From patchwork Tue Apr 25 17:47:44 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yonghong Song X-Patchwork-Id: 13223637 X-Patchwork-Delegate: bpf@iogearbox.net 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 20306C6FD18 for ; Tue, 25 Apr 2023 17:48:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234690AbjDYRsC (ORCPT ); Tue, 25 Apr 2023 13:48:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46938 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230429AbjDYRsB (ORCPT ); Tue, 25 Apr 2023 13:48:01 -0400 Received: from mx0a-00082601.pphosted.com (mx0a-00082601.pphosted.com [67.231.145.42]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3A650AD0F for ; Tue, 25 Apr 2023 10:48:00 -0700 (PDT) Received: from pps.filterd (m0044012.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 33PGDP1O002245 for ; Tue, 25 Apr 2023 10:48:00 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : content-type : content-transfer-encoding : mime-version; s=facebook; bh=G2aTf0mrxc4MBcUVcjGxQOvKF6xdhVDbMmvJ7gxVRBQ=; b=UlYQKp/SCHQgaMVrg/3047pWyR2AU94gn9U3B+yGH37j+8TV3UeMgLKPVXVAbl6jVAlg DHNzie7vsrCWee1Bg1Vvd8s3MM65KX4uA/8ItpCKrCFfFoBCR+l1yLeyGeZfU9KjLa8P hX7Xze+VIw7xvONU3ZZYxxkXwUkIf6Hc1Dk= Received: from maileast.thefacebook.com ([163.114.130.16]) by mx0a-00082601.pphosted.com (PPS) with ESMTPS id 3q687r4ek8-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Tue, 25 Apr 2023 10:47:59 -0700 Received: from twshared4902.04.ash8.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 15.1.2507.23; Tue, 25 Apr 2023 10:47:58 -0700 Received: by devbig309.ftw3.facebook.com (Postfix, from userid 128203) id B7D901E2535E7; Tue, 25 Apr 2023 10:47:44 -0700 (PDT) From: Yonghong Song To: CC: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , , Martin KaFai Lau Subject: [PATCH bpf-next] selftests/bpf: Fix selftest test_global_funcs/global_func1 failure with latest clang Date: Tue, 25 Apr 2023 10:47:44 -0700 Message-ID: <20230425174744.1758515-1-yhs@fb.com> X-Mailer: git-send-email 2.34.1 X-FB-Internal: Safe X-Proofpoint-ORIG-GUID: OWisvOZtxdo9wDJAW19mmdvVh7a3G3iA X-Proofpoint-GUID: OWisvOZtxdo9wDJAW19mmdvVh7a3G3iA X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.254,Aquarius:18.0.942,Hydra:6.0.573,FMLib:17.11.170.22 definitions=2023-04-25_08,2023-04-25_01,2023-02-09_01 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net The selftest test_global_funcs/global_func1 failed with the latest clang17. The reason is due to upstream ArgumentPromotionPass ([1]), which may manipulate static function parameters and cause inlining although the funciton is marked as noinline. The original code: static __attribute__ ((noinline)) int f0(int var, struct __sk_buff *skb) { return skb->len; } __attribute__ ((noinline)) int f1(struct __sk_buff *skb) { ... return f0(0, skb) + skb->len; } ... SEC("tc") __failure __msg("combined stack size of 4 calls is 544") int global_func1(struct __sk_buff *skb) { return f0(1, skb) + f1(skb) + f2(2, skb) + f3(3, skb, 4); } After ArgumentPromotionPass, the code is translated to static __attribute__ ((noinline)) int f0(int var, int skb_len) { return skb_len; } __attribute__ ((noinline)) int f1(struct __sk_buff *skb) { ... return f0(0, skb->len) + skb->len; } ... SEC("tc") __failure __msg("combined stack size of 4 calls is 544") int global_func1(struct __sk_buff *skb) { return f0(1, skb->len) + f1(skb) + f2(2, skb) + f3(3, skb, 4); } And later llvm InstCombine phase recognized that f0() simplify returns the value of the second argument and removed f0() completely and the final code looks like: __attribute__ ((noinline)) int f1(struct __sk_buff *skb) { ... return skb->len + skb->len; } ... SEC("tc") __failure __msg("combined stack size of 4 calls is 544") int global_func1(struct __sk_buff *skb) { return skb->len + f1(skb) + f2(2, skb) + f3(3, skb, 4); } If f0() is not inlined, the verification will fail with stack size 544 for a particular callchain. With f0() inlined, the maximum stack size is 512 which is in the limit. Let us add a `asm volatile ("")` in f0() to prevent ArgumentPromotionPass from hoisting the code to its caller, and this fixed the test failure. [1] https://reviews.llvm.org/D148269 Signed-off-by: Yonghong Song --- tools/testing/selftests/bpf/progs/test_global_func1.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/tools/testing/selftests/bpf/progs/test_global_func1.c b/tools/testing/selftests/bpf/progs/test_global_func1.c index b85fc8c423ba..17a9f59bf5f3 100644 --- a/tools/testing/selftests/bpf/progs/test_global_func1.c +++ b/tools/testing/selftests/bpf/progs/test_global_func1.c @@ -10,6 +10,8 @@ static __attribute__ ((noinline)) int f0(int var, struct __sk_buff *skb) { + asm volatile (""); + return skb->len; }