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[2620:137:e000::1:20]) by mx.google.com with ESMTP id bs193-20020a6328ca000000b0054201a3f08dsi3566210pgb.592.2023.07.12.14.12.22; Wed, 12 Jul 2023 14:12:34 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@t-8ch.de header.s=mail header.b=Q8awcXtz; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231694AbjGLUjn (ORCPT + 99 others); Wed, 12 Jul 2023 16:39:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53860 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229446AbjGLUjl (ORCPT ); Wed, 12 Jul 2023 16:39:41 -0400 Received: from todd.t-8ch.de (todd.t-8ch.de [159.69.126.157]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 65665C0; Wed, 12 Jul 2023 13:39:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=t-8ch.de; s=mail; t=1689194377; bh=Bv1FBLS0imEYqyDXO06WSOGp+LcvozRCbruE7WI3Jd4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Q8awcXtzB6DxFLJ+qYGSHN6okWFP0MeMDxEv2DsDe8HOSZWS4zJ/oPzDPK74JHCqF CmZjzXLhGgAItOrcctkBK4SJ4pJckjjEXi0cB2Y6D9+ia8tyVc/GbfRLcekO+FpjsQ oGp0IIiD5uFg5j7YZjT8C4Gyiu1mo65VHYov7c7c= Date: Wed, 12 Jul 2023 22:39:36 +0200 From: Thomas =?utf-8?Q?Wei=C3=9Fschuh?= To: Zhangjin Wu Cc: w@1wt.eu, arnd@arndb.de, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v3 02/11] tools/nolibc: add new crt.h with _start_c Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_BLOCKED, SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023-07-12 17:17:39+0800, Zhangjin Wu wrote: > As the environ and _auxv support added for nolibc, the assembly _start > function becomes more and more complex and therefore makes the porting > of nolibc to new architectures harder and harder. > > To simplify portability, this C version of _start_c() is added to do > most of the assembly start operations in C, which reduces the complexity > a lot and will eventually simplify the porting of nolibc to the new > architectures. > > The new _start_c() only requires a stack pointer argument, it will find > argv, envp and _auxv for us, and then call main(), finally, it exit() > with main's return status. With this new _start_c(), the future new > architectures only require to add very few assembly instructions. > > As suggested by Thomas, users may use a different signature of main > (e.g. void main(void)), a _nolibc_main alias is added for main to > silence the warning about potential conflicting types. > > Suggested-by: Thomas Weißschuh > Link: https://lore.kernel.org/lkml/90fdd255-32f4-4caf-90ff-06456b53dac3@t-8ch.de/ > Signed-off-by: Zhangjin Wu > --- > tools/include/nolibc/Makefile | 1 + > tools/include/nolibc/crt.h | 59 +++++++++++++++++++++++++++++++++++ > 2 files changed, 60 insertions(+) > create mode 100644 tools/include/nolibc/crt.h > > diff --git a/tools/include/nolibc/Makefile b/tools/include/nolibc/Makefile > index 64d67b080744..909b6eb500fe 100644 > --- a/tools/include/nolibc/Makefile > +++ b/tools/include/nolibc/Makefile > @@ -27,6 +27,7 @@ nolibc_arch := $(patsubst arm64,aarch64,$(ARCH)) > arch_file := arch-$(nolibc_arch).h > all_files := \ > compiler.h \ > + crt.h \ > ctype.h \ > errno.h \ > nolibc.h \ > diff --git a/tools/include/nolibc/crt.h b/tools/include/nolibc/crt.h > new file mode 100644 > index 000000000000..f9db2389acd2 > --- /dev/null > +++ b/tools/include/nolibc/crt.h > @@ -0,0 +1,59 @@ > +/* SPDX-License-Identifier: LGPL-2.1 OR MIT */ > +/* > + * C Run Time support for NOLIBC > + * Copyright (C) 2023 Zhangjin Wu > + */ > + > +#ifndef _NOLIBC_CRT_H > +#define _NOLIBC_CRT_H > + > +char **environ __attribute__((weak)); > +const unsigned long *_auxv __attribute__((weak)); > + > +typedef int (_nolibc_main_fn)(int, char **, char **); What's the advantage of the typedef over using the pointer type inline? > +static void exit(int); > + > +void _start_c(long *sp) > +{ > + int argc, i; > + char **argv; > + char **envp; > + /* silence potential warning: conflicting types for 'main' */ > + _nolibc_main_fn _nolibc_main __asm__ ("main"); What about the stackprotector initialization? It would really fit great into this series. > + > + /* > + * sp : argc <-- argument count, required by main() > + * argv: argv[0] <-- argument vector, required by main() > + * argv[1] > + * ... > + * argv[argc-1] > + * null > + * envp: envp[0] <-- environment variables, required by main() and getenv() > + * envp[1] > + * ... > + * null > + * _auxv: auxv[0] <-- auxiliary vector, required by getauxval() > + * auxv[1] > + * ... > + * null > + */ > + > + /* assign argc and argv */ > + argc = sp[0]; > + argv = (void *)(sp + 1); Bit of a weird mismatch between array syntax and pointer arithmetic. > + > + /* find envp */ > + envp = argv + argc + 1; > + environ = envp; Is envp really needed? Could just be assigned directly to environ. > + > + /* find auxv */ > + i = 0; > + while (envp[i]) > + i++; > + _auxv = (void *)(envp + i + 1); Could be simplified a bit: _auxv = (void *) envp; while (_auxv) _auxv++; > + > + /* go to application */ > + exit(_nolibc_main(argc, argv, envp)); > +} > + > +#endif /* _NOLIBC_CRT_H */ > -- > 2.25.1 >