warning::buildid(7stap) — Linux manual page

NAME | DESCRIPTION | SEE ALSO | COLOPHON

WARNING::BUILDID(7stap)                          WARNING::BUILDID(7stap)

NAME         top

       warning::buildid - build-id verification failures

DESCRIPTION         top

       Because systemtap's script translation / execution stages may be
       executed at different times and places, it is sometimes necessary
       to verify 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) compilers/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 stapprobes(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 warning 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 different 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.  Someone
       may have rebuilt a new kernel image, but preserved the previous
       version numbers.  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 .debug files may not exactly match
       the main binaries.

       To disable build-id verification warnings, if one is confident
       that they are an artefact of build accidents rather than a real
       mismatch, one might try the -DSTP_NO_BUILDID_CHECK option.

SEE ALSO         top

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

COLOPHON         top

       This page is part of the systemtap (a tracing and live-system
       analysis tool) project.  Information about the project can be
       found at ⟨https://sourceware.org/systemtap/⟩.  If you have a bug
       report for this manual page, send it to systemtap@sourceware.org.
       This page was obtained from the project's upstream Git repository
       ⟨git://sourceware.org/git/systemtap.git⟩ on 2021-06-20.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2021-06-18.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to
       man-pages@man7.org

                                                 WARNING::BUILDID(7stap)

Pages that refer to this page: error::dwarf(7stap)