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=-3.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 903FCC433E0 for ; Mon, 1 Jun 2020 17:38:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4B0B120734 for ; Mon, 1 Jun 2020 17:38:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="JKLe5DmL" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726944AbgFARiv (ORCPT ); Mon, 1 Jun 2020 13:38:51 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:51882 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726017AbgFARiv (ORCPT ); Mon, 1 Jun 2020 13:38:51 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1591033129; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=j3La3/IwaxnOET8NRtQwxdy61w/eF/NkEHGvpZshyBY=; b=JKLe5DmLz1adpubRzhUPATFIk7wVuyaQjMAOhxXZK/7YGpy0EGIz4s0+lE3TikgV29uN0q oEB2SzZj/YwzBDx8/SHgMCaqgMffNpqgq4SFA05VifF3SutAtCkLvdrEskdPjyc4sOHZhd BkgiTlhymTvghlKOXb3ge1k+pSFwj4o= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-513-kg2Xm74kMjmoQlPnsXLHJw-1; Mon, 01 Jun 2020 13:38:47 -0400 X-MC-Unique: kg2Xm74kMjmoQlPnsXLHJw-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 9E130800053; Mon, 1 Jun 2020 17:38:45 +0000 (UTC) Received: from treble (ovpn-116-170.rdu2.redhat.com [10.10.116.170]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E984210013C1; Mon, 1 Jun 2020 17:38:42 +0000 (UTC) Date: Mon, 1 Jun 2020 12:38:40 -0500 From: Josh Poimboeuf To: changhuaixin Cc: linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org, bp@alien8.de, hpa@zytor.com, luto@amacapital.net, michal.lkml@markovi.net, mingo@redhat.com, peterz@infradead.org, tglx@linutronix.de, x86@kernel.org, yamada.masahiro@socionext.com Subject: Re: [PATCH 0/2] Build ORC fast lookup table in scripts/sorttable tool Message-ID: <20200601173840.3f36m6l4fsu5bill@treble> References: <20200429064626.16389-1-changhuaixin@linux.alibaba.com> <20200522182815.ezanmvbemhzq2fmm@treble> <482837A8-E9D9-4229-B7B1-8E14403FB2AC@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <482837A8-E9D9-4229-B7B1-8E14403FB2AC@linux.alibaba.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, May 31, 2020 at 01:26:54PM +0800, changhuaixin wrote: > It turned out to be an alignment problem. If sh_size of previous section > orc_unwind is not 4-byte aligned, sh_offset of the following orc_lookup > section is not 4-byte aligned too. However, the VMA of section orc_lookup > is aligned to the nearest 4-byte. Thus, the orc_lookup section means two > different ares for scripts/sorttable tool and kernel. > > Sections headers look like this when it happens: > > 12 .orc_unwind_ip 00172124  ffffffff82573b28  0000000002573b28  01773b28 >  2**0 >                  CONTENTS, ALLOC, LOAD, RELOC, READONLY, DATA > 13 .orc_unwind   0022b1b6  ffffffff826e5c4c  00000000026e5c4c  018e5c4c >  2**0 >                  CONTENTS, ALLOC, LOAD, READONLY, DATA > 14 .orc_lookup   0003003c  ffffffff82910e04  0000000002910e04  01b10e02 >  2**0 >                  ALLOC > 15 .vvar         00001000  ffffffff82941000  0000000002941000  01b41000 >  2**4 >                  CONTENTS, ALLOC, LOAD, DATA > > Sorttable tool uses the are starting with offset 0x01b10e02 for 0x0003003c > bytes. While kernel use the area starting with VMA at  0xffffffff82910e04 > for 0x0003003c bytes, meaning that each entry in this table used by kernel > is actually 2 bytes behind the corresponding entry set from sorttable > tool. > > Any suggestion on fixing this？ The VMA and LMA are both 4-byte aligned. The file offset alignment (0x01b10e02) shouldn't matter. Actually it looks like the problem is that the section doesn't have CONTENTS, so it's just loaded as a BSS section (all zeros). The section needs to be type SHT_PROGBITS instead of SHT_NOBITS. $ readelf -S vmlinux |grep orc_lookup [16] .orc_lookup NOBITS ffffffff82b68418 01d68418 I tried to fix it with diff --git a/scripts/sorttable.h b/scripts/sorttable.h index a36c76c17be4..76adb1fb88f8 100644 --- a/scripts/sorttable.h +++ b/scripts/sorttable.h @@ -341,6 +341,7 @@ static int do_sort(Elf_Ehdr *ehdr, param.lookup_table_size = s->sh_size; param.orc_lookup_table = (unsigned int *) ((void *)ehdr + s->sh_offset); + w(SHT_PROGBITS, &s->sh_type); } if (!strcmp(secstrings + idx, ".text")) { param.text_size = s->sh_size; But that makes kallsyms unhappy, so I guess we need to do it from the linker script where .orc_lookup is created. Linker script doesn't seem to allow manual specification of the section type, so this is the best I could come up with: diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index db600ef218d7..49f4f5bc6165 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -826,6 +826,8 @@ . += (((SIZEOF(.text) + LOOKUP_BLOCK_SIZE - 1) / \ LOOKUP_BLOCK_SIZE) + 1) * 4; \ orc_lookup_end = .; \ + /* HACK: force SHT_PROGBITS so sorttable can edit: */ \ + BYTE(1); \ } #else #define ORC_UNWIND_TABLE