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Date: Tue, 12 Feb 2019 08:52:51 -0700
From: Khalid Aziz <khalid.aziz@...cle.com>
To: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc: juergh@...il.com, tycho@...ho.ws, jsteckli@...zon.de, ak@...ux.intel.com,
torvalds@...ux-foundation.org, liran.alon@...cle.com,
keescook@...gle.com, Juerg Haefliger <juerg.haefliger@...onical.com>,
deepa.srinivasan@...cle.com, chris.hyser@...cle.com,
tyhicks@...onical.com, dwmw@...zon.co.uk, andrew.cooper3@...rix.com,
jcm@...hat.com, boris.ostrovsky@...cle.com, kanth.ghatraju@...cle.com,
joao.m.martins@...cle.com, jmattson@...gle.com,
pradeep.vincent@...cle.com, john.haxby@...cle.com, tglx@...utronix.de,
kirill.shutemov@...ux.intel.com, hch@....de, steven.sistare@...cle.com,
kernel-hardening@...ts.openwall.com, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
Tycho Andersen <tycho@...ker.com>
Subject: Re: [RFC PATCH v7 05/16] arm64/mm: Add support for XPFO
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@...onical.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@...ts.infradead.org
>> Signed-off-by: Juerg Haefliger <juerg.haefliger@...onical.com>
>> Signed-off-by: Tycho Andersen <tycho@...ker.com>
>> Signed-off-by: Khalid Aziz <khalid.aziz@...cle.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@....com>
>> + * Vasileios P. Kemerlis <vpk@...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
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