variable: copy VariableSpec.Type during initial assignment and during copy

elf_reader.go

@@ -1233,7 +1233,9 @@ func (ec *elfCode) loadDataSections() error {
 						return fmt.Errorf("data section %s: variable %s size in datasec (%d) doesn't match ELF symbol size (%d)", sec.Name, name, v.Size, ev.size)
 					}
 
-					ev.t = vt
+					// Decouple the Var in the VariableSpec from the underlying DataSec in
+					// the MapSpec to avoid modifications from affecting map loads later on.
+					ev.t = btf.Copy(vt).(*btf.Var)
 				}
 			}
 		}

variable.go

@@ -112,7 +112,9 @@ func (s *VariableSpec) copy(cpy *CollectionSpec) *VariableSpec {
 		name:   s.name,
 		offset: s.offset,
 		size:   s.size,
-		t:      s.t,
+	}
+	if s.t != nil {
+		out.t = btf.Copy(s.t).(*btf.Var)
 	}
 
 	// Attempt to find a MapSpec with the same name in the copied CollectionSpec.

variable_test.go

@@ -62,6 +62,14 @@ func TestVariableSpecCopy(t *testing.T) {
 	// Verify that the original underlying MapSpec was not modified.
 	zero := make([]byte, 4)
 	qt.Assert(t, qt.DeepEquals(spec.Maps[".rodata"].Contents[0].Value.([]byte), zero))
+
+	// Check that modifications to the VariableSpec's Type don't affect the
+	// underlying MapSpec's type information on either the original or the copy.
+	cpy.Variables["var_rodata"].Type().Name = "modified"
+	spec.Variables["var_rodata"].Type().Name = "modified"
+
+	qt.Assert(t, qt.Equals(cpy.Maps[".rodata"].Value.(*btf.Datasec).Vars[0].Type.(*btf.Var).Name, "var_rodata"))
+	qt.Assert(t, qt.Equals(spec.Maps[".rodata"].Value.(*btf.Datasec).Vars[0].Type.(*btf.Var).Name, "var_rodata"))
 }
 
 func mustReturn(tb testing.TB, prog *Program, value uint32) {