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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1FBE8C04A95 for ; Wed, 28 Sep 2022 09:55:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233580AbiI1JzV convert rfc822-to-8bit (ORCPT ); Wed, 28 Sep 2022 05:55:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39790 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233136AbiI1Jy4 (ORCPT ); Wed, 28 Sep 2022 05:54:56 -0400 Received: from eu-smtp-delivery-151.mimecast.com (eu-smtp-delivery-151.mimecast.com [185.58.86.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C8BCEEEB7E for ; Wed, 28 Sep 2022 02:53:32 -0700 (PDT) Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id uk-mta-57-4AXFK-2tOtOGBa0m-7JKrw-1; Wed, 28 Sep 2022 10:53:29 +0100 X-MC-Unique: 4AXFK-2tOtOGBa0m-7JKrw-1 Received: from AcuMS.Aculab.com (10.202.163.4) by AcuMS.aculab.com (10.202.163.4) with Microsoft SMTP Server (TLS) id 15.0.1497.38; Wed, 28 Sep 2022 10:53:27 +0100 Received: from AcuMS.Aculab.com ([::1]) by AcuMS.aculab.com ([::1]) with mapi id 15.00.1497.040; Wed, 28 Sep 2022 10:53:27 +0100 From: David Laight To: 'Masahiro Yamada' , "linux-kbuild@vger.kernel.org" CC: "linux-arch@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-ia64@vger.kernel.org" , Al Viro , Ard Biesheuvel , Nicolas Pitre , Nick Desaulniers , "Michal Marek" Subject: RE: [PATCH v3 6/8] modpost: use null string instead of NULL pointer for default namespace Thread-Topic: [PATCH v3 6/8] modpost: use null string instead of NULL pointer for default namespace Thread-Index: AQHY0wWSIlQw/El0SkCvsnOrFVUd1K30meQQ Date: Wed, 28 Sep 2022 09:53:26 +0000 Message-ID: <06cf88841dfb48d8ba89dd22adcd1db9@AcuMS.aculab.com> References: <20220928063947.299333-1-masahiroy@kernel.org> <20220928063947.299333-7-masahiroy@kernel.org> In-Reply-To: <20220928063947.299333-7-masahiroy@kernel.org> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Masahiro Yamada > Sent: 28 September 2022 07:40 > > The default namespace is the null string, "". > > When set, the null string "" is converted to NULL: > > s->namespace = namespace[0] ? NOFAIL(strdup(namespace)) : NULL; > > When printed, the NULL pointer is get back to the null string: > > sym->namespace ?: "" > > This saves 1 byte memory allocated for "", but loses the readability. The code size changes are far larger that any data sizes. > In kernel-space, we strive to save memory, but modpost is a userspace > tool used to build the kernel. On modern systems, such small piece of > memory is not a big deal. > > Handle the namespace string as is. > > Signed-off-by: Masahiro Yamada > Reviewed-by: Nick Desaulniers > --- > > (no changes since v1) > > scripts/mod/modpost.c | 17 +++++++++++------ > 1 file changed, 11 insertions(+), 6 deletions(-) > > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c > index 0bb5bbd176b4..29f30558a398 100644 > --- a/scripts/mod/modpost.c > +++ b/scripts/mod/modpost.c > @@ -297,6 +297,13 @@ static bool contains_namespace(struct list_head *head, const char *namespace) > { > struct namespace_list *list; > > + /* > + * The default namespace is null string "", which is always implicitly > + * contained. > + */ > + if (!namespace[0]) > + return true; > + > list_for_each_entry(list, head, list) { > if (!strcmp(list->namespace, namespace)) > return true; > @@ -366,7 +373,7 @@ static struct symbol *sym_add_exported(const char *name, struct module *mod, > s = alloc_symbol(name); > s->module = mod; > s->is_gpl_only = gpl_only; > - s->namespace = namespace[0] ? NOFAIL(strdup(namespace)) : NULL; > + s->namespace = NOFAIL(strdup(namespace)); > list_add_tail(&s->list, &mod->exported_symbols); > hash_add_symbol(s); > > @@ -1928,8 +1935,7 @@ static void check_exports(struct module *mod) > else > basename = mod->name; > > - if (exp->namespace && > - !contains_namespace(&mod->imported_namespaces, exp->namespace)) { > + if (!contains_namespace(&mod->imported_namespaces, exp->namespace)) { Do you still need to optimise/check for the default namespace? David > modpost_log(allow_missing_ns_imports ? LOG_WARN : LOG_ERROR, > "module %s uses symbol %s from namespace %s, but does not import it.\n", > basename, exp->name, exp->namespace); > @@ -2015,8 +2021,7 @@ static void add_exported_symbols(struct buffer *buf, struct module *mod) > list_for_each_entry(sym, &mod->exported_symbols, list) > buf_printf(buf, "KSYMTAB_%s(%s, \"%s\", \"%s\");\n", > sym->is_func ? "FUNC" : "DATA", sym->name, > - sym->is_gpl_only ? "_gpl" : "", > - sym->namespace ?: ""); > + sym->is_gpl_only ? "_gpl" : "", sym->namespace); > > if (!modversions) > return; > @@ -2284,7 +2289,7 @@ static void write_dump(const char *fname) > buf_printf(&buf, "0x%08x\t%s\t%s\tEXPORT_SYMBOL%s\t%s\n", > sym->crc, sym->name, mod->name, > sym->is_gpl_only ? "_GPL" : "", > - sym->namespace ?: ""); > + sym->namespace); > } > } > write_buf(&buf, fname); > -- > 2.34.1 - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)