error::pass4(7stap) [centos man page]

ERROR::PASS4(7stap)													       ERROR::PASS4(7stap)

NAME

       error::pass4 - systemtap pass-4 errors

DESCRIPTION

       Errors that occur during pass 4 (compilation) have generally only a few causes:

       kernel or OS version changes
	      The systemtap runtime and embedded-C fragments in the tapset library are designed to be portable across a wide range of OS versions.
	      However, incompatibilities can occur when some OS changes occur, such as kernel  modifications  that  change  functions,	types,	or
	      macros referenced by systemtap.  Upstream builds of systemtap are often quickly updated to include relevant fixes, so try getting or
	      making an updated build.	If the issue persists, report the problem to the systemtap developers.

       buggy embedded-C code
	      Embedded-C code in your own guru-mode script cannot be checked by systemtap, and is passed through verbatim to the compiler.  Errors
	      in such snippets of code may be found during the pass-4 compiler invocation, though may be hard to identify by the compiler errors.

       incompatible embedded-C code
	      The  interface standards between systemtap-generated code and embedded-C code occasionally change.  For example, before version 1.8,
	      arguments were passed using macros THIS->foo and THIS->__retvalue but from version 1.8 onward, using STAP_ARG_foo and STAP_RETVALUE.
	      Adjust your embedded-C code to current standards, or use the stap --compatible=VERSION option to make systemtap use a different one.

GATHERING MORE INFORMATION

       It  may	be  necessary  to run systemtap with -k or -p3 to examine the generated C code.  Increasing the verbosity of pass-4 with an option
       such as --vp 0001 can also help pinpoint the problem.

SEE ALSO

       stap(1),
       error::reporting(7stap)

															       ERROR::PASS4(7stap)

ERROR::BUILDID(7stap)													     ERROR::BUILDID(7stap)

NAME

       error::buildid - build-id verification failures

DESCRIPTION

       Because	systemtap's script translation / execution stages may be executed at different times and places, it is sometimes necessary to ver-
       ify certain invariants.	One such invariant is that if a script was informed by translate-time analysis of  executables,  then  those  same
       executables  need  to  be  used	at run time.  This checking is done based upon the build-id, a binary hash that modern (post-2007) compil-
       ers/toolchains add as an NT_GNU_BUILD_ID ELF note to object files and executables.  Use the readelf -n command to examine the build-ids	of
       binaries, if you are interested.

       Only  scripts  are sensitive to executables' build-ids: generally those that perform deep analysis of the binaries or their debuginfo.  For
       example, scripts that place .function or .statement probes, or use stack  backtrace-related  tapset  functions  may  be	sensitive.   Other
       scripts	that  rely  only  on  process.mark  or kernel.trace probes do not require debuginfo.  See the DWARF DEBUGINFO section in the stap-
       probes(3stap) man page.

       During translation, systemtap saves a copy of the relevant files' build-ids within the compiled modules.  At run-time, the modules  compare
       the saved ones to the actual run-time build-ids in memory.  The error message indicates that they did not match, so the module will decline
       placing a probe that was computed based upon obsolete data.  This is important for safety, as placing  them  at	an  inappropriate  address
       could crash the programs.  However, this is not necessarily a fatal error, since probes unrelated to the mismatching binaries may operate.

       A build-id mismatch could be caused by a few different situations.  The main one is where the executable versions or architecture were dif-
       ferent between the systemtap translation and execution times/places.  For example, one may run a stap-server on a slightly  different  ver-
       sion of the OS distribution.  The kernel running on the workstation may be slightly different from the version being targeted - perhaps due
       to a pending kernel upgrade leaving different files on disk versus running in memory.  If your  OS  distribution  uses  separate  debuginfo
       packages, the split .IR .debug files may not exactly match the main binaries.

SEE ALSO

       http://fedoraproject.org/wiki/Releases/FeatureBuildId,
       stap(1),
       stapprobes(3stap),
       warning::debuginfo(7stap),
       error::reporting(7stap)

															     ERROR::BUILDID(7stap)