Messages in this thread Patch in this message | | | Subject | Re: [RFC PATCH v7 05/16] arm64/mm: Add support for XPFO | From | Khalid Aziz <> | Date | Tue, 12 Feb 2019 13:34:15 -0700 |
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On 2/12/19 1:01 PM, Laura Abbott wrote: > On 2/12/19 7:52 AM, Khalid Aziz wrote: >> On 1/23/19 7:24 AM, Konrad Rzeszutek Wilk wrote: >>> On Thu, Jan 10, 2019 at 02:09:37PM -0700, Khalid Aziz wrote: >>>> From: Juerg Haefliger <juerg.haefliger@canonical.com> >>>> >>>> Enable support for eXclusive Page Frame Ownership (XPFO) for arm64 and >>>> provide a hook for updating a single kernel page table entry (which is >>>> required by the generic XPFO code). >>>> >>>> v6: use flush_tlb_kernel_range() instead of __flush_tlb_one() >>>> >>>> CC: linux-arm-kernel@lists.infradead.org >>>> Signed-off-by: Juerg Haefliger <juerg.haefliger@canonical.com> >>>> Signed-off-by: Tycho Andersen <tycho@docker.com> >>>> Signed-off-by: Khalid Aziz <khalid.aziz@oracle.com> >>>> --- >>>> arch/arm64/Kconfig | 1 + >>>> arch/arm64/mm/Makefile | 2 ++ >>>> arch/arm64/mm/xpfo.c | 58 >>>> ++++++++++++++++++++++++++++++++++++++++++ >>>> 3 files changed, 61 insertions(+) >>>> create mode 100644 arch/arm64/mm/xpfo.c >>>> >>>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig >>>> index ea2ab0330e3a..f0a9c0007d23 100644 >>>> --- a/arch/arm64/Kconfig >>>> +++ b/arch/arm64/Kconfig >>>> @@ -171,6 +171,7 @@ config ARM64 >>>> select SWIOTLB >>>> select SYSCTL_EXCEPTION_TRACE >>>> select THREAD_INFO_IN_TASK >>>> + select ARCH_SUPPORTS_XPFO >>>> help >>>> ARM 64-bit (AArch64) Linux support. >>>> diff --git a/arch/arm64/mm/Makefile b/arch/arm64/mm/Makefile >>>> index 849c1df3d214..cca3808d9776 100644 >>>> --- a/arch/arm64/mm/Makefile >>>> +++ b/arch/arm64/mm/Makefile >>>> @@ -12,3 +12,5 @@ KASAN_SANITIZE_physaddr.o += n >>>> obj-$(CONFIG_KASAN) += kasan_init.o >>>> KASAN_SANITIZE_kasan_init.o := n >>>> + >>>> +obj-$(CONFIG_XPFO) += xpfo.o >>>> diff --git a/arch/arm64/mm/xpfo.c b/arch/arm64/mm/xpfo.c >>>> new file mode 100644 >>>> index 000000000000..678e2be848eb >>>> --- /dev/null >>>> +++ b/arch/arm64/mm/xpfo.c >>>> @@ -0,0 +1,58 @@ >>>> +/* >>>> + * Copyright (C) 2017 Hewlett Packard Enterprise Development, L.P. >>>> + * Copyright (C) 2016 Brown University. All rights reserved. >>>> + * >>>> + * Authors: >>>> + * Juerg Haefliger <juerg.haefliger@hpe.com> >>>> + * Vasileios P. Kemerlis <vpk@cs.brown.edu> >>>> + * >>>> + * This program is free software; you can redistribute it and/or >>>> modify it >>>> + * under the terms of the GNU General Public License version 2 as >>>> published by >>>> + * the Free Software Foundation. >>>> + */ >>>> + >>>> +#include <linux/mm.h> >>>> +#include <linux/module.h> >>>> + >>>> +#include <asm/tlbflush.h> >>>> + >>>> +/* >>>> + * Lookup the page table entry for a virtual address and return a >>>> pointer to >>>> + * the entry. Based on x86 tree. >>>> + */ >>>> +static pte_t *lookup_address(unsigned long addr) >>>> +{ >>>> + pgd_t *pgd; >>>> + pud_t *pud; >>>> + pmd_t *pmd; >>>> + >>>> + pgd = pgd_offset_k(addr); >>>> + if (pgd_none(*pgd)) >>>> + return NULL; >>>> + >>>> + pud = pud_offset(pgd, addr); >>>> + if (pud_none(*pud)) >>>> + return NULL; >>>> + >>>> + pmd = pmd_offset(pud, addr); >>>> + if (pmd_none(*pmd)) >>>> + return NULL; >>>> + >>>> + return pte_offset_kernel(pmd, addr); >>>> +} >>>> + >>>> +/* Update a single kernel page table entry */ >>>> +inline void set_kpte(void *kaddr, struct page *page, pgprot_t prot) >>>> +{ >>>> + pte_t *pte = lookup_address((unsigned long)kaddr); >>>> + >>>> + set_pte(pte, pfn_pte(page_to_pfn(page), prot)); >>> >>> Thought on the other hand.. what if the page is PMD? Do you really want >>> to do this? >>> >>> What if 'pte' is NULL? >>>> +} >>>> + >>>> +inline void xpfo_flush_kernel_tlb(struct page *page, int order) >>>> +{ >>>> + unsigned long kaddr = (unsigned long)page_address(page); >>>> + unsigned long size = PAGE_SIZE; >>>> + >>>> + flush_tlb_kernel_range(kaddr, kaddr + (1 << order) * size); >>> >>> Ditto here. You are assuming it is PTE, but it may be PMD or such. >>> Or worts - the lookup_address could be NULL. >>> >>>> +} >>>> -- >>>> 2.17.1 >>>> >> >> Hi Konrad, >> >> This makes sense. x86 version of set_kpte() checks pte for NULL and also >> checks if the page is PMD. Now what you said about adding level to >> lookup_address() for arm makes more sense. >> >> Can someone with knowledge of arm64 mmu make recommendations here? >> >> Thanks, >> Khalid >> > > arm64 can't split larger pages and requires everything must be > mapped as pages (see [RFC PATCH v7 08/16] arm64/mm: disable > section/contiguous mappings if XPFO is enabled) . Any > situation where we would get something other than a pte > would be a bug.
Thanks, Laura! That helps a lot. I would think checking for NULL pte in set_kpte() would still make sense since lookup_address() can return NULL. Something like:
--- arch/arm64/mm/xpfo.c 2019-01-30 13:36:39.857185612 -0700 +++ arch/arm64/mm/xpfo.c.new 2019-02-12 13:26:47.471633031 -0700 @@ -46,6 +46,11 @@ { pte_t *pte = lookup_address((unsigned long)kaddr);
+ if (unlikely(!pte)) { + WARN(1, "xpfo: invalid address %p\n", kaddr); + return; + } + set_pte(pte, pfn_pte(page_to_pfn(page), prot)); }
-- Khalid[unhandled content-type:application/pgp-keys] | |