[Bug runtime/19360] New: Verify that examples and tapsets with return probes use @entry for function arguments

[Bug runtime/19360] New: Verify that examples and tapsets with return probes use @entry for function arguments

[wcohen at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=19360

            Bug ID: 19360
           Summary: Verify that examples and tapsets with return probes
                    use @entry for function arguments
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: runtime
          Assignee: systemtap at sourceware dot org
          Reporter: wcohen at redhat dot com
  Target Milestone: ---

When reviewing test results on aarch64 I found that the systemtap lwtools
examples fslatency-nd.stp and fsslower-nd.stp were not using correct values of
arguments for return probe.  This is because the aarch64 arguments are stored
in registers that can be overwritten in the function.  These uses should be
wrapped by @entry to make sure the value from the function entry is used.  It
would be very wise to review the other scripts and tapsets in systemtap to
ensure that this problem is not lurking elsewhere. For problem entries do
something like what is done in:

https://sourceware.org/git/gitweb.cgi?p=systemtap.git;a=commit;h=3d0c2f452f09a64b800aabe68508f8f0183f0ea1

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[Bug runtime/19360] Verify that examples and tapsets with return probes use @entry for function arguments

[wcohen at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=19360

William Cohen <wcohen at redhat dot com> changed:

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

--- Comment #1 from William Cohen <wcohen at redhat dot com> ---
Reviewed the examples in testsuite/systmetap.examples.  Found a couple
corrections needed to be made in fslatency-nd.stp and fsslower-nd.stp.

commit 01261944787df5c757d55fe2ec081b70a1723ab0 (HEAD -> master, origin/master,
origin/HEAD)
Author: William Cohen <wcohen@redhat.com>
Date:   Thu Feb 15 15:01:53 2024 -0500

    PR19360: Correct lwtools fslatency-nd.stp and fsslower-nd.stp

    Reviewed examples to ensure that the entry value for a function
    argument is used for function return probes. Found that
    __vfs_write.return probes aliases were missing ".return" and needed an
    @entry() for the argument fetch in fslatency-nd.stp and
    fsslower-nd.stp.

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