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| author | Masami Hiramatsu <mhiramat@kernel.org> | 2019-05-15 07:38:42 +0200 |
|---|---|---|
| committer | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2019-05-26 05:04:42 +0200 |
| commit | e65f7ae7f4da56622ecf8f1eaed333b9a13f9435 (patch) | |
| tree | 41eeedabb989b5c5fb0671213d15e40a45349e08 /kernel/trace/trace.c | |
| parent | tracing/probe: Add ustring type for user-space string (diff) | |
| download | linux-e65f7ae7f4da56622ecf8f1eaed333b9a13f9435.tar.xz linux-e65f7ae7f4da56622ecf8f1eaed333b9a13f9435.zip | |
tracing/probe: Support user-space dereference
Support user-space dereference syntax for probe event arguments
to dereference the data-structure or array in user-space.
The syntax is just adding 'u' before an offset value.
+|-u<OFFSET>(<FETCHARG>)
e.g. +u8(%ax), +u0(+0(%si))
For example, if you probe do_sched_setscheduler(pid, policy,
param) and record param->sched_priority, you can add new
probe as below;
p do_sched_setscheduler priority=+u0($arg3)
Note that kprobe event provides this and it doesn't change the
dereference method automatically because we do not know whether
the given address is in userspace or kernel on some archs.
So as same as "ustring", this is an option for user, who has to
carefully choose the dereference method.
Link: http://lkml.kernel.org/r/155789872187.26965.4468456816590888687.stgit@devnote2
Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace/trace.c')
| -rw-r--r-- | kernel/trace/trace.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index d3a477a16e70..6b3b5b0495a8 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -4842,10 +4842,11 @@ static const char readme_msg[] = "\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" + "\t $stack<index>, $stack, $retval, $comm, $arg<N>,\n" #else - "\t $stack<index>, $stack, $retval, $comm\n" + "\t $stack<index>, $stack, $retval, $comm,\n" #endif + "\t +|-[u]<offset>(<fetcharg>)\n" "\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>, ustring,\n" "\t <type>\\[<array-size>\\]\n" |