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[2620:137:e000::3:2]) by mx.google.com with ESMTPS id x14-20020a17090a46ce00b002867eb143afsi1506638pjg.133.2023.12.07.10.44.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 07 Dec 2023 10:44:46 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:2 as permitted sender) client-ip=2620:137:e000::3:2; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20230601 header.b=csTXh3rM; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:2 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Received: from out1.vger.email (depot.vger.email [IPv6:2620:137:e000::3:0]) by agentk.vger.email (Postfix) with ESMTP id 739B98026AA6; Thu, 7 Dec 2023 10:44:42 -0800 (PST) X-Virus-Status: Clean X-Virus-Scanned: clamav-milter 0.103.11 at agentk.vger.email Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1443761AbjLGSod (ORCPT + 99 others); Thu, 7 Dec 2023 13:44:33 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51090 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233289AbjLGSoc (ORCPT ); Thu, 7 Dec 2023 13:44:32 -0500 Received: from mail-ej1-x634.google.com (mail-ej1-x634.google.com [IPv6:2a00:1450:4864:20::634]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1C7F210EB; Thu, 7 Dec 2023 10:44:38 -0800 (PST) Received: by mail-ej1-x634.google.com with SMTP id a640c23a62f3a-a1e2f34467aso124795466b.2; Thu, 07 Dec 2023 10:44:38 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1701974676; x=1702579476; 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=oXf2lAj8XDVwxOmvMwYO09ccy2NUDabGlY5Knm7jvKw=; b=csTXh3rMFTJhvJb/goSS2xFjOHdvRpHl/E9wUz/5twSHunuH2vjuythL8OssMn3tJZ nusyhB0pBjPy4MS5SRPN6ctKZRPlpWxUjGeMEueB8CTxhQEQZTB6QSWoYYJGzEw2ZCu4 NdJrliLFFHagl3BJBwMNUANDtlxVDpUoT+jGlZL6YHgLr4azcKuucrOtiLXvRiovgfVz CagHFsmHxb00C5BrOcBhjYbazlchuAkcKKPa+CQfoTlTKXewa1VopR3fvmFTFNQ1GkZ7 8z8vRHJD2lnGGwLaPHT8xKv3qiZziiFqqfMQwtifLgv6MCeDal8o32pwf/aV4k+vdpS2 ZG3w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1701974676; x=1702579476; 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=oXf2lAj8XDVwxOmvMwYO09ccy2NUDabGlY5Knm7jvKw=; b=J/JPoqvnZn9NUpFKBrEn3BE25c9uuj9EmvkgYqC6Hsns0sdjGAQ80Zrru/meUEyh5r mzWCJVXhN2e3Ys/uZ2WkNy39lPZKOOGXoXEjME3h5rWxP6A3aFcAQv7lZltNEgA/4EXK oje1BgYJ1cGgiG+85InxKymRdSLiUQhL7qbPZ0+f1hPJOjvapzGe9TsYJx4G7gK1gza7 yiVBNHKHHxbvO1Ey9ysE9fK5p/UpX0OgDivokuyUsU4+83ABknHirCrQVY2stSarRgIu SKrMugJ5bQmYGSmrlrszlWaGBEgEfrilYCEE2IBdRW3L/6t9dQWvQeR7IjaaJTBy1cQk ch3g== X-Gm-Message-State: AOJu0Yy8vKUkK6MMur631Onrh4GeWv2UNJT9XyeVHUCaU2hop63HF798 k+RQMCgbemkXdLnB9kbcRw== X-Received: by 2002:a17:907:bb90:b0:a12:635d:fcd1 with SMTP id xo16-20020a170907bb9000b00a12635dfcd1mr1717463ejc.35.1701974675864; Thu, 07 Dec 2023 10:44:35 -0800 (PST) Received: from p183 ([46.53.254.107]) by smtp.gmail.com with ESMTPSA id tz4-20020a170907c78400b00a1aad4d92dbsm69623ejc.123.2023.12.07.10.44.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 07 Dec 2023 10:44:35 -0800 (PST) Date: Thu, 7 Dec 2023 21:44:33 +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, Eric Biederman , Kees Cook , linux-mm@kvack.org Subject: [PATCH v3] ELF: AT_PAGE_SHIFT_MASK -- supply userspace with available page shifts Message-ID: <8582f7c9-b49d-4d21-8948-59d580e5317c@p183> References: <6b399b86-a478-48b0-92a1-25240a8ede54@p183> <87v89dvuxg.fsf@oldenburg.str.redhat.com> <1d679805-8a82-44a4-ba14-49d4f28ff597@p183> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1d679805-8a82-44a4-ba14-49d4f28ff597@p183> X-Spam-Status: No, score=-0.6 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on agentk.vger.email Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (agentk.vger.email [0.0.0.0]); Thu, 07 Dec 2023 10:44:42 -0800 (PST) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1784649809333452110 X-GMAIL-MSGID: 1784649809333452110 Report available page shifts in arch independent manner, so that userspace developers won't have to parse /proc/cpuinfo hunting for arch specific strings. Main users are supposed to be libhugetlbfs-like libraries which try to abstract huge mappings across multiple architectures. Regular code which queries hugepage support before using them benefits too because it doesn't have to deal with descriptors and parsing sysfs hierarchies while enjoying the simplicity and speed of getauxval(AT_PAGE_SHIFT_MASK). Note! This is strictly for userspace, if some page size is shutdown due to kernel command line option or CPU bug workaround, than it 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 always reports one smallest page size which is not interesting. Signed-off-by: Alexey Dobriyan --- v3: better comment and changelog v2: switch to page shifts, rename to ARCH_AT_PAGE_SHIFT_MASK arch/x86/include/asm/elf.h | 12 ++++++++++++ fs/binfmt_elf.c | 3 +++ include/uapi/linux/auxvec.h | 13 +++++++++++++ 3 files changed, 28 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)) \ #define COMPAT_ELF_ET_DYN_BASE (TASK_UNMAPPED_BASE + 0x1000000) +#define ARCH_AT_PAGE_SHIFT_MASK \ + do { \ + u32 val = 1 << 12; \ + if (boot_cpu_has(X86_FEATURE_PSE)) { \ + val |= 1 << 21; \ + } \ + if (boot_cpu_has(X86_FEATURE_GBPAGES)) { \ + val |= 1 << 30; \ + } \ + NEW_AUX_ENT(AT_PAGE_SHIFT_MASK, val); \ + } while (0) + #endif /* !CONFIG_X86_32 */ #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 struct 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 +33,19 @@ #define AT_RSEQ_FEATURE_SIZE 27 /* rseq supported feature size */ #define AT_RSEQ_ALIGN 28 /* rseq allocation alignment */ +/* + * All page sizes supported by CPU encoded as bitmask. + * + * Example: x86_64 system with pse, pdpe1gb /proc/cpuinfo flags + * reports 4 KiB, 2 MiB and 1 GiB page support. + * + * $ LD_SHOW_AUXV=1 $(which true) | grep -e AT_PAGE_SHIFT_MASK + * AT_PAGE_SHIFT_MASK: 0x40201000 + * + * For 2^64 hugepage support please contact your Universe sales representative. + */ +#define AT_PAGE_SHIFT_MASK 29 + #define AT_EXECFN 31 /* filename of program */ #ifndef AT_MINSIGSTKSZ