tracing: probeevent: Add $argN for accessing function args

[linux.git] / Documentation / trace / kprobetrace.rst

diff --git a/Documentation/trace/kprobetrace.rst b/Documentation/trace/kprobetrace.rst
index 2dfed7a1ea6f7e934a537708b8f9d166d215865a..47e765c2f2c379851393084405aa8f45f52b5944 100644 (file)
--- a/Documentation/trace/kprobetrace.rst
+++ b/Documentation/trace/kprobetrace.rst
@@ -45,16 +45,18 @@ Synopsis of kprobe_events
   @SYM[+|-offs]        : Fetch memory at SYM +|- offs (SYM should be a data symbol)
   $stackN      : Fetch Nth entry of stack (N >= 0)
   $stack       : Fetch stack address.
-  $retval      : Fetch return value.(*)
+  $argN                : Fetch the Nth function argument. (N >= 1) (\*1)
+  $retval      : Fetch return value.(\*2)
   $comm                : Fetch current task comm.
-  +|-offs(FETCHARG) : Fetch memory at FETCHARG +|- offs address.(**)
+  +|-offs(FETCHARG) : Fetch memory at FETCHARG +|- offs address.(\*3)
   NAME=FETCHARG : Set NAME as the argument name of FETCHARG.
   FETCHARG:TYPE : Set TYPE as the type of FETCHARG. Currently, basic types
                  (u8/u16/u32/u64/s8/s16/s32/s64), hexadecimal types
                  (x8/x16/x32/x64), "string" and bitfield are supported.
 
-  (*) only for return probe.
-  (**) this is useful for fetching a field of data structures.
+  (\*1) only for the probe on function entry (offs == 0).
+  (\*2) only for return probe.
+  (\*3) this is useful for fetching a field of data structures.
 
 Types
 -----