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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: lttng-dev@lists.lttng.org • 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/v2.10.6/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:mathieu.desnoyers@efficios.com>.
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 man-pages@man7.org.
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fetched from ⟨https://lttng.org/files/lttng-ust/⟩ on 2019-11-19.
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LTTng 2.10.6 10/17/2019 LTTNG-UST-DL(3)
Pages that refer to this page: lttng-ust(3), babeltrace2-filter.lttng-utils.debug-info(7)