[RFD] perf syscall error handling

[Peter Zijlstra <peterz@infradead.org>]

Hi,

Earlier today I was reminded that perf syscall error handling sucks arse
-- albeit not in those words.

Now I know we've had this discussion before, but nothing really
happened. I think back then the suggestion was having the kernel write a
string back or somesuch.

The problem with a string is, its hard for machines to interpret, its
English, so near impossible for some humans too.

So would something simple, like an offset into the struct
perf_event_attr pointing at the current field we're trying to process
make sense? Maybe with negative offsets to indicate the syscall
arguments?

That would narrow down the 'WTF is wrong noaw' a lot I think. But then,
I've not actually done a lot of userspace the last few years, so maybe
I'm just dreaming things.

Anybody?