If a non-root user tries to specify a trace event and the tracefs files can't be read, it will tell about it in a somewhat cryptic way and as well say that the tracepoint is unknown, which is obvious, since the tracefs files were not read.

Current output:

[acme@zoo linux]$ perf record -e sched:sched_switch* usleep 1
Can't open event dir: Permission denied
event syntax error: 'sched:sched_switch*'
                     \___ unknown tracepoint
Run 'perf list' for a list of valid events

 usage: perf record [<options>] [<command>]
    or: perf record [<options>] -- <command> [<options>]

    -e, --event <event>   event selector. use 'perf list' to list available events
[acme@zoo linux]$

------------

It should instead restrict it to the first line and improve it to provide a hint, like the one provided by the 'perf trace' tool:

[acme@zoo linux]$ trace usleep 1
Error:	No permissions to read /sys/kernel/debug/tracing/events/raw_syscalls/sys_(enter|exit)
Hint:	Try 'sudo mount -o remount,mode=755 /sys/kernel/debug'

[acme@zoo linux]$