ERROR::BUILDID(7stap)ERROR::BUILDID(7stap)NAMEerror::buildid - build-id verification failures
DESCRIPTION
Because systemtap's script translation / execution stages may be exe‐
cuted 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 com‐
pare 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 differ‐
ent between the systemtap translation and execution times/places. For
example, one may run a stap-server on a slightly different version 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), stap‐
probes(3stap), warning::debuginfo(7stap), error::reporting(7stap)ERROR::BUILDID(7stap)
