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=-3.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 D44D2C33CB2 for ; Fri, 31 Jan 2020 06:16:52 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 8F98C2173E for ; Fri, 31 Jan 2020 06:16:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="Q163R0DG" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8F98C2173E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 34AB76B0589; Fri, 31 Jan 2020 01:16:52 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 2FEBF6B058B; Fri, 31 Jan 2020 01:16:52 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 12B626B058C; Fri, 31 Jan 2020 01:16:52 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0137.hostedemail.com [216.40.44.137]) by kanga.kvack.org (Postfix) with ESMTP id E4EA66B0589 for ; Fri, 31 Jan 2020 01:16:51 -0500 (EST) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 9E44F180AD802 for ; Fri, 31 Jan 2020 06:16:51 +0000 (UTC) X-FDA: 76436921022.27.coach17_3bd9bfea99519 X-HE-Tag: coach17_3bd9bfea99519 X-Filterd-Recvd-Size: 3887 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf50.hostedemail.com (Postfix) with ESMTP for ; Fri, 31 Jan 2020 06:16:51 +0000 (UTC) Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 690F02173E; Fri, 31 Jan 2020 06:16:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1580451410; bh=ZHVBqPQOLpj/r6odAheZj+Pin4VAjirJKZiE64ax/Hk=; h=Date:From:To:Subject:In-Reply-To:From; b=Q163R0DGEWsqcDKNfpJMfYPpMeM290/pcwfiFSPxUWf7b+DLdHjyqTZn7OnWUO8dq 6dTdUjYvuMlYEmKu4HmxBdMAKdOU6jVmM7OHbc22Hwo06XG2pPE04PpVhbFMnUEi/x 3DsCxdfvY8JuhKP7TGpvJija0EvsLG0Q2KsYn4ZA= Date: Thu, 30 Jan 2020 22:16:50 -0800 From: Andrew Morton To: adobriyan@gmail.com, akpm@linux-foundation.org, linux-mm@kvack.org, mm-commits@vger.kernel.org, torvalds@linux-foundation.org Subject: [patch 103/118] fs/binfmt_elf.c: smaller code generation around auxv vector fill Message-ID: <20200131061650.eU7j4dHkx%akpm@linux-foundation.org> In-Reply-To: <20200130221021.5f0211c56346d5485af07923@linux-foundation.org> User-Agent: s-nail v14.8.16 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Alexey Dobriyan Subject: fs/binfmt_elf.c: smaller code generation around auxv vector fill 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 Link: http://lkml.kernel.org/r/20191208172301.GD19716@avx2 Signed-off-by: Alexey Dobriyan Reviewed-by: Andrew Morton Signed-off-by: Andrew Morton --- fs/binfmt_elf.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) --- a/fs/binfmt_elf.c~elf-smaller-code-generation-around-auxv-vector-fill +++ a/fs/binfmt_elf.c @@ -176,7 +176,7 @@ create_elf_tables(struct linux_binprm *b 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; @@ -230,8 +230,8 @@ create_elf_tables(struct linux_binprm *b /* 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 @@ -275,12 +275,13 @@ create_elf_tables(struct linux_binprm *b } #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; @@ -338,7 +339,7 @@ create_elf_tables(struct linux_binprm *b 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; } _