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tracing: probeevent: Add $argN for accessing function args

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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>
This commit is contained in:
Masami Hiramatsu
2018-04-25 21:21:26 +09:00
committed by Steven Rostedt (VMware)
parent 3c88ee194c
commit a1303af5d7
6 changed files with 55 additions and 24 deletions
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4
kernel/trace/trace.c
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@@ -4625,7 +4625,11 @@ static const char readme_msg[] =
#endif
"\t args: <name>=fetcharg[:type]\n"
"\t fetcharg: %<register>, @<address>, @<symbol>[+|-<offset>],\n"
#ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
"\t $stack<index>, $stack, $retval, $comm, $arg<N>\n"
#else
"\t $stack<index>, $stack, $retval, $comm\n"
#endif
"\t type: s8/16/32/64, u8/16/32/64, x8/16/32/64, string, symbol,\n"
"\t b<bit-width>@<bit-offset>/<container-size>,\n"
"\t <type>\\[<array-size>\\]\n"