NAME | SYNOPSIS | DESCRIPTION | BUGS | RESOURCES | COPYRIGHTS | THANKS | AUTHORS | SEE ALSO | COLOPHON

LTTNG-UST-DL(3)                 LTTng Manual                 LTTNG-UST-DL(3)

NAME         top

       lttng-ust-dl - Dynamic linker tracing (LTTng-UST helper)

SYNOPSIS         top

       Launch your application by preloading liblttng-ust-dl.so:

       $ LD_PRELOAD=liblttng-ust-dl.so my-app

DESCRIPTION         top

       When the liblttng-ust-dl.so library is preloaded before a given
       application starts, it causes all calls to dlopen(3) and dlclose(3)
       in said application to be traced with LTTng-UST (see lttng-ust(3)).

       See lttng(1) to learn more about how to control LTTng tracing
       sessions.

           Important
           This LTTng-UST helper can also emit shared library load/unload
           events (see Shared library load/unload tracking in lttng-ust(3)).
           You should NOT use the event records generated by this LTTng-UST
           helper (prefixed with lttng_ust_dl:) to track the loading and
           unloading of shared libraries, especially in situations where a
           dynamically loaded library loads its own dependencies. Instead,
           do preload liblttng-ust-dl.so, but use the shared library
           load/unload event records, which are more reliable, for your
           tracking analysis.

       The following LTTng-UST events are available when using this library.

       lttng_ust_dl:dlopen
           Emitted when dlopen(3) is called.

           Fields:

           ┌───────────────┬───────────────────────────┐
           │Field name     Description               │
           ├───────────────┼───────────────────────────┤
           │baddr          │ Base address of loaded    │
           │               │ library.                  │
           ├───────────────┼───────────────────────────┤
           │memsz          │ Size of loaded library in │
           │               │ memory.                   │
           ├───────────────┼───────────────────────────┤
           │flags          │ Flags passed to           │
           │               │ dlopen(3).                │
           ├───────────────┼───────────────────────────┤
           │path           │ Path to loaded library    │
           │               │ file.                     │
           ├───────────────┼───────────────────────────┤
           │has_build_id   │ Whether or not the loaded │
           │               │ library has a build ID.   │
           │               │ If this field is 1, you   │
           │               │ can expect that an        │
           │               │ lttng_ust_dl:build_id     │
           │               │ event record follows this │
           │               │ one (not necessarily      │
           │               │ immediately after).       │
           ├───────────────┼───────────────────────────┤
           │has_debug_link │ Whether or not the loaded │
           │               │ library has debug link    │
           │               │ information. If this      │
           │               │ field is 1, you can       │
           │               │ expect that an            │
           │               │ lttng_ust_dl:debug_link   │
           │               │ event record follows this │
           │               │ one (not necessarily      │
           │               │ immediately after).       │
           └───────────────┴───────────────────────────┘

       lttng_ust_dl:dlmopen
           Emitted when dlmopen(3) is called.

           Fields:

           ┌───────────────┬───────────────────────────┐
           │Field name     Description               │
           ├───────────────┼───────────────────────────┤
           │baddr          │ Base address of loaded    │
           │               │ library.                  │
           ├───────────────┼───────────────────────────┤
           │memsz          │ Size of loaded library in │
           │               │ memory.                   │
           ├───────────────┼───────────────────────────┤
           │nsid           │ ID of the namespace in    │
           │               │ which the library is      │
           │               │ loaded (as passed to      │
           │               │ dlmopen(3)).              │
           ├───────────────┼───────────────────────────┤
           │flags          │ Flags passed to           │
           │               │ dlmopen(3).               │
           ├───────────────┼───────────────────────────┤
           │path           │ Path to loaded library    │
           │               │ file.                     │
           ├───────────────┼───────────────────────────┤
           │has_build_id   │ Whether or not the loaded │
           │               │ library has a build ID.   │
           │               │ If this field is 1, you   │
           │               │ can expect that an        │
           │               │ lttng_ust_dl:build_id     │
           │               │ event record follows this │
           │               │ one (not necessarily      │
           │               │ immediately after).       │
           ├───────────────┼───────────────────────────┤
           │has_debug_link │ Whether or not the loaded │
           │               │ library has debug link    │
           │               │ information. If this      │
           │               │ field is 1, you can       │
           │               │ expect that an            │
           │               │ lttng_ust_dl:debug_link   │
           │               │ event record follows this │
           │               │ one (not necessarily      │
           │               │ immediately after).       │
           └───────────────┴───────────────────────────┘

       lttng_ust_dl:dlclose
           Emitted when dlclose(3) is called.

           Fields:

           ┌───────────┬────────────────────────┐
           │Field name Description            │
           ├───────────┼────────────────────────┤
           │baddr      │ Base address of loaded │
           │           │ library.               │
           └───────────┴────────────────────────┘

       lttng_ust_dl:debug_link
           Emitted when debug link information is found when loading a
           library with dlopen(3). See Debugging Information in Separate
           Files <https://sourceware.org/gdb/onlinedocs/gdb/Separate-Debug-
           Files.html> for more information about debug links.

           Fields:

           ┌───────────┬────────────────────────┐
           │Field name Description            │
           ├───────────┼────────────────────────┤
           │baddr      │ Base address of loaded │
           │           │ library.               │
           ├───────────┼────────────────────────┤
           │filename   │ Debug link file name.  │
           ├───────────┼────────────────────────┤
           │crc        │ Debug link file’s CRC. │
           └───────────┴────────────────────────┘

       lttng_ust_dl:build_id
           Emitted when a build ID is found when loading a library with
           dlopen(3). See Debugging Information in Separate Files
           <https://sourceware.org/gdb/onlinedocs/gdb/Separate-Debug-
           Files.html> for more information about build IDs.

           Fields:

           ┌───────────┬────────────────────────┐
           │Field name Description            │
           ├───────────┼────────────────────────┤
           │baddr      │ Base address of loaded │
           │           │ library.               │
           ├───────────┼────────────────────────┤
           │build_id   │ Build ID.              │
           └───────────┴────────────────────────┘

BUGS         top

       If you encounter any issue or usability problem, please report it on
       the LTTng bug tracker <https://bugs.lttng.org/projects/lttng-ust>.

RESOURCES         top

       ·   LTTng project website <http://lttng.org>

       ·   LTTng documentation <http://lttng.org/docs>

       ·   Git repositories <http://git.lttng.org>

       ·   GitHub organization <http://github.com/lttng>

       ·   Continuous integration <http://ci.lttng.org/>

       ·   Mailing list <http://lists.lttng.org> for support and
           development: lttng-dev@lists.lttng.org

       ·   IRC channel <irc://irc.oftc.net/lttng>: #lttng on irc.oftc.net

COPYRIGHTS         top

       This library is part of the LTTng-UST project.

       This library is distributed under the GNU Lesser General Public
       License, version 2.1 <http://www.gnu.org/licenses/old-
       licenses/lgpl-2.1.en.html>. See the COPYING
       <https://github.com/lttng/lttng-ust/blob/master/COPYING> file for
       more details.

THANKS         top

       Thanks to Ericsson for funding this work, providing real-life use
       cases, and testing.

       Special thanks to Michel Dagenais and the DORSAL laboratory
       <http://www.dorsal.polymtl.ca/> at École Polytechnique de Montréal
       for the LTTng journey.

AUTHORS         top

       LTTng-UST was originally written by Mathieu Desnoyers, with
       additional contributions from various other people. It is currently
       maintained by Mathieu Desnoyers
       <mailto:mathieu.desnoyers@efficios.com>.

SEE ALSO         top

       lttng-ust(3), dlopen(3), lttng(1)

COLOPHON         top

       This page is part of the LTTng-UST (    LTTng Userspace Tracer)
       project.  Information about the project can be found at 
       ⟨http://lttng.org/⟩.  It is not known how to report bugs for this man
       page; if you know, please send a mail to man-pages@man7.org.  This
       page was obtained from the project's upstream Git repository 
       ⟨git://git.lttng.org/lttng-ust.git⟩ on 2017-09-15.  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

LTTng 2.10.0-rc1                 08/02/2017                  LTTNG-UST-DL(3)

Pages that refer to this page: lttng-ust(3)