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NAME | SYNOPSIS | DESCRIPTION | BUGS | RESOURCES | COPYRIGHTS | THANKS | AUTHORS | SEE ALSO | COLOPHON |
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LTTNG-UST-DL(3) LTTng Manual LTTNG-UST-DL(3)
lttng-ust-dl - Dynamic linker tracing (LTTng-UST helper)
Launch your application by preloading liblttng-ust-dl.so:
$ LD_PRELOAD=liblttng-ust-dl.so my-app
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. │
└────────────┴────────────────────────┘
If you encounter any issue or usability problem, please report it
on the LTTng bug tracker <https://bugs.lttng.org/projects/lttng-
ust>.
• 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: [email protected]
• IRC channel <irc://irc.oftc.net/lttng>: #lttng on irc.oftc.net
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/v2.14/COPYING> file for
more details.
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.
LTTng-UST was originally written by Mathieu Desnoyers, with
additional contributions from various other people. It is
currently maintained by Mathieu Desnoyers
<mailto:[email protected]>.
lttng-ust(3), dlopen(3), lttng(1)
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 [email protected].
This page was obtained from the tarball fetched from
⟨https://lttng.org/files/lttng-ust/⟩ on 2025-08-11. 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 [email protected]
LTTng 2.14.0-pre 06/07/2024 LTTNG-UST-DL(3)
Pages that refer to this page: lttng-ust(3), babeltrace2-filter.lttng-utils.debug-info(7)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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