[DTrace-devel] [PATCH] Allow arbitrary tracefs mount points

[Eugene Loh]

The whole thing with dtp->dt_tracefs_file is...  interesting. We store a 
temporary string in dtp-> just (if I understand correctly) to simplify 
its free.  It's kind of a cool trick but also kind of ugly.  We'll see 
what Kris says.

In dt_prov_dtrace.c attach():

*)  We should convert "len=snprintf(NULL, 0, ...); snprintf(fn, len, 
...)" into asprintf() for the format file name.  I realize that in some 
sense that is "beyond the scope of this patch," but it seems like we've 
used a couple of patches recently an an opportunity to fix this sort of 
thing.

*)  Using the variable uprobe_events first for "uprobe_events" and later 
for "events" seems confusing.  At the very least, how about naming 
uprobe_events to be something more generic.

Those two comments also apply to dt_prov_fbt.c kprobe_attach().

And...

On 11/6/24 11:46, Nick Alcock wrote:
> So as of kernel 6.3 (upstream commit 2455f0e124d317dd08d337a75), the
> canonical tracefs location has moved to /sys/kernel/tracing.  Unfortunately
> this requires an explicit mount, and a great many installations have not
> done this and perhaps never will.  So if the debugfs is mounted on
> /sys/kernel/debug, it automatically makes /sys/kernel/debug/tracing appear
> as it used to, as another tracefs mount. And of course there's nothing
> special about the "canonical location": it's up to the admin, who might
> choose to remount the thing anywhere at all.

Anywhere at all?  But the scripts in test/ only look in two places.

Speaking of which, could runtest.sh look for TRACEFS and then make that 
available to any test script that needs it?