From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753376AbbCYSCD (ORCPT ); Wed, 25 Mar 2015 14:02:03 -0400 Received: from smtprelay0084.hostedemail.com ([216.40.44.84]:58529 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752677AbbCYSCA (ORCPT ); Wed, 25 Mar 2015 14:02:00 -0400 X-Session-Marker: 6A6F6540706572636865732E636F6D X-Spam-Summary: 50,0,0,,d41d8cd98f00b204,joe@perches.com,:::::,RULES_HIT:41:355:379:541:599:960:967:973:988:989:1260:1263:1277:1311:1313:1314:1345:1359:1373:1437:1515:1516:1518:1534:1542:1593:1594:1711:1730:1747:1777:1792:2393:2525:2565:2682:2685:2828:2859:2933:2937:2939:2942:2945:2947:2951:2954:3022:3138:3139:3140:3141:3142:3354:3622:3657:3770:3865:3866:3867:3870:3871:3872:3873:3874:3934:3936:3938:3941:3944:3947:3950:3953:3956:3959:4250:4321:4361:4605:5007:6117:6119:6261:7903:7904:8599:8828:8957:9010:9025:9388:10004:10400:10450:10455:10848:11232:11253:11658:11854:11914:12043:12214:12517:12519:12555:12679:12740:12776:13019:13095:13845:14096:14097:19904:19999:21080,0,RBL:none,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:fn,MSBL:0,DNSBL:none,Custom_rules:0:0:0 X-HE-Tag: blade04_4b69f5584d21c X-Filterd-Recvd-Size: 3175 Message-ID: <1427306517.2717.0.camel@perches.com> Subject: Re: String literals in __init functions From: Joe Perches To: Mason Cc: Linux ARM , LKML Date: Wed, 25 Mar 2015 11:01:57 -0700 In-Reply-To: <5512F6C6.1020304@free.fr> References: <5512F6C6.1020304@free.fr> Content-Type: text/plain; charset="ISO-8859-1" X-Mailer: Evolution 3.12.10-0ubuntu1~14.10.1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2015-03-25 at 18:56 +0100, Mason wrote: > Hello everyone, > > AFAIU, functions only used at system init are tagged __init to have > the linker store them in a separate .init.text section, so memory can > be reclaimed once initialization is complete. Is that correct? > > The corresponding tag for data is __initdata (section .init.data) > > I started wondering if the string literals used in an __init functions > were automatically marked __initdata. > > Looking at the objdump output, I see that the string literals are, > in fact, stored in the .rodata section. I suppose that .rodata is NOT > reclaimed after init? > > This way seems to work: > > static char XyZa[] __initdata = KERN_ALERT "foo"; > static const char XyZb[] __initconst = KERN_ALERT "bar"; > void __init XyZc(void) { printk(XyZa); printk(XyZb); } > > $ arm-linux-gnueabihf-objdump -xd arch/arm/mach-tangox/time.o | grep XyZ > 00000000 l O .init.data 00000006 XyZa > 00000000 l O .init.rodata 00000006 XyZb > 00000000 g F .init.text 00000028 XyZc > 00000000 : > > $ arm-linux-gnueabihf-objdump -xd vmlinux | grep XyZ > c021e360 l O .init.data 00000006 XyZa > c0220090 l O .init.data 00000006 XyZb > c020d928 g F .init.text 00000028 XyZc > c020d928 : > > c020d928 : > c020d928: e1a0c00d mov ip, sp > c020d92c: e92dd800 push {fp, ip, lr, pc} > c020d930: e24cb004 sub fp, ip, #4 > c020d934: e30e0360 movw r0, #58208 ; 0xe360 > c020d938: e34c0021 movt r0, #49185 ; 0xc021 > c020d93c: ebfe00c9 bl c018dc68 > c020d940: e3000090 movw r0, #144 ; 0x90 > c020d944: e34c0022 movt r0, #49186 ; 0xc022 > c020d948: ebfe00c6 bl c018dc68 > c020d94c: e89da800 ldm sp, {fp, sp, pc} > > Did I miss something in init.h? > Or should it be done like above to reclaim string literals? No, you didn't miss anything. One proposal: https://lkml.org/lkml/2014/8/21/255 > Regards. > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/