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

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Message-ID: <20150312173901.GA12225@redhat.com>
Date:	Thu, 12 Mar 2015 18:39:01 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andy Lutomirski <luto@...capital.net>
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 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.

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.

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