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-rw-r--r--Documentation/trace/fprobetrace.rst8
1 files changed, 6 insertions, 2 deletions
diff --git a/Documentation/trace/fprobetrace.rst b/Documentation/trace/fprobetrace.rst
index 8e9bebcf0a..e35e6b18df 100644
--- a/Documentation/trace/fprobetrace.rst
+++ b/Documentation/trace/fprobetrace.rst
@@ -59,8 +59,12 @@ Synopsis of fprobe-events
and bitfield are supported.
(\*1) This is available only when BTF is enabled.
- (\*2) only for the probe on function entry (offs == 0).
- (\*3) only for return probe.
+ (\*2) only for the probe on function entry (offs == 0). Note, this argument access
+ is best effort, because depending on the argument type, it may be passed on
+ the stack. But this only support the arguments via registers.
+ (\*3) only for return probe. Note that this is also best effort. Depending on the
+ return value type, it might be passed via a pair of registers. But this only
+ accesses one register.
(\*4) this is useful for fetching a field of data structures.
(\*5) "u" means user-space dereference.