[Bug tapsets/14690] New: the syscall tapsets could be written to prefer the 'syscalls' tracepoints

[Bug tapsets/14690] New: the syscall tapsets could be written to prefer the 'syscalls' tracepoints

[dsmith at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14690

             Bug #: 14690
           Summary: the syscall tapsets could be written to prefer the
                    'syscalls' tracepoints
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: tapsets
        AssignedTo: systemtap@sourceware.org
        ReportedBy: dsmith@redhat.com
        Depends on: 14689
    Classification: Unclassified


If systemtap could find the 'syscalls' set of tracepoints, the syscall tapsets
could be written to prefer those tracepoints over using kprobes.  As an
example:

====
probe syscall.access = kernel.trace("sys_enter_access") !,
      kernel.function("sys_access").call
{
  # ... we'd probably need to use @defined() to get the correct arguments
}
====

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[Bug tapsets/14690] the syscall tapsets could be written to prefer the 'syscalls' tracepoints

[jistone at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14690

Josh Stone <jistone at redhat dot com> changed:

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

--- Comment #1 from Josh Stone <jistone at redhat dot com> 2012-10-09 20:14:12 UTC ---
(In reply to comment #0)
> probe syscall.access = kernel.trace("sys_enter_access") !,
>       kernel.function("sys_access").call
> {
>   # ... we'd probably need to use @defined() to get the correct arguments
> }

IMO, when we already know what variables should be used in which probe point,
it's better to split the aliases than use @defined, e.g.

probe syscall.access = tp_syscall.access!, kp_syscall.access
{ /* common stuff */ }
probe tp_syscall.access = kernel.trace("sys_enter_access")
{ /* tracepoint specifics */ }
probe kp_syscall.access = kernel.function("sys_access").call
{ /* kprobe specifics */ }

We might even choose to unify nd_syscall.access in there too.

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[Bug tapsets/14690] the syscall tapsets could be written to prefer the 'syscalls' tracepoints

[fche at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=14690

Frank Ch. Eigler <fche at redhat dot com> changed:

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

--- Comment #2 from Frank Ch. Eigler <fche at redhat dot com> ---
This little toy script checks whether the _stp_syscall_nr() function provides a
good-enough substitute for the missing $id parameter from the sys_exit
tracepoint.  It turns out that generally yes, at least on x86_64.


global i% 

probe kernel.trace("sys_enter") { __set_usermode_pt_regs($regs) x=$id
y=_stp_syscall_nr(); i[tid()]=x; if (x!=y) println("entry ", x, " ", y) } 

probe kernel.trace("sys_exit") { __set_usermode_pt_regs($regs) y =
_stp_syscall_nr(); x=i[tid()]; delete i[tid()] ; if(x!=y) println("exit ", x, "
", y) }

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[Bug tapsets/14690] the syscall tapsets could be written to prefer the 'syscalls' tracepoints

[juddin at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=14690

Jafeer Uddin <juddin at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |juddin at redhat dot com
         Resolution|---                         |FIXED
           Assignee|systemtap at sourceware dot org    |juddin at redhat dot com

--- Comment #3 from Jafeer Uddin <juddin at redhat dot com> ---
All syscall tracepoints have been added in commit
8b8c9b636389b67a2288e31eb1f9b14a3992bc18

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