1 files changed, 53 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/base/link.go b/src/cmd/compile/internal/base/link.go
new file mode 100644
index 0000000..d8aa5a7
--- /dev/null
+++ b/src/cmd/compile/internal/base/link.go
@@ -0,0 +1,53 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package base
+
+import (
+	"cmd/internal/obj"
+)
+
+// ReservedImports are import paths used internally for generated
+// symbols by the compiler.
+//
+// The linker uses the magic symbol prefixes "go:" and "type:".
+// Avoid potential confusion between import paths and symbols
+// by rejecting these reserved imports for now. Also, people
+// "can do weird things in GOPATH and we'd prefer they didn't
+// do _that_ weird thing" (per rsc). See also #4257.
+var ReservedImports = map[string]bool{
+	"go":   true,
+	"type": true,
+}
+
+var Ctxt *obj.Link
+
+// TODO(mdempsky): These should probably be obj.Link methods.
+
+// PkgLinksym returns the linker symbol for name within the given
+// package prefix. For user packages, prefix should be the package
+// path encoded with objabi.PathToPrefix.
+func PkgLinksym(prefix, name string, abi obj.ABI) *obj.LSym {
+	if name == "_" {
+		// TODO(mdempsky): Cleanup callers and Fatalf instead.
+		return linksym(prefix, "_", abi)
+	}
+	sep := "."
+	if ReservedImports[prefix] {
+		sep = ":"
+	}
+	return linksym(prefix, prefix+sep+name, abi)
+}
+
+// Linkname returns the linker symbol for the given name as it might
+// appear within a //go:linkname directive.
+func Linkname(name string, abi obj.ABI) *obj.LSym {
+	return linksym("_", name, abi)
+}
+
+// linksym is an internal helper function for implementing the above
+// exported APIs.
+func linksym(pkg, name string, abi obj.ABI) *obj.LSym {
+	return Ctxt.LookupABIInit(name, abi, func(r *obj.LSym) { r.Pkg = pkg })
+}