From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934362AbcAMODN (ORCPT ); Wed, 13 Jan 2016 09:03:13 -0500 Received: from mail-ig0-f175.google.com ([209.85.213.175]:36250 "EHLO mail-ig0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934272AbcAMODK (ORCPT ); Wed, 13 Jan 2016 09:03:10 -0500 MIME-Version: 1.0 In-Reply-To: <1452635187-8057-1-git-send-email-labbott@fedoraproject.org> References: <1452635187-8057-1-git-send-email-labbott@fedoraproject.org> Date: Wed, 13 Jan 2016 15:03:09 +0100 Message-ID: Subject: Re: [PATCH] arm64: Allow vmalloc regions to be set with set_memory_* From: Ard Biesheuvel To: Laura Abbott Cc: Catalin Marinas , Will Deacon , Mark Rutland , Kees Cook , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12 January 2016 at 22:46, Laura Abbott wrote: > > The range of set_memory_* is currently restricted to the module address > range because of difficulties in breaking down larger block sizes. > vmalloc maps PAGE_SIZE pages so it is safe to use as well. Update the > function ranges and add a comment explaining why the range is restricted > the way it is. > > Signed-off-by: Laura Abbott > --- > This should let the protections for the eBPF work as expected, I don't > know if there is some sort of self test for thatL. This is going to conflict with my KASLR implementation, since it puts the kernel image right in the middle of the vmalloc area, and the kernel is obviously mapped with block mappings. In fact, I am proposing enabling huge-vmap for arm64 as well, since it seems an improvement generally, but also specifically allows me to unmap the __init section using the generic vunmap code (remove_vm_area). But in general, I think the assumption that the whole vmalloc area is mapped using pages is not tenable. AFAICT, vmalloc still use pages exclusively even with huge-vmap (but ioremap does not). So perhaps it would make sense to check for the VM_ALLOC bit in the VMA flags (which I will not set for the kernel regions either) > --- > arch/arm64/mm/pageattr.c | 25 +++++++++++++++++++++---- > 1 file changed, 21 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c > index 3571c73..274208e 100644 > --- a/arch/arm64/mm/pageattr.c > +++ b/arch/arm64/mm/pageattr.c > @@ -36,6 +36,26 @@ static int change_page_range(pte_t *ptep, pgtable_t token, unsigned long addr, > return 0; > } > > +static bool validate_addr(unsigned long start, unsigned long end) > +{ > + /* > + * This check explicitly excludes most kernel memory. Most kernel > + * memory is mapped with a larger page size and breaking down the > + * larger page size without causing TLB conflicts is very difficult. > + * > + * If you need to call set_memory_* on a range, the recommendation is > + * to use vmalloc since that range is mapped with pages. > + */ > + if (start >= MODULES_VADDR && start < MODULES_END && > + end >= MODULES_VADDR && end < MODULES_END) > + return true; > + > + if (is_vmalloc_addr(start) && is_vmalloc_addr(end)) > + return true; > + > + return false; > +} > + > static int change_memory_common(unsigned long addr, int numpages, > pgprot_t set_mask, pgprot_t clear_mask) > { > @@ -51,10 +71,7 @@ static int change_memory_common(unsigned long addr, int numpages, > WARN_ON_ONCE(1); > } > > - if (start < MODULES_VADDR || start >= MODULES_END) > - return -EINVAL; > - > - if (end < MODULES_VADDR || end >= MODULES_END) > + if (!validate_addr(start, end)) > return -EINVAL; > > data.set_mask = set_mask; > -- > 2.5.0 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel