error::pass5 - systemtap pass-5 errors
Errors that occur during pass 5 (execution) can have a variety of causes.
- exceptional events during script execution
- The systemtap translator and runtime include numerous error checks that aim to protect the systems and the users from mistakes or transient conditions. The script may deliberately call the error() tapset function to signal a problem. Some memory needed for accessing $context variables may be temporarily unavailable. Consider using the try/catch construct to wrap script fragments in exception-handling code. Consider using the stap --suppress-handler-errors or stap --skip-badvars option.
- resource exhaustion
- One of several types of space or time resource limits may be exceeded by the script, including system overload, too many tuples to be stored in an array, etc. Some of the error messages identify the constraint by macro name, which may be individually raised. Consider using the stap --suppress-handler-errors and/or stap -g --suppress-time-limits options. Extend or disable individual resource limits using the stap -DSOME_LIMIT=NNNN option. The stap -t option may identify those probes that are taking too long.
- remote execution server problems
- If you use the stap --remote option to direct a systemtap script to be executed somewhere else, ensure that an SSH connection may be made to the remote host, and that it has the current systemtap runtime installed & available.
- installation/permission problems
- It is possible that your copy of systemtap was not correctly installed. For example, the /usr/bin/staprun program may lack the necessary setuid permissions, or your invoking userid might not have sufficient privileges (root, or stapusr and related group memberships). Environment variables may interfere with locating /usr/libexec/.../stapio.
- security configuration
- SecureBoot or other module signing machinery may be in effect, preventing
.ko module loading. A local or remote stap-server service
would be necessary to securely manage keys. This situation is detected
automatically on most kernels, but on some, the SYSTEMTAP_SIGN
environment varible may have to be set to trigger this extra
The normal kernel-module based systemtap backend may be more than your script requires. Try stap --runtime=bpf and/or stap --runtime=dyninst backends. Though they have inherent limitations, they operate with lesser privileges and perceived risks.
It may be possible to disable secure/lockdown measures temporarily with the SysRQ+x keystroke, or permanently with sudo mokutil --disable-validation and a reboot.
- errors from target program
- The program invoked by the stap -c CMD option may exit with a non-zero code.
- uncaught exceptions in the target program
- When using --runtime=dyninst you may encounter an issue where the target program aborts with a message like "terminate called after throwing an instance of 'foo_exception'". This is unfortunately a limitation of Dyninst, which sometimes prevents exceptions from properly unwinding through instrumented code.
GATHERING MORE INFORMATION¶
Increasing the verbosity of pass-5 with an option such as --vp 00001 can help pinpoint the problem.
stap(1), http://sourceware.org/systemtap/wiki/TipExhaustedResourceErrors, error::fault(7stap), error::reporting(7stap) warning::pass5(7stap)