linux-kernel - Re: vvar, gup && coredump

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Message-ID: <CALCETrW=qNvg9aoJcOPKzY1yM=n=nJqHOY2-1P=w0OF0SjcQqA@mail.gmail.com>
Date:	Thu, 12 Mar 2015 10:55:46 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Jan Kratochvil <jan.kratochvil@...hat.com>,
	Sergio Durigan Junior <sergiodj@...hat.com>,
	GDB Patches <gdb-patches@...rceware.org>,
	Pedro Alves <palves@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: vvar, gup && coredump

On Thu, Mar 12, 2015 at 10:39 AM, Oleg Nesterov <oleg@...hat.com> wrote:
> On 03/12, Andy Lutomirski wrote:
>>
>> On Thu, Mar 12, 2015 at 9:54 AM, Oleg Nesterov <oleg@...hat.com> wrote:
>> > On 03/12, Andy Lutomirski wrote:
>> >>
>> > As for 32-bit applications. Yes, this can't work because 32-bit simply
>> > can't access this "high" memory. But you know, it would be very nice to
>> > have the fixmap-like "global" area in init_mm which is also visible to
>> > compat applications. If we had it, uprobes could work without xol vma's.
>> >
>> It could work for 32-bit native, but not for 32-bit compat.
>
> Yes, yes, I meant 32-bit compat apps. Once again, it would be nice if we
> had the "low" fixmaps in init_mm. But unlikely this is possible...
>
>> On a related note, I'm hoping to rework the mm part pretty heavily:
>>
>> http://lkml.kernel.org/r/cover.1414629045.git.luto@amacapital.net
>
> OK... not that I really understand this email.
>
> Well. Speaking of vdso. I understand that unlikely we can do this, but
> for uprobes it would be nice to have a anon-inode file behind this mapping,
> so that vma_interval_tree_foreach() could work, etc. OK, this is completely
> off-topic, please forget.

Couldn't you do that directly in the uprobes code?  That is, create an
anon_inode file and just map it the old-fashioned way?

--Andy

>
>
>
> And I noticed that I didn't read your previous email carefully enough...
>
>> That sounds reasonable to me.  I'll write the patch later today.
>
> Sure, please send a patch if you want to do this.
>
>> gdb will still need changes, though, right?
>
> This is up to gdb developers. To me, it should simply skip this
> VM_DONTDUMP vma.
>
> Oleg.
>



-- 
Andy Lutomirski
AMA Capital Management, LLC
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