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=-2.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 D923CC433DB for ; Fri, 12 Mar 2021 03:18:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ABA5064F8D for ; Fri, 12 Mar 2021 03:18:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231650AbhCLDS1 (ORCPT ); Thu, 11 Mar 2021 22:18:27 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55806 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231664AbhCLDSH (ORCPT ); Thu, 11 Mar 2021 22:18:07 -0500 Received: from mail-qt1-x834.google.com (mail-qt1-x834.google.com [IPv6:2607:f8b0:4864:20::834]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 74C34C061574; Thu, 11 Mar 2021 19:18:07 -0800 (PST) Received: by mail-qt1-x834.google.com with SMTP id f12so2830661qtq.4; Thu, 11 Mar 2021 19:18:07 -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:mail-followup-to:references :mime-version:content-disposition:in-reply-to; bh=6s7aZDqIh5c7QwDOhan9TstA2/Xr1K2QMo7FCDdlyBo=; b=T4OQFB66k30ubxSV9gRAG0sZGTambgWeuupbvEr22jNOK7+vK13ZnJzFS338VUwl0g JXdWe+1L9IdmWhMSBCzKF5V114ma5sIszr/weI1wT6nmOwDlkYuc+hMD+vw2zGTISm91 lscDoakYPZJVOVVZdNzQzUaRjBP6lUjLgiPla8k7blFhU1exhOBfn5TRSDrvyzZnVjid TNIrPy9RIGI0ASk1rFeMOM8J1Tg0BMVNyZQxvFU11mBGVx6jbw9NH+h4GRHD9Tw0BP/v V2Hp4gjijvgcsftsYupz1Drf7gpqHyQAe/lL8e3PX+T6CYnafbTGbMcbmMpyhMM9t/Zp X6fw== 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 :mail-followup-to:references:mime-version:content-disposition :in-reply-to; bh=6s7aZDqIh5c7QwDOhan9TstA2/Xr1K2QMo7FCDdlyBo=; b=Y+66Y16Olf+R7VDAorcK36bej73y2k+gqg8MQ1dAMV/R6peySKbVCtEZIsrxaQA0+5 BokcNYQYTznpiK2h79l219ZWCySfShC0ppJoyNlTu8ERM+FUiWeqpzNjNaxRNjzF/jIt b0u/A1KNtRfUC31xToKymSKEVkVp0M1s8Yku062N3IwD03UjToQANQ6kiRh4LF/AeyWf HoYkVG4sWNlXTz+MOxGyBtzyiPW8a/BQ6LK1L/eOkmcUi9YIuu1m0lHbDwz88WCttXJr Imw/6P4rgTD3Q2m5GA0DFSCJKvoOWE/vaRwwGVF34Qpw9I2iNSGGiVykR1bCtm4UYusa L4bA== X-Gm-Message-State: AOAM533t0s/s0JzUwJCfjHUg6wFs7i0EZr/dLiQ9P9ZEzaq4EqjhQ6tt RENZ3E9mG162KfqcbuqEOlhHxMYea5g2VyT4 X-Google-Smtp-Source: ABdhPJzRY92UlNkLxUZSslSacXp9ZxxY+woT8JqRC+Bpt6L8dZuV8xz7IXOkkAx5vIAcLDqtBaCpDA== X-Received: by 2002:ac8:b49:: with SMTP id m9mr10303587qti.182.1615519086608; Thu, 11 Mar 2021 19:18:06 -0800 (PST) Received: from Gentoo ([143.244.44.200]) by smtp.gmail.com with ESMTPSA id 85sm3696440qkf.58.2021.03.11.19.18.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 11 Mar 2021 19:18:05 -0800 (PST) Date: Fri, 12 Mar 2021 08:47:58 +0530 From: Bhaskar Chowdhury To: Masahiro Yamada Cc: Linux Kernel Mailing List , linux-api@vger.kernel.org Subject: Re: Why is the bit size different between a syscall and its wrapper? Message-ID: Mail-Followup-To: Bhaskar Chowdhury , Masahiro Yamada , Linux Kernel Mailing List , linux-api@vger.kernel.org References: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="Tq7vG0cIx+jTMAax" Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org --Tq7vG0cIx+jTMAax Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline On 11:48 Fri 12 Mar 2021, Masahiro Yamada wrote: >Hi. > >I think I am missing something, but >is there any particular reason to >use a different bit size between >a syscall and its userspace wrapper? > > > >For example, for the unshare syscall, > >unshare(2) says the parameter is int. > > >SYNOPSIS > #define _GNU_SOURCE > #include > > int unshare(int flags); > > > > >In the kernel, it is unsigned long. > > >SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) >{ > return ksys_unshare(unshare_flags); >} > > > > >I guess the upper 32-bit will be >zeroed out in the c library when >sizeof(int) != sizeof(unsigned long) >(i.e. 64-bit system), but I'd like to know >why we do it this way. > > Small nit! never mind ...but eye catching, Masahiro :) ...are you typing this on narrowed device, which allow only this much line length?? It's bloody narrow...don't you think so? Sorry, for the deviation. ~Bhaskar >-- >Best Regards >Masahiro Yamada --Tq7vG0cIx+jTMAax Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCAAdFiEEnwF+nWawchZUPOuwsjqdtxFLKRUFAmBK3WMACgkQsjqdtxFL KRU3nwf/ZL/k1UIFts05kpo+C0zQCoovf4iCPT+Xdx43C6W4t8uk+cYNudnTcs9c Cfd5MmuZ9smrdglDnx7tFBZ4vuB5jZoze4g3zrz3qcFCJu9IZj3Y0V+ACJ1QpK9l 4qZoRLUoP2LhLxbCQtUuxPy4XTq85VhhDJhqVG3ArizebKjmjOHHWsp8hnrogSOq mwjdypgrolCMEs45umeA/gPVNchoY4a4k05A/Publz0s++KZtDRGc4SEGYP20HJq +eLeNg7t1a9uujIKkbf+ESoFIeJgJu15KxBmAmWF8oclpKo7wxvLprgabkq5s3J9 sJEnPseSffefo9qgr3yxIATPzw3etg== =tJ53 -----END PGP SIGNATURE----- --Tq7vG0cIx+jTMAax--