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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,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 DB3C0C4332D for ; Wed, 3 Mar 2021 20:57:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B065264EFC for ; Wed, 3 Mar 2021 20:57:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1836595AbhCCSsI (ORCPT ); Wed, 3 Mar 2021 13:48:08 -0500 Received: from pegase1.c-s.fr ([93.17.236.30]:3482 "EHLO pegase1.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1352260AbhCCR6r (ORCPT ); Wed, 3 Mar 2021 12:58:47 -0500 Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 4DrMCF1XV1z9v4QZ; Wed, 3 Mar 2021 18:57:13 +0100 (CET) X-Virus-Scanned: Debian amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [192.168.12.234]) (amavisd-new, port 10024) with ESMTP id QezXv5b5bs7A; Wed, 3 Mar 2021 18:57:13 +0100 (CET) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 4DrMCD6mvcz9ttC2; Wed, 3 Mar 2021 18:57:12 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 3CFC08B7DB; Wed, 3 Mar 2021 18:57:13 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id HfuXNu-LNDVW; Wed, 3 Mar 2021 18:57:13 +0100 (CET) Received: from [192.168.4.90] (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 3EC2D8B7E6; Wed, 3 Mar 2021 18:57:12 +0100 (CET) Subject: Re: [PATCH v2 1/7] cmdline: Add generic function to build command line. To: Will Deacon 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 References: <20210303172810.GA19713@willie-the-truck> <20210303174627.GC19713@willie-the-truck> From: Christophe Leroy Message-ID: Date: Wed, 3 Mar 2021 18:57:09 +0100 User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: <20210303174627.GC19713@willie-the-truck> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Le 03/03/2021 à 18:46, Will Deacon a écrit : > 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. I don't think it is possible to setup an earlier early shadow. At the point we are in prom_init, the code is not yet relocated at the address it was linked for, and it is running with the MMU set by the bootloader, I can't imagine being able to setup MMU entries for the early shadow KASAN yet without breaking everything. Is it really worth trying to point to the normal library routines by default ? It is really only a few lines of code hence only not many bytes, and anyway they are in __init section so they get discarded at the end. > >>>> +/* >>>> + * 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). Ok I'll simplify that when I re-spin. Christophe