Add support to pin kprobe perf link

As suggested by Lorenz removing perfEventLink Pin/UnPin so the RawLink Pin/Unpi methods take over and implement pinning for perf link kprobes. Signed-off-by: Jiri Olsa <[email protected]>
cilium · Jun 26, 2024 · c37accb · c37accb
1 parent 3abc993
commit c37accb
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Showing 2 changed files with 11 additions and 20 deletions.
diff --git a/link/link.go b/link/link.go
@@ -119,7 +119,7 @@ func wrapRawLink(raw *RawLink) (_ Link, err error) {
 	case UprobeMultiType:
 		return &uprobeMultiLink{*raw}, nil
 	case PerfEventType:
-		return nil, fmt.Errorf("recovering perf event fd: %w", ErrNotSupported)
+		return &perfEventLink{*raw, nil}, nil
 	case TCXType:
 		return &tcxLink{*raw}, nil
 	case NetfilterType:

diff --git a/link/perf_event.go b/link/perf_event.go
@@ -99,30 +99,16 @@ type perfEventLink struct {
 
 func (pl *perfEventLink) isLink() {}
 
-// Pinning requires the underlying perf event FD to stay open.
-//
-// | PerfEvent FD | BpfLink FD | Works |
-// |--------------|------------|-------|
-// | Open         | Open       | Yes   |
-// | Closed       | Open       | No    |
-// | Open         | Closed     | No (Pin() -> EINVAL) |
-// | Closed       | Closed     | No (Pin() -> EINVAL) |
-//
-// There is currently no pretty way to recover the perf event FD
-// when loading a pinned link, so leave as not supported for now.
-func (pl *perfEventLink) Pin(string) error {
-	return fmt.Errorf("perf event link pin: %w", ErrNotSupported)
-}
-
-func (pl *perfEventLink) Unpin() error {
-	return fmt.Errorf("perf event link unpin: %w", ErrNotSupported)
-}
-
 func (pl *perfEventLink) Close() error {
 	if err := pl.fd.Close(); err != nil {
 		return fmt.Errorf("perf link close: %w", err)
 	}
 
+	// when created from pinned link
+	if pl.pe == nil {
+		return nil
+	}
+
 	if err := pl.pe.Close(); err != nil {
 		return fmt.Errorf("perf event close: %w", err)
 	}
@@ -136,6 +122,11 @@ func (pl *perfEventLink) Update(prog *ebpf.Program) error {
 var _ PerfEvent = (*perfEventLink)(nil)
 
 func (pl *perfEventLink) PerfEvent() (*os.File, error) {
+	// when created from pinned link
+	if pl.pe == nil {
+		return nil, ErrNotSupported
+	}
+
 	fd, err := pl.pe.fd.Dup()
 	if err != nil {
 		return nil, err