| 1 | lttng-ust-dl(3) |
| 2 | =============== |
| 3 | :object-type: library |
| 4 | |
| 5 | |
| 6 | NAME |
| 7 | ---- |
| 8 | lttng-ust-dl - Dynamic linker tracing (LTTng-UST helper) |
| 9 | |
| 10 | |
| 11 | SYNOPSIS |
| 12 | -------- |
| 13 | Launch your application by preloading `liblttng-ust-dl.so`: |
| 14 | |
| 15 | [role="term"] |
| 16 | [verse] |
| 17 | *LD_PRELOAD=liblttng-ust-dl.so* my-app |
| 18 | |
| 19 | |
| 20 | DESCRIPTION |
| 21 | ----------- |
| 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 |
| 25 | man:lttng-ust(3)). |
| 26 | |
| 27 | See man:lttng(1) to learn more about how to control LTTng tracing |
| 28 | sessions. |
| 29 | |
| 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. |
| 38 | |
| 39 | The following LTTng-UST events are available when using this library. |
| 40 | |
| 41 | |
| 42 | `lttng_ust_dl:dlopen`:: |
| 43 | Emitted when man:dlopen(3) is called. |
| 44 | + |
| 45 | Fields: |
| 46 | + |
| 47 | [options="header"] |
| 48 | |=== |
| 49 | |Field name |Description |
| 50 | |
| 51 | |`baddr` |
| 52 | |Base address of loaded library. |
| 53 | |
| 54 | |`memsz` |
| 55 | |Size of loaded library in memory. |
| 56 | |
| 57 | |`path` |
| 58 | |Path to loaded library file. |
| 59 | |=== |
| 60 | |
| 61 | `lttng_ust_dl:dlclose`:: |
| 62 | Emitted when man:dlclose(3) is called. |
| 63 | + |
| 64 | Fields: |
| 65 | + |
| 66 | [options="header"] |
| 67 | |=== |
| 68 | |Field name |Description |
| 69 | |
| 70 | |`baddr` |
| 71 | |Base address of loaded library. |
| 72 | |=== |
| 73 | |
| 74 | `lttng_ust_dl:debug_link`:: |
| 75 | Emitted when debug link information is found when loading a library |
| 76 | with man:dlopen(3). See |
| 77 | https://sourceware.org/gdb/onlinedocs/gdb/Separate-Debug-Files.html[Debugging Information in Separate Files] |
| 78 | for more information about debug links. |
| 79 | + |
| 80 | Fields: |
| 81 | + |
| 82 | [options="header"] |
| 83 | |=== |
| 84 | |Field name |Description |
| 85 | |
| 86 | |`baddr` |
| 87 | |Base address of loaded library. |
| 88 | |
| 89 | |`filename` |
| 90 | |Debug link file name. |
| 91 | |
| 92 | |`crc` |
| 93 | |Debug link file's CRC. |
| 94 | |=== |
| 95 | |
| 96 | `lttng_ust_dl:build_id`:: |
| 97 | Emitted when a build ID is found when loading a library |
| 98 | with man:dlopen(3). See |
| 99 | https://sourceware.org/gdb/onlinedocs/gdb/Separate-Debug-Files.html[Debugging Information in Separate Files] |
| 100 | for more information about build IDs. |
| 101 | + |
| 102 | Fields: |
| 103 | + |
| 104 | [options="header"] |
| 105 | |=== |
| 106 | |Field name |Description |
| 107 | |
| 108 | |`baddr` |
| 109 | |Base address of loaded library. |
| 110 | |
| 111 | |`build_id` |
| 112 | |Build ID. |
| 113 | |=== |
| 114 | |
| 115 | |
| 116 | include::common-footer.txt[] |
| 117 | |
| 118 | include::common-copyrights.txt[] |
| 119 | |
| 120 | include::common-authors.txt[] |
| 121 | |
| 122 | |
| 123 | SEE ALSO |
| 124 | -------- |
| 125 | man:lttng-ust(3), |
| 126 | man:dlopen(3), |
| 127 | man:lttng(1) |