Add user memory access attribute for kprobe event arguments.
If a given 'local variable' is in user-space, User can
specify memory access method by '@user' suffix. This is
not only for string but also for data structure.
If we access a field of data structure in user memory from
kernel on some arch, it will fail. e.g.
perf probe -a "sched_setscheduler param->sched_priority"
This will fail to access the "param->sched_priority" because
the param is __user pointer. Instead, we can now specify
@user suffix for such argument.
perf probe -a "sched_setscheduler param->sched_priority@user"
Note that kernel memory access with "@user" must always fail
on any arch.
Link: http://lkml.kernel.org/r/155789874562.26965.10836126971405890891.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>
1e032f7cfa