnJcAoi5NNtV8d79fY CqmWIBIgQhr1zX+wESVAMDgh5bp5+y7ilwRHIPfI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732725AbfL2Ryi (ORCPT ); Sun, 29 Dec 2019 12:54:38 -0500 Received: from mail.kernel.org ([198.145.29.99]:42658 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731919AbfL2Ryi (ORCPT ); Sun, 29 Dec 2019 12:54:38 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9178B21D7E; Sun, 29 Dec 2019 17:54:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1577642077; bh=OSw2OidlEAr8cvvBNF4Jmh30draQsb4AfRlRw2pxhbE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gGKoUo53l1Wk5uqvBF3aNP5wwwrOrg64qJ2p6GckCVqhYM7ax9mmxSjTacUEbXnQt VuWyosEM2drqLBBiBuP6e1tMMnDoxJKNM7pPu+A3SFCfKYv/uIeyCPc16I+QpBdW4J tJp5+YR+nXB/JEu2YcIPUcnSXt/dL7nZXPdK7DoY= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Yonghong Song , Daniel Borkmann , Andrii Nakryiko , Sasha Levin Subject: [PATCH 5.4 325/434] selftests, bpf: Workaround an alu32 sub-register spilling issue Date: Sun, 29 Dec 2019 18:26:18 +0100 Message-Id: <20191229172723.557643742@linuxfoundation.org> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20191229172702.393141737@linuxfoundation.org> References: <20191229172702.393141737@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Yonghong Song [ Upstream commit 2ea2612b987ad703235c92be21d4e98ee9c2c67c ] Currently, with latest llvm trunk, selftest test_progs failed obj file test_seg6_loop.o with the following error in verifier: infinite loop detected at insn 76 The byte code sequence looks like below, and noted that alu32 has been turned off by default for better generated codes in general: 48: w3 = 100 49: *(u32 *)(r10 - 68) = r3 ... ; if (tlv.type == SR6_TLV_PADDING) { 76: if w3 == 5 goto -18 ... 85: r1 = *(u32 *)(r10 - 68) ; for (int i = 0; i < 100; i++) { 86: w1 += -1 87: if w1 == 0 goto +5 88: *(u32 *)(r10 - 68) = r1 The main reason for verification failure is due to partial spills at r10 - 68 for induction variable "i". Current verifier only handles spills with 8-byte values. The above 4-byte value spill to stack is treated to STACK_MISC and its content is not saved. For the above example: w3 = 100 R3_w=inv100 fp-64_w=inv1086626730498 *(u32 *)(r10 - 68) = r3 R3_w=inv100 fp-64_w=inv1086626730498 ... r1 = *(u32 *)(r10 - 68) R1_w=inv(id=0,umax_value=4294967295,var_off=(0x0; 0xffffffff)) fp-64=inv1086626730498 To resolve this issue, verifier needs to be extended to track sub-registers in spilling, or llvm needs to enhanced to prevent sub-register spilling in register allocation phase. The former will increase verifier complexity and the latter will need some llvm "hacking". Let us workaround this issue by declaring the induction variable as "long" type so spilling will happen at non sub-register level. We can revisit this later if sub-register spilling causes similar or other verification issues. Signed-off-by: Yonghong Song Signed-off-by: Daniel Borkmann Acked-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20191117214036.1309510-1-yhs@fb.com Signed-off-by: Sasha Levin --- tools/testing/selftests/bpf/progs/test_seg6_loop.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/bpf/progs/test_seg6_loop.c b/tools/testing/selftests/bpf/progs/test_seg6_loop.c index c4d104428643..69880c1e7700 100644 --- a/tools/testing/selftests/bpf/progs/test_seg6_loop.c +++ b/tools/testing/selftests/bpf/progs/test_seg6_loop.c @@ -132,8 +132,10 @@ static __always_inline int is_valid_tlv_boundary(struct __sk_buff *skb, *pad_off = 0; // we can only go as far as ~10 TLVs due to the BPF max stack size + // workaround: define induction variable "i" as "long" instead + // of "int" to prevent alu32 sub-register spilling. #pragma clang loop unroll(disable) - for (int i = 0; i < 100; i++) { + for (long i = 0; i < 100; i++) { struct sr6_tlv_t tlv; if (cur_off == *tlv_off) -- 2.20.1