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=-8.6 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,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 CCFDEC3F2D1 for ; Thu, 5 Mar 2020 13:47:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A348A2146E for ; Thu, 5 Mar 2020 13:47:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583416058; bh=ESM0K3lRAlX6bHImm+yTGw5WfyuYJ8LXuHdmvQZv3vA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=wy4qa+SkbomnSneJuEqbn7gCZB0bNgWQLnAvL3knjMUxmU4ELkrjkNiK7IpjngQkY LTIkSpsVA9ouI/BbHYU7cSU/uLoS3wi0WbFwLpOKpnYV2SQqCaeySyE7LaEQpUcyzX noXcZmSLU7BVBBgxixMUxD6lsDHwNVY3NFzsO1qA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726099AbgCENrh (ORCPT ); Thu, 5 Mar 2020 08:47:37 -0500 Received: from mail.kernel.org ([198.145.29.99]:45798 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725990AbgCENrh (ORCPT ); Thu, 5 Mar 2020 08:47:37 -0500 Received: from linux-8ccs.fritz.box (p5B2812F9.dip0.t-ipconnect.de [91.40.18.249]) (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 75F472073D; Thu, 5 Mar 2020 13:47:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583416056; bh=ESM0K3lRAlX6bHImm+yTGw5WfyuYJ8LXuHdmvQZv3vA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=2UZc6+0QtQ8CoeG+HLn6Hr1cidv/r079yyJGTZXtOOpNKwoLnc2BwNPCYhy5uxxcE PwPX1jDL3XOM7na5s0CKRFvzH4at5QRF66a4rG02ATOJayz3pi5T4RRoh2tkcrUbkn dK+0b+1s9uXT2JU9ulrKw6W/5InxP5afWIfgbeVY= Date: Thu, 5 Mar 2020 14:47:32 +0100 From: Jessica Yu To: Matthias Maennich Cc: Masahiro Yamada , Lucas De Marchi , linux-kernel@vger.kernel.org Subject: Re: [PATCH] modpost: move the namespace field in Module.symvers last Message-ID: <20200305134732.GA1637@linux-8ccs.fritz.box> References: <20200304170345.21218-1-jeyu@kernel.org> <20200305085948.GD119445@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20200305085948.GD119445@google.com> X-OS: Linux linux-8ccs 5.5.0-lp150.12.61-default x86_64 User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org +++ Matthias Maennich [05/03/20 08:59 +0000]: >Hi Jessica! >Thanks for working on this! > >On Wed, Mar 04, 2020 at 06:03:45PM +0100, Jessica Yu wrote: >>In order to preserve backwards compatability with kmod tools, we have to >>move the namespace field in Module.symvers last, as the depmod -e -E >>option looks at the first three fields in Module.symvers to check symbol >>versions (and it's expected they stay in the original order of crc, >>symbol, module). >> >>Fixes: cb9b55d21fe0 ("modpost: add support for symbol namespaces") >>Cc: stable@vger.kernel.org > >Please note, this patch did not actually go to stable@. Hi Matthias! Thanks, I missed that. >>Signed-off-by: Jessica Yu >>--- >>Documentation/kbuild/modules.rst | 4 ++-- >>scripts/export_report.pl | 2 +- >>scripts/mod/modpost.c | 24 ++++++++++++------------ >>3 files changed, 15 insertions(+), 15 deletions(-) >> >>diff --git a/Documentation/kbuild/modules.rst b/Documentation/kbuild/modules.rst >>index 69fa48ee93d6..e0b45a257f21 100644 >>--- a/Documentation/kbuild/modules.rst >>+++ b/Documentation/kbuild/modules.rst >>@@ -470,9 +470,9 @@ build. >> >> The syntax of the Module.symvers file is:: >> >>- >>+ >> >>- 0xe1cc2a05 usb_stor_suspend USB_STORAGE drivers/usb/storage/usb-storage EXPORT_SYMBOL_GPL >>+ 0xe1cc2a05 usb_stor_suspend drivers/usb/storage/usb-storage EXPORT_SYMBOL_GPL USB_STORAGE >> >> The fields are separated by tabs and values may be empty (e.g. >> if no namespace is defined for an exported symbol). >>diff --git a/scripts/export_report.pl b/scripts/export_report.pl >>index 548330e8c4e7..feb3d5542a62 100755 >>--- a/scripts/export_report.pl >>+++ b/scripts/export_report.pl >>@@ -94,7 +94,7 @@ if (defined $opt{'o'}) { >># >>while ( <$module_symvers> ) { >> chomp; >>- my (undef, $symbol, $namespace, $module, $gpl) = split('\t'); >>+ my (undef, $symbol, $module, $gpl, $namespace) = split('\t'); >> $SYMBOL { $symbol } = [ $module , "0" , $symbol, $gpl]; >>} >>close($module_symvers); >>diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c >>index 7edfdb2f4497..6ab235354f36 100644 >>--- a/scripts/mod/modpost.c >>+++ b/scripts/mod/modpost.c >>@@ -2427,7 +2427,7 @@ static void write_if_changed(struct buffer *b, const char *fname) >>} >> >>/* parse Module.symvers file. line format: >>- * 0x12345678symbolmodule[[export]something] >>+ * 0x12345678symbolmoduleexportnamespace >> **/ >>static void read_dump(const char *fname, unsigned int kernel) >>{ >>@@ -2440,7 +2440,7 @@ static void read_dump(const char *fname, unsigned int kernel) >> return; >> >> while ((line = get_next_line(&pos, file, size))) { >>- char *symname, *namespace, *modname, *d, *export, *end; >>+ char *symname, *namespace, *modname, *d, *export; >> unsigned int crc; >> struct module *mod; >> struct symbol *s; >>@@ -2448,16 +2448,16 @@ static void read_dump(const char *fname, unsigned int kernel) >> if (!(symname = strchr(line, '\t'))) >> goto fail; >> *symname++ = '\0'; >>- if (!(namespace = strchr(symname, '\t'))) >>- goto fail; >>- *namespace++ = '\0'; >>- if (!(modname = strchr(namespace, '\t'))) >>+ if (!(modname = strchr(symname, '\t'))) >> goto fail; >> *modname++ = '\0'; >>- if ((export = strchr(modname, '\t')) != NULL) >>- *export++ = '\0'; >>- if (export && ((end = strchr(export, '\t')) != NULL)) >>- *end = '\0'; >>+ if (!(export = strchr(modname, '\t'))) >>+ goto fail; >>+ *export++ = '\0'; >>+ if (!(namespace = strchr(export, '\t'))) > >As mentioned below, we should probably treat namespace as an optional >field. Then this needs adjusting to handle that case. Similar to how >optional cases were handled before. Hm, I think introducing optional fields would add unnecessary complexity, and make future parsing harder. For example, say in the distant future we add another field. If fields are optional, we are no longer able to tell if the 4th field is a namespace or the new_field. Whereas, if we made the fields mandatory (even if empty), we would see crcsymbolmoduleexport_typenew_field, and it's clear that the namespace is empty. I hope that makes sense... IMO, I think it's easiest to just establish the fact that Module.symvers has 5 fields, and fields can be empty. If a field an empty, then the next delimiter or end of line will just follow immediately. Just to reiterate, it is true namespaces are optional, and in the case of no namespace, I would prefer it to be an empty string/field rather than omitting it entirely. >>+ goto fail; >>+ *namespace++ = '\0'; >>+ >> crc = strtoul(line, &d, 16); >> if (*symname == '\0' || *modname == '\0' || *d != '\0') >> goto fail; >>@@ -2508,9 +2508,9 @@ static void write_dump(const char *fname) >> namespace = symbol->namespace; >> buf_printf(&buf, "0x%08x\t%s\t%s\t%s\t%s\n", > >This creates trailing tabs for symbols without namespace. If we treat >'namespace' as an optional field, we should probably make the tab >conditional as well? What do you think? Yeah you're right, the trailing tab after an empty namespace looks weird...but for reasons I cited above, I would like to keep it simple, unless there are huge objections. Thank you for the review! Jessica