doc/man/lttng-ust-dl.3.txt

   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)