[Bug uprobes/13489] New: support upstream inode-based uprobes

[Bug uprobes/13489] New: support upstream inode-based uprobes

[jistone at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=13489

             Bug #: 13489
           Summary: support upstream inode-based uprobes
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: uprobes
        AssignedTo: systemtap@sourceware.org
        ReportedBy: jistone@redhat.com
    Classification: Unclassified


Srikar Dronamraju is working hard on getting uprobes into the upstream kernel. 
It is currently integrating in the linux-next tree.

Being divorced from utrace, and based on inode+offset rather than memory
addresses, we need to do some work in stap to support it.

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[Bug uprobes/13489] support upstream inode-based uprobes

[jistone at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=13489

--- Comment #1 from Josh Stone <jistone at redhat dot com> 2011-12-09 23:22:31 UTC ---
I started a branch a while back to add initial support for this with commit
2b69faaf.  That has recently been merged into our git-master.  The issues that
I mentioned in my announcement still mostly stand:
  http://sourceware.org/ml/systemtap/2011-q2/msg00206.html

For testing purposes, Anton Arapov has prepared Fedora kernel packages that
skip utrace and apply the inode-uprobes patchset.
  http://repos.fedorapeople.org/repos/aarapov/kernel-uprobes/

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[Bug uprobes/13489] support upstream inode-based uprobes

[jistone at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=13489

--- Comment #2 from Josh Stone <jistone at redhat dot com> 2011-12-09 23:42:35 UTC ---
Created attachment 6101
  --> http://sourceware.org/bugzilla/attachment.cgi?id=6101
prototype support for sdt semaphores

This adds process/mmap tracking with David Smith's new task_finder2
implementation, so we can increment and decrement semaphores for SDT probes. 
This seems to work on F16, but shows warnings when running on rawhide.  It
seems that callbacks in this new task_finder are not allowed to sleep, which
makes the get/put_user problematic.  I'm not sure how to make progress on this
without finding a sleepy context.

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[Bug uprobes/13489] support upstream inode-based uprobes

[dsmith at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=13489

David Smith <dsmith at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |dsmith at redhat dot com
         Resolution|                            |FIXED

--- Comment #3 from David Smith <dsmith at redhat dot com> 2012-06-20 19:50:57 UTC ---
As Josh mentioned in comment #2, finding a sleepy context was the main holdup
here.  Kernels >= 3.5 have a feature called "task_work" that we're now using to
provide that sleepy context.

There are still missing features when compared to the old utrace-based uprobes
(like uretprobes), but we now support the upstream inode-based uprobes.  Any
remaining bugs in the new inode-based uprobes support we can track separately.

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