Problem with ftrace uprobes on ARM

[Christian Ascheberg]

Thanks, your answer was really helpful. I did not know that Thumb 
instructions were not supported, which solved my initial problem when 
using Perf as well.

Is there any documentation regarding limitations of perf/ftrace support 
on ARM (compared to x86)?

For example, I also noticed that 'perf help' lists 'trace' command, but 
running 'perf trace' says 'is not a perf-command'.