NAME

       error::pass2 - systemtap pass-2 errors

DESCRIPTION

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

       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.

       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.

GATHERING MORE INFORMATION

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

SEE ALSO

       stap(1),
       stap-prep(1),
       stapprobes(3stap),
       probe::*(3stap),
       error::dwarf(7stap),
       error::inode-uprobes(7stap),
       warning::debuginfo(7stap),
       error::reporting(7stap)

                                                                                             ERROR::PASS2(7stap)