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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 084BFC04A6A for ; Sun, 13 Aug 2023 09:00:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230462AbjHMJAp (ORCPT ); Sun, 13 Aug 2023 05:00:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40866 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229729AbjHMJAo (ORCPT ); Sun, 13 Aug 2023 05:00:44 -0400 Received: from 1wt.eu (ded1.1wt.eu [163.172.96.212]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 7317C10E5; Sun, 13 Aug 2023 02:00:46 -0700 (PDT) Received: (from willy@localhost) by pcw.home.local (8.15.2/8.15.2/Submit) id 37D90bCo008591; Sun, 13 Aug 2023 11:00:37 +0200 Date: Sun, 13 Aug 2023 11:00:37 +0200 From: Willy Tarreau To: Zhangjin Wu Cc: david.laight@aculab.com, arnd@arndb.de, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, tanyuan@tinylab.org, thomas@t-8ch.de Subject: Re: [PATCH v6 2/2] tools/nolibc: fix up size inflate regression Message-ID: <20230813090037.GE8237@1wt.eu> References: <96624cc918092737d35dd539d184de06dba7a9b8.1691788036.git.falcon@tinylab.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <96624cc918092737d35dd539d184de06dba7a9b8.1691788036.git.falcon@tinylab.org> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Aug 12, 2023 at 05:51:53AM +0800, Zhangjin Wu wrote: > As reported and suggested by Willy, the inline __sysret() helper > introduces three types of conversions and increases the size: > > (1) the "unsigned long" argument to __sysret() forces a sign extension > from all sys_* functions that used to return 'int' > > (2) the comparison with the error range now has to be performed on a > 'unsigned long' instead of an 'int' > > (3) the return value from __sysret() is a 'long' (note, a signed long) > which then has to be turned back to an 'int' before being returned by the > caller to satisfy the caller's prototype. > > To fix up this, firstly, let's use macro instead of inline function to > preserves the input type and avoids these useless conversions (1), (3). > > Secondly, since all of the sys_* functions have been converted to return > integer, now, it is able to remove comparison to a 'unsigned long' > -MAX_ERRNO (2) and restore the simple sign comparison as before. > (...) > +/* Syscall return helper, set errno as -ret when ret < 0 */ > +#define __sysret(arg) \ > +({ \ > + __typeof__(arg) __ret = (arg); \ > + if (__ret < 0) { \ > + SET_ERRNO(-__ret); \ > + __ret = -1L; \ > + } \ > + __ret; \ > +}) Except that this now breaks brk(), mmap() and sbrk() by taking any value with MSB set as an error. Also you've re-introduced the problem you've faced with const. See my simplification in the other thread by using "?:" which does avoids any assignment. Let's just roll brk(), mmap() and sbrk() to their original, working, definition: static __attribute__((unused)) void *mmap(void *addr, size_t length, int prot, int flags, int fd, off_t offset) { void *ret = sys_mmap(addr, length, prot, flags, fd, offset); if ((unsigned long)ret >= -MAX_ERRNO) { SET_ERRNO(-(long)ret); ret = MAP_FAILED; } return ret; } And we're done, you can then keep the simplified __sysret() macro for all other call places. Willy