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 384F3C433F5 for ; Mon, 6 Dec 2021 14:10:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245620AbhLFONi (ORCPT ); Mon, 6 Dec 2021 09:13:38 -0500 Received: from szxga08-in.huawei.com ([45.249.212.255]:29091 "EHLO szxga08-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231344AbhLFONh (ORCPT ); Mon, 6 Dec 2021 09:13:37 -0500 Received: from dggpemm500023.china.huawei.com (unknown [172.30.72.55]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4J74xg4ZhZz1DJsx; Mon, 6 Dec 2021 22:07:19 +0800 (CST) Received: from dggpemm500001.china.huawei.com (7.185.36.107) by dggpemm500023.china.huawei.com (7.185.36.83) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.20; Mon, 6 Dec 2021 22:10:07 +0800 Received: from [10.174.177.243] (10.174.177.243) by dggpemm500001.china.huawei.com (7.185.36.107) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2308.20; Mon, 6 Dec 2021 22:10:07 +0800 Message-ID: <52a86012-026e-12e5-2c56-7e86537bab73@huawei.com> Date: Mon, 6 Dec 2021 22:10:06 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.2.0 Subject: Re: [PATCH] arm64: mm: Make randomization works again in some case Content-Language: en-US To: Catalin Marinas , Will Deacon , Ard Biesheuvel , , LKML References: <20211104062747.55206-1-wangkefeng.wang@huawei.com> From: Kefeng Wang In-Reply-To: <20211104062747.55206-1-wangkefeng.wang@huawei.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: dggeme707-chm.china.huawei.com (10.1.199.103) To dggpemm500001.china.huawei.com (7.185.36.107) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello， Ard and Catalin, kindly ping... On 2021/11/4 14:27, Kefeng Wang wrote: > After commit 97d6786e0669 ("arm64: mm: account for hotplug memory when > randomizing the linear region"), the KASLR could not work well in some > case, eg, without memory hotplug and with va=39/pa=44, that is, linear > region size < CPU's addressable PA range, the KASLR fails now but could > work before this commit. Let's calculate pa range by memblock end/start > without CONFIG_RANDOMIZE_BASE. > > Meanwhile, let's add a warning message if linear region size is too small > for randomization. > > Signed-off-by: Kefeng Wang > --- > Hi Ard, one more question, the parange from mmfr0 register may also too large, > then even with this patch, the randomization still could not work. > > If we know the max physical memory range(including hotplug memory), could we > add a way(maybe cmdline) to set max parange, then we could make randomization > works in more cases, any thought? > > arch/arm64/mm/init.c | 30 +++++++++++++++++++++--------- > 1 file changed, 21 insertions(+), 9 deletions(-) > > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c > index a8834434af99..27ec7f2c6fdb 100644 > --- a/arch/arm64/mm/init.c > +++ b/arch/arm64/mm/init.c > @@ -284,21 +284,33 @@ void __init arm64_memblock_init(void) > > if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) { > extern u16 memstart_offset_seed; > - u64 mmfr0 = read_cpuid(ID_AA64MMFR0_EL1); > - int parange = cpuid_feature_extract_unsigned_field( > - mmfr0, ID_AA64MMFR0_PARANGE_SHIFT); > - s64 range = linear_region_size - > - BIT(id_aa64mmfr0_parange_to_phys_shift(parange)); > + s64 range; > + > + if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG)) { > + u64 mmfr0 = read_cpuid(ID_AA64MMFR0_EL1); > + int parange = cpuid_feature_extract_unsigned_field( > + mmfr0, ID_AA64MMFR0_PARANGE_SHIFT); > + range = linear_region_size - > + BIT(id_aa64mmfr0_parange_to_phys_shift(parange)); > + > + } else { > + range = linear_region_size - > + (memblock_end_of_DRAM() - memblock_start_of_DRAM()); > + } > > /* > * If the size of the linear region exceeds, by a sufficient > * margin, the size of the region that the physical memory can > * span, randomize the linear region as well. > */ > - if (memstart_offset_seed > 0 && range >= (s64)ARM64_MEMSTART_ALIGN) { > - range /= ARM64_MEMSTART_ALIGN; > - memstart_addr -= ARM64_MEMSTART_ALIGN * > - ((range * memstart_offset_seed) >> 16); > + if (memstart_offset_seed > 0) { > + if (range < (s64)ARM64_MEMSTART_ALIGN) { > + pr_warn("linear mappings size is too small for KASLR\n"); > + } else { > + range /= ARM64_MEMSTART_ALIGN; > + memstart_addr -= ARM64_MEMSTART_ALIGN * > + ((range * memstart_offset_seed) >> 16); > + } > } > } >