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| author | Masami Hiramatsu <mhiramat@kernel.org> | 2019-06-19 17:08:27 +0200 |
|---|---|---|
| committer | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2019-08-31 18:19:39 +0200 |
| commit | 6218bf9f4d2942e88d97b60abc8c2ca0532e41a8 (patch) | |
| tree | cb0b878e89295891667eefc528e75e69650fc52c /Documentation/trace/kprobetrace.rst | |
| parent | tracing/uprobe: Add per-probe delete from event (diff) | |
| download | linux-6218bf9f4d2942e88d97b60abc8c2ca0532e41a8.tar.xz linux-6218bf9f4d2942e88d97b60abc8c2ca0532e41a8.zip | |
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/trace/kprobetrace.rst')
| -rw-r--r-- | Documentation/trace/kprobetrace.rst | 1 |
1 files changed, 1 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 |