Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760228AbYFTUqM (ORCPT ); Fri, 20 Jun 2008 16:46:12 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756216AbYFTUbQ (ORCPT ); Fri, 20 Jun 2008 16:31:16 -0400 Received: from out02.mta.xmission.com ([166.70.13.232]:35623 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762146AbYFTUbL (ORCPT ); Fri, 20 Jun 2008 16:31:11 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: Mike Travis Cc: Jeremy Fitzhardinge , Christoph Lameter , Linux Kernel Mailing List , "H. Peter Anvin" , "Eric W. Biederman" References: <20080604003018.538497000@polaris-admin.engr.sgi.com> <20080605102222.GA21319@elte.hu> <484EF29C.7080100@sgi.com> <485947A8.8060801@goop.org> <4859511E.5050605@sgi.com> <48596315.6020104@goop.org> <48596893.4040908@sgi.com> <485AADAC.3070301@sgi.com> <485AB78B.5090904@goop.org> <485AC120.6010202@sgi.com> <485AC5D4.6040302@goop.org> <485ACA8F.10006@sgi.com> <485ACD92.8050109@sgi.com> <485AD138.4010404@goop.org> <485ADA12.5010505@sgi.com> <485ADC73.60009@goop.org> <485BDB04.4090709@sgi.com> <485BE80E.10209@goop.org> <485BF8F5.6010802@goop.org> <485BFFC5.6020404@sgi.com> Date: Fri, 20 Jun 2008 13:25:06 -0700 In-Reply-To: <485BFFC5.6020404@sgi.com> (Mike Travis's message of "Fri, 20 Jun 2008 12:06:45 -0700") Message-ID: User-Agent: Gnus/5.110006 (No Gnus v0.6) Emacs/21.4 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-SA-Exim-Connect-IP: 24.130.11.59 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-DCC: XMission; sa02 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;Mike Travis X-Spam-Relay-Country: X-Spam-Report: * -1.8 ALL_TRUSTED Passed through trusted hosts only via SMTP * 0.0 T_TM2_M_HEADER_IN_MSG BODY: T_TM2_M_HEADER_IN_MSG * -2.6 BAYES_00 BODY: Bayesian spam probability is 0 to 1% * [score: 0.0000] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa02 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 XM_SPF_Neutral SPF-Neutral Subject: Re: [crash, bisected] Re: [PATCH 3/4] x86_64: Fold pda into per cpu area X-SA-Exim-Version: 4.2 (built Thu, 03 Mar 2005 10:44:12 +0100) X-SA-Exim-Scanned: Yes (on mgr1.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2387 Lines: 56 Mike Travis writes: > Jeremy Fitzhardinge wrote: >> >> >> BTW, I think __per_cpu_load will cause trouble if you make a relocatable >> kernel, being an absolute symbol. But I have relocation off at the moment. >> > ... > Here's where it's defined (in include/asm-generic/vmlinux.lds.h): > > #ifdef CONFIG_HAVE_ZERO_BASED_PER_CPU > #define PERCPU(align) \ > . = ALIGN(align); \ > percpu : { } :percpu \ > __per_cpu_load = .; \ > .data.percpu 0 : AT(__per_cpu_load - LOAD_OFFSET) { \ > *(.data.percpu.first) \ > *(.data.percpu.shared_aligned) \ > *(.data.percpu) \ > *(.data.percpu.page_aligned) \ > ____per_cpu_size = .; \ > } \ > . = __per_cpu_load + ____per_cpu_size; \ > data : { } :data > #else > > Can we generate a new symbol which would account for LOAD_OFFSET? Ouch. Absolute symbols indeed. On the 32bit kernel that may play havoc with the relocatable kernel, although we have had similar absolute logic for the last year. With __per_cpu_start and __per_cpu_end so it may not be a problem. To initialize the percpu data you do want to talk to the virtual address at __per_coup_load. But it is absolute Ugh. It might be worth saying something like. .data.percpu.start : AT(.data.percpu.dummy - LOAD_OFFSET) { DATA(0) . = ALIGN(align); __per_cpu_load = . ; } To make __per_cpu_load a relative symbol. ld has a bad habit of taking symbols out of empty sections and making them absolute. Which is why I added the DATA(0). Still I don't think that would be the 64bit problem. Eric -- 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/