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[2620:137:e000::3:4]) by mx.google.com with ESMTPS id s22-20020a656456000000b00573fdbc93c0si1909728pgv.892.2023.09.14.12.16.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 14 Sep 2023 12:16:10 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:4 as permitted sender) client-ip=2620:137:e000::3:4; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:4 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: from out1.vger.email (depot.vger.email [IPv6:2620:137:e000::3:0]) by howler.vger.email (Postfix) with ESMTP id 46D018226AC4; Thu, 14 Sep 2023 10:02:15 -0700 (PDT) X-Virus-Status: Clean X-Virus-Scanned: clamav-milter 0.103.10 at howler.vger.email Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231588AbjINRCF convert rfc822-to-8bit (ORCPT + 33 others); Thu, 14 Sep 2023 13:02:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41188 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230502AbjINRCE (ORCPT ); Thu, 14 Sep 2023 13:02:04 -0400 Received: from mx0a-00082601.pphosted.com (mx0a-00082601.pphosted.com [67.231.145.42]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E460A1BD9 for ; Thu, 14 Sep 2023 10:01:59 -0700 (PDT) Received: from pps.filterd (m0148461.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 38EF3xYJ002794 for ; Thu, 14 Sep 2023 10:01:59 -0700 Received: from maileast.thefacebook.com ([163.114.130.16]) by mx0a-00082601.pphosted.com (PPS) with ESMTPS id 3t44fu958x-4 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Thu, 14 Sep 2023 10:01:59 -0700 Received: from twshared24695.38.frc1.facebook.com (2620:10d:c0a8:1b::2d) by mail.thefacebook.com (2620:10d:c0a8:82::b) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.23; Thu, 14 Sep 2023 10:01:55 -0700 Received: by devbig932.frc1.facebook.com (Postfix, from userid 4523) id D443F2458D1EB; Thu, 14 Sep 2023 10:01:50 -0700 (PDT) From: Song Liu To: CC: , Song Liu , Ricardo Ribalda , Sami Tolvanen , , , Subject: [PATCH v3] x86/purgatory: Remove LTO flags Date: Thu, 14 Sep 2023 10:01:38 -0700 Message-ID: <20230914170138.995606-1-song@kernel.org> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-ORIG-GUID: ifomU8eacBZTOObm3QW3u4GgR1DBcA-U X-Proofpoint-GUID: ifomU8eacBZTOObm3QW3u4GgR1DBcA-U X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.267,Aquarius:18.0.980,Hydra:6.0.601,FMLib:17.11.176.26 definitions=2023-09-14_09,2023-09-14_01,2023-05-22_02 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (howler.vger.email [0.0.0.0]); Thu, 14 Sep 2023 10:02:15 -0700 (PDT) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1777040479066943738 X-GMAIL-MSGID: 1777041640022652417 -flto* implies -ffunction-sections. With LTO enabled, ld.lld generates multiple .text sections for purgatory.ro: $ readelf -S purgatory.ro | grep " .text" [ 1] .text PROGBITS 0000000000000000 00000040 [ 7] .text.purgatory PROGBITS 0000000000000000 000020e0 [ 9] .text.warn PROGBITS 0000000000000000 000021c0 [13] .text.sha256_upda PROGBITS 0000000000000000 000022f0 [15] .text.sha224_upda PROGBITS 0000000000000000 00002be0 [17] .text.sha256_fina PROGBITS 0000000000000000 00002bf0 [19] .text.sha224_fina PROGBITS 0000000000000000 00002cc0 This cause WARNING from kexec_purgatory_setup_sechdrs(): WARNING: CPU: 26 PID: 110894 at kernel/kexec_file.c:919 kexec_load_purgatory+0x37f/0x390 Fix this by disabling LTO for purgatory. We could also fix this with an explicit linker script to rejoin .text.* sections back into .text. However, given the benefit of LTOing pugatory is small, simply disable the production of more .text.* sections for now. Fixes: b33fff07e3e3 ("x86, build: allow LTO to be selected") Cc: Ricardo Ribalda Cc: Sami Tolvanen Cc: kexec@lists.infradead.org Cc: linux-kernel@vger.kernel.org Cc: x86@kernel.org Cc: llvm@lists.linux.dev Signed-off-by: Song Liu Reviewed-by: Sami Tolvanen --- AFAICT, x86 is the only arch that supports LTO and purgatory. Changes in v3: 1. Fix "Fixes" tag. (Nick Desaulniers) 2. Add description of an alternative fix, with linker script. (Nick Desaulniers) Changes in v2: 1. Use CC_FLAGS_LTO instead of hardcode -flto. (Nick Desaulniers) --- arch/x86/purgatory/Makefile | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile index c2a29be35c01..08aa0f25f12a 100644 --- a/arch/x86/purgatory/Makefile +++ b/arch/x86/purgatory/Makefile @@ -19,6 +19,10 @@ CFLAGS_sha256.o := -D__DISABLE_EXPORTS -D__NO_FORTIFY # optimization flags. KBUILD_CFLAGS := $(filter-out -fprofile-sample-use=% -fprofile-use=%,$(KBUILD_CFLAGS)) +# When LTO is enabled, llvm emits many text sections, which is not supported +# by kexec. Remove -flto=* flags. +KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_LTO),$(KBUILD_CFLAGS)) + # When linking purgatory.ro with -r unresolved symbols are not checked, # also link a purgatory.chk binary without -r to check for unresolved symbols. PURGATORY_LDFLAGS := -e purgatory_start -z nodefaultlib