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Re: vvar, gup && coredump
- From: Oleg Nesterov <oleg at redhat dot com>
- To: Andy Lutomirski <luto at amacapital dot net>
- Cc: Jan Kratochvil <jan dot kratochvil at redhat dot com>, Sergio Durigan Junior <sergiodj at redhat dot com>, GDB Patches <gdb-patches at sourceware dot org>, Pedro Alves <palves at redhat dot com>, "linux-kernel at vger dot kernel dot org" <linux-kernel at vger dot kernel dot org>
- Date: Thu, 12 Mar 2015 18:39:01 +0100
- Subject: Re: vvar, gup && coredump
- Authentication-results: sourceware.org; auth=none
- References: <878ufc9kau dot fsf at redhat dot com> <20150305154827 dot GA9441 at host1 dot jankratochvil dot net> <87zj7r5fpz dot fsf at redhat dot com> <20150305205744 dot GA13165 at host1 dot jankratochvil dot net> <20150311200052 dot GA22654 at redhat dot com> <20150312143438 dot GA4338 at redhat dot com> <CALCETrW5rmAHutzm_OwK2LTd_J0XByV3pvWGyW=AmC=v7rLfhQ at mail dot gmail dot com> <20150312165423 dot GA10073 at redhat dot com> <CALCETrUGu5Wc7BbbQ4_tn29JGbyotUJay67EHBEgSa8-bz01Jg at mail dot gmail dot com>
On 03/12, Andy Lutomirski wrote:
>
> On Thu, Mar 12, 2015 at 9:54 AM, Oleg Nesterov <oleg@redhat.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.