diff --git a/android/config_bp2build.go b/android/config_bp2build.go
new file mode 100644
index 0000000..80b09fc
--- /dev/null
+++ b/android/config_bp2build.go
@@ -0,0 +1,435 @@
+// Copyright 2021 Google Inc. All rights reserved.
+//
+// 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 android
+
+import (
+	"fmt"
+	"reflect"
+	"regexp"
+	"sort"
+	"strings"
+
+	"android/soong/bazel"
+	"android/soong/starlark_fmt"
+
+	"github.com/google/blueprint"
+)
+
+// BazelVarExporter is a collection of configuration variables that can be exported for use in Bazel rules
+type BazelVarExporter interface {
+	// asBazel expands strings of configuration variables into their concrete values
+	asBazel(Config, ExportedStringVariables, ExportedStringListVariables, ExportedConfigDependingVariables) []bazelConstant
+}
+
+// ExportedVariables is a collection of interdependent configuration variables
+type ExportedVariables struct {
+	// Maps containing toolchain variables that are independent of the
+	// environment variables of the build.
+	exportedStringVars         ExportedStringVariables
+	exportedStringListVars     ExportedStringListVariables
+	exportedStringListDictVars ExportedStringListDictVariables
+
+	exportedVariableReferenceDictVars ExportedVariableReferenceDictVariables
+
+	/// Maps containing variables that are dependent on the build config.
+	exportedConfigDependingVars ExportedConfigDependingVariables
+
+	pctx PackageContext
+}
+
+// NewExportedVariables creats an empty ExportedVariables struct with non-nil maps
+func NewExportedVariables(pctx PackageContext) ExportedVariables {
+	return ExportedVariables{
+		exportedStringVars:                ExportedStringVariables{},
+		exportedStringListVars:            ExportedStringListVariables{},
+		exportedStringListDictVars:        ExportedStringListDictVariables{},
+		exportedVariableReferenceDictVars: ExportedVariableReferenceDictVariables{},
+		exportedConfigDependingVars:       ExportedConfigDependingVariables{},
+		pctx:                              pctx,
+	}
+}
+
+func (ev ExportedVariables) asBazel(config Config,
+	stringVars ExportedStringVariables, stringListVars ExportedStringListVariables, cfgDepVars ExportedConfigDependingVariables) []bazelConstant {
+	ret := []bazelConstant{}
+	ret = append(ret, ev.exportedStringVars.asBazel(config, stringVars, stringListVars, cfgDepVars)...)
+	ret = append(ret, ev.exportedStringListVars.asBazel(config, stringVars, stringListVars, cfgDepVars)...)
+	ret = append(ret, ev.exportedStringListDictVars.asBazel(config, stringVars, stringListVars, cfgDepVars)...)
+	// Note: ExportedVariableReferenceDictVars collections can only contain references to other variables and must be printed last
+	ret = append(ret, ev.exportedVariableReferenceDictVars.asBazel(config, stringVars, stringListVars, cfgDepVars)...)
+	return ret
+}
+
+// ExportStringStaticVariable declares a static string variable and exports it to
+// Bazel's toolchain.
+func (ev ExportedVariables) ExportStringStaticVariable(name string, value string) {
+	ev.pctx.StaticVariable(name, value)
+	ev.exportedStringVars.set(name, value)
+}
+
+// ExportStringListStaticVariable declares a static variable and exports it to
+// Bazel's toolchain.
+func (ev ExportedVariables) ExportStringListStaticVariable(name string, value []string) {
+	ev.pctx.StaticVariable(name, strings.Join(value, " "))
+	ev.exportedStringListVars.set(name, value)
+}
+
+// ExportVariableConfigMethod declares a variable whose value is evaluated at
+// runtime via a function with access to the Config and exports it to Bazel's
+// toolchain.
+func (ev ExportedVariables) ExportVariableConfigMethod(name string, method interface{}) blueprint.Variable {
+	ev.exportedConfigDependingVars.set(name, method)
+	return ev.pctx.VariableConfigMethod(name, method)
+}
+
+// ExportSourcePathVariable declares a static "source path" variable and exports
+// it to Bazel's toolchain.
+func (ev ExportedVariables) ExportSourcePathVariable(name string, value string) {
+	ev.pctx.SourcePathVariable(name, value)
+	ev.exportedStringVars.set(name, value)
+}
+
+// ExportString only exports a variable to Bazel, but does not declare it in Soong
+func (ev ExportedVariables) ExportString(name string, value string) {
+	ev.exportedStringVars.set(name, value)
+}
+
+// ExportStringList only exports a variable to Bazel, but does not declare it in Soong
+func (ev ExportedVariables) ExportStringList(name string, value []string) {
+	ev.exportedStringListVars.set(name, value)
+}
+
+// ExportStringListDict only exports a variable to Bazel, but does not declare it in Soong
+func (ev ExportedVariables) ExportStringListDict(name string, value map[string][]string) {
+	ev.exportedStringListDictVars.set(name, value)
+}
+
+// ExportVariableReferenceDict only exports a variable to Bazel, but does not declare it in Soong
+func (ev ExportedVariables) ExportVariableReferenceDict(name string, value map[string]string) {
+	ev.exportedVariableReferenceDictVars.set(name, value)
+}
+
+// ExportedConfigDependingVariables is a mapping of variable names to functions
+// of type func(config Config) string which return the runtime-evaluated string
+// value of a particular variable
+type ExportedConfigDependingVariables map[string]interface{}
+
+func (m ExportedConfigDependingVariables) set(k string, v interface{}) {
+	m[k] = v
+}
+
+// Ensure that string s has no invalid characters to be generated into the bzl file.
+func validateCharacters(s string) string {
+	for _, c := range []string{`\n`, `"`, `\`} {
+		if strings.Contains(s, c) {
+			panic(fmt.Errorf("%s contains illegal character %s", s, c))
+		}
+	}
+	return s
+}
+
+type bazelConstant struct {
+	variableName       string
+	internalDefinition string
+	sortLast           bool
+}
+
+// ExportedStringVariables is a mapping of variable names to string values
+type ExportedStringVariables map[string]string
+
+func (m ExportedStringVariables) set(k string, v string) {
+	m[k] = v
+}
+
+func (m ExportedStringVariables) asBazel(config Config,
+	stringVars ExportedStringVariables, stringListVars ExportedStringListVariables, cfgDepVars ExportedConfigDependingVariables) []bazelConstant {
+	ret := make([]bazelConstant, 0, len(m))
+	for k, variableValue := range m {
+		expandedVar, err := expandVar(config, variableValue, stringVars, stringListVars, cfgDepVars)
+		if err != nil {
+			panic(fmt.Errorf("error expanding config variable %s: %s", k, err))
+		}
+		if len(expandedVar) > 1 {
+			panic(fmt.Errorf("%s expands to more than one string value: %s", variableValue, expandedVar))
+		}
+		ret = append(ret, bazelConstant{
+			variableName:       k,
+			internalDefinition: fmt.Sprintf(`"%s"`, validateCharacters(expandedVar[0])),
+		})
+	}
+	return ret
+}
+
+// ExportedStringListVariables is a mapping of variable names to a list of strings
+type ExportedStringListVariables map[string][]string
+
+func (m ExportedStringListVariables) set(k string, v []string) {
+	m[k] = v
+}
+
+func (m ExportedStringListVariables) asBazel(config Config,
+	stringScope ExportedStringVariables, stringListScope ExportedStringListVariables,
+	exportedVars ExportedConfigDependingVariables) []bazelConstant {
+	ret := make([]bazelConstant, 0, len(m))
+	// For each exported variable, recursively expand elements in the variableValue
+	// list to ensure that interpolated variables are expanded according to their values
+	// in the variable scope.
+	for k, variableValue := range m {
+		var expandedVars []string
+		for _, v := range variableValue {
+			expandedVar, err := expandVar(config, v, stringScope, stringListScope, exportedVars)
+			if err != nil {
+				panic(fmt.Errorf("Error expanding config variable %s=%s: %s", k, v, err))
+			}
+			expandedVars = append(expandedVars, expandedVar...)
+		}
+		// Assign the list as a bzl-private variable; this variable will be exported
+		// out through a constants struct later.
+		ret = append(ret, bazelConstant{
+			variableName:       k,
+			internalDefinition: starlark_fmt.PrintStringList(expandedVars, 0),
+		})
+	}
+	return ret
+}
+
+// ExportedStringListDictVariables is a mapping from variable names to a
+// dictionary which maps keys to lists of strings
+type ExportedStringListDictVariables map[string]map[string][]string
+
+func (m ExportedStringListDictVariables) set(k string, v map[string][]string) {
+	m[k] = v
+}
+
+// Since dictionaries are not supported in Ninja, we do not expand variables for dictionaries
+func (m ExportedStringListDictVariables) asBazel(_ Config, _ ExportedStringVariables,
+	_ ExportedStringListVariables, _ ExportedConfigDependingVariables) []bazelConstant {
+	ret := make([]bazelConstant, 0, len(m))
+	for k, dict := range m {
+		ret = append(ret, bazelConstant{
+			variableName:       k,
+			internalDefinition: starlark_fmt.PrintStringListDict(dict, 0),
+		})
+	}
+	return ret
+}
+
+// ExportedVariableReferenceDictVariables is a mapping from variable names to a
+// dictionary which references previously defined variables. This is used to
+// create a Starlark output such as:
+// 		string_var1 = "string1
+// 		var_ref_dict_var1 = {
+// 			"key1": string_var1
+// 		}
+// This type of variable collection must be expanded last so that it recognizes
+// previously defined variables.
+type ExportedVariableReferenceDictVariables map[string]map[string]string
+
+func (m ExportedVariableReferenceDictVariables) set(k string, v map[string]string) {
+	m[k] = v
+}
+
+func (m ExportedVariableReferenceDictVariables) asBazel(_ Config, _ ExportedStringVariables,
+	_ ExportedStringListVariables, _ ExportedConfigDependingVariables) []bazelConstant {
+	ret := make([]bazelConstant, 0, len(m))
+	for n, dict := range m {
+		for k, v := range dict {
+			matches, err := variableReference(v)
+			if err != nil {
+				panic(err)
+			} else if !matches.matches {
+				panic(fmt.Errorf("Expected a variable reference, got %q", v))
+			} else if len(matches.fullVariableReference) != len(v) {
+				panic(fmt.Errorf("Expected only a variable reference, got %q", v))
+			}
+			dict[k] = "_" + matches.variable
+		}
+		ret = append(ret, bazelConstant{
+			variableName:       n,
+			internalDefinition: starlark_fmt.PrintDict(dict, 0),
+			sortLast:           true,
+		})
+	}
+	return ret
+}
+
+// BazelToolchainVars expands an ExportedVariables collection and returns a string
+// of formatted Starlark variable definitions
+func BazelToolchainVars(config Config, exportedVars ExportedVariables) string {
+	results := exportedVars.asBazel(
+		config,
+		exportedVars.exportedStringVars,
+		exportedVars.exportedStringListVars,
+		exportedVars.exportedConfigDependingVars,
+	)
+
+	sort.Slice(results, func(i, j int) bool {
+		if results[i].sortLast != results[j].sortLast {
+			return !results[i].sortLast
+		}
+		return results[i].variableName < results[j].variableName
+	})
+
+	definitions := make([]string, 0, len(results))
+	constants := make([]string, 0, len(results))
+	for _, b := range results {
+		definitions = append(definitions,
+			fmt.Sprintf("_%s = %s", b.variableName, b.internalDefinition))
+		constants = append(constants,
+			fmt.Sprintf("%[1]s%[2]s = _%[2]s,", starlark_fmt.Indention(1), b.variableName))
+	}
+
+	// Build the exported constants struct.
+	ret := bazel.GeneratedBazelFileWarning
+	ret += "\n\n"
+	ret += strings.Join(definitions, "\n\n")
+	ret += "\n\n"
+	ret += "constants = struct(\n"
+	ret += strings.Join(constants, "\n")
+	ret += "\n)"
+
+	return ret
+}
+
+type match struct {
+	matches               bool
+	fullVariableReference string
+	variable              string
+}
+
+func variableReference(input string) (match, error) {
+	// e.g. "${ExternalCflags}"
+	r := regexp.MustCompile(`\${(?:config\.)?([a-zA-Z0-9_]+)}`)
+
+	matches := r.FindStringSubmatch(input)
+	if len(matches) == 0 {
+		return match{}, nil
+	}
+	if len(matches) != 2 {
+		return match{}, fmt.Errorf("Expected to only match 1 subexpression in %s, got %d", input, len(matches)-1)
+	}
+	return match{
+		matches:               true,
+		fullVariableReference: matches[0],
+		// Index 1 of FindStringSubmatch contains the subexpression match
+		// (variable name) of the capture group.
+		variable: matches[1],
+	}, nil
+}
+
+// expandVar recursively expand interpolated variables in the exportedVars scope.
+//
+// We're using a string slice to track the seen variables to avoid
+// stackoverflow errors with infinite recursion. it's simpler to use a
+// string slice than to handle a pass-by-referenced map, which would make it
+// quite complex to track depth-first interpolations. It's also unlikely the
+// interpolation stacks are deep (n > 1).
+func expandVar(config Config, toExpand string, stringScope ExportedStringVariables,
+	stringListScope ExportedStringListVariables, exportedVars ExportedConfigDependingVariables) ([]string, error) {
+
+	// Internal recursive function.
+	var expandVarInternal func(string, map[string]bool) (string, error)
+	expandVarInternal = func(toExpand string, seenVars map[string]bool) (string, error) {
+		var ret string
+		remainingString := toExpand
+		for len(remainingString) > 0 {
+			matches, err := variableReference(remainingString)
+			if err != nil {
+				panic(err)
+			}
+			if !matches.matches {
+				return ret + remainingString, nil
+			}
+			matchIndex := strings.Index(remainingString, matches.fullVariableReference)
+			ret += remainingString[:matchIndex]
+			remainingString = remainingString[matchIndex+len(matches.fullVariableReference):]
+
+			variable := matches.variable
+			// toExpand contains a variable.
+			if _, ok := seenVars[variable]; ok {
+				return ret, fmt.Errorf(
+					"Unbounded recursive interpolation of variable: %s", variable)
+			}
+			// A map is passed-by-reference. Create a new map for
+			// this scope to prevent variables seen in one depth-first expansion
+			// to be also treated as "seen" in other depth-first traversals.
+			newSeenVars := map[string]bool{}
+			for k := range seenVars {
+				newSeenVars[k] = true
+			}
+			newSeenVars[variable] = true
+			if unexpandedVars, ok := stringListScope[variable]; ok {
+				expandedVars := []string{}
+				for _, unexpandedVar := range unexpandedVars {
+					expandedVar, err := expandVarInternal(unexpandedVar, newSeenVars)
+					if err != nil {
+						return ret, err
+					}
+					expandedVars = append(expandedVars, expandedVar)
+				}
+				ret += strings.Join(expandedVars, " ")
+			} else if unexpandedVar, ok := stringScope[variable]; ok {
+				expandedVar, err := expandVarInternal(unexpandedVar, newSeenVars)
+				if err != nil {
+					return ret, err
+				}
+				ret += expandedVar
+			} else if unevaluatedVar, ok := exportedVars[variable]; ok {
+				evalFunc := reflect.ValueOf(unevaluatedVar)
+				validateVariableMethod(variable, evalFunc)
+				evaluatedResult := evalFunc.Call([]reflect.Value{reflect.ValueOf(config)})
+				evaluatedValue := evaluatedResult[0].Interface().(string)
+				expandedVar, err := expandVarInternal(evaluatedValue, newSeenVars)
+				if err != nil {
+					return ret, err
+				}
+				ret += expandedVar
+			} else {
+				return "", fmt.Errorf("Unbound config variable %s", variable)
+			}
+		}
+		return ret, nil
+	}
+	var ret []string
+	for _, v := range strings.Split(toExpand, " ") {
+		val, err := expandVarInternal(v, map[string]bool{})
+		if err != nil {
+			return ret, err
+		}
+		ret = append(ret, val)
+	}
+
+	return ret, nil
+}
+
+func validateVariableMethod(name string, methodValue reflect.Value) {
+	methodType := methodValue.Type()
+	if methodType.Kind() != reflect.Func {
+		panic(fmt.Errorf("method given for variable %s is not a function",
+			name))
+	}
+	if n := methodType.NumIn(); n != 1 {
+		panic(fmt.Errorf("method for variable %s has %d inputs (should be 1)",
+			name, n))
+	}
+	if n := methodType.NumOut(); n != 1 {
+		panic(fmt.Errorf("method for variable %s has %d outputs (should be 1)",
+			name, n))
+	}
+	if kind := methodType.Out(0).Kind(); kind != reflect.String {
+		panic(fmt.Errorf("method for variable %s does not return a string",
+			name))
+	}
+}