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Subject: Re: [RFC PATCH v7 07/16] arm64/mm, xpfo: temporarily map dcache
 regions
To:     Tycho Andersen <tycho@tycho.ws>
Cc:     juergh@gmail.com, jsteckli@amazon.de, ak@linux.intel.com,
        torvalds@linux-foundation.org, liran.alon@oracle.com,
        keescook@google.com, konrad.wilk@oracle.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
References: <cover.1547153058.git.khalid.aziz@oracle.com>
 <eba179acbfdea5a646c5548cb82138c1c3b74aa2.1547153058.git.khalid.aziz@oracle.com>
 <20190111145445.GA4102@cisco>
From:   Khalid Aziz <khalid.aziz@oracle.com>
Organization: Oracle Corp
Message-ID: <19e61a22-bbae-d0ae-8d41-158d4b46bf01@oracle.com>
Date:   Fri, 11 Jan 2019 11:28:19 -0700
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On 1/11/19 7:54 AM, Tycho Andersen wrote:
> On Thu, Jan 10, 2019 at 02:09:39PM -0700, Khalid Aziz wrote:
>> From: Juerg Haefliger <juerg.haefliger@canonical.com>
>>
>> If the page is unmapped by XPFO, a data cache flush results in a fatal=

>> page fault, so let's temporarily map the region, flush the cache, and =
then
>> unmap it.
>>
>> v6: actually flush in the face of xpfo, and temporarily map the underl=
ying
>>     memory so it can be flushed correctly
>>
>> 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/mm/flush.c | 7 +++++++
>>  1 file changed, 7 insertions(+)
>>
>> diff --git a/arch/arm64/mm/flush.c b/arch/arm64/mm/flush.c
>> index 30695a868107..f12f26b60319 100644
>> --- a/arch/arm64/mm/flush.c
>> +++ b/arch/arm64/mm/flush.c
>> @@ -20,6 +20,7 @@
>>  #include <linux/export.h>
>>  #include <linux/mm.h>
>>  #include <linux/pagemap.h>
>> +#include <linux/xpfo.h>
>> =20
>>  #include <asm/cacheflush.h>
>>  #include <asm/cache.h>
>> @@ -28,9 +29,15 @@
>>  void sync_icache_aliases(void *kaddr, unsigned long len)
>>  {
>>  	unsigned long addr =3D (unsigned long)kaddr;
>> +	unsigned long num_pages =3D XPFO_NUM_PAGES(addr, len);
>> +	void *mapping[num_pages];
>=20
> Does this still compile with -Wvla? It was a bad hack on my part, and
> we should probably just drop it and come up with something else :)

I will make a note of it. I hope someone with better knowledge of arm64
than me can come up with a better solution ;)

--
Khalid

>=20
> Tycho
>=20
>>  	if (icache_is_aliasing()) {
>> +		xpfo_temp_map(kaddr, len, mapping,
>> +			      sizeof(mapping[0]) * num_pages);
>>  		__clean_dcache_area_pou(kaddr, len);
>> +		xpfo_temp_unmap(kaddr, len, mapping,
>> +			        sizeof(mapping[0]) * num_pages);
>>  		__flush_icache_all();
>>  	} else {
>>  		flush_icache_range(addr, addr + len);
>> --=20
>> 2.17.1
>>


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