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authorMasami Hiramatsu2018-04-25 21:21:26 +0900
committerSteven Rostedt (VMware)2018-10-10 22:19:11 -0400
commita1303af5d79eb13a658633a9fb0ce3aed0f7decf (patch)
tree06ab7627ff3bec7afcba894432a5798babd3e0bc /Documentation/trace
parent3c88ee194c288205733d248b51f0aca516ff4940 (diff)
tracing: probeevent: Add $argN for accessing function args
Add $argN special fetch variable for accessing function arguments. This allows user to trace the Nth argument easily at the function entry. Note that this returns most probably assignment of registers and stacks. In some case, it may not work well. If you need to access correct registers or stacks you should use perf-probe. Link: http://lkml.kernel.org/r/152465888632.26224.3412465701570253696.stgit@devbox Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'Documentation/trace')
-rw-r--r--Documentation/trace/kprobetrace.rst10
1 files changed, 6 insertions, 4 deletions
diff --git a/Documentation/trace/kprobetrace.rst b/Documentation/trace/kprobetrace.rst
index 2dfed7a1ea6f..47e765c2f2c3 100644
--- 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
-----