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LTTNG-UST-DL(3) LTTng Manual LTTNG-UST-DL(3) NAME lttng-ust-dl - Dynamic linker tracing (LTTng-UST helper) SYNOPSIS Launch your application by preloading liblttng-ust-dl.so: $ LD_PRELOAD=liblttng-ust-dl.so my-app DESCRIPTION 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 li- braries, 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 reli- able, 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 li- | | | brary. | +----------------+-----------------------------+ | 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 lt- | | | tng_ust_dl:build_id event | | | record follows this one | | | (not necessarily immedi- | | | ately after). | +----------------+-----------------------------+ | has_debug_link | Whether or not the loaded | | | library has debug link in- | | | formation. If this field is | | | 1, you can expect that an | | | lttng_ust_dl:debug_link | | | event record follows this | | | one (not necessarily imme- | | | diately after). | +----------------+-----------------------------+ lttng_ust_dl:dlmopen Emitted when dlmopen(3) is called. Fields: +----------------+-----------------------------+ | Field name | Description | +----------------+-----------------------------+ | baddr | Base address of loaded li- | | | brary. | +----------------+-----------------------------+ | 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 lt- | | | tng_ust_dl:build_id event | | | record follows this one | | | (not necessarily immedi- | | | ately after). | +----------------+-----------------------------+ | has_debug_link | Whether or not the loaded | | | library has debug link in- | | | formation. If this field is | | | 1, you can expect that an | | | lttng_ust_dl:debug_link | | | event record follows this | | | one (not necessarily imme- | | | diately after). | +----------------+-----------------------------+ lttng_ust_dl:dlclose Emitted when dlclose(3) is called. Fields: +------------+-----------------------------+ | Field name | Description | +------------+-----------------------------+ | baddr | Base address of loaded li- | | | brary. | +------------+-----------------------------+ 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 li- | | | brary. | +------------+-----------------------------+ | 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://source- ware.org/gdb/onlinedocs/gdb/Separate-Debug-Files.html> for more infor- mation about build IDs. Fields: +------------+-----------------------------+ | Field name | Description | +------------+-----------------------------+ | baddr | Base address of loaded li- | | | brary. | +------------+-----------------------------+ | build_id | Build ID. | +------------+-----------------------------+ BUGS If you encounter any issue or usability problem, please report it on the LTTng bug tracker <https://bugs.lttng.org/projects/lttng-ust>. RESOURCES * 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: lt- tng-dev@lists.lttng.org * IRC channel <irc://irc.oftc.net/lttng>: #lttng on irc.oftc.net COPYRIGHTS 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/v2.13/COPYING> file for more details. THANKS 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 Ecole Polytechnique de Montreal for the LTTng journey. AUTHORS LTTng-UST was originally written by Mathieu Desnoyers, with additional con- tributions from various other people. It is currently maintained by Mathieu Desnoyers <mailto:mathieu.desnoyers@efficios.com>. SEE ALSO lttng-ust(3), dlopen(3), lttng(1) LTTng 2.13.9 04/14/2025 LTTNG-UST-DL(3)
NAME | SYNOPSIS | DESCRIPTION | BUGS | RESOURCES | COPYRIGHTS | THANKS | AUTHORS | SEE ALSO
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