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-rw-r--r--Documentation/trace/ftrace-uses.rst10
1 files changed, 9 insertions, 1 deletions
diff --git a/Documentation/trace/ftrace-uses.rst b/Documentation/trace/ftrace-uses.rst
index 1fbc69894eed..2a05e770618a 100644
--- a/Documentation/trace/ftrace-uses.rst
+++ b/Documentation/trace/ftrace-uses.rst
@@ -146,7 +146,7 @@ FTRACE_OPS_FL_RECURSION_SAFE
itself or any nested functions that those functions call.
If this flag is set, it is possible that the callback will also
- be called with preemption enabled (when CONFIG_PREEMPT is set),
+ be called with preemption enabled (when CONFIG_PREEMPTION is set),
but this is not guaranteed.
FTRACE_OPS_FL_IPMODIFY
@@ -170,6 +170,14 @@ FTRACE_OPS_FL_RCU
a callback may be executed and RCU synchronization will not protect
it.
+FTRACE_OPS_FL_PERMANENT
+ If this is set on any ftrace ops, then the tracing cannot disabled by
+ writing 0 to the proc sysctl ftrace_enabled. Equally, a callback with
+ the flag set cannot be registered if ftrace_enabled is 0.
+
+ Livepatch uses it not to lose the function redirection, so the system
+ stays protected.
+
Filtering which functions to trace
==================================