From 3d599bcbf6771def1076c3e9561bc748956dfc94 Mon Sep 17 00:00:00 2001
From: Johannes Stoelp <johannes.stoelp@gmail.com>
Date: Sat, 9 Nov 2024 11:41:49 +0100
Subject: ltrace: example to trace dlopen-ed libraries

---
 src/trace_profile/ltrace.md | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/src/trace_profile/ltrace.md b/src/trace_profile/ltrace.md
index cfa3fae..12bd4b3 100644
--- a/src/trace_profile/ltrace.md
+++ b/src/trace_profile/ltrace.md
@@ -7,6 +7,8 @@ ltrace [opts] [prg]
   -o <file> ... log output into <file>
   -l <filter> . show who calls into lib matched by <filter>
   -C .......... demangle
+  -x <filter> . which symbol table entry points to trace
+                (can be of form sym_pattern@lib_pattern)
 ```
 
 # Example
@@ -15,3 +17,17 @@ List which program/libs call into `libstdc++`:
 ```bash
 ltrace -l '*libstdc++*' -C -o ltrace.log ./main
 ```
+
+Trace symbols from `dlopen(3)`ed libraries.
+```bash
+# Assume libfoo.so would be dynamically loaded via dlopen.
+ltrace -x '@libfoo.so'
+
+# Trace all dlopened symbols.
+ltrace -x '*'
+# Trace all symbols from dlopened libraries which name match the
+# pattern "liby*".
+ltrace -x '@liby*'
+# Trace symbol "foo" from all dlopened libraries matching the pattern.
+ltrace -x 'foo@liby*'
+```
\ No newline at end of file
-- 
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