error::pass2(7stap) — Linux manual page


ERROR::PASS2(7stap)                                  ERROR::PASS2(7stap)

NAME         top

       error::pass2 - systemtap pass-2 errors

DESCRIPTION         top

       Errors that occur during pass 2 (elaboration) can have a variety
       of causes.  Common types include:

       missing debuginfo
              The script requires debuginfo to resolve a probe point,
              but could not find any.  See error::dwarf(7stap) and
              warning::debuginfo(7stap) for more details.

       unavailable probe point classes
              Some types of probe points are only available on certain
              system versions, architectures, and configurations.  For
              example, user-space process.*  probes may require utrace
              or uprobes capability in the kernel for this architecture.

       unavailable probe points
              Some probe points may be individually unavailable even
              when their class is fine.  For example,
              kprobe.function("foobar") may fail if function foobar does
              not exist in the kernel any more.  Debugging or symbol
              data may be absent for some types of .function or
              .statement probes; check for availability of debuginfo.
              Try the stap-prep program to download possibly-required
              debuginfo.  Use a wildcard parameter such as stap -l
              'kprobe.function("*foo*")' to locate still-existing
              variants.  Use ! or ?  probe point suffixes to denote
              optional / preferred-alternatives, to let the working
              parts of a script continue.

       typos  There might be a spelling error in the probe point name
              ("sycsall" vs.  "syscall").  Wildcard probes may not find
              a match at all in the tapsets.  Recheck the names using
              stap -l PROBEPOINT.  Another common mistake is to use the
              .  operator instead of the correct -> when dereferencing
              context variable subfields or pointers: $foo->bar->baz
              even if in C one would say foo->bar.baz.

       unavailable context variables
              Systemtap scripts often wish to refer to variables from
              the context of the probed programs using $variable
              notation.  These variables may not always be available,
              depending on versions of the compiler,
              debugging/optimization flags used, architecture, etc.  Use
              stap -L PROBEPOINT to list available context variables for
              given probes.  Use the @defined() expression to test for
              the resolvability of a context variable expression.
              Consider using the stap --skip-badvars option to silently
              replace misbehaving context variable expressions with
              zero.  Experiment with the stap --prologue-searching

       module cache inconsistencies
              Occasionally, the systemtap module cache
              ($HOME/.systemtap/cache) might contain obsolete
              information from a prior system configuration/version, and
              produce false results as systemtap attempts to reuse it.
              Retrying with stap --poison-cache ...  forces new
              information to be generated.  Note: this should not happen
              and likely represents a systemtap bug.  Please report it.


       Increasing the verbosity of pass-2 with an option such as --vp 02
       can help pinpoint the problem.

SEE ALSO         top


COLOPHON         top

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