Bug 100781
| Summary: | Avoid confusing messages when not able to read trace events files | ||
|---|---|---|---|
| Product: | Tracing/Profiling | Reporter: | Arnaldo Carvalho de Melo (acme) |
| Component: | Perf tool | Assignee: | Arnaldo Carvalho de Melo (acme) |
| Status: | RESOLVED PATCH_ALREADY_AVAILABLE | ||
| Severity: | low | CC: | check0918, irogers |
| Priority: | P1 | ||
| Hardware: | All | ||
| OS: | Linux | ||
| Kernel Version: | All | Subsystem: | |
| Regression: | No | Bisected commit-id: | |
This was fixed by acme in 4.4 :-) https://lore.kernel.org/lkml/1442330917-21464-1-git-send-email-acme@kernel.org/ |
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]$