8 lttng-ust-dl - Dynamic linker tracing (LTTng-UST helper)
13 Launch your application by preloading `liblttng-ust-dl.so`:
17 $ *LD_PRELOAD=liblttng-ust-dl.so* my-app
22 When the `liblttng-ust-dl.so` library is preloaded before a given
23 application starts, it causes all calls to man:dlopen(3) and
24 man:dlclose(3) in said application to be traced with LTTng-UST (see
27 See man:lttng(1) to learn more about how to control LTTng tracing
30 IMPORTANT: This LTTng-UST helper can also emit _shared library
31 load/unload_ events (see _Shared library load/unload tracking_ in
32 man:lttng-ust(3)). You should :not: use the event records generated by
33 this LTTng-UST helper (prefixed with `lttng_ust_dl:`) to track the
34 loading and unloading of shared libraries, especially in situations
35 where a dynamically loaded library loads its own dependencies. Instead,
36 do preload `liblttng-ust-dl.so`, but use the shared library load/unload
37 event records, which are more reliable, for your tracking analysis.
39 The following LTTng-UST events are available when using this library.
42 `lttng_ust_dl:dlopen`::
43 Emitted when man:dlopen(3) is called.
49 |Field name |Description
52 |Base address of loaded library.
55 |Size of loaded library in memory.
58 |Flags passed to man:dlopen(3).
61 |Path to loaded library file.
64 |Whether or not the loaded library has a build ID. If this field is 1,
65 you can expect that an `lttng_ust_dl:build_id` event record
66 follows this one (not necessarily immediately after).
69 |Whether or not the loaded library has debug link information. If this
70 field is 1, you can expect that an `lttng_ust_dl:debug_link` event
71 record follows this one (not necessarily immediately after).
74 `lttng_ust_dl:dlmopen`::
75 Emitted when man:dlmopen(3) is called.
81 |Field name |Description
84 |Base address of loaded library.
87 |Size of loaded library in memory.
90 |ID of the namespace in which the library is loaded (as passed
94 |Flags passed to man:dlmopen(3).
97 |Path to loaded library file.
100 |Whether or not the loaded library has a build ID. If this field is 1,
101 you can expect that an `lttng_ust_dl:build_id` event record
102 follows this one (not necessarily immediately after).
105 |Whether or not the loaded library has debug link information. If this
106 field is 1, you can expect that an `lttng_ust_dl:debug_link` event
107 record follows this one (not necessarily immediately after).
110 `lttng_ust_dl:dlclose`::
111 Emitted when man:dlclose(3) is called.
117 |Field name |Description
120 |Base address of loaded library.
123 `lttng_ust_dl:debug_link`::
124 Emitted when debug link information is found when loading a library
125 with man:dlopen(3). See
126 https://sourceware.org/gdb/onlinedocs/gdb/Separate-Debug-Files.html[Debugging Information in Separate Files]
127 for more information about debug links.
133 |Field name |Description
136 |Base address of loaded library.
139 |Debug link file name.
142 |Debug link file's CRC.
145 `lttng_ust_dl:build_id`::
146 Emitted when a build ID is found when loading a library
147 with man:dlopen(3). See
148 https://sourceware.org/gdb/onlinedocs/gdb/Separate-Debug-Files.html[Debugging Information in Separate Files]
149 for more information about build IDs.
155 |Field name |Description
158 |Base address of loaded library.
165 include::common-footer.txt[]
167 include::common-copyrights.txt[]
169 include::common-authors.txt[]