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Date: Sat, 12 Aug 2017 12:17:34 +0100
From: Mark Rutland <mark.rutland@....com>
To: Tycho Andersen <tycho@...ker.com>
Cc: Laura Abbott <labbott@...hat.com>, linux-kernel@...r.kernel.org,
linux-mm@...ck.org, kernel-hardening@...ts.openwall.com,
Marco Benatto <marco.antonio.780@...il.com>,
Juerg Haefliger <juerg.haefliger@...onical.com>
Subject: Re: [PATCH v5 06/10] arm64/mm: Disable section
mappings if XPFO is enabled
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.
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