Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762733AbYF3R5t (ORCPT ); Mon, 30 Jun 2008 13:57:49 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753148AbYF3R5i (ORCPT ); Mon, 30 Jun 2008 13:57:38 -0400 Received: from relay2.sgi.com ([192.48.171.30]:42247 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1762190AbYF3R5d (ORCPT ); Mon, 30 Jun 2008 13:57:33 -0400 Message-ID: <48691E8B.4040605@sgi.com> Date: Mon, 30 Jun 2008 10:57:31 -0700 From: Mike Travis User-Agent: Thunderbird 2.0.0.6 (X11/20070801) MIME-Version: 1.0 To: "H. Peter Anvin" CC: "Eric W. Biederman" , Jeremy Fitzhardinge , Christoph Lameter , Linux Kernel Mailing List Subject: Re: [crash, bisected] Re: [PATCH 3/4] x86_64: Fold pda into per cpu area 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> <486912C4.8070705@sgi.com> <48691556.2080208@zytor.com> In-Reply-To: <48691556.2080208@zytor.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2925 Lines: 66 H. Peter Anvin wrote: > Mike Travis wrote: >> >> FYI, I did try this out and it caused the bootloader to scramble the >> loaded data. The first corruption I found was the .x86cpuvendor.init >> section contained all zeroes. >> > > Explain what you mean with "the bootloader" in this context. > > -hpa After the code was loaded (the compressed code, it seems that my GRUB doesn't support uncompressed loading), the above section contained zeroes. I snapped it fairly early, around secondary_startup_64, and then printed it in x86_64_start_kernel. The object file had the correct data (as displayed by objdump) so I'm assuming that the bootloading process didn't load the section correctly. Below was the linker script I used: --- linux-2.6.tip.orig/include/asm-generic/vmlinux.lds.h +++ linux-2.6.tip/include/asm-generic/vmlinux.lds.h @@ -373,9 +373,13 @@ #ifdef CONFIG_HAVE_ZERO_BASED_PER_CPU #define PERCPU(align) \ - . = ALIGN(align); \ + .data.percpu.abs = .; \ percpu : { } :percpu \ - __per_cpu_load = .; \ + .data.percpu.rel : AT(.data.percpu.abs - LOAD_OFFSET) { \ + BYTE(0) \ + . = ALIGN(align); \ + __per_cpu_load = .; \ + } \ .data.percpu 0 : AT(__per_cpu_load - LOAD_OFFSET) { \ *(.data.percpu.first) \ *(.data.percpu.shared_aligned) \ @@ -383,8 +387,8 @@ *(.data.percpu.page_aligned) \ ____per_cpu_size = .; \ } \ - . = __per_cpu_load + ____per_cpu_size; \ - data : { } :data + . = __per_cpu_load + ____per_cpu_size; + #else #define PERCPU(align) \ . = ALIGN(align); \ It showed all the correct address in the map and __per_cpu_load was a relative symbol (which was the objective.) Btw, our simulator, which only loads uncompressed code, had the data correct, so it *may* only be a result of the code being compressed. Thanks, Mike -- 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/