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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 1C322C3279B for ; Fri, 6 Jul 2018 14:41:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D0FF323FD2 for ; Fri, 6 Jul 2018 14:41:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D0FF323FD2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932905AbeGFOlM (ORCPT ); Fri, 6 Jul 2018 10:41:12 -0400 Received: from foss.arm.com ([217.140.101.70]:37882 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932714AbeGFOlL (ORCPT ); Fri, 6 Jul 2018 10:41:11 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id BAFB5ED1; Fri, 6 Jul 2018 07:41:10 -0700 (PDT) Received: from [10.1.206.34] (melchizedek.cambridge.arm.com [10.1.206.34]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8A9C43F2EA; Fri, 6 Jul 2018 07:41:09 -0700 (PDT) Subject: Re: [PATCH v3 3/5] arm64/mm: Create initial page tables in init_pg_dir From: James Morse To: Jun Yao Cc: linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, will.deacon@arm.com, suzuki.poulose@arm.com, linux-kernel@vger.kernel.org References: <20180702111659.25570-1-yaojun8558363@gmail.com> <20180702111659.25570-4-yaojun8558363@gmail.com> <3977afaa-63ae-e390-7660-4d25146140b8@arm.com> Message-ID: <41a18121-c91d-f9ec-87c3-8dba7931b517@arm.com> Date: Fri, 6 Jul 2018 15:41:07 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: <3977afaa-63ae-e390-7660-4d25146140b8@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Jun, On 06/07/18 09:58, James Morse wrote: > The series so far fails to boot from me. This is because the kaslr code tries to > read the kaslr-seed from the DT, via the fixmap. To do this, it needs the fixmap > tables installed, which early_fixmap_init() does. > > early_fixmap_init() calls pgd_offset_k(), which assumes init_mm.pgd is in use, > so we hit a BUG_ON() when trying to setup the fixmap because we added the tables > to the wrong page tables. > > If you enable 'CONFIG_RANDOMIZE_BASE', even without EFI you should see the same > thing happen. > > > I think we should move this hunk: >> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c >> index 30ad2f085d1f..b065c08d4008 100644 >> --- a/arch/arm64/kernel/setup.c >> +++ b/arch/arm64/kernel/setup.c >> @@ -249,6 +249,7 @@ void __init setup_arch(char **cmdline_p) >> init_mm.end_code = (unsigned long) _etext; >> init_mm.end_data = (unsigned long) _edata; >> init_mm.brk = (unsigned long) _end; >> + init_mm.pgd = init_pg_dir; >> >> *cmdline_p = boot_command_line; >> > > into early_fixmap_init(), which is the first thing setup_arch() calls. > Something like [0] fixes it. > > This looks to be the only thing that goes near init_mm.pgd before paging_init(). I missed one: head.S has a call to kasan_early_init() before start_kernel(), this goes messing with the page tables, and calls pgd_offset_k(), which pulls in swapper_pg_dir. This one is enabled by CONFIG_KASAN. Something like that same hunk [0] in kasan_early_init() fixes it. This is still within arch/arm64, so I still think we should get away without some #ifdeffery to override the core-code's initial setup of swapper_pg_dir... Thanks, James > [0] make sure fixmap tables go in the init page tables > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index 117d080639b3..e097c78a66f8 100644 > --- a/arch/arm64/mm/mmu.c > +++ b/arch/arm64/mm/mmu.c > @@ -770,6 +771,13 @@ void __init early_fixmap_init(void) > pmd_t *pmdp; > unsigned long addr = FIXADDR_START; > > + /* > + * During early setup we use init_pg_dir, update init_mm so its > + * implicit use by pgd_offset_k() gets the live page tables. > + * swapper_pg_dir is restored by paging_init(). > + */ > + init_mm.pgd = init_pg_dir; > + > pgdp = pgd_offset_k(addr); > pgd = READ_ONCE(*pgdp); > if (CONFIG_PGTABLE_LEVELS > 3 && > > >