From: Balbir Singh <bsingharora@gmail.com>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: linuxppc-dev@lists.ozlabs.org,
"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
Michael Neuling <michael.neuling@au1.ibm.com>,
Balbir Singh <bsingharora@gmail.com>
Subject: Re: [PATCH] powerpc/mm: Fix spurrious segfaults on radix with Autonuma
Date: Mon, 6 Feb 2017 16:15:09 +0530 [thread overview]
Message-ID: <20170206104509.GA26240@dhcp-9-109-223-240.in.ibm.com> (raw)
In-Reply-To: <1486102228.4850.52.camel@kernel.crashing.org>
On Fri, Feb 03, 2017 at 05:10:28PM +1100, Benjamin Herrenschmidt wrote:
> When autonuma marks a PTE inaccessible it clears all the protection
> bits but leave the PTE valid.
>
> With the Radix MMU, an attempt at executing from such a PTE will
> take a fault with bit 35 of SRR1 set "SRR1_ISI_N_OR_G".
>
> It is thus incorrect to treat all such faults as errors. We should
> pass them to handle_mm_fault() for autonuma to deal with. The case
> of pages that are really not executable is handled by the existing
> test for VM_EXEC further down.
>
> That leaves us with catching the kernel attempts at executing user
> pages. We can catch that earlier, even before we do find_vma.
>
> It is never valid on powerpc for the kernel to take an exec fault
> to begin with. So fold that test with the existing test for the
> kernel faulting on kernel addresses to bail out early.
>
> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Fixes: 1d18ad0 ("powerpc/mm: Detect instruction fetch denied and report")
> Fixes: 0ab5171 ("powerpc/mm: Fix no execute fault handling on pre-POWER5")
> ---
>
Acked-by: Balbir Singh <bsingharora@gmail.com>
next prev parent reply other threads:[~2017-02-06 10:45 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-03 6:10 [PATCH] powerpc/mm: Fix spurrious segfaults on radix with Autonuma Benjamin Herrenschmidt
2017-02-03 6:30 ` Aneesh Kumar K.V
2017-02-03 10:58 ` Balbir Singh
2017-02-06 10:45 ` Balbir Singh [this message]
2017-02-09 13:20 ` Michael Ellerman
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