feat(parquet): surface epoll_ctl op/target-fd/events metadata

epoll_ctl's BPF handler already decodes the operation (args[1]),
target descriptor (args[2]), and requested event mask (args[3]->events)
into an EpollCtlEvent, but the single resolved-epfd `fd` column was the
only epoll detail reaching the output schema. Consumers could not see
which descriptor was registered nor the operation performed.

Surface the metadata as three additive, backward-compatible columns,
mirroring the existing dedicated optional-column convention used by
requested_sleep_ns and address_space_bytes:

- epoll_op (String): ADD/MOD/DEL, or the raw decimal for unknown ops;
  empty for non-epoll_ctl rows.
- epoll_target_fd (Int32): registered descriptor (args[2]); 0 otherwise.
- epoll_events (UInt32): requested event mask; 0 otherwise.

Data flows EpollCtlEvent -> event.Pair (new EpollCtl/HasEpoll fields,
populated in handleEpollCtlExit) -> streamrow.Row -> parquet.Record.
The op-to-string mapping lives on event.EpollCtl.OpName.

Docs (docs/parquet-querying.md) and the Magefile parquetValidate column
list updated in lockstep (also adding the previously-undocumented
address_space_bytes/requested_sleep_ns columns). The polling parquet
integration test now asserts epoll_ctl rows carry a decoded op and a
valid target fd, and that other syscalls leave epoll_op empty.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/internal/eventloop_exit.go b/internal/eventloop_exit.go
index ae085c6..105d9ac 100644
--- a/internal/eventloop_exit.go
+++ b/internal/eventloop_exit.go
@@ -385,7 +385,16 @@ func (e *eventLoop) handleEventfdExit(ep *event.Pair, eventfdEv *types.EventfdEv
 }
 
 func (e *eventLoop) handleEpollCtlExit(ep *event.Pair, epollCtlEv *types.EpollCtlEvent) bool {
+	// File resolves to the epoll instance (epfd); the decoded op/target-fd/events
+	// are surfaced separately via ep.Epoll so consumers can see which descriptor
+	// was registered and the operation performed.
 	ep.File = e.fdState().resolve(epollCtlEv.Epfd, epollCtlEv.Pid)
+	ep.Epoll = event.EpollCtl{
+		Op:       epollCtlEv.Op,
+		TargetFD: epollCtlEv.Fd,
+		Events:   epollCtlEv.Events,
+	}
+	ep.HasEpoll = true
 	return e.finishPairForTid(ep, epollCtlEv.GetTid())
 }