From patchwork Thu Feb 13 14:59:26 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ard Biesheuvel X-Patchwork-Id: 206584 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=ham 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 A7B3FC2BA83 for ; Thu, 13 Feb 2020 14:59:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7FEF224650 for ; Thu, 13 Feb 2020 14:59:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581605992; bh=dzXGEwPuXZ+ThiLE83ovGglZj5LrVvfa4e0a9juvxuU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=LLRNi68VG3XfbFaEd0SyM1H7FJGCaqheTfUbCfh0alIkQ//L/kW30/qsx+tvgrSdQ fOn1Gw2F9ypkcLidWtkPYLPDg1kEF3hldkrLKfcMVH+W635eeUUuYAbZv6St3p4Q7i RcvG16HFS9JSWCitMUzirSX4IiGA40U8VwUDynQY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727683AbgBMO7w (ORCPT ); Thu, 13 Feb 2020 09:59:52 -0500 Received: from mail.kernel.org ([198.145.29.99]:41354 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726968AbgBMO7w (ORCPT ); Thu, 13 Feb 2020 09:59:52 -0500 Received: from cam-smtp0.cambridge.arm.com (fw-tnat.cambridge.arm.com [217.140.96.140]) (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 96EF3218AC; Thu, 13 Feb 2020 14:59:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581605990; bh=dzXGEwPuXZ+ThiLE83ovGglZj5LrVvfa4e0a9juvxuU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=wtHnBCqALVbLhbo8hURER56BK+MTrVKkiDo3sAmQyWwtVEJUfFeLWNd3DfzUChHJj 1a86/2gx5cxXcZly4NqcuM1CuZ0BxDerG5+fiLyaKNQWVu2ANeSFLHBYU3f8AeyIJI ODQB3FiQakHD+n7/ZrMPEzbyZjygZ1UcscBEcNsQ= From: Ard Biesheuvel To: linux-efi@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org, Ard Biesheuvel , lersek@redhat.com, leif@nuviainc.com, pjones@redhat.com, mjg59@google.com, agraf@csgraf.de, daniel.kiper@oracle.com, hdegoede@redhat.com, nivedita@alum.mit.edu, mbrown@fensystems.co.uk, mingo@kernel.org Subject: [RFC PATCH 1/3] efi/x86: drop redundant .bss section Date: Thu, 13 Feb 2020 15:59:26 +0100 Message-Id: <20200213145928.7047-2-ardb@kernel.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200213145928.7047-1-ardb@kernel.org> References: <20200213145928.7047-1-ardb@kernel.org> Sender: linux-efi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-efi@vger.kernel.org In commit c7fb93ec51d462ec ("x86/efi: Include a .bss section within the PE/COFF headers"), we added a separate .bss section to the PE/COFF header of the compressed kernel describing the static memory footprint of the decompressor, to ensure that it has enough headroom to decompress itself. We can achieve the exact same result by increasing the virtual size of the .text section, without changing the raw size, which, as per the PE/COFF specification, requires the loader to zero initialize the delta. Doing so frees up a slot in the section table, which we will use later to describe the mixed mode entrypoint. Signed-off-by: Ard Biesheuvel --- arch/x86/boot/header.S | 21 +----------- arch/x86/boot/tools/build.c | 35 ++++++++------------ 2 files changed, 14 insertions(+), 42 deletions(-) diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S index 97d9b6d6c1af..d59f6604bb42 100644 --- a/arch/x86/boot/header.S +++ b/arch/x86/boot/header.S @@ -106,7 +106,7 @@ coff_header: #else .word 0x8664 # x86-64 #endif - .word 4 # nr_sections + .word 3 # nr_sections .long 0 # TimeDateStamp .long 0 # PointerToSymbolTable .long 1 # NumberOfSymbols @@ -248,25 +248,6 @@ section_table: .word 0 # NumberOfLineNumbers .long 0x60500020 # Characteristics (section flags) - # - # The offset & size fields are filled in by build.c. - # - .ascii ".bss" - .byte 0 - .byte 0 - .byte 0 - .byte 0 - .long 0 - .long 0x0 - .long 0 # Size of initialized data - # on disk - .long 0x0 - .long 0 # PointerToRelocations - .long 0 # PointerToLineNumbers - .word 0 # NumberOfRelocations - .word 0 # NumberOfLineNumbers - .long 0xc8000080 # Characteristics (section flags) - #endif /* CONFIG_EFI_STUB */ # Kernel attributes; used by setup. This is part 1 of the diff --git a/arch/x86/boot/tools/build.c b/arch/x86/boot/tools/build.c index 55e669d29e54..0c8c5a52f1f0 100644 --- a/arch/x86/boot/tools/build.c +++ b/arch/x86/boot/tools/build.c @@ -203,10 +203,12 @@ static void update_pecoff_setup_and_reloc(unsigned int size) put_unaligned_le32(10, &buf[reloc_offset + 4]); } -static void update_pecoff_text(unsigned int text_start, unsigned int file_sz) +static void update_pecoff_text(unsigned int text_start, unsigned int file_sz, + unsigned int init_sz) { unsigned int pe_header; unsigned int text_sz = file_sz - text_start; + unsigned int bss_sz = init_sz - file_sz; pe_header = get_unaligned_le32(&buf[0x3c]); @@ -216,28 +218,19 @@ static void update_pecoff_text(unsigned int text_start, unsigned int file_sz) */ put_unaligned_le32(file_sz - 512, &buf[pe_header + 0x1c]); - /* - * Address of entry point for PE/COFF executable - */ - put_unaligned_le32(text_start + efi_pe_entry, &buf[pe_header + 0x28]); - - update_pecoff_section_header(".text", text_start, text_sz); -} - -static void update_pecoff_bss(unsigned int file_sz, unsigned int init_sz) -{ - unsigned int pe_header; - unsigned int bss_sz = init_sz - file_sz; - - pe_header = get_unaligned_le32(&buf[0x3c]); - /* Size of uninitialized data */ put_unaligned_le32(bss_sz, &buf[pe_header + 0x24]); /* Size of image */ put_unaligned_le32(init_sz, &buf[pe_header + 0x50]); - update_pecoff_section_header_fields(".bss", file_sz, bss_sz, 0, 0); + /* + * Address of entry point for PE/COFF executable + */ + put_unaligned_le32(text_start + efi_pe_entry, &buf[pe_header + 0x28]); + + update_pecoff_section_header_fields(".text", text_start, text_sz + bss_sz, + text_sz, text_start); } static int reserve_pecoff_reloc_section(int c) @@ -278,9 +271,8 @@ static void efi_stub_entry_update(void) static inline void update_pecoff_setup_and_reloc(unsigned int size) {} static inline void update_pecoff_text(unsigned int text_start, - unsigned int file_sz) {} -static inline void update_pecoff_bss(unsigned int file_sz, - unsigned int init_sz) {} + unsigned int file_sz, + unsigned int init_sz) {} static inline void efi_stub_defaults(void) {} static inline void efi_stub_entry_update(void) {} @@ -406,9 +398,8 @@ int main(int argc, char ** argv) buf[0x1f1] = setup_sectors-1; put_unaligned_le32(sys_size, &buf[0x1f4]); - update_pecoff_text(setup_sectors * 512, i + (sys_size * 16)); init_sz = get_unaligned_le32(&buf[0x260]); - update_pecoff_bss(i + (sys_size * 16), init_sz); + update_pecoff_text(setup_sectors * 512, i + (sys_size * 16), init_sz); efi_stub_entry_update();