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=-5.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,USER_AGENT_MUTT 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 5479CC28CC0 for ; Wed, 29 May 2019 21:37:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 295F224231 for ; Wed, 29 May 2019 21:37:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Bv1ATfN1" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726489AbfE2VhN (ORCPT ); Wed, 29 May 2019 17:37:13 -0400 Received: from mail-wr1-f65.google.com ([209.85.221.65]:46325 "EHLO mail-wr1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726018AbfE2VhN (ORCPT ); Wed, 29 May 2019 17:37:13 -0400 Received: by mail-wr1-f65.google.com with SMTP id r7so2729863wrr.13; Wed, 29 May 2019 14:37:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:mime-version:content-disposition :user-agent; bh=Z/j/DHIs2LqXKNaoMidLfEH1GNjBTo+f8bWLzrCEysU=; b=Bv1ATfN1zsW6uwRy1fi6lD0r6158DlYKWB1iHSlxbtZLTCLWO48hXOcjLTsvfukM0c uZc4mQN63CrBjtfNEUsMTEtqpBcbKwC8WvG/VJpaOnQtqewPJV/WX9/R+IRegg7koMZr VkzIgnSs2A2SdDmY9ufjuzDt0yG6U+rt+L5orEXCmkmyNfXJJ9F2rKialWY+BzlZz4qQ HZ7dcmKvt2ZEC1dnGoxlgH+zq2w5L/QqStA145O3dGzkb3aPy111zy6YvwuF5HLgl3gz 9p+hUA9e5didovXiUbxrZ36gTbwPScINaO+bhd1EDrizJQbqTRxhKWnsLyKiAdXU9DjR xtsw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:mime-version :content-disposition:user-agent; bh=Z/j/DHIs2LqXKNaoMidLfEH1GNjBTo+f8bWLzrCEysU=; b=SZT2aKqYn5zrJEWvq9t0WIoPmTmibX1bKJ7PpeaaammIkW0b9BR4cBpgbjQJxHS8hX qbC91okrs7McV3Oywq5cz/pzKs8dgPewMouiUJ50so3rStNxKcWG2JtcLSqbMneJGQx0 eLfl3Hmlbf1KQtfiYkiMLbr6Tx7HuuB8shiRDcSf4UKl0Uz6BwGNxVnpy51IW3JnY8Iy FXT2NYVvscRMZead9fnW5Oe7+wHD3SFM3o5t9m6Mw8FNxWvs3zKiOn8Mif61o+pe6PIu hUpZiHvh37EYL0g5tJph7jkcGl1Oetg+SZLXkiWeVFeX5aaoe6N0GsvuSaEFuIUEhPzb 0hkQ== X-Gm-Message-State: APjAAAWKPBHHJ77mtwoJLikU6V2d+KEGn+GXGJS95bdrLLeAOy1zxo1R mqMWM2yQxZNyGcLEHa4Jdgybdg8= X-Google-Smtp-Source: APXvYqz5Xs2abGWOV1nrmofmFEGyNuelZ+2JOzdItYbOs4FrMLpP6BFT+kh/GE1JcLfJTv/k9T06/A== X-Received: by 2002:a5d:4fc1:: with SMTP id h1mr105094wrw.323.1559165831399; Wed, 29 May 2019 14:37:11 -0700 (PDT) Received: from avx2 ([46.53.251.224]) by smtp.gmail.com with ESMTPSA id 67sm1083679wmd.38.2019.05.29.14.37.10 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 29 May 2019 14:37:10 -0700 (PDT) Date: Thu, 30 May 2019 00:37:08 +0300 From: Alexey Dobriyan To: akpm@linux-foundation.org Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org Subject: [PATCH] elf: align AT_RANDOM bytes Message-ID: <20190529213708.GA10729@avx2> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org AT_RANDOM content is always misaligned on x86_64: $ LD_SHOW_AUXV=1 /bin/true | grep AT_RANDOM AT_RANDOM: 0x7fff02101019 glibc copies first few bytes for stack protector stuff, aligned access should be slightly faster. Signed-off-by: Alexey Dobriyan --- fs/binfmt_elf.c | 10 ++++++++++ 1 file changed, 10 insertions(+) --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -144,11 +144,15 @@ static int padzero(unsigned long elf_bss) #define STACK_ALLOC(sp, len) ({ \ elf_addr_t __user *old_sp = (elf_addr_t __user *)sp; sp += len; \ old_sp; }) +#define STACK_ALIGN(sp, align) \ + ((typeof(sp))(((unsigned long)sp + (int)align - 1) & ~((int)align - 1))) #else #define STACK_ADD(sp, items) ((elf_addr_t __user *)(sp) - (items)) #define STACK_ROUND(sp, items) \ (((unsigned long) (sp - items)) &~ 15UL) #define STACK_ALLOC(sp, len) ({ sp -= len ; sp; }) +#define STACK_ALIGN(sp, align) \ + ((typeof(sp))((unsigned long)sp & ~((int)align - 1))) #endif #ifndef ELF_BASE_PLATFORM @@ -217,6 +221,12 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec, return -EFAULT; } + /* + * glibc copies first bytes for stack protector purposes + * which are misaligned on x86_64 because strlen("x86_64") + 1 == 7. + */ + p = STACK_ALIGN(p, sizeof(long)); + /* * Generate 16 random bytes for userspace PRNG seeding. */