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=-0.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,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 2CB31C2D0DB for ; Thu, 30 Jan 2020 20:21:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DC5332083E for ; Thu, 30 Jan 2020 20:21:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="dSaB8Xzx" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727626AbgA3UVI (ORCPT ); Thu, 30 Jan 2020 15:21:08 -0500 Received: from mail-ot1-f67.google.com ([209.85.210.67]:39505 "EHLO mail-ot1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726514AbgA3UVH (ORCPT ); Thu, 30 Jan 2020 15:21:07 -0500 Received: by mail-ot1-f67.google.com with SMTP id 77so4359881oty.6 for ; Thu, 30 Jan 2020 12:21:06 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=fOJEE1fkLwQsVSnFFDCeiNMIe7GX26OPeYKy9HbEFGg=; b=dSaB8Xzxl0tgYBnY8WWqccFO4aKhOpEKCcG8OYcXKqhigHa4cX5a+yQ6m3OoPjKe2a 9KtGInNtcrHL82kDG1PHJCpk15YLNm4JbKkuAz58+CPLeNUN/BzlL4RZHZx4wzj0F8zv gIo2SXPaWtKj5ASJEqCiWPC4BKKt5TXBMSvmSalsF4BA1EkOpS+NFqlFsc1o8s4ZOyZF RYLSwGwLF1T3Z6mw+kMgBJqs2HwgokfUxtN5xRXKyrWvLTXCKZdSHoa9TqV7uEiX7NLx E9meXMT/aBKgHxVSzDSh7eFntmyec2YfC8nOp2aNXD7V6Isx3eU3sKBB3/5QlMHxxANl Hg8Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=fOJEE1fkLwQsVSnFFDCeiNMIe7GX26OPeYKy9HbEFGg=; b=oaCTJt/zp2FGCk56qgcfIFZ5JLjxWH1XY1lGuLwIlnrU1IyQjiCPriHPh7sY7FFRdX r1I0ZIkJkKufbMHj33QNOxySaUGxKlNMMAdWTWPtTgGUZkM2R3LBB23sO3+ZLe4gkaEC UI9fPANc7NXNrNluR+vuYASOsIvYkr988dyHURcTGdBgD1lVSgXTDWLDPIH5YffE4jyx yjTt1kYm5VdFkNlFRa4EOUHZR3ZD9g+XqgHMNbrYUfAAyB5mQRdxDyBK6uydqBRhVsvV EVGfgz2aPIXWeGsaVYL+hInoHw0cQQeGONedjrLTBgY2fDifJ81BtLlYt21Xwmatos7P 5vtg== X-Gm-Message-State: APjAAAUw/9erOMX7gMCh3OsJr6HZTQoG1k/Gb/bRgR6+iZlRQwdAugml oVl/wwO9rQyeMN6tPwFb9U+ivHXg+0S3xlcvC+I= X-Google-Smtp-Source: APXvYqzDM8OCFgNpvqzUl2WS7ghEHAAo5ALxx1Xwxs+PJKijo5lCEE8CT8lEB9ddQyjzOMjy6M3gmCPlGP6jjUGEAPw= X-Received: by 2002:a05:6830:1e30:: with SMTP id t16mr5070986otr.220.1580415665784; Thu, 30 Jan 2020 12:21:05 -0800 (PST) MIME-Version: 1.0 References: <20200124181819.4840-1-hjl.tools@gmail.com> <20200124181819.4840-3-hjl.tools@gmail.com> <202001271531.B9ACE2A@keescook> <202001301143.288B55DCC1@keescook> <202001301206.13AF0512@keescook> In-Reply-To: <202001301206.13AF0512@keescook> From: "H.J. Lu" Date: Thu, 30 Jan 2020 12:20:30 -0800 Message-ID: Subject: Re: [PATCH 2/2] x86: Discard .note.gnu.property sections in vmlinux To: Kees Cook Cc: LKML , Andy Lutomirski , Thomas Gleixner , Thomas Lendacky , Sami Tolvanen , Heiko Carstens , Ingo Molnar , Borislav Petkov , "H . Peter Anvin" , "the arch/x86 maintainers" , Yu-cheng Yu Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 30, 2020 at 12:08 PM Kees Cook wrote: > > On Thu, Jan 30, 2020 at 12:04:54PM -0800, H.J. Lu wrote: > > > I don't understand this. "may not be incompatible"? Is there an error > > > generated? If so, what does it look like? > > > > When -mx86-used-note=yes is passed to assembler, with my patch, I got > > > > [hjl@gnu-skx-1 linux]$ readelf -n vmlinux > > > > Displaying notes found in: .notes > > Owner Data size Description > > Xen 0x00000006 Unknown note type: (0x00000006) > > description data: 6c 69 6e 75 78 00 > > Xen 0x00000004 Unknown note type: (0x00000007) > > description data: 32 2e 36 00 > > Xen 0x00000008 Unknown note type: (0x00000005) > > description data: 78 65 6e 2d 33 2e 30 00 > > Xen 0x00000008 Unknown note type: (0x00000003) > > description data: 00 00 00 80 ff ff ff ff > > Xen 0x00000008 Unknown note type: (0x0000000f) > > description data: 00 00 00 00 80 00 00 00 > > Xen 0x00000008 NT_VERSION (version) > > description data: 80 a1 ba 82 ff ff ff ff > > Xen 0x00000008 NT_ARCH (architecture) > > description data: 00 10 00 81 ff ff ff ff > > Xen 0x00000029 Unknown note type: (0x0000000a) > > description data: 21 77 72 69 74 61 62 6c 65 5f 70 61 67 65 5f 74 > > 61 62 6c 65 73 7c 70 61 65 5f 70 67 64 69 72 5f 61 62 6f 76 65 5f 34 > > 67 62 > > Xen 0x00000004 Unknown note type: (0x00000011) > > description data: 01 88 00 00 > > Xen 0x00000004 Unknown note type: (0x00000009) > > description data: 79 65 73 00 > > Xen 0x00000008 Unknown note type: (0x00000008) > > description data: 67 65 6e 65 72 69 63 00 > > Xen 0x00000010 Unknown note type: (0x0000000d) > > description data: 01 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 > > Xen 0x00000004 Unknown note type: (0x0000000e) > > description data: 01 00 00 00 > > Xen 0x00000004 Unknown note type: (0x00000010) > > description data: 01 00 00 00 > > Xen 0x00000008 Unknown note type: (0x0000000c) > > description data: 00 00 00 00 00 80 ff ff > > Xen 0x00000008 Unknown note type: (0x00000004) > > description data: 00 00 00 00 00 00 00 00 > > GNU 0x00000014 NT_GNU_BUILD_ID (unique build ID bitstring) > > Build ID: 11c73de2922f593e1b35b92ab3c70eaa1a80fa83 > > Linux 0x00000018 OPEN > > description data: 35 2e 33 2e 39 2d 32 30 30 2e 30 2e 66 63 33 30 > > 2e 78 38 36 5f 36 34 00 > > Xen 0x00000008 Unknown note type: (0x00000012) > > description data: 70 04 00 01 00 00 00 00 > > [hjl@gnu-skx-1 linux]$ > > > > Without my patch, > > > > [hjl@gnu-skx-1 linux]$ readelf -n vmlinux > > > > Displaying notes found in: .notes > > Owner Data size Description > > Xen 0x00000006 Unknown note type: (0x00000006) > > description data: 6c 69 6e 75 78 00 > > Xen 0x00000004 Unknown note type: (0x00000007) > > description data: 32 2e 36 00 > > xen-3.0 0x00000005 Unknown note type: (0x006e6558) > > description data: 08 00 00 00 03 > > readelf: Warning: note with invalid namesz and/or descsz found at offset 0x50 > > readelf: Warning: type: 0xffffffff, namesize: 0x006e6558, descsize: > > 0x80000000, alignment: 8 > > [hjl@gnu-skx-1 linux]$ > > What is the source of this failure? Does readelf need updating instead? > Is the linking step producing an invalid section? It seems like > discarding the properties isn't the right solution here? With the command-line option, -mx86-used-note=yes, the x86 assembler in binutils 2.32 and above generates a program property note in a note section, .note.gnu.property, to encode used x86 ISAs and features. But x86 kernel linker script only contains a signle NOTE segment: PHDRS { text PT_LOAD FLAGS(5); data PT_LOAD FLAGS(6); percpu PT_LOAD FLAGS(6); init PT_LOAD FLAGS(7); note PT_NOTE FLAGS(0); } SECTIONS { ... .notes : AT(ADDR(.notes) - 0xffffffff80000000) { __start_notes = .; KEEP(*(.not e.*)) __stop_notes = .; } :text :note ... } But .note.gnu.property must be 8-byte aligned. Linker deals with it by generating 2 PT_NOTE segments, one has 4-byte alignment and the other has 8-byte alignment: [hjl@gnu-cfl-1 ~]$ readelf -l /usr/local/bin/ld Elf file type is EXEC (Executable file) Entry point 0x404530 There are 13 program headers, starting at offset 64 Program Headers: Type Offset VirtAddr PhysAddr FileSiz MemSiz Flags Align PHDR 0x0000000000000040 0x0000000000400040 0x0000000000400040 0x00000000000002d8 0x00000000000002d8 R 0x8 INTERP 0x0000000000000318 0x0000000000400318 0x0000000000400318 0x000000000000001c 0x000000000000001c R 0x1 [Requesting program interpreter: /lib64/ld-linux-x86-64.so.2] LOAD 0x0000000000000000 0x0000000000400000 0x0000000000400000 0x0000000000002a30 0x0000000000002a30 R 0x1000 LOAD 0x0000000000003000 0x0000000000403000 0x0000000000403000 0x00000000000d7b35 0x00000000000d7b35 R E 0x1000 LOAD 0x00000000000db000 0x00000000004db000 0x00000000004db000 0x0000000000179248 0x0000000000179248 R 0x1000 LOAD 0x0000000000254de0 0x0000000000655de0 0x0000000000655de0 0x00000000000062e8 0x000000000000ba68 RW 0x1000 DYNAMIC 0x0000000000254df0 0x0000000000655df0 0x0000000000655df0 0x0000000000000200 0x0000000000000200 RW 0x8 NOTE 0x0000000000000338 0x0000000000400338 0x0000000000400338 0x0000000000000030 0x0000000000000030 R 0x8 NOTE 0x0000000000000368 0x0000000000400368 0x0000000000400368 0x0000000000000044 0x0000000000000044 R 0x4 GNU_PROPERTY 0x0000000000000338 0x0000000000400338 0x0000000000400338 0x0000000000000030 0x0000000000000030 R 0x8 GNU_EH_FRAME 0x0000000000233efc 0x0000000000633efc 0x0000000000633efc 0x000000000000478c 0x000000000000478c R 0x4 GNU_STACK 0x0000000000000000 0x0000000000000000 0x0000000000000000 0x0000000000000000 0x0000000000000000 RW 0x10 GNU_RELRO 0x0000000000254de0 0x0000000000655de0 0x0000000000655de0 0x0000000000000220 0x0000000000000220 R 0x1 Section to Segment mapping: Segment Sections... 00 01 .interp 02 .interp .note.gnu.property .note.gnu.build-id .note.ABI-tag .hash .gnu.hash .dynsym .dynstr .gnu.version .gnu.version_r .rela.dyn .rela.plt 03 .init .plt .text .fini 04 .rodata .eh_frame_hdr .eh_frame 05 .init_array .fini_array .dynamic .got .got.plt .data .bss 06 .dynamic 07 .note.gnu.property 08 .note.gnu.build-id .note.ABI-tag 09 .note.gnu.property 10 .eh_frame_hdr 11 12 .init_array .fini_array .dynamic .got [hjl@gnu-cfl-1 ~]$ Since .note.gnu.property in vmlinux is unused, it can be discarded. -- H.J.