[Bug runtime/14883] New: let probefunc() not fail - or fail more informatively, on non-uprobes kernels

[Bug runtime/14883] New: let probefunc() not fail - or fail more informatively, on non-uprobes kernels

[fche at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14883

             Bug #: 14883
           Summary: let probefunc() not fail - or fail more informatively,
                    on non-uprobes kernels
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: runtime
        AssignedTo: systemtap@sourceware.org
        ReportedBy: fche@redhat.com
    Classification: Unclassified


Bug #13693 rewrote probefunc() to go to usymname(uaddr()) if user_mode, which
in turn activates the whole task-finder mechanism.  If the kernel is not up to
that, the user gets a bewildering error message:

user-space facilities not available without kernel CONFIG_UTRACE or
CONFIG_TRACEPOINTS/CONFIG_ARCH_SUPPORTS_UPROBES/CONFIG_UPROBES

Running with --compatible=1.8 makes things work.

We should improve this; some options:
- change usym*() to tolerate absence of the utrace/uprobes goo, and return
empty or hex strings
- or one level down: change the runtime for pragma:vma without utrace/uprobes
to succeed with a stub dummy
- improve the error message in its own right (probably don't list CONFIG*
literals)

-- 
Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are the assignee for the bug.

[Bug runtime/14883] let probefunc() not fail - or fail more informatively, on non-uprobes kernels

[smakarov at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14883

Serguei Makarov <smakarov at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |smakarov at redhat dot com

--- Comment #1 from Serguei Makarov <smakarov at redhat dot com> 2012-12-19 21:37:29 UTC ---
Pushed a set of stub functions for task_finder and vma that output warning
messages to inform the user that functionality may not be available, e.g.:

WARNING: cannot track target in process
'/opt/codebase/build/testsuite/towers.x'
WARNING: cannot track target in process 'XXX'
WARNING: process-tracking facilities are not available in this kernel

while still allowing the script in question to proceed. (All of the
corresponding task_finder callback registrations are ignored silently, and the
callbacks are never called.)

This is probably better than the prior behaviour, which could readily run into
an error at the C compilation stage (when error messages are most confusing).

-- 
Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are the assignee for the bug.

[Bug runtime/14883] let probefunc() not fail - or fail more informatively, on non-uprobes kernels

[smakarov at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14883

Serguei Makarov <smakarov at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED

--- Comment #2 from Serguei Makarov <smakarov at redhat dot com> 2012-12-21 20:50:53 UTC ---
Alright, the initial error ("user-space facilities not available") also refers
to the explanatory manpage. Closing the bug, since things either work or fail
in an informative manner now.

-- 
Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are the assignee for the bug.