On Mon, 4 Jan 2016, Philip Mucci wrote:
> Greetings and Happy New Year Stephane,
> Ok, thanks to your tips, and digging through Vince’s perf_event_tests codes,
> I tracked down this bug - it’s the exclude_guest = 1 flag. The systems I’m
> running on are paranoid level 2. Here’s the GDB log… What’s the right way to
> fix this? I have a patched library working for me, but it’s not generalized.
> Let me know and I’ll send you a patch.
This is the perf_event "ABI compatability" stuff that causes lots of
trouble if you want to use more recent features (such as exclude_guest).
There's really no good way to find out what version of the ABI the kernel
expects. They have the size field to detect extra additions to the end of
the attr (but that has issues due to a buggy implementation) but there's
really no way at all to detect how big the kernel expects the big "union"
in the middle to be (where the exclude_guest flags are).
PAPI ran into this a while ago and I think the "solution" was to always
force exclude_guest off.
Vince
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