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=-17.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 939DBC15514 for ; Thu, 4 Mar 2021 00:49:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 78DE164F16 for ; Thu, 4 Mar 2021 00:49:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239977AbhCDAtR (ORCPT ); Wed, 3 Mar 2021 19:49:17 -0500 Received: from mail.kernel.org ([198.145.29.99]:57598 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1573650AbhCCRrO (ORCPT ); Wed, 3 Mar 2021 12:47:14 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 3E69D64DE8; Wed, 3 Mar 2021 17:46:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1614793593; bh=zHovqmMgSn4g07KjIGQ3GddG/B+TRQhDfe0NCPpSiOw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=hEUphPQ96zB/JRoKj9iukjVpFhvPt4O78R/PYwyDsJJCuX1/CS7JwuaoOEH35BCPO PEMEGix9ooCQgp+hbOQENw6SUK1IIm3A+lgyfgp9fpoN7xLENjzuVQ/IUCSakK6oSK XQps8gJRFEm9e2XueANVMhnqazwsU74buqS5004WiXZ5wgyPciFIwXLyh5Azi/QItx +AesAOBL75e28NostLCcUZSnCgvmKjyQGAU/RK9j0tJTyNqgkCclwj8OXUwZlNE4qe JFgAyqC+yZgWr6PSWugGHZKML8mrpCCSajWidxc5wfwh3wy38w9ngkj0ZCq03C4UCi gh11pwSWVe6dQ== Date: Wed, 3 Mar 2021 17:46:28 +0000 From: Will Deacon To: Christophe Leroy Cc: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , danielwa@cisco.com, robh@kernel.org, daniel@gimpelevich.san-francisco.ca.us, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-arch@vger.kernel.org, devicetree@vger.kernel.org Subject: Re: [PATCH v2 1/7] cmdline: Add generic function to build command line. Message-ID: <20210303174627.GC19713@willie-the-truck> References: <20210303172810.GA19713@willie-the-truck> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Wed, Mar 03, 2021 at 06:38:16PM +0100, Christophe Leroy wrote: > Le 03/03/2021 à 18:28, Will Deacon a écrit : > > On Tue, Mar 02, 2021 at 05:25:17PM +0000, Christophe Leroy wrote: > > > This code provides architectures with a way to build command line > > > based on what is built in the kernel and what is handed over by the > > > bootloader, based on selected compile-time options. > > > > > > Signed-off-by: Christophe Leroy > > > --- > > > include/linux/cmdline.h | 62 +++++++++++++++++++++++++++++++++++++++++ > > > 1 file changed, 62 insertions(+) > > > create mode 100644 include/linux/cmdline.h > > > > > > diff --git a/include/linux/cmdline.h b/include/linux/cmdline.h > > > new file mode 100644 > > > index 000000000000..ae3610bb0ee2 > > > --- /dev/null > > > +++ b/include/linux/cmdline.h > > > @@ -0,0 +1,62 @@ > > > +/* SPDX-License-Identifier: GPL-2.0 */ > > > +#ifndef _LINUX_CMDLINE_H > > > +#define _LINUX_CMDLINE_H > > > + > > > +static __always_inline size_t cmdline_strlen(const char *s) > > > +{ > > > + const char *sc; > > > + > > > + for (sc = s; *sc != '\0'; ++sc) > > > + ; /* nothing */ > > > + return sc - s; > > > +} > > > + > > > +static __always_inline size_t cmdline_strlcat(char *dest, const char *src, size_t count) > > > +{ > > > + size_t dsize = cmdline_strlen(dest); > > > + size_t len = cmdline_strlen(src); > > > + size_t res = dsize + len; > > > + > > > + /* This would be a bug */ > > > + if (dsize >= count) > > > + return count; > > > + > > > + dest += dsize; > > > + count -= dsize; > > > + if (len >= count) > > > + len = count - 1; > > > + memcpy(dest, src, len); > > > + dest[len] = 0; > > > + return res; > > > +} > > > > Why are these needed instead of using strlen and strlcat directly? > > Because on powerpc (at least), it will be used in prom_init, it is very > early in the boot and KASAN shadow memory is not set up yet so calling > generic string functions would crash the board. Hmm. We deliberately setup a _really_ early shadow on arm64 for this, can you not do something similar? Failing that, I think it would be better to offer the option for an arch to implement cmdline_*, but have then point to the normal library routines by default. > > > +/* > > > + * This function will append a builtin command line to the command > > > + * line provided by the bootloader. Kconfig options can be used to alter > > > + * the behavior of this builtin command line. > > > + * @dest: The destination of the final appended/prepended string. > > > + * @src: The starting string or NULL if there isn't one. Must not equal dest. > > > + * @length: the length of dest buffer. > > > + */ > > > +static __always_inline void cmdline_build(char *dest, const char *src, size_t length) > > > +{ > > > + if (length <= 0) > > > + return; > > > + > > > + dest[0] = 0; > > > + > > > +#ifdef CONFIG_CMDLINE > > > + if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || !src || !src[0]) { > > > + cmdline_strlcat(dest, CONFIG_CMDLINE, length); > > > + return; > > > + } > > > +#endif > > > > CONFIG_CMDLINE_FORCE implies CONFIG_CMDLINE, and even if it didn't, > > CONFIG_CMDLINE is at worst an empty string. Can you drop the #ifdef? > > Ah yes, since cbe46bd4f510 ("powerpc: remove CONFIG_CMDLINE #ifdef mess") it > is feasible. I can change that now. > > > > > > + if (dest != src) > > > + cmdline_strlcat(dest, src, length); > > > +#ifdef CONFIG_CMDLINE > > > + if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) && sizeof(CONFIG_CMDLINE) > 1) > > > + cmdline_strlcat(dest, " " CONFIG_CMDLINE, length); > > > +#endif > > > > Likewise, but also I'm not sure why the sizeof() is required. > > It is to avoid adding a white space at the end of the command line when > CONFIG_CMDLINE is empty. But maybe it doesn't matter ? If CONFIG_CMDLINE is empty, I don't think you can select CONFIG_CMDLINE_EXTEND (but even if you could, I don't think it matters). Will