From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Je+fNcYY" Received: from mail-wm1-x336.google.com (mail-wm1-x336.google.com [IPv6:2a00:1450:4864:20::336]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B54C290; Tue, 5 Dec 2023 06:26:26 -0800 (PST) Received: by mail-wm1-x336.google.com with SMTP id 5b1f17b1804b1-40b5155e154so61390465e9.3; Tue, 05 Dec 2023 06:26:26 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1701786385; x=1702391185; 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=Op8EMMLSn4u+aBPhlPBNq3QMTgHXM3GBpRsFBgi0BfQ=; b=Je+fNcYYEL+oFZXHBG4vyEm4q3MDARjCNpqHxjZnjM73qqZMRPVD7xWZibgPTy3/qZ cZ8IXlBB5x0tjJMdxDVWKk3z3BjzFi3X1paWRN+UEdh+T3DddyG+cimxxBfEEFaBW6E/ ksHVOnfKLbiMXQk9AGNjof23UTBc9YcjXzmsaZH5pbEVa6P+wzBYPzH5cu7dKdJtrQMh uKQ/r54G+UJpU6cqaRA3UmR9U7XTCcCTE2WMnHPL8Epk49F602I7KbEMwBGF1/hvwnNo dOXjcZoiWBK9RZeYs5Fi76sJn4nFe7doVl6pARNwGz4QT1cIckkCePFkTQLeXxmbSHUG gxHw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1701786385; x=1702391185; 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=Op8EMMLSn4u+aBPhlPBNq3QMTgHXM3GBpRsFBgi0BfQ=; b=dzH6VgYL2LMwnS30vzjJhaVXTq31R7cx0QQDTbh92Wrco9v9OBnX8Lc8ST1acPKaPU VZL56HFq97M/uWJv4ERUImKDOo6fdDRLu7zpBgqyaIdexAav3qJZKTAMLGQ9uoQki/cQ NBQgparuqcNzUelqonsVzhTJ14wXb4vW8/nCt1jH0RaX9TuVEXKOnwxkvWCyGaIBlI8G nwazp/4BLRmfxQePJgk1/I0Si5Rn6tCw1uHu+DLwT5m4wGOgACiGJ/nVLbei6YyBU80t ezpCKatvYywYsIjnqgc74uQmGhwPUaoLT6/2yegvHwvIMYiegkfCj+DcvOs7zlByIMoy 2t+Q== X-Gm-Message-State: AOJu0YwzAzKu92baV5gGxaknFvOj9FhAHzuvVJJIljX+N/DtMD+DePBx judPtpq3C2Tfz64Ke2OgfGhN0bjE6Q== X-Google-Smtp-Source: AGHT+IHHROYIemcb/wsY8oPQMU7gMIn1gsTtBT9VDn93wCGrv8ctub0VOQUxcGsJwZ8m28SEOnej3w== X-Received: by 2002:a05:600c:4f50:b0:40b:5e1f:6fd9 with SMTP id m16-20020a05600c4f5000b0040b5e1f6fd9mr501528wmq.46.1701786384964; Tue, 05 Dec 2023 06:26:24 -0800 (PST) Received: from p183 ([46.53.254.107]) by smtp.gmail.com with ESMTPSA id t20-20020a05600c451400b004094e565e71sm19022491wmo.23.2023.12.05.06.26.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 05 Dec 2023 06:26:24 -0800 (PST) Date: Tue, 5 Dec 2023 17:26:22 +0300 From: Alexey Dobriyan To: Florian Weimer Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, x86@kernel.org Subject: Re: [PATCH] ELF: supply userspace with available page shifts (AT_PAGE_SHIFT_LIST) Message-ID: <75344429-1f34-4a14-ab10-8613846d694e@p183> References: <6b399b86-a478-48b0-92a1-25240a8ede54@p183> <87v89dvuxg.fsf@oldenburg.str.redhat.com> Precedence: bulk X-Mailing-List: linux-api@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <87v89dvuxg.fsf@oldenburg.str.redhat.com> On Tue, Dec 05, 2023 at 10:51:39AM +0100, Florian Weimer wrote: > * Alexey Dobriyan: > > > +/* > > + * Page sizes available for mmap(2) encoded as 1 page shift per byte in > > + * increasing order. > > + * > > + * Thus 32-bit systems get 4 shifts, 64-bit systems get 8 shifts tops. > > Couldn't you use the bits in a long instead, to indicate which shifts > are present? That's always going to be enough. Yes! I was so proud of myself for this line: val |= 21 << (s += 8); Now it is boring bitmask again :-)