diff --git a/mk2rbc/soong_variables.go b/mk2rbc/soong_variables.go
new file mode 100644
index 0000000..de46925
--- /dev/null
+++ b/mk2rbc/soong_variables.go
@@ -0,0 +1,151 @@
+// Copyright 2021 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package mk2rbc
+
+import (
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"regexp"
+	"strings"
+
+	mkparser "android/soong/androidmk/parser"
+)
+
+type context struct {
+	includeFileScope mkparser.Scope
+	registrar        variableRegistrar
+}
+
+// Scans the makefile Soong uses to generate soong.variables file,
+// collecting variable names and types from the lines that look like this:
+//    $(call add_json_XXX,  <...>,             $(VAR))
+//
+func FindSoongVariables(mkFile string, includeFileScope mkparser.Scope, registrar variableRegistrar) error {
+	ctx := context{includeFileScope, registrar}
+	return ctx.doFind(mkFile)
+}
+
+func (ctx *context) doFind(mkFile string) error {
+	mkContents, err := ioutil.ReadFile(mkFile)
+	if err != nil {
+		return err
+	}
+	parser := mkparser.NewParser(mkFile, bytes.NewBuffer(mkContents))
+	nodes, errs := parser.Parse()
+	if len(errs) > 0 {
+		for _, e := range errs {
+			fmt.Fprintln(os.Stderr, "ERROR:", e)
+		}
+		return fmt.Errorf("cannot parse %s", mkFile)
+	}
+	for _, node := range nodes {
+		switch t := node.(type) {
+		case *mkparser.Variable:
+			ctx.handleVariable(t)
+		case *mkparser.Directive:
+			ctx.handleInclude(t)
+		}
+	}
+	return nil
+}
+
+func (ctx context) NewSoongVariable(name, typeString string) {
+	var valueType starlarkType
+	switch typeString {
+	case "bool":
+		valueType = starlarkTypeBool
+	case "csv":
+		// Only PLATFORM_VERSION_ALL_CODENAMES, and it's a list
+		valueType = starlarkTypeList
+	case "list":
+		valueType = starlarkTypeList
+	case "str":
+		valueType = starlarkTypeString
+	case "val":
+		// Only PLATFORM_SDK_VERSION uses this, and it's integer
+		valueType = starlarkTypeInt
+	default:
+		panic(fmt.Errorf("unknown Soong variable type %s", typeString))
+	}
+
+	ctx.registrar.NewVariable(name, VarClassSoong, valueType)
+}
+
+func (ctx context) handleInclude(t *mkparser.Directive) {
+	if t.Name != "include" && t.Name != "-include" {
+		return
+	}
+	includedPath := t.Args.Value(ctx.includeFileScope)
+	err := ctx.doFind(includedPath)
+	if err != nil && t.Name == "include" {
+		fmt.Fprintf(os.Stderr, "cannot include %s: %s", includedPath, err)
+	}
+}
+
+var callFuncRex = regexp.MustCompile("^call +add_json_(str|val|bool|csv|list) *,")
+
+func (ctx context) handleVariable(t *mkparser.Variable) {
+	// From the variable reference looking as follows:
+	//  $(call json_add_TYPE,arg1,$(VAR))
+	// we infer that the type of $(VAR) is TYPE
+	// VAR can be a simple variable name, or another call
+	// (e.g., $(call invert_bool, $(X)), from which we can infer
+	// that the type of X is bool
+	if prefix, v, ok := prefixedVariable(t.Name); ok && strings.HasPrefix(prefix, "call add_json") {
+		if match := callFuncRex.FindStringSubmatch(prefix); match != nil {
+			ctx.inferSoongVariableType(match[1], v)
+			// NOTE(asmundak): sometimes arg1 (the name of the Soong variable defined
+			// in this statement) may indicate that there is a Make counterpart. E.g, from
+			//     $(call add_json_bool, DisablePreopt, $(call invert_bool,$(ENABLE_PREOPT)))
+			// it may be inferred that there is a Make boolean variable DISABLE_PREOPT.
+			// Unfortunately, Soong variable names have no 1:1 correspondence to Make variables,
+			// for instance,
+			//       $(call add_json_list, PatternsOnSystemOther, $(SYSTEM_OTHER_ODEX_FILTER))
+			// does not mean that there is PATTERNS_ON_SYSTEM_OTHER
+			// Our main interest lies in finding the variables whose values are lists, and
+			// so far there are none that can be found this way, so it is not important.
+		} else {
+			panic(fmt.Errorf("cannot match the call: %s", prefix))
+		}
+	}
+}
+
+var (
+	callInvertBoolRex = regexp.MustCompile("^call +invert_bool *, *$")
+	callFilterBoolRex = regexp.MustCompile("^(filter|filter-out) +(true|false), *$")
+)
+
+func (ctx context) inferSoongVariableType(vType string, n *mkparser.MakeString) {
+	if n.Const() {
+		ctx.NewSoongVariable(n.Strings[0], vType)
+		return
+	}
+	if prefix, v, ok := prefixedVariable(n); ok {
+		if callInvertBoolRex.MatchString(prefix) || callFilterBoolRex.MatchString(prefix) {
+			// It is $(call invert_bool, $(VAR)) or $(filter[-out] [false|true],$(VAR))
+			ctx.inferSoongVariableType("bool", v)
+		}
+	}
+}
+
+// If MakeString is foo$(BAR), returns 'foo', BAR(as *MakeString) and true
+func prefixedVariable(s *mkparser.MakeString) (string, *mkparser.MakeString, bool) {
+	if len(s.Strings) != 2 || s.Strings[1] != "" {
+		return "", nil, false
+	}
+	return s.Strings[0], s.Variables[0].Name, true
+}