1 files changed, 112 insertions, 0 deletions
diff --git a/libgo/go/runtime/debug/mod.go b/libgo/go/runtime/debug/mod.go
new file mode 100644
index 00000000000..f2948c65cbd
--- /dev/null
+++ b/libgo/go/runtime/debug/mod.go
@@ -0,0 +1,112 @@
+// Copyright 2018 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 debug
+
+import (
+	"strings"
+	_ "unsafe" // for go:linkname
+)
+
+// set using cmd/go/internal/modload.ModInfoProg
+var modinfo string
+
+// setmodinfo is visible to code generated by cmd/go/internal/modload.ModInfoProg.
+//go:linkname setmodinfo runtime..z2fdebug.setmodinfo
+func setmodinfo(s string) {
+	modinfo = s
+}
+
+// ReadBuildInfo returns the build information embedded
+// in the running binary. The information is available only
+// in binaries built with module support.
+func ReadBuildInfo() (info *BuildInfo, ok bool) {
+	return readBuildInfo(modinfo)
+}
+
+// BuildInfo represents the build information read from
+// the running binary.
+type BuildInfo struct {
+	Path string    // The main package path
+	Main Module    // The main module information
+	Deps []*Module // Module dependencies
+}
+
+// Module represents a module.
+type Module struct {
+	Path    string  // module path
+	Version string  // module version
+	Sum     string  // checksum
+	Replace *Module // replaced by this module
+}
+
+func readBuildInfo(data string) (*BuildInfo, bool) {
+	if len(data) < 32 {
+		return nil, false
+	}
+	data = data[16 : len(data)-16]
+
+	const (
+		pathLine = "path\t"
+		modLine  = "mod\t"
+		depLine  = "dep\t"
+		repLine  = "=>\t"
+	)
+
+	info := &BuildInfo{}
+
+	var line string
+	// Reverse of cmd/go/internal/modload.PackageBuildInfo
+	for len(data) > 0 {
+		i := strings.IndexByte(data, '\n')
+		if i < 0 {
+			break
+		}
+		line, data = data[:i], data[i+1:]
+		switch {
+		case strings.HasPrefix(line, pathLine):
+			elem := line[len(pathLine):]
+			info.Path = elem
+		case strings.HasPrefix(line, modLine):
+			elem := strings.Split(line[len(modLine):], "\t")
+			if len(elem) != 3 {
+				return nil, false
+			}
+			info.Main = Module{
+				Path:    elem[0],
+				Version: elem[1],
+				Sum:     elem[2],
+			}
+		case strings.HasPrefix(line, depLine):
+			elem := strings.Split(line[len(depLine):], "\t")
+			if len(elem) != 2 && len(elem) != 3 {
+				return nil, false
+			}
+			sum := ""
+			if len(elem) == 3 {
+				sum = elem[2]
+			}
+			info.Deps = append(info.Deps, &Module{
+				Path:    elem[0],
+				Version: elem[1],
+				Sum:     sum,
+			})
+		case strings.HasPrefix(line, repLine):
+			elem := strings.Split(line[len(repLine):], "\t")
+			if len(elem) != 3 {
+				return nil, false
+			}
+			last := len(info.Deps) - 1
+			if last < 0 {
+				return nil, false
+			}
+			info.Deps[last].Replace = &Module{
+				Path:    elem[0],
+				Version: elem[1],
+				Sum:     elem[2],
+			}
+		}
+	}
+	return info, true
+}