On Wed, Feb 21, 2024 at 10:21:04AM -0500, Steven Rostedt wrote: > On Wed, 14 Feb 2024 17:50:44 +0000 > Beau Belgrave <be...@linux.microsoft.com> wrote: > > > Currently user_events supports 1 event with the same name and must have > > the exact same format when referenced by multiple programs. This opens > > an opportunity for malicous or poorly thought through programs to > > create events that others use with different formats. Another scenario > > is user programs wishing to use the same event name but add more fields > > later when the software updates. Various versions of a program may be > > running side-by-side, which is prevented by the current single format > > requirement. > > > > Add a new register flag (USER_EVENT_REG_MULTI_FORMAT) which indicates > > the user program wishes to use the same user_event name, but may have > > several different formats of the event in the future. When this flag is > > "of the event in the future." Does it have to be in the future? Is there > use case where an application might legitimately want the same event name > with different formats? >
You're right, our use cases are mostly around future facing/compat. There are valid cases where you just want several different formats with the same name. I'll drop the "in the future", so it'll just be "several different formats". Thanks, -Beau > -- Steve > > > used, create the underlying tracepoint backing the user_event with a > > unique name per-version of the format. It's important that existing ABI > > users do not get this logic automatically, even if one of the multi > > format events matches the format. This ensures existing programs that > > create events and assume the tracepoint name will match exactly continue > > to work as expected. Add logic to only check multi-format events with > > other multi-format events and single-format events to only check > > single-format events during find. > >