From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934343AbcAKRcU (ORCPT ); Mon, 11 Jan 2016 12:32:20 -0500 Received: from foss.arm.com ([217.140.101.70]:57140 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932940AbcAKRcQ (ORCPT ); Mon, 11 Jan 2016 12:32:16 -0500 Date: Mon, 11 Jan 2016 17:31:54 +0000 From: Mark Rutland To: Ard Biesheuvel Cc: "linux-arm-kernel@lists.infradead.org" , kernel-hardening@lists.openwall.com, Will Deacon , Catalin Marinas , Leif Lindholm , Kees Cook , "linux-kernel@vger.kernel.org" , Stuart Yoder , Sharma Bhupesh , Arnd Bergmann , Marc Zyngier , Christoffer Dall Subject: Re: [PATCH v3 06/21] arm64: pgtable: implement static [pte|pmd|pud]_offset variants Message-ID: <20160111173154.GB6105@leverpostej> References: <1452518355-4606-1-git-send-email-ard.biesheuvel@linaro.org> <1452518355-4606-7-git-send-email-ard.biesheuvel@linaro.org> <20160111162449.GP6499@leverpostej> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 11, 2016 at 06:28:51PM +0100, Ard Biesheuvel wrote: > On 11 January 2016 at 17:24, Mark Rutland wrote: > > On Mon, Jan 11, 2016 at 02:18:59PM +0100, Ard Biesheuvel wrote: > >> The page table accessors pte_offset(), pud_offset() and pmd_offset() > >> rely on __va translations, so they can only be used after the linear > >> mapping has been installed. For the early fixmap and kasan init routines, > >> whose page tables are allocated statically in the kernel image, these > >> functions will return bogus values. So implement pmd_offset_kimg() and > >> pud_offset_kimg(), which can be used instead before any page tables have > >> been allocated dynamically. > >> > >> Signed-off-by: Ard Biesheuvel > > > > This looks good to me. One possible suggsetion below, but either way: > > > > Reviewed-by: Mark Rutland > > > >> --- > >> arch/arm64/include/asm/pgtable.h | 13 +++++++++++++ > >> 1 file changed, 13 insertions(+) > >> > >> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h > >> index 6129f6755081..7b4e16068c9f 100644 > >> --- a/arch/arm64/include/asm/pgtable.h > >> +++ b/arch/arm64/include/asm/pgtable.h > >> @@ -449,6 +449,9 @@ static inline phys_addr_t pmd_page_paddr(pmd_t pmd) > >> > >> #define pmd_page(pmd) pfn_to_page(__phys_to_pfn(pmd_val(pmd) & PHYS_MASK)) > >> > >> +/* use ONLY for statically allocated translation tables */ > >> +#define pte_offset_kimg(dir,addr) ((pte_t *)__phys_to_kimg(pte_offset_phys((dir), (addr)))) > >> + > > > > Given that we're probably only going to use this during one-off setup, > > maybe it's worth something like: > > > > #define IN_KERNEL_IMAGE(p) ({ \ > > unsigned long __p = (unsigned long)p; \ > > KIMAGE_VADDR <= __p && __p < _end; \ > > }) > > > > #define pte_offset_kimg(dir,addr) ({ \ > > BUG_ON(!IN_KERNEL_IMAGE(dir)); \ > > ((pte_t *)__phys_to_kimg(pte_offset_phys((dir), (addr)))); \ > > }) > > > > That might be overkill, though, given all it does is turn one runtime > > failure into another runtime failure. > > > > Yes. I did consider implementing them out of line, with __init > annotations so you at least get complaints if you refer to them from > non-init code, but I don't see how we would ever need these anywhere > beyond fixmap and kasan anyway Ok. Let's forget about that for now then. :) Mark.