Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933016AbaGUQqs (ORCPT ); Mon, 21 Jul 2014 12:46:48 -0400 Received: from gw-1.arm.linux.org.uk ([78.32.30.217]:46697 "EHLO pandora.arm.linux.org.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932543AbaGUQqr (ORCPT ); Mon, 21 Jul 2014 12:46:47 -0400 Date: Mon, 21 Jul 2014 17:46:34 +0100 From: Russell King - ARM Linux To: Daniel Thompson Cc: Thomas Gleixner , Jason Cooper , Marek Vasut , Harro Haan , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, patches@linaro.org, linaro-kernel@lists.linaro.org, John Stultz Subject: Re: [PATCH RFC 5/9] ARM: Add L1 PTE non-secure mapping Message-ID: <20140721164634.GF21766@n2100.arm.linux.org.uk> References: <1405954040-30399-1-git-send-email-daniel.thompson@linaro.org> <1405954040-30399-6-git-send-email-daniel.thompson@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1405954040-30399-6-git-send-email-daniel.thompson@linaro.org> User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 21, 2014 at 03:47:16PM +0100, Daniel Thompson wrote: > From: Marek Vasut > > Add new device type, MT_DEVICE_NS. This type sets the NS bit in L1 PTE [1]. > Accesses to a memory region which is mapped this way generate non-secure > access to that memory area. One must be careful here, since the NS bit is > only available in L1 PTE, therefore when creating the mapping, the mapping > must be at least 1 MiB big and must be aligned to 1 MiB. If that condition > was false, the kernel would use regular L2 page mapping for this area instead > and the NS bit setting would be ineffective. Right, so this says that PTE mappings are not permissible. > + [MT_DEVICE_NS] = { /* Non-secure accesses from secure mode */ > + .prot_pte = PROT_PTE_DEVICE | L_PTE_MT_DEV_SHARED | > + L_PTE_SHARED, > + .prot_l1 = PMD_TYPE_TABLE, However, by filling in prot_pte and prot_l1, you're telling the code that it /can/ setup such a mapping. This is screwed. If you want to deny anything but section mappings (because they don't work) then you omit prot_pte and prot_l1. With those omitted, if someone tries to abuse this mapping type, then this check in create_mapping() will trigger: if (type->prot_l1 == 0 && ((addr | phys | length) & ~SECTION_MASK)) { printk(KERN_WARNING "BUG: map for 0x%08llx at 0x%08lx can not " "be mapped using pages, ignoring.\n", (long long)__pfn_to_phys(md->pfn), addr); return; } ioremap doesn't have that check; it assumes that it will always be setting up PTE mappings via ioremap_page_range(). In fact, on many platforms that's the only option. So making this interface available via ioremap() seems pointless - but more importantly it's extremely error-prone. So, MT_DEVICE_NS shouldn't be using 4 at all, shouldn't be in asm/io.h, but should be with the private MT_* definitions in map.h. -- FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up according to speedtest.net. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/