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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 E68D1C388F9 for ; Fri, 20 Nov 2020 02:43:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9F230221FB for ; Fri, 20 Nov 2020 02:43:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726385AbgKTCn3 (ORCPT ); Thu, 19 Nov 2020 21:43:29 -0500 Received: from mail.loongson.cn ([114.242.206.163]:60688 "EHLO loongson.cn" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725890AbgKTCn2 (ORCPT ); Thu, 19 Nov 2020 21:43:28 -0500 Received: from [10.130.0.170] (unknown [113.200.148.30]) by mail.loongson.cn (Coremail) with SMTP id AQAAf9AxutBKLbdfVlITAA--.31068S3; Fri, 20 Nov 2020 10:43:23 +0800 (CST) Subject: Re: [PATCH 3/3] MIPS: KASLR: Make relocation_address can be configured To: Thomas Bogendoerfer References: <1605752954-10368-1-git-send-email-hejinyang@loongson.cn> <1605752954-10368-3-git-send-email-hejinyang@loongson.cn> <20201119124544.GB4936@alpha.franken.de> Cc: Huacai Chen , Jiaxun Yang , linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org From: Jinyang He Message-ID: <55b35e07-7491-7404-1ab5-03fd059aac79@loongson.cn> Date: Fri, 20 Nov 2020 10:43:22 +0800 User-Agent: Mozilla/5.0 (X11; Linux mips64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: <20201119124544.GB4936@alpha.franken.de> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-CM-TRANSID: AQAAf9AxutBKLbdfVlITAA--.31068S3 X-Coremail-Antispam: 1UD129KBjvJXoW7uFykCF4DGF4UJF1rCw43trb_yoW8WrW5pr ZrGr45G3yDKFy2krWDXw4rCr15A393Ja4xG34DJrWrZ34ag3Zayw1UWr1xKas5Krn7Jw43 ZFWq9rW29FWYyaUanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUvSb7Iv0xC_KF4lb4IE77IF4wAFF20E14v26r1j6r4UM7CY07I2 0VC2zVCF04k26cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rw A2F7IY1VAKz4vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_Xr0_Ar1l84ACjcxK6xII jxv20xvEc7CjxVAFwI0_Cr0_Gr1UM28EF7xvwVC2z280aVAFwI0_Gr1j6F4UJwA2z4x0Y4 vEx4A2jsIEc7CjxVAFwI0_Cr1j6rxdM2AIxVAIcxkEcVAq07x20xvEncxIr21l5I8CrVAC Y4xI64kE6c02F40Ex7xfMcIj6xIIjxv20xvE14v26r106r15McIj6I8E87Iv67AKxVWUJV W8JwAm72CE4IkC6x0Yz7v_Jr0_Gr1lF7xvr2IY64vIr41lc7I2V7IY0VAS07AlzVAYIcxG 8wCY02Avz4vE14v_Gr1l42xK82IYc2Ij64vIr41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1lx2 IqxVAqx4xG67AKxVWUJVWUGwC20s026x8GjcxK67AKxVWUGVWUWwC2zVAF1VAY17CE14v2 6r126r1DMIIYrxkI7VAKI48JMIIF0xvE2Ix0cI8IcVAFwI0_Jr0_JF4lIxAIcVC0I7IYx2 IY6xkF7I0E14v26r1j6r4UMIIF0xvE42xK8VAvwI8IcIk0rVWrZr1j6s0DMIIF0xvEx4A2 jsIE14v26r1j6r4UMIIF0xvEx4A2jsIEc7CjxVAFwI0_Jr0_GrUvcSsGvfC2KfnxnUUI43 ZEXa7IU8sa93UUUUU== X-CM-SenderInfo: pkhmx0p1dqwqxorr0wxvrqhubq/ Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 11/19/2020 08:45 PM, Thomas Bogendoerfer wrote: > On Thu, Nov 19, 2020 at 10:29:14AM +0800, Jinyang He wrote: >> When CONFIG_RANDOMIZE_BASE is not set, determine_relocation_address() >> always returns a constant. It is not friendly to users if the address >> cannot be used. Make it can be configured at Kconfig. > and how do I get the information which address I need to enter ? > This looks more like platforms need to supply a working address and > not the user configuring the kernel... You are right. We only have two address to enter if CONFIG_RANDOMIZE_BASE disabled. One is 0xffffffff81000000 in the current if succeed, the other is the orignal address if failed. From relocation_addr_valid() we see that the avaliable address need to higher than &_end to avoid overlaps original kernel. E.g. 0xffffffff83000000 and 0xffffffff84000000 both is avaliable on Loongson64 platform when &_end == 0xffffffff82213f80. But 0xffffffff82000000 is not available in that case. In reality test, I compiled kernel first and got &_end. And then modified the relocate_address to avaliable and compiled kernel once more. It is a bad idea. Is it different from modifying CONFIG_PHYSICAL_START when just relocate one address? Does it make sense if only one address to relocate? Morever, RANDOMIZE_BASE is normally avaliable. Can we add a kernel parameter like "relocation=0xffffffff81000000" to direct address? At least, other architecture disabling RANDOMIZE_BASE looks like "nokaslr". Thus, can we delete these code which RANDOMIZE_BASE disabled? Thanks! :-) Jinyang > Thomas. >