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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 4534CC352A1 for ; Wed, 5 Feb 2020 22:40:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 22A53214AF for ; Wed, 5 Feb 2020 22:40:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727635AbgBEWkA (ORCPT ); Wed, 5 Feb 2020 17:40:00 -0500 Received: from mga02.intel.com ([134.134.136.20]:60113 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727541AbgBEWjj (ORCPT ); Wed, 5 Feb 2020 17:39:39 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga101.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 05 Feb 2020 14:39:38 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,407,1574150400"; d="scan'208";a="225092471" Received: from unknown (HELO localhost.jf.intel.com) ([10.54.75.26]) by fmsmga007.fm.intel.com with ESMTP; 05 Feb 2020 14:39:38 -0800 From: Kristen Carlson Accardi To: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, arjan@linux.intel.com, keescook@chromium.org Cc: rick.p.edgecombe@intel.com, x86@kernel.org, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com, Kristen Carlson Accardi Subject: [RFC PATCH 11/11] x86/boot: Move "boot heap" out of .bss Date: Wed, 5 Feb 2020 14:39:50 -0800 Message-Id: <20200205223950.1212394-12-kristen@linux.intel.com> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200205223950.1212394-1-kristen@linux.intel.com> References: <20200205223950.1212394-1-kristen@linux.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Kees Cook Currently the on-disk decompression image includes the "dynamic" heap region that is used for malloc() during kernel extraction, relocation, and decompression ("boot_heap" of BOOT_HEAP_SIZE bytes in the .bss section). It makes no sense to balloon the bzImage with "boot_heap" as it is zeroed at boot, and acts much more like a "brk" region. This seems to be a trivial change because head_{64,32}.S already only copies up to the start of the .bss section, so any growth in the .bss area was already not meaningful when placing the image in memory. The .bss size is, however, reflected in the boot params "init_size", so the memory range calculations included the "boot_heap" region. Instead of wasting the on-disk image size bytes, just account for this heap area when identifying the mem_avoid ranges, and leave it out of the .bss section entirely. For good measure, also zero initialize it, as this was already happening for when zeroing the entire .bss section. While the bzImage size is dominated by the compressed vmlinux, the difference removes 64KB for all compressors except bzip2, which removes 4MB. For example, this is less than 1% under CONFIG_KERNEL_XZ: -rw-r--r-- 1 kees kees 7813168 Feb 2 23:39 arch/x86/boot/bzImage.stock-xz -rw-r--r-- 1 kees kees 7747632 Feb 2 23:42 arch/x86/boot/bzImage.brk-xz but much more pronounced under CONFIG_KERNEL_BZIP2 (~27%): -rw-r--r-- 1 kees kees 15231024 Feb 2 23:44 arch/x86/boot/bzImage.stock-bzip2 -rw-r--r-- 1 kees kees 11036720 Feb 2 23:47 arch/x86/boot/bzImage.brk-bzip2 For the future fine-grain KASLR work, this will avoid significant pain, as the ELF section parser will use much more memory during boot and filling the bzImage with megabytes of zeros seemed like a poor idea. :) Signed-off-by: Kees Cook Signed-off-by: Kristen Carlson Accardi --- arch/x86/boot/compressed/head_32.S | 5 ++--- arch/x86/boot/compressed/head_64.S | 7 +++---- arch/x86/boot/compressed/kaslr.c | 2 +- arch/x86/boot/compressed/misc.c | 3 +++ arch/x86/boot/compressed/vmlinux.lds.S | 1 + 5 files changed, 10 insertions(+), 8 deletions(-) diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S index f2dfd6d083ef..1f3de8efd40e 100644 --- a/arch/x86/boot/compressed/head_32.S +++ b/arch/x86/boot/compressed/head_32.S @@ -59,6 +59,7 @@ .hidden _ebss .hidden _got .hidden _egot + .hidden _brk __HEAD SYM_FUNC_START(startup_32) @@ -249,7 +250,7 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated) pushl $z_input_len /* input_len */ leal input_data(%ebx), %eax pushl %eax /* input_data */ - leal boot_heap(%ebx), %eax + leal _brk(%ebx), %eax pushl %eax /* heap area */ pushl %esi /* real mode pointer */ call extract_kernel /* returns kernel location in %eax */ @@ -276,8 +277,6 @@ efi32_config: */ .bss .balign 4 -boot_heap: - .fill BOOT_HEAP_SIZE, 1, 0 boot_stack: .fill BOOT_STACK_SIZE, 1, 0 boot_stack_end: diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index ee60b81944a7..850bc5220a8d 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -42,6 +42,7 @@ .hidden _ebss .hidden _got .hidden _egot + .hidden _brk __HEAD .code32 @@ -534,7 +535,7 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated) */ pushq %rsi /* Save the real mode argument */ movq %rsi, %rdi /* real mode address */ - leaq boot_heap(%rip), %rsi /* malloc area for uncompression */ + leaq _brk(%rip), %rsi /* malloc area for uncompression */ leaq input_data(%rip), %rdx /* input_data */ movl $z_input_len, %ecx /* input_len */ movq %rbp, %r8 /* output target address */ @@ -701,12 +702,10 @@ SYM_DATA_END(efi64_config) #endif /* CONFIG_EFI_STUB */ /* - * Stack and heap for uncompression + * Stack for placement and uncompression */ .bss .balign 4 -SYM_DATA_LOCAL(boot_heap, .fill BOOT_HEAP_SIZE, 1, 0) - SYM_DATA_START_LOCAL(boot_stack) .fill BOOT_STACK_SIZE, 1, 0 SYM_DATA_END_LABEL(boot_stack, SYM_L_LOCAL, boot_stack_end) diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c index ae4dce76a9bd..da64d2cdbb42 100644 --- a/arch/x86/boot/compressed/kaslr.c +++ b/arch/x86/boot/compressed/kaslr.c @@ -397,7 +397,7 @@ static void handle_mem_options(void) static void mem_avoid_init(unsigned long input, unsigned long input_size, unsigned long output) { - unsigned long init_size = boot_params->hdr.init_size; + unsigned long init_size = boot_params->hdr.init_size + BOOT_HEAP_SIZE; u64 initrd_start, initrd_size; u64 cmd_line, cmd_line_size; char *ptr; diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c index 977da0911ce7..cb12da264b59 100644 --- a/arch/x86/boot/compressed/misc.c +++ b/arch/x86/boot/compressed/misc.c @@ -463,6 +463,9 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap, debug_putstr("early console in extract_kernel\n"); + /* Zero what is effectively our .brk section. */ + memset((void *)heap, 0, BOOT_HEAP_SIZE); + debug_putaddr(heap); free_mem_ptr = heap; /* Heap */ free_mem_end_ptr = heap + BOOT_HEAP_SIZE; diff --git a/arch/x86/boot/compressed/vmlinux.lds.S b/arch/x86/boot/compressed/vmlinux.lds.S index 508cfa6828c5..3ce690474940 100644 --- a/arch/x86/boot/compressed/vmlinux.lds.S +++ b/arch/x86/boot/compressed/vmlinux.lds.S @@ -73,4 +73,5 @@ SECTIONS #endif . = ALIGN(PAGE_SIZE); /* keep ZO size page aligned */ _end = .; + _brk = .; } -- 2.24.1