linux-kernel - Re: [PATCH] title: no lookup

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Date:	Wed, 16 Jul 2014 20:50:38 -0400
From:	Nick Krause <xerofoify@...il.com>
To:	Chris Metcalf <cmetcalf@...era.com>
Cc:	Paul Bolle <pebolle@...cali.nl>,
	Johannes Weiner <hannes@...xchg.org>, mhocko <mhocko@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	zlu <zlu@...era.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] title: no lookup_page for if statement

On Mon, Jul 14, 2014 at 3:35 PM, Chris Metcalf <cmetcalf@...era.com> wrote:
> On 7/14/2014 2:59 PM, Paul Bolle wrote:
>>
>> On Mon, 2014-07-14 at 14:49 -0400, Nicholas Krause wrote:
>>>
>>> >This patch removes the if define statement for page_lookup in order
>>> >to remove a fix me of this not being defined as of yet.
>>> >
>>> >Signed-off-by: Nicholas Krause<xerofoify@...il.com>
>
>
> Nicholas, you can't just enable this code; it will break the
> build, since there is no lookup_address() symbol on tile.
>
> I'd like to encourage you to look for more substantive kinds of
> changes to submit to LKML.  This one and the last one (adding some
> underscores to some obsolete symbols) both have ended up costing me
> some time to look at and figure out what's actually going on, but
> for no real value.  I suspect there may be "janitor" tasks that
> are more useful if you are looking for small starting points
> (Google for "linux kernel janitors").
>
> That said I'm going to go ahead and check in the following change
> which actually does work, now that my attention has been drawn here.
>
> diff --git a/arch/tile/mm/fault.c b/arch/tile/mm/fault.c
> index 6c0571216a9d..7e884001ca6a 100644
> --- a/arch/tile/mm/fault.c
> +++ b/arch/tile/mm/fault.c
> @@ -513,17 +513,14 @@ no_context:
>
>         bust_spinlocks(1);
>
> -       /* FIXME: no lookup_address() yet */
> -#ifdef SUPPORT_LOOKUP_ADDRESS
> -       if (fault_num == INT_ITLB_MISS) {
> -               pte_t *pte = lookup_address(address);
> +       if (fault_num == INT_ITLB_MISS && address >= PAGE_OFFSET) {
> +               pte_t *pte = virt_to_kpte(address);
>
> -               if (pte && pte_present(*pte) && !pte_exec_kernel(*pte))
> -                       pr_crit("kernel tried to execute"
> -                              " non-executable page - exploit attempt?"
> -                              " (uid: %d)\n", current->uid);
> +               if (pte && pte_present(*pte) && !pte_exec(*pte))
> +                       pr_crit("kernel tried to execute non-executable
> page"
> +                               " - exploit attempt? (uid: %d)\n",
> +                               from_kuid(&init_user_ns, current_uid()));
>         }
> -#endif
>         if (address < PAGE_SIZE)
>                 pr_alert("Unable to handle kernel NULL pointer
> dereference\n");
>         else
>
> --
> Chris Metcalf, Tilera Corp.
> http://www.tilera.com
>
Chris,
Understood I screwed up here. I am doing other changes with build and
warning errors. Plus some
fix me issues that are simple. I will double check my patches and the
code they are relating to more
carefully. I should have asked you before writing this patch:(.
Nick
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