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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 A9036C433E1 for ; Sat, 23 May 2020 12:00:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7F6AF207FB for ; Sat, 23 May 2020 12:00:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590235252; bh=hF++qON33FDEhXyfOJT5GlLwxjX0LMfIv3Aguj9zmVs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=bM5hoVs7nznhFR0BwCB3RZetja6B1z2MhAWphkxtGaJg8AJtgoyuHilD8vyV3GUaD EefW2ngFIQ7R3ZnWuwiZnVWEAwrRQpCZ5RKx4HWSP4lvKXSnXSG/SXuYkJUzETSqxZ WmeutL+3m+L+eA7lbi2yfOT/gvCUgWpUndt/vM2g= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731227AbgEWMAl (ORCPT ); Sat, 23 May 2020 08:00:41 -0400 Received: from mail.kernel.org ([198.145.29.99]:40948 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728749AbgEWMAk (ORCPT ); Sat, 23 May 2020 08:00:40 -0400 Received: from localhost.localdomain (82-64-249-211.subs.proxad.net [82.64.249.211]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9551720812; Sat, 23 May 2020 12:00:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590235240; bh=hF++qON33FDEhXyfOJT5GlLwxjX0LMfIv3Aguj9zmVs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=U4vQgeI26LH6oA7w3U3atCFRouqfnq0TVguU+x+BFFwEbX2cKIaUIp+Im2HB0wnf3 Gzr9jDQVVbGzozpYJnyrfPUE/NoM9pT5F2fSFZeyuEjcStFvFkGIym5T7fk1D/lGel cLmLWI8VA2D/Tf2pIeh/hAkttznd4iStuxr8pCCk= From: Ard Biesheuvel To: linux-efi@vger.kernel.org Cc: x86@kernel.org, linux-kernel@vger.kernel.org, Ard Biesheuvel , Maarten Lankhorst , Linus Torvalds , Arvind Sankar Subject: [PATCH v2 1/3] x86/boot/compressed: move .got.plt entries out of the .got section Date: Sat, 23 May 2020 14:00:19 +0200 Message-Id: <20200523120021.34996-2-ardb@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200523120021.34996-1-ardb@kernel.org> References: <20200523120021.34996-1-ardb@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-efi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-efi@vger.kernel.org The .got.plt section contains the part of the GOT which is used by PLT entries, and which gets updated lazily by the dynamic loader when function calls are dispatched through those PLT entries. On fully linked binaries such as the kernel proper or the decompressor, this never happens, and so in practice, the .got.plt section consists only of the first 3 magic entries that are meant to point at the _DYNAMIC section and at the fixup routine in the loader. However, since we don't use a dynamic loader, those entries are never populated or used. This means that treating those entries like ordinary GOT entries, and updating their values based on the actual placement of the executable in memory is completely pointless, and we can just ignore the .got.plt section entirely, provided that it has no additional entries beyond the first 3 ones. So add an assertion in the linker script to ensure that this assumption holds, and move the contents out of the [_got, _egot) memory range that is modified by the GOT fixup routines. Signed-off-by: Ard Biesheuvel --- arch/x86/boot/compressed/vmlinux.lds.S | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/arch/x86/boot/compressed/vmlinux.lds.S b/arch/x86/boot/compressed/vmlinux.lds.S index 0dc5c2b9614b..ce3fdfb93b57 100644 --- a/arch/x86/boot/compressed/vmlinux.lds.S +++ b/arch/x86/boot/compressed/vmlinux.lds.S @@ -44,10 +44,13 @@ SECTIONS } .got : { _got = .; - KEEP(*(.got.plt)) KEEP(*(.got)) _egot = .; } + .got.plt : { + KEEP(*(.got.plt)) + } + .data : { _data = . ; *(.data) @@ -75,3 +78,11 @@ SECTIONS . = ALIGN(PAGE_SIZE); /* keep ZO size page aligned */ _end = .; } + +#ifdef CONFIG_X86_64 +ASSERT (SIZEOF(.got.plt) == 0 || SIZEOF(.got.plt) == 0x18, + "Unexpected GOT/PLT entries detected!") +#else +ASSERT (SIZEOF(.got.plt) == 0 || SIZEOF(.got.plt) == 0xc, + "Unexpected GOT/PLT entries detected!") +#endif -- 2.20.1