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authorMasami Hiramatsu <mhiramat@kernel.org>2019-06-20 00:08:27 +0900
committerSteven Rostedt (VMware) <rostedt@goodmis.org>2019-08-31 12:19:39 -0400
commit6218bf9f4d2942e88d97b60abc8c2ca0532e41a8 (patch)
treecb0b878e89295891667eefc528e75e69650fc52c /Documentation
parentab10d69eb714961d1eca4129e4f8cda5e0618f66 (diff)
tracing/probe: Add immediate parameter support
Add immediate value parameter (\1234) support to probe events. This allows you to specify an immediate (or dummy) parameter instead of fetching from memory or register. This feature looks odd, but imagine when you put a probe on a code to trace some data. If the code is compiled into 2 instructions and 1 instruction has a value but other has nothing since it is optimized out. In that case, you can not fold those into one event, even if ftrace supported multiple probes on one event. With this feature, you can set a dummy value like foo=\deadbeef instead of something like foo=%di. Link: http://lkml.kernel.org/r/156095690733.28024.13258186548822649469.stgit@devnote2 Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/trace/kprobetrace.rst1
-rw-r--r--Documentation/trace/uprobetracer.rst1
2 files changed, 2 insertions, 0 deletions
diff --git a/Documentation/trace/kprobetrace.rst b/Documentation/trace/kprobetrace.rst
index fbb314bfa112..55993055902c 100644
--- a/Documentation/trace/kprobetrace.rst
+++ b/Documentation/trace/kprobetrace.rst
@@ -52,6 +52,7 @@ Synopsis of kprobe_events
$retval : Fetch return value.(\*2)
$comm : Fetch current task comm.
+|-[u]OFFS(FETCHARG) : Fetch memory at FETCHARG +|- OFFS address.(\*3)(\*4)
+ \IMM : Store an immediate value to the argument.
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
diff --git a/Documentation/trace/uprobetracer.rst b/Documentation/trace/uprobetracer.rst
index 6e75a6c5a2c8..98cde99939d7 100644
--- a/Documentation/trace/uprobetracer.rst
+++ b/Documentation/trace/uprobetracer.rst
@@ -45,6 +45,7 @@ Synopsis of uprobe_tracer
$retval : Fetch return value.(\*1)
$comm : Fetch current task comm.
+|-[u]OFFS(FETCHARG) : Fetch memory at FETCHARG +|- OFFS address.(\*2)(\*3)
+ \IMM : Store an immediate value to the argument.
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