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. │
└───────────┴────────────────────────┘
