Re: [kernel-hardening] [PATCH v5 06/10] arm64/mm: Disable section mappings if XPFO is enabled

[Tycho Andersen]

On Mon, Aug 14, 2017 at 11:42:45AM -0700, Laura Abbott wrote:
> On 08/14/2017 09:22 AM, Tycho Andersen wrote:
> > On Sat, Aug 12, 2017 at 12:17:34PM +0100, Mark Rutland wrote:
> >> Hi,
> >>
> >> On Fri, Aug 11, 2017 at 03:13:02PM -0600, Tycho Andersen wrote:
> >>> On Fri, Aug 11, 2017 at 10:25:14AM -0700, Laura Abbott wrote:
>  On 08/09/2017 01:07 PM, Tycho Andersen wrote:
> > @@ -190,7 +202,7 @@ static void init_pmd(pud_t *pud, unsigned long 
> > addr, unsigned long end,
> > next = pmd_addr_end(addr, end);
> >  
> > /* try section mapping first */
> > -   if (((addr | next | phys) & ~SECTION_MASK) == 0 &&
> > +   if (use_section_mapping(addr, next, phys) &&
> > (flags & NO_BLOCK_MAPPINGS) == 0) {
> > pmd_set_huge(pmd, phys, prot);
> >  
> >
> 
>  There is already similar logic to disable section mappings for
>  debug_pagealloc at the start of map_mem, can you take advantage
>  of that?
> >>>
> >>> You're suggesting something like this instead? Seems to work fine.
> >>>
> >>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> >>> index 38026b3ccb46..3b2c17bbbf12 100644
> >>> --- a/arch/arm64/mm/mmu.c
> >>> +++ b/arch/arm64/mm/mmu.c
> >>> @@ -434,6 +434,8 @@ static void __init map_mem(pgd_t *pgd)
> >>>  
> >>>   if (debug_pagealloc_enabled())
> >>>   flags = NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
> >>> + if (IS_ENABLED(CONFIG_XPFO))
> >>> + flags |= NO_BLOCK_MAPPINGS;
> >>>  
> >>
> >> IIUC, XPFO carves out individual pages just like DEBUG_PAGEALLOC, so you'll
> >> also need NO_CONT_MAPPINGS.
> > 
> > Yes, thanks!
> > 
> > Tycho
> > 
> 
> Setting NO_CONT_MAPPINGS fixes the TLB conflict aborts I was seeing
> on my machine.

Great, thanks for testing! I've also fixed the lookup_page_ext bug you
noted in the other thread.

Tycho

Re: [kernel-hardening] [PATCH v5 06/10] arm64/mm: Disable section mappings if XPFO is enabled

[Tycho Andersen]

On Mon, Aug 14, 2017 at 11:42:45AM -0700, Laura Abbott wrote:
> On 08/14/2017 09:22 AM, Tycho Andersen wrote:
> > On Sat, Aug 12, 2017 at 12:17:34PM +0100, Mark Rutland wrote:
> >> Hi,
> >>
> >> On Fri, Aug 11, 2017 at 03:13:02PM -0600, Tycho Andersen wrote:
> >>> On Fri, Aug 11, 2017 at 10:25:14AM -0700, Laura Abbott wrote:
>  On 08/09/2017 01:07 PM, Tycho Andersen wrote:
> > @@ -190,7 +202,7 @@ static void init_pmd(pud_t *pud, unsigned long 
> > addr, unsigned long end,
> > next = pmd_addr_end(addr, end);
> >  
> > /* try section mapping first */
> > -   if (((addr | next | phys) & ~SECTION_MASK) == 0 &&
> > +   if (use_section_mapping(addr, next, phys) &&
> > (flags & NO_BLOCK_MAPPINGS) == 0) {
> > pmd_set_huge(pmd, phys, prot);
> >  
> >
> 
>  There is already similar logic to disable section mappings for
>  debug_pagealloc at the start of map_mem, can you take advantage
>  of that?
> >>>
> >>> You're suggesting something like this instead? Seems to work fine.
> >>>
> >>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> >>> index 38026b3ccb46..3b2c17bbbf12 100644
> >>> --- a/arch/arm64/mm/mmu.c
> >>> +++ b/arch/arm64/mm/mmu.c
> >>> @@ -434,6 +434,8 @@ static void __init map_mem(pgd_t *pgd)
> >>>  
> >>>   if (debug_pagealloc_enabled())
> >>>   flags = NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
> >>> + if (IS_ENABLED(CONFIG_XPFO))
> >>> + flags |= NO_BLOCK_MAPPINGS;
> >>>  
> >>
> >> IIUC, XPFO carves out individual pages just like DEBUG_PAGEALLOC, so you'll
> >> also need NO_CONT_MAPPINGS.
> > 
> > Yes, thanks!
> > 
> > Tycho
> > 
> 
> Setting NO_CONT_MAPPINGS fixes the TLB conflict aborts I was seeing
> on my machine.

Great, thanks for testing! I've also fixed the lookup_page_ext bug you
noted in the other thread.

Tycho

Re: [kernel-hardening] [PATCH v5 06/10] arm64/mm: Disable section mappings if XPFO is enabled

[Laura Abbott]

On 08/14/2017 09:22 AM, Tycho Andersen wrote:
> On Sat, Aug 12, 2017 at 12:17:34PM +0100, Mark Rutland wrote:
>> Hi,
>>
>> On Fri, Aug 11, 2017 at 03:13:02PM -0600, Tycho Andersen wrote:
>>> On Fri, Aug 11, 2017 at 10:25:14AM -0700, Laura Abbott wrote:
 On 08/09/2017 01:07 PM, Tycho Andersen wrote:
> @@ -190,7 +202,7 @@ static void init_pmd(pud_t *pud, unsigned long addr, 
> unsigned long end,
>   next = pmd_addr_end(addr, end);
>  
>   /* try section mapping first */
> - if (((addr | next | phys) & ~SECTION_MASK) == 0 &&
> + if (use_section_mapping(addr, next, phys) &&
>   (flags & NO_BLOCK_MAPPINGS) == 0) {
>   pmd_set_huge(pmd, phys, prot);
>  
>

 There is already similar logic to disable section mappings for
 debug_pagealloc at the start of map_mem, can you take advantage
 of that?
>>>
>>> You're suggesting something like this instead? Seems to work fine.
>>>
>>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
>>> index 38026b3ccb46..3b2c17bbbf12 100644
>>> --- a/arch/arm64/mm/mmu.c
>>> +++ b/arch/arm64/mm/mmu.c
>>> @@ -434,6 +434,8 @@ static void __init map_mem(pgd_t *pgd)
>>>  
>>> if (debug_pagealloc_enabled())
>>> flags = NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
>>> +   if (IS_ENABLED(CONFIG_XPFO))
>>> +   flags |= NO_BLOCK_MAPPINGS;
>>>  
>>
>> IIUC, XPFO carves out individual pages just like DEBUG_PAGEALLOC, so you'll
>> also need NO_CONT_MAPPINGS.
> 
> Yes, thanks!
> 
> Tycho
> 

Setting NO_CONT_MAPPINGS fixes the TLB conflict aborts I was seeing
on my machine.

Thanks,
Laura

Re: [kernel-hardening] [PATCH v5 06/10] arm64/mm: Disable section mappings if XPFO is enabled

[Laura Abbott]

On 08/14/2017 09:22 AM, Tycho Andersen wrote:
> On Sat, Aug 12, 2017 at 12:17:34PM +0100, Mark Rutland wrote:
>> Hi,
>>
>> On Fri, Aug 11, 2017 at 03:13:02PM -0600, Tycho Andersen wrote:
>>> On Fri, Aug 11, 2017 at 10:25:14AM -0700, Laura Abbott wrote:
 On 08/09/2017 01:07 PM, Tycho Andersen wrote:
> @@ -190,7 +202,7 @@ static void init_pmd(pud_t *pud, unsigned long addr, 
> unsigned long end,
>   next = pmd_addr_end(addr, end);
>  
>   /* try section mapping first */
> - if (((addr | next | phys) & ~SECTION_MASK) == 0 &&
> + if (use_section_mapping(addr, next, phys) &&
>   (flags & NO_BLOCK_MAPPINGS) == 0) {
>   pmd_set_huge(pmd, phys, prot);
>  
>

 There is already similar logic to disable section mappings for
 debug_pagealloc at the start of map_mem, can you take advantage
 of that?
>>>
>>> You're suggesting something like this instead? Seems to work fine.
>>>
>>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
>>> index 38026b3ccb46..3b2c17bbbf12 100644
>>> --- a/arch/arm64/mm/mmu.c
>>> +++ b/arch/arm64/mm/mmu.c
>>> @@ -434,6 +434,8 @@ static void __init map_mem(pgd_t *pgd)
>>>  
>>> if (debug_pagealloc_enabled())
>>> flags = NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
>>> +   if (IS_ENABLED(CONFIG_XPFO))
>>> +   flags |= NO_BLOCK_MAPPINGS;
>>>  
>>
>> IIUC, XPFO carves out individual pages just like DEBUG_PAGEALLOC, so you'll
>> also need NO_CONT_MAPPINGS.
> 
> Yes, thanks!
> 
> Tycho
> 

Setting NO_CONT_MAPPINGS fixes the TLB conflict aborts I was seeing
on my machine.

Thanks,
Laura

Re: [kernel-hardening] [PATCH v5 06/10] arm64/mm: Disable section mappings if XPFO is enabled

[Tycho Andersen]

On Sat, Aug 12, 2017 at 12:17:34PM +0100, Mark Rutland wrote:
> Hi,
> 
> On Fri, Aug 11, 2017 at 03:13:02PM -0600, Tycho Andersen wrote:
> > On Fri, Aug 11, 2017 at 10:25:14AM -0700, Laura Abbott wrote:
> > > On 08/09/2017 01:07 PM, Tycho Andersen wrote:
> > > > @@ -190,7 +202,7 @@ static void init_pmd(pud_t *pud, unsigned long 
> > > > addr, unsigned long end,
> > > > next = pmd_addr_end(addr, end);
> > > >  
> > > > /* try section mapping first */
> > > > -   if (((addr | next | phys) & ~SECTION_MASK) == 0 &&
> > > > +   if (use_section_mapping(addr, next, phys) &&
> > > > (flags & NO_BLOCK_MAPPINGS) == 0) {
> > > > pmd_set_huge(pmd, phys, prot);
> > > >  
> > > > 
> > > 
> > > There is already similar logic to disable section mappings for
> > > debug_pagealloc at the start of map_mem, can you take advantage
> > > of that?
> > 
> > You're suggesting something like this instead? Seems to work fine.
> > 
> > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> > index 38026b3ccb46..3b2c17bbbf12 100644
> > --- a/arch/arm64/mm/mmu.c
> > +++ b/arch/arm64/mm/mmu.c
> > @@ -434,6 +434,8 @@ static void __init map_mem(pgd_t *pgd)
> >  
> > if (debug_pagealloc_enabled())
> > flags = NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
> > +   if (IS_ENABLED(CONFIG_XPFO))
> > +   flags |= NO_BLOCK_MAPPINGS;
> >  
> 
> IIUC, XPFO carves out individual pages just like DEBUG_PAGEALLOC, so you'll
> also need NO_CONT_MAPPINGS.

Yes, thanks!

Tycho

Re: [kernel-hardening] [PATCH v5 06/10] arm64/mm: Disable section mappings if XPFO is enabled

[Tycho Andersen]

On Sat, Aug 12, 2017 at 12:17:34PM +0100, Mark Rutland wrote:
> Hi,
> 
> On Fri, Aug 11, 2017 at 03:13:02PM -0600, Tycho Andersen wrote:
> > On Fri, Aug 11, 2017 at 10:25:14AM -0700, Laura Abbott wrote:
> > > On 08/09/2017 01:07 PM, Tycho Andersen wrote:
> > > > @@ -190,7 +202,7 @@ static void init_pmd(pud_t *pud, unsigned long 
> > > > addr, unsigned long end,
> > > > next = pmd_addr_end(addr, end);
> > > >  
> > > > /* try section mapping first */
> > > > -   if (((addr | next | phys) & ~SECTION_MASK) == 0 &&
> > > > +   if (use_section_mapping(addr, next, phys) &&
> > > > (flags & NO_BLOCK_MAPPINGS) == 0) {
> > > > pmd_set_huge(pmd, phys, prot);
> > > >  
> > > > 
> > > 
> > > There is already similar logic to disable section mappings for
> > > debug_pagealloc at the start of map_mem, can you take advantage
> > > of that?
> > 
> > You're suggesting something like this instead? Seems to work fine.
> > 
> > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> > index 38026b3ccb46..3b2c17bbbf12 100644
> > --- a/arch/arm64/mm/mmu.c
> > +++ b/arch/arm64/mm/mmu.c
> > @@ -434,6 +434,8 @@ static void __init map_mem(pgd_t *pgd)
> >  
> > if (debug_pagealloc_enabled())
> > flags = NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
> > +   if (IS_ENABLED(CONFIG_XPFO))
> > +   flags |= NO_BLOCK_MAPPINGS;
> >  
> 
> IIUC, XPFO carves out individual pages just like DEBUG_PAGEALLOC, so you'll
> also need NO_CONT_MAPPINGS.

Yes, thanks!

Tycho

Re: [kernel-hardening] [PATCH v5 06/10] arm64/mm: Disable section mappings if XPFO is enabled

[Mark Rutland]

Hi,

On Fri, Aug 11, 2017 at 03:13:02PM -0600, Tycho Andersen wrote:
> On Fri, Aug 11, 2017 at 10:25:14AM -0700, Laura Abbott wrote:
> > On 08/09/2017 01:07 PM, Tycho Andersen wrote:
> > > @@ -190,7 +202,7 @@ static void init_pmd(pud_t *pud, unsigned long addr, 
> > > unsigned long end,
> > >   next = pmd_addr_end(addr, end);
> > >  
> > >   /* try section mapping first */
> > > - if (((addr | next | phys) & ~SECTION_MASK) == 0 &&
> > > + if (use_section_mapping(addr, next, phys) &&
> > >   (flags & NO_BLOCK_MAPPINGS) == 0) {
> > >   pmd_set_huge(pmd, phys, prot);
> > >  
> > > 
> > 
> > There is already similar logic to disable section mappings for
> > debug_pagealloc at the start of map_mem, can you take advantage
> > of that?
> 
> You're suggesting something like this instead? Seems to work fine.
> 
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 38026b3ccb46..3b2c17bbbf12 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -434,6 +434,8 @@ static void __init map_mem(pgd_t *pgd)
>  
>   if (debug_pagealloc_enabled())
>   flags = NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
> + if (IS_ENABLED(CONFIG_XPFO))
> + flags |= NO_BLOCK_MAPPINGS;
>  

IIUC, XPFO carves out individual pages just like DEBUG_PAGEALLOC, so you'll
also need NO_CONT_MAPPINGS.

Thanks
Mark.

Re: [kernel-hardening] [PATCH v5 06/10] arm64/mm: Disable section mappings if XPFO is enabled

[Mark Rutland]

Hi,

On Fri, Aug 11, 2017 at 03:13:02PM -0600, Tycho Andersen wrote:
> On Fri, Aug 11, 2017 at 10:25:14AM -0700, Laura Abbott wrote:
> > On 08/09/2017 01:07 PM, Tycho Andersen wrote:
> > > @@ -190,7 +202,7 @@ static void init_pmd(pud_t *pud, unsigned long addr, 
> > > unsigned long end,
> > >   next = pmd_addr_end(addr, end);
> > >  
> > >   /* try section mapping first */
> > > - if (((addr | next | phys) & ~SECTION_MASK) == 0 &&
> > > + if (use_section_mapping(addr, next, phys) &&
> > >   (flags & NO_BLOCK_MAPPINGS) == 0) {
> > >   pmd_set_huge(pmd, phys, prot);
> > >  
> > > 
> > 
> > There is already similar logic to disable section mappings for
> > debug_pagealloc at the start of map_mem, can you take advantage
> > of that?
> 
> You're suggesting something like this instead? Seems to work fine.
> 
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 38026b3ccb46..3b2c17bbbf12 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -434,6 +434,8 @@ static void __init map_mem(pgd_t *pgd)
>  
>   if (debug_pagealloc_enabled())
>   flags = NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
> + if (IS_ENABLED(CONFIG_XPFO))
> + flags |= NO_BLOCK_MAPPINGS;
>  

IIUC, XPFO carves out individual pages just like DEBUG_PAGEALLOC, so you'll
also need NO_CONT_MAPPINGS.

Thanks
Mark.

Re: [kernel-hardening] [PATCH v5 06/10] arm64/mm: Disable section mappings if XPFO is enabled

[Tycho Andersen]

On Fri, Aug 11, 2017 at 03:13:02PM -0600, Tycho Andersen wrote:
> You're suggesting something like this instead? Seems to work fine.

And in fact, using this patch instead means that booting on 4k pages
works too... I guess because NO_BLOCK_MAPPINGS is looked at in a few
other places that matter too? Anyway, I'll use this patch instead,
thanks for the suggestion!

Tycho

Re: [kernel-hardening] [PATCH v5 06/10] arm64/mm: Disable section mappings if XPFO is enabled

[Tycho Andersen]

On Fri, Aug 11, 2017 at 03:13:02PM -0600, Tycho Andersen wrote:
> You're suggesting something like this instead? Seems to work fine.

And in fact, using this patch instead means that booting on 4k pages
works too... I guess because NO_BLOCK_MAPPINGS is looked at in a few
other places that matter too? Anyway, I'll use this patch instead,
thanks for the suggestion!

Tycho

Re: [kernel-hardening] [PATCH v5 06/10] arm64/mm: Disable section mappings if XPFO is enabled

[Tycho Andersen]

Hi Laura,

On Fri, Aug 11, 2017 at 10:25:14AM -0700, Laura Abbott wrote:
> On 08/09/2017 01:07 PM, Tycho Andersen wrote:
> > From: Juerg Haefliger 
> > 
> > XPFO (eXclusive Page Frame Ownership) doesn't support section mappings
> > yet, so disable it if XPFO is turned on.
> > 
> > Signed-off-by: Juerg Haefliger 
> > Tested-by: Tycho Andersen 
> > ---
> >  arch/arm64/mm/mmu.c | 14 +-
> >  1 file changed, 13 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> > index f1eb15e0e864..38026b3ccb46 100644
> > --- a/arch/arm64/mm/mmu.c
> > +++ b/arch/arm64/mm/mmu.c
> > @@ -176,6 +176,18 @@ static void alloc_init_cont_pte(pmd_t *pmd, unsigned 
> > long addr,
> > } while (addr = next, addr != end);
> >  }
> >  
> > +static inline bool use_section_mapping(unsigned long addr, unsigned long 
> > next,
> > +   unsigned long phys)
> > +{
> > +   if (IS_ENABLED(CONFIG_XPFO))
> > +   return false;
> > +
> > +   if (((addr | next | phys) & ~SECTION_MASK) != 0)
> > +   return false;
> > +
> > +   return true;
> > +}
> > +
> >  static void init_pmd(pud_t *pud, unsigned long addr, unsigned long end,
> >  phys_addr_t phys, pgprot_t prot,
> >  phys_addr_t (*pgtable_alloc)(void), int flags)
> > @@ -190,7 +202,7 @@ static void init_pmd(pud_t *pud, unsigned long addr, 
> > unsigned long end,
> > next = pmd_addr_end(addr, end);
> >  
> > /* try section mapping first */
> > -   if (((addr | next | phys) & ~SECTION_MASK) == 0 &&
> > +   if (use_section_mapping(addr, next, phys) &&
> > (flags & NO_BLOCK_MAPPINGS) == 0) {
> > pmd_set_huge(pmd, phys, prot);
> >  
> > 
> 
> There is already similar logic to disable section mappings for
> debug_pagealloc at the start of map_mem, can you take advantage
> of that?

You're suggesting something like this instead? Seems to work fine.

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 38026b3ccb46..3b2c17bbbf12 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -434,6 +434,8 @@ static void __init map_mem(pgd_t *pgd)
 
if (debug_pagealloc_enabled())
flags = NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
+   if (IS_ENABLED(CONFIG_XPFO))
+   flags |= NO_BLOCK_MAPPINGS;
 
/*
 * Take care not to create a writable alias for the

Cheers,

Tycho

Re: [kernel-hardening] [PATCH v5 06/10] arm64/mm: Disable section mappings if XPFO is enabled

[Tycho Andersen]

Hi Laura,

On Fri, Aug 11, 2017 at 10:25:14AM -0700, Laura Abbott wrote:
> On 08/09/2017 01:07 PM, Tycho Andersen wrote:
> > From: Juerg Haefliger 
> > 
> > XPFO (eXclusive Page Frame Ownership) doesn't support section mappings
> > yet, so disable it if XPFO is turned on.
> > 
> > Signed-off-by: Juerg Haefliger 
> > Tested-by: Tycho Andersen 
> > ---
> >  arch/arm64/mm/mmu.c | 14 +-
> >  1 file changed, 13 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> > index f1eb15e0e864..38026b3ccb46 100644
> > --- a/arch/arm64/mm/mmu.c
> > +++ b/arch/arm64/mm/mmu.c
> > @@ -176,6 +176,18 @@ static void alloc_init_cont_pte(pmd_t *pmd, unsigned 
> > long addr,
> > } while (addr = next, addr != end);
> >  }
> >  
> > +static inline bool use_section_mapping(unsigned long addr, unsigned long 
> > next,
> > +   unsigned long phys)
> > +{
> > +   if (IS_ENABLED(CONFIG_XPFO))
> > +   return false;
> > +
> > +   if (((addr | next | phys) & ~SECTION_MASK) != 0)
> > +   return false;
> > +
> > +   return true;
> > +}
> > +
> >  static void init_pmd(pud_t *pud, unsigned long addr, unsigned long end,
> >  phys_addr_t phys, pgprot_t prot,
> >  phys_addr_t (*pgtable_alloc)(void), int flags)
> > @@ -190,7 +202,7 @@ static void init_pmd(pud_t *pud, unsigned long addr, 
> > unsigned long end,
> > next = pmd_addr_end(addr, end);
> >  
> > /* try section mapping first */
> > -   if (((addr | next | phys) & ~SECTION_MASK) == 0 &&
> > +   if (use_section_mapping(addr, next, phys) &&
> > (flags & NO_BLOCK_MAPPINGS) == 0) {
> > pmd_set_huge(pmd, phys, prot);
> >  
> > 
> 
> There is already similar logic to disable section mappings for
> debug_pagealloc at the start of map_mem, can you take advantage
> of that?

You're suggesting something like this instead? Seems to work fine.

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 38026b3ccb46..3b2c17bbbf12 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -434,6 +434,8 @@ static void __init map_mem(pgd_t *pgd)
 
if (debug_pagealloc_enabled())
flags = NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
+   if (IS_ENABLED(CONFIG_XPFO))
+   flags |= NO_BLOCK_MAPPINGS;
 
/*
 * Take care not to create a writable alias for the

Cheers,

Tycho

Re: [kernel-hardening] [PATCH v5 06/10] arm64/mm: Disable section mappings if XPFO is enabled

[Laura Abbott]

On 08/09/2017 01:07 PM, Tycho Andersen wrote:
> From: Juerg Haefliger 
> 
> XPFO (eXclusive Page Frame Ownership) doesn't support section mappings
> yet, so disable it if XPFO is turned on.
> 
> Signed-off-by: Juerg Haefliger 
> Tested-by: Tycho Andersen 
> ---
>  arch/arm64/mm/mmu.c | 14 +-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index f1eb15e0e864..38026b3ccb46 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -176,6 +176,18 @@ static void alloc_init_cont_pte(pmd_t *pmd, unsigned 
> long addr,
>   } while (addr = next, addr != end);
>  }
>  
> +static inline bool use_section_mapping(unsigned long addr, unsigned long 
> next,
> + unsigned long phys)
> +{
> + if (IS_ENABLED(CONFIG_XPFO))
> + return false;
> +
> + if (((addr | next | phys) & ~SECTION_MASK) != 0)
> + return false;
> +
> + return true;
> +}
> +
>  static void init_pmd(pud_t *pud, unsigned long addr, unsigned long end,
>phys_addr_t phys, pgprot_t prot,
>phys_addr_t (*pgtable_alloc)(void), int flags)
> @@ -190,7 +202,7 @@ static void init_pmd(pud_t *pud, unsigned long addr, 
> unsigned long end,
>   next = pmd_addr_end(addr, end);
>  
>   /* try section mapping first */
> - if (((addr | next | phys) & ~SECTION_MASK) == 0 &&
> + if (use_section_mapping(addr, next, phys) &&
>   (flags & NO_BLOCK_MAPPINGS) == 0) {
>   pmd_set_huge(pmd, phys, prot);
>  
> 

There is already similar logic to disable section mappings for
debug_pagealloc at the start of map_mem, can you take advantage
of that?

Thanks,
Laura

Re: [kernel-hardening] [PATCH v5 06/10] arm64/mm: Disable section mappings if XPFO is enabled

[Laura Abbott]

On 08/09/2017 01:07 PM, Tycho Andersen wrote:
> From: Juerg Haefliger 
> 
> XPFO (eXclusive Page Frame Ownership) doesn't support section mappings
> yet, so disable it if XPFO is turned on.
> 
> Signed-off-by: Juerg Haefliger 
> Tested-by: Tycho Andersen 
> ---
>  arch/arm64/mm/mmu.c | 14 +-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index f1eb15e0e864..38026b3ccb46 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -176,6 +176,18 @@ static void alloc_init_cont_pte(pmd_t *pmd, unsigned 
> long addr,
>   } while (addr = next, addr != end);
>  }
>  
> +static inline bool use_section_mapping(unsigned long addr, unsigned long 
> next,
> + unsigned long phys)
> +{
> + if (IS_ENABLED(CONFIG_XPFO))
> + return false;
> +
> + if (((addr | next | phys) & ~SECTION_MASK) != 0)
> + return false;
> +
> + return true;
> +}
> +
>  static void init_pmd(pud_t *pud, unsigned long addr, unsigned long end,
>phys_addr_t phys, pgprot_t prot,
>phys_addr_t (*pgtable_alloc)(void), int flags)
> @@ -190,7 +202,7 @@ static void init_pmd(pud_t *pud, unsigned long addr, 
> unsigned long end,
>   next = pmd_addr_end(addr, end);
>  
>   /* try section mapping first */
> - if (((addr | next | phys) & ~SECTION_MASK) == 0 &&
> + if (use_section_mapping(addr, next, phys) &&
>   (flags & NO_BLOCK_MAPPINGS) == 0) {
>   pmd_set_huge(pmd, phys, prot);
>  
> 

There is already similar logic to disable section mappings for
debug_pagealloc at the start of map_mem, can you take advantage
of that?

Thanks,
Laura

[PATCH v5 06/10] arm64/mm: Disable section mappings if XPFO is enabled

[Tycho Andersen]

From: Juerg Haefliger 

XPFO (eXclusive Page Frame Ownership) doesn't support section mappings
yet, so disable it if XPFO is turned on.

Signed-off-by: Juerg Haefliger 
Tested-by: Tycho Andersen 
---
 arch/arm64/mm/mmu.c | 14 +-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index f1eb15e0e864..38026b3ccb46 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -176,6 +176,18 @@ static void alloc_init_cont_pte(pmd_t *pmd, unsigned long 
addr,
} while (addr = next, addr != end);
 }
 
+static inline bool use_section_mapping(unsigned long addr, unsigned long next,
+   unsigned long phys)
+{
+   if (IS_ENABLED(CONFIG_XPFO))
+   return false;
+
+   if (((addr | next | phys) & ~SECTION_MASK) != 0)
+   return false;
+
+   return true;
+}
+
 static void init_pmd(pud_t *pud, unsigned long addr, unsigned long end,
 phys_addr_t phys, pgprot_t prot,
 phys_addr_t (*pgtable_alloc)(void), int flags)
@@ -190,7 +202,7 @@ static void init_pmd(pud_t *pud, unsigned long addr, 
unsigned long end,
next = pmd_addr_end(addr, end);
 
/* try section mapping first */
-   if (((addr | next | phys) & ~SECTION_MASK) == 0 &&
+   if (use_section_mapping(addr, next, phys) &&
(flags & NO_BLOCK_MAPPINGS) == 0) {
pmd_set_huge(pmd, phys, prot);
 
-- 
2.11.0

[PATCH v5 06/10] arm64/mm: Disable section mappings if XPFO is enabled

[Tycho Andersen]

From: Juerg Haefliger 

XPFO (eXclusive Page Frame Ownership) doesn't support section mappings
yet, so disable it if XPFO is turned on.

Signed-off-by: Juerg Haefliger 
Tested-by: Tycho Andersen 
---
 arch/arm64/mm/mmu.c | 14 +-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index f1eb15e0e864..38026b3ccb46 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -176,6 +176,18 @@ static void alloc_init_cont_pte(pmd_t *pmd, unsigned long 
addr,
} while (addr = next, addr != end);
 }
 
+static inline bool use_section_mapping(unsigned long addr, unsigned long next,
+   unsigned long phys)
+{
+   if (IS_ENABLED(CONFIG_XPFO))
+   return false;
+
+   if (((addr | next | phys) & ~SECTION_MASK) != 0)
+   return false;
+
+   return true;
+}
+
 static void init_pmd(pud_t *pud, unsigned long addr, unsigned long end,
 phys_addr_t phys, pgprot_t prot,
 phys_addr_t (*pgtable_alloc)(void), int flags)
@@ -190,7 +202,7 @@ static void init_pmd(pud_t *pud, unsigned long addr, 
unsigned long end,
next = pmd_addr_end(addr, end);
 
/* try section mapping first */
-   if (((addr | next | phys) & ~SECTION_MASK) == 0 &&
+   if (use_section_mapping(addr, next, phys) &&
(flags & NO_BLOCK_MAPPINGS) == 0) {
pmd_set_huge(pmd, phys, prot);
 
-- 
2.11.0