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=-5.1 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_SANE_1 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 5D38DC43603 for ; Sun, 8 Dec 2019 17:23:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1FD8A20692 for ; Sun, 8 Dec 2019 17:23:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="uuzg0mJZ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726506AbfLHRXH (ORCPT ); Sun, 8 Dec 2019 12:23:07 -0500 Received: from mail-wm1-f68.google.com ([209.85.128.68]:39860 "EHLO mail-wm1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726472AbfLHRXH (ORCPT ); Sun, 8 Dec 2019 12:23:07 -0500 Received: by mail-wm1-f68.google.com with SMTP id s14so12374275wmh.4 for ; Sun, 08 Dec 2019 09:23:05 -0800 (PST) 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=TCJmDBLYuV/jWqc0iBCCs2tprqUMEIazO4OrAHZKLfw=; b=uuzg0mJZTMfj6yBQSj2Y0Vu0/IKwg1wRZ73Cd+dUIkTUYO809Djo7/nyFdkNX++KyF wl51N6LC8cyuXh4W5JdytzCFC0LzRUWUiAuDMCb0uEnWwnpgzA0on2BmJhqJ769V3OfK Qth3XiMqVaWMv9mDRO7j1/PdOLzt88dZ+7lIgjxOaGQverIRRk9p/+D8Tp2rL1yhs1lS Q95ZqZwlCuOtru4d9uIfI8RHfhbaKlS5otsQv+Pv+05cYkjzuYevogIPd0BmouIyemBH XxjJ8mM6I8HOtuPKDH/OquE2HUut+hnaMyxfaKKDO/ULegd/GAtu6v4bdvpxmrcu7Eor 7Nrg== 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=TCJmDBLYuV/jWqc0iBCCs2tprqUMEIazO4OrAHZKLfw=; b=oczAxWQjdelJyyWuECqcsd4t0ZpMC74ky7J9QJabYHlsTTqmgc2mQhDrmak9KLVk6X bsJKGSSDRXcR2PMU+5EKEhBXgM/UVl7Lp8cQglEK2v91DjccB2f8FCO+LBEKUCoAYzPD akthtY2WaDljFtvEv8f22VaJRnnS3dS/5OCCZY6GgsNHSfTQFLkO3iCSPH6Ehjp9cL+I uvRPTsuAjF5rR0ktiTffGSW44VHbVQdAIXa2Wm60X6GEuqIYMlacnH5yYss/3/8cEunW yLhxz46jxJbjYEjt0Z/xRVPUUYq9CKpkFtcEoecI4KiRdnAzX6IfCS2Vqp83WFS4+kK8 dOGw== X-Gm-Message-State: APjAAAUl2sLdNikhka7rmq73vcsmIOxcEa5cxXkWsT+NL/YU0HgbJj7x LlBk/gFZsiRmLRBQ49ixlti3VEI= X-Google-Smtp-Source: APXvYqwjfKyDgkVT30izndYAtXJS80kI/3gW8VNhHD0oJzHfdaJC5Pyld4r8NTpaFb9zIOwhVMvfzg== X-Received: by 2002:a7b:c851:: with SMTP id c17mr19474644wml.71.1575825785048; Sun, 08 Dec 2019 09:23:05 -0800 (PST) Received: from avx2 ([46.53.249.42]) by smtp.gmail.com with ESMTPSA id k11sm1497102wmc.20.2019.12.08.09.23.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 08 Dec 2019 09:23:04 -0800 (PST) Date: Sun, 8 Dec 2019 20:23:01 +0300 From: Alexey Dobriyan To: akpm@linux-foundation.org Cc: linux-kernel@vger.kernel.org Subject: [PATCH] ELF: smaller code generation around auxv vector fill Message-ID: <20191208172301.GD19716@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 Filling auxv vector as array with index (auxv[i++] = ...) generates terrible code. "saved_auxv" should be reworked because it is the worst member of mm_struct by size/usefullness ratio but do it later. Meanwhile help gcc a little with *auxv++ idiom. Space savings on x86_64: add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-127 (-127) Function old new delta load_elf_binary 5470 5343 -127 Signed-off-by: Alexey Dobriyan --- fs/binfmt_elf.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -177,7 +177,7 @@ create_elf_tables(struct linux_binprm *bprm, const struct elfhdr *exec, unsigned char k_rand_bytes[16]; int items; elf_addr_t *elf_info; - int ei_index = 0; + int ei_index; const struct cred *cred = current_cred(); struct vm_area_struct *vma; @@ -231,8 +231,8 @@ create_elf_tables(struct linux_binprm *bprm, const struct elfhdr *exec, /* update AT_VECTOR_SIZE_BASE if the number of NEW_AUX_ENT() changes */ #define NEW_AUX_ENT(id, val) \ do { \ - elf_info[ei_index++] = id; \ - elf_info[ei_index++] = val; \ + *elf_info++ = id; \ + *elf_info++ = val; \ } while (0) #ifdef ARCH_DLINFO @@ -276,12 +276,13 @@ create_elf_tables(struct linux_binprm *bprm, const struct elfhdr *exec, } #undef NEW_AUX_ENT /* AT_NULL is zero; clear the rest too */ - memset(&elf_info[ei_index], 0, - sizeof current->mm->saved_auxv - ei_index * sizeof elf_info[0]); + memset(elf_info, 0, (char *)current->mm->saved_auxv + + sizeof(current->mm->saved_auxv) - (char *)elf_info); /* And advance past the AT_NULL entry. */ - ei_index += 2; + elf_info += 2; + ei_index = elf_info - (elf_addr_t *)current->mm->saved_auxv; sp = STACK_ADD(p, ei_index); items = (argc + 1) + (envc + 1) + 1; @@ -339,7 +340,7 @@ create_elf_tables(struct linux_binprm *bprm, const struct elfhdr *exec, current->mm->env_end = p; /* Put the elf_info on the stack in the right place. */ - if (copy_to_user(sp, elf_info, ei_index * sizeof(elf_addr_t))) + if (copy_to_user(sp, current->mm->saved_auxv, ei_index * sizeof(elf_addr_t))) return -EFAULT; return 0; }