lttng-ust-dl(3) =============== :object-type: library NAME ---- lttng-ust-dl - Dynamic linker tracing (LTTng-UST helper) SYNOPSIS -------- Launch your application by preloading `liblttng-ust-dl.so`: [role="term"] [verse] $ *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 man:dlopen(3) and man:dlclose(3) in said application to be traced with LTTng-UST (see man:lttng-ust(3)). See man: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 man: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 man:dlopen(3) is called. + Fields: + [options="header"] |=== |Field name |Description |`baddr` |Base address of loaded library. |`memsz` |Size of loaded library in memory. |`flags` |Flags passed to man: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 man:dlmopen(3) is called. + Fields: + [options="header"] |=== |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 man:dlmopen(3)). |`flags` |Flags passed to man: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 man:dlclose(3) is called. + Fields: + [options="header"] |=== |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 man:dlopen(3). See https://sourceware.org/gdb/onlinedocs/gdb/Separate-Debug-Files.html[Debugging Information in Separate Files] for more information about debug links. + Fields: + [options="header"] |=== |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 man:dlopen(3). See https://sourceware.org/gdb/onlinedocs/gdb/Separate-Debug-Files.html[Debugging Information in Separate Files] for more information about build IDs. + Fields: + [options="header"] |=== |Field name |Description |`baddr` |Base address of loaded library. |`build_id` |Build ID. |=== include::common-footer.txt[] include::common-copyrights.txt[] include::common-authors.txt[] SEE ALSO -------- man:lttng-ust(3), man:dlopen(3), man:lttng(1)