btf: make stringTable.LookupCached concurrency safe

stringTable has to be safe for concurrent use since it is shared
between multiple decoders. Document this and add a lock to LookupCached
to make it safe.

Signed-off-by: Lorenz Bauer <[email protected]>

Author: lmb

btf/strings.go

@@ -7,12 +7,17 @@ import (
 	"io"
 	"maps"
 	"strings"
+	"sync"
 )
 
+// stringTable is contains a sequence of null-terminated strings.
+//
+// It is safe for concurrent use.
 type stringTable struct {
 	base  *stringTable
 	bytes []byte
 
+	mu    sync.Mutex
 	cache map[uint32]string
 }
 
@@ -98,6 +103,9 @@ func (cst *stringTable) LookupCached(offset uint32) (string, error) {
 		return "", nil
 	}
 
+	cst.mu.Lock()
+	defer cst.mu.Unlock()
+
 	if str, ok := cst.cache[offset]; ok {
 		return str, nil
 	}