From nobody Sun Dec 28 19:32:19 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4F3F8C4167B for ; Tue, 5 Dec 2023 16:01:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346936AbjLEQBk (ORCPT ); Tue, 5 Dec 2023 11:01:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47318 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235614AbjLEQBd (ORCPT ); Tue, 5 Dec 2023 11:01:33 -0500 Received: from mail-wr1-x434.google.com (mail-wr1-x434.google.com [IPv6:2a00:1450:4864:20::434]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1ABC01AB; Tue, 5 Dec 2023 08:01:39 -0800 (PST) Received: by mail-wr1-x434.google.com with SMTP id ffacd0b85a97d-3333224c7b9so3711757f8f.1; Tue, 05 Dec 2023 08:01:39 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1701792097; x=1702396897; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=Tvo/9rnArZ8fI0hFLD0+8fIJyDMuJ5boJQpNSGg0de4=; b=Ua44hSie5AoBdpKopXuz6XgZ4mVi8FN/VOwnnUMYnfUYsNcd6eJ3/x53YNLEo7xgim f/ZhmeoTXKDWSLDX7KvuO5yGQth/g1a8bZAkGRQynVUs1MOhIQMT1jRFwxzoA2ZPOmRU EqLNpvZegCB+wYnsUCWKcPQNxSaAV+2YsQMbdgXjyb/KQcW/oMAAgKMiMz8ZUgKk+XtA 5H9DX+0KjHNPGO9vQLmeXzu8/4NaxXAzzWXIe5n4ji6P0ySLOErqzDaJQCr0zjidjjif 56NOZxSinLA+Ar4kzkUUovi/jn8CWUURiTwlNqRvM7lafyN0+TabPRcW+po5OTqWgDZi 6JoQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1701792097; x=1702396897; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=Tvo/9rnArZ8fI0hFLD0+8fIJyDMuJ5boJQpNSGg0de4=; b=WlcMUCOIDrVGv/wcWvNtjLJ3i31U1+mr/SIDJu6lgY3g8icXq9q5srzDOdLNA+vh/7 GpqG5nSqNQjfYcE2KvKTrBZ/Hgc67Igc89DzQDfnpY7LJ6bgwZtOnc12QtrWkRgpYx9k QfRt7l8eyF1MK+dO195vowrBmF6/uv8Wr9euNKNg9ZlUSGclMer3bf1YLHvJlSCFFjZm 0xzrGkM0lBJU7OnfdVe9q9NINHPJR+E89Wj/clW9moeNP4wvelGw0KHZCLZ/PfjaixZ7 KJaXfjbJ7nCjJyzMJNtkJR3jz2VFIp8fMpQ+AaVJsX+r7F/yztYdDdvIE2gp36L18DDo HFkQ== X-Gm-Message-State: AOJu0YxqNdPTCMSO4qj7u9Bip/ed6fMPfTqFBEokZEzIX3+nDCH0huyw OMs7zRe8eIuKk/kTc7BHdnJf5W3RKA== X-Google-Smtp-Source: AGHT+IGVDOHWf2/MsqsnRu1T0vHj++2BZvSkVNdgYatcywQjkipt57Ds2m07DrWUWbWeutZCjMzx6A== X-Received: by 2002:adf:e349:0:b0:333:4862:8520 with SMTP id n9-20020adfe349000000b0033348628520mr2133188wrj.138.1701792097218; Tue, 05 Dec 2023 08:01:37 -0800 (PST) Received: from p183 ([46.53.254.107]) by smtp.gmail.com with ESMTPSA id r13-20020a056000014d00b003333fc2cb92sm8295598wrx.58.2023.12.05.08.01.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 05 Dec 2023 08:01:36 -0800 (PST) Date: Tue, 5 Dec 2023 19:01:34 +0300 From: Alexey Dobriyan To: Andrew Morton Cc: Florian Weimer , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, x86@kernel.org Subject: [PATCH v2] ELF: supply userspace with available page shifts (AT_PAGE_SHIFT_MASK) Message-ID: <1d679805-8a82-44a4-ba14-49d4f28ff597@p183> References: <6b399b86-a478-48b0-92a1-25240a8ede54@p183> <87v89dvuxg.fsf@oldenburg.str.redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <87v89dvuxg.fsf@oldenburg.str.redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Report available page shifts in arch independent manner, so that userspace developers won't have to parse /proc/cpuinfo hunting for arch specific strings: Note! This is strictly for userspace, if some page size is shutdown due to kernel command line option or CPU bug workaround, than is must not be reported in aux vector! x86_64 machine with 1 GiB pages: 00000030 06 00 00 00 00 00 00 00 00 10 00 00 00 00 00 00 00000040 1d 00 00 00 00 00 00 00 00 10 20 40 00 00 00 00 x86_64 machine with 2 MiB pages only: 00000030 06 00 00 00 00 00 00 00 00 10 00 00 00 00 00 00 00000040 1d 00 00 00 00 00 00 00 00 10 20 00 00 00 00 00 AT_PAGESZ is always 4096 which is not that interesting. Signed-off-by: Alexey Dobriyan --- v2: switch to 1 bit per page shift (bitmask) arch/x86/include/asm/elf.h | 12 ++++++++++++ fs/binfmt_elf.c | 3 +++ include/uapi/linux/auxvec.h | 14 ++++++++++++++ 3 files changed, 29 insertions(+) --- a/arch/x86/include/asm/elf.h +++ b/arch/x86/include/asm/elf.h @@ -358,6 +358,18 @@ else if (IS_ENABLED(CONFIG_IA32_EMULATION)) \ =20 #define COMPAT_ELF_ET_DYN_BASE (TASK_UNMAPPED_BASE + 0x1000000) =20 +#define ARCH_AT_PAGE_SHIFT_MASK \ + do { \ + u32 val =3D 1 << 12; \ + if (boot_cpu_has(X86_FEATURE_PSE)) { \ + val |=3D 1 << 21; \ + } \ + if (boot_cpu_has(X86_FEATURE_GBPAGES)) { \ + val |=3D 1 << 30; \ + } \ + NEW_AUX_ENT(AT_PAGE_SHIFT_MASK, val); \ + } while (0) + #endif /* !CONFIG_X86_32 */ =20 #define VDSO_CURRENT_BASE ((unsigned long)current->mm->context.vdso) --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -240,6 +240,9 @@ create_elf_tables(struct linux_binprm *bprm, const stru= ct elfhdr *exec, #endif NEW_AUX_ENT(AT_HWCAP, ELF_HWCAP); NEW_AUX_ENT(AT_PAGESZ, ELF_EXEC_PAGESIZE); +#ifdef ARCH_AT_PAGE_SHIFT_MASK + ARCH_AT_PAGE_SHIFT_MASK; +#endif NEW_AUX_ENT(AT_CLKTCK, CLOCKS_PER_SEC); NEW_AUX_ENT(AT_PHDR, phdr_addr); NEW_AUX_ENT(AT_PHENT, sizeof(struct elf_phdr)); --- a/include/uapi/linux/auxvec.h +++ b/include/uapi/linux/auxvec.h @@ -33,6 +33,20 @@ #define AT_RSEQ_FEATURE_SIZE 27 /* rseq supported feature size */ #define AT_RSEQ_ALIGN 28 /* rseq allocation alignment */ =20 +/* + * Page sizes available for mmap(2) encoded as bitmask. + * + * Example: x86_64 system with pse, pdpe1gb /proc/cpuinfo flags reports + * 4 KiB, 2 MiB and 1 GiB page support. + * + * $ hexdump -C /proc/self/auxv + * 00000030 06 00 00 00 00 00 00 00 00 10 00 00 00 00 00 00 + * 00000040 1d 00 00 00 00 00 00 00 00 10 20 40 00 00 00 00 + * + * For 2^64 hugepage support please contact your Universe sales representa= tive. + */ +#define AT_PAGE_SHIFT_MASK 29 + #define AT_EXECFN 31 /* filename of program */ =20 #ifndef AT_MINSIGSTKSZ