From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755037AbcGFQwr (ORCPT ); Wed, 6 Jul 2016 12:52:47 -0400 Received: from mail-db5eur01on0055.outbound.protection.outlook.com ([104.47.2.55]:48984 "EHLO EUR01-DB5-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754136AbcGFQwp (ORCPT ); Wed, 6 Jul 2016 12:52:45 -0400 Authentication-Results: spf=none (sender IP is ) smtp.mailfrom=cmetcalf@mellanox.com; Subject: Re: [PATCH v2 4/4] dynamic_debug: add jump label support To: Jason Baron , Arnd Bergmann References: <587263b37406eda0d2ab84874a9fd4c81eaeca1d.1463778029.git.jbaron@akamai.com> <3796097.4dlb9d7Id8@wuerfel> <575B3108.1020409@akamai.com> <5c98fce0-7d90-14ec-6ff5-6fd5cde673b8@mellanox.com> <577C1F43.9090209@akamai.com> CC: , , , , "David S. Miller" , From: Chris Metcalf Message-ID: Date: Wed, 6 Jul 2016 12:52:23 -0400 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.1.1 MIME-Version: 1.0 In-Reply-To: <577C1F43.9090209@akamai.com> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [12.216.194.146] X-ClientProxiedBy: BY2PR04CA0006.namprd04.prod.outlook.com (10.255.247.16) To HE1PR05MB1689.eurprd05.prod.outlook.com (10.169.119.155) X-MS-Office365-Filtering-Correlation-Id: 83ac4d24-baf8-41d6-477c-08d3a5bdf20f X-Microsoft-Exchange-Diagnostics: 1;HE1PR05MB1689;2:zKpbPKUeLiH2Ikr7VgiPucGASDPTTs9tnaonR1FQ0w7HWJMph6Rim9TE7NTB+DxM11riiDdQtsR2RbnsELArOANCO0/VWZAwRFn2P6O8Jx9dipGmwG48KMfLgnkZSRCMUs0ExegwC07c9Av8+dvinDKGtr2YpmXPT5v+GnnY946yGMbn+zX0fjIS6giHPvVv;3:8pxTul95jnDSmEZlWwSyBNt1PPYAHRUM6uEpori5ceKAB9ArqkzB6ofo2XlnJg2k9Rzo3n7AEPNMB7QJehcYJbEpCCiMi9ScogSAVwQdEE06Bght0igXdoIGZIcuaXem;25:BCjeX37YU5hi/6GOgYjAU9wkqFPPfqpsdjnID/N7scZ/qhkVasMh0k6FXCClRlPSgmL+9cRER9k33Twq87Kd34+NqalKCNiumAKmA9NFHfC/3XDjr+QncHMd33OEx35tUZUUB3tk7mMdobvzCrLBXeMdiP4//B3oWYjHWoqykhns5lHlDNSDor5kYF8ZKq/1mpo81HbvvOXDPPu7dRpYeQ1oHHIrWd+RnJqI84tFUpsMHqG1gQOh797OlNrHI/XHxw9rzF1tIi1Iug8wxetdP+8eD6Le3eMxBgFTsNtg8AuOcXQTmNrZXMKbNOExIwkOGmL21aVBwYXFMJ/dWoepsPvdkbFdCinaVC6ASIIPuZMEgyiC3XySeLZgCUGm2MDY2IqGO+ZD5SjYSu+SF+UfiOFkSOGcMkY50KO6ALHW/eY=;31:+Aj0jkcakTPVrVZJ5NFIeNpWymVdFmbYE8atVMb4Jh7G5j99k4XXES9Uyc4jItzMw8Xfyr9cLR1f3OOCT02RYY+XkAi10TWDJ6AcWmlQTibJrJH8dEFJ19qez8VxjIqPDQMitcbcmnVjAOD/FtjlM+tl2HHPo6nR1rruAb6vgMsW2u+3teZULaVigTWF9abObKqDViR/QHYF6MgSIEMIMA== X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:;SRVR:HE1PR05MB1689; 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Thus, we can end up with >>> references in the __jump_table to addresses that may be in an >>> __exit section. The jump label code already protects itself >>> from touch code in the init sections after it has been freed. >>> Thus, simply having functions marked with __exit in the init >>> section is sufficient here. >> How does this patch work instead? >> >> diff --git a/arch/tile/kernel/vmlinux.lds.S >> b/arch/tile/kernel/vmlinux.lds.S >> index 378f5d8d1ec8..5e83d2689def 100644 >> --- a/arch/tile/kernel/vmlinux.lds.S >> +++ b/arch/tile/kernel/vmlinux.lds.S >> @@ -58,7 +58,15 @@ SECTIONS >> _etext = .; >> >> /* "Init" is divided into two areas with very different virtual >> addresses. */ >> - INIT_TEXT_SECTION(PAGE_SIZE) >> + . = ALIGN(PAGE_SIZE); >> + .init.text : AT(ADDR(.init.text) - LOAD_OFFSET) { >> + VMLINUX_SYMBOL(_sinittext) = .; >> + INIT_TEXT >> +#ifdef CONFIG_JUMP_LABEL /* __jump_table may reference __exit text */ >> + EXIT_TEXT >> +#endif >> + VMLINUX_SYMBOL(_einittext) = .; >> + } >> >> /* Now we skip back to PAGE_OFFSET for the data. */ >> . = (. - TEXT_OFFSET + PAGE_OFFSET); >> > > Hi Chris, > > Thanks for the patch. I can confirm that it resolves the following > compilation issue: > > `.exit.text' referenced in section `__jump_table' of fs/built-in.o: > defined in discarded section `.exit.text' of fs/built-in.o > `.exit.text' referenced in section `__jump_table' of fs/built-in.o: > defined in discarded section `.exit.text' of fs/built-in.o > > I was able to create the issue by simply adding a > static_key_unlikely() branch to an __exit section that ends > up being built-in (non-module). > > So this issue is really independent of this patch series... > Should I add your patch to my series when I re-post? I'm happy to just take a version of this into the tile tree instead, since you're right, it's a pre-existing problem. I'll post the revised change shortly and cc you. Thanks! -- Chris Metcalf, Mellanox Technologies http://www.mellanox.com