Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [RFC PATCH v7 05/16] arm64/mm: Add support for XPFO
To:     Laura Abbott <labbott@redhat.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc:     juergh@gmail.com, tycho@tycho.ws, jsteckli@amazon.de,
        ak@linux.intel.com, torvalds@linux-foundation.org,
        liran.alon@oracle.com, keescook@google.com,
        Juerg Haefliger <juerg.haefliger@canonical.com>,
        deepa.srinivasan@oracle.com, chris.hyser@oracle.com,
        tyhicks@canonical.com, dwmw@amazon.co.uk,
        andrew.cooper3@citrix.com, jcm@redhat.com,
        boris.ostrovsky@oracle.com, kanth.ghatraju@oracle.com,
        joao.m.martins@oracle.com, jmattson@google.com,
        pradeep.vincent@oracle.com, john.haxby@oracle.com,
        tglx@linutronix.de, kirill.shutemov@linux.intel.com, hch@lst.de,
        steven.sistare@oracle.com, kernel-hardening@lists.openwall.com,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        Tycho Andersen <tycho@docker.com>
References: <cover.1547153058.git.khalid.aziz@oracle.com>
 <89f03091af87f5ab27bd6cafb032236d5bd81d65.1547153058.git.khalid.aziz@oracle.com>
 <20190123142410.GC19289@Konrads-MacBook-Pro.local>
 <4dfba458-1bf6-25ff-df4c-b96a1221cd95@oracle.com>
 <7497bd44-1fda-e073-ba7f-18a76577b64a@redhat.com>
From:   Khalid Aziz <khalid.aziz@oracle.com>
Organization: Oracle Corp
Message-ID: <76668db0-e87a-5294-1d71-2ab42a48425c@oracle.com>
Date:   Tue, 12 Feb 2019 13:34:15 -0700
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101
 Thunderbird/60.4.0
MIME-Version: 1.0
In-Reply-To: <7497bd44-1fda-e073-ba7f-18a76577b64a@redhat.com>
Content-Type: multipart/mixed;
 boundary="------------9CCCB4AA5B3B70FD078792E2"
Content-Language: en-US
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

This is a multi-part message in MIME format.
--------------9CCCB4AA5B3B70FD078792E2
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable

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 a=
nd
>>>> 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>
>>>> ---
>>>> =C2=A0 arch/arm64/Kconfig=C2=A0=C2=A0=C2=A0=C2=A0 |=C2=A0 1 +
>>>> =C2=A0 arch/arm64/mm/Makefile |=C2=A0 2 ++
>>>> =C2=A0 arch/arm64/mm/xpfo.c=C2=A0=C2=A0 | 58
>>>> ++++++++++++++++++++++++++++++++++++++++++
>>>> =C2=A0 3 files changed, 61 insertions(+)
>>>> =C2=A0 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
>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 select SWIOTLB
>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 select SYSCTL_EXCEPTION_TRACE
>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 select THREAD_INFO_IN_TASK
>>>> +=C2=A0=C2=A0=C2=A0 select ARCH_SUPPORTS_XPFO
>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 help
>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 ARM 64-bit (AArch64) Linu=
x support.
>>>> =C2=A0 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=C2=A0=C2=A0=C2=A0 +=3D n=

>>>> =C2=A0 =C2=A0 obj-$(CONFIG_KASAN)=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0 +=3D kasan_init.o
>>>> =C2=A0 KASAN_SANITIZE_kasan_init.o=C2=A0=C2=A0=C2=A0 :=3D n
>>>> +
>>>> +obj-$(CONFIG_XPFO)=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 +=3D x=
pfo.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:
>>>> + *=C2=A0=C2=A0 Juerg Haefliger <juerg.haefliger@hpe.com>
>>>> + *=C2=A0=C2=A0 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)
>>>> +{
>>>> +=C2=A0=C2=A0=C2=A0 pgd_t *pgd;
>>>> +=C2=A0=C2=A0=C2=A0 pud_t *pud;
>>>> +=C2=A0=C2=A0=C2=A0 pmd_t *pmd;
>>>> +
>>>> +=C2=A0=C2=A0=C2=A0 pgd =3D pgd_offset_k(addr);
>>>> +=C2=A0=C2=A0=C2=A0 if (pgd_none(*pgd))
>>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return NULL;
>>>> +
>>>> +=C2=A0=C2=A0=C2=A0 pud =3D pud_offset(pgd, addr);
>>>> +=C2=A0=C2=A0=C2=A0 if (pud_none(*pud))
>>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return NULL;
>>>> +
>>>> +=C2=A0=C2=A0=C2=A0 pmd =3D pmd_offset(pud, addr);
>>>> +=C2=A0=C2=A0=C2=A0 if (pmd_none(*pmd))
>>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return NULL;
>>>> +
>>>> +=C2=A0=C2=A0=C2=A0 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)=

>>>> +{
>>>> +=C2=A0=C2=A0=C2=A0 pte_t *pte =3D lookup_address((unsigned long)kad=
dr);
>>>> +
>>>> +=C2=A0=C2=A0=C2=A0 set_pte(pte, pfn_pte(page_to_pfn(page), prot));
>>>
>>> Thought on the other hand.. what if the page is PMD? Do you really wa=
nt
>>> to do this?
>>>
>>> What if 'pte' is NULL?
>>>> +}
>>>> +
>>>> +inline void xpfo_flush_kernel_tlb(struct page *page, int order)
>>>> +{
>>>> +=C2=A0=C2=A0=C2=A0 unsigned long kaddr =3D (unsigned long)page_addr=
ess(page);
>>>> +=C2=A0=C2=A0=C2=A0 unsigned long size =3D PAGE_SIZE;
>>>> +
>>>> +=C2=A0=C2=A0=C2=A0 flush_tlb_kernel_range(kaddr, kaddr + (1 << orde=
r) * size);
>>>
>>> Ditto here. You are assuming it is PTE, but it may be PMD or such.
>>> Or worts - the lookup_address could be NULL.
>>>
>>>> +}
>>>> --=C2=A0
>>>> 2.17.1
>>>>
>>
>> Hi Konrad,
>>
>> This makes sense. x86 version of set_kpte() checks pte for NULL and al=
so
>> 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
>>
>=20
> 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 =3D 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

--------------9CCCB4AA5B3B70FD078792E2
Content-Type: application/pgp-keys;
 name="pEpkey.asc"
Content-Transfer-Encoding: quoted-printable
Content-Disposition: attachment;
 filename="pEpkey.asc"

-----BEGIN PGP PUBLIC KEY BLOCK-----
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3D=3D
=3DnPqY
-----END PGP PUBLIC KEY BLOCK-----

--------------9CCCB4AA5B3B70FD078792E2--