diff --git a/core/build_id.rbc b/core/build_id.rbc
new file mode 100644
index 0000000000..4f33833575
--- /dev/null
+++ b/core/build_id.rbc
@@ -0,0 +1,21 @@
+
+# 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
+#
+#      https://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.
+
+# This file has been manually converted from build_id.mk
+def init(g):
+
+    # BUILD_ID is usually used to specify the branch name (like "MAIN") or a branch name and a release candidate
+    # (like "CRB01").  It must be a single word, and is capitalized by convention.
+    g["BUILD_ID"]="AOSP.MASTER"
\ No newline at end of file
diff --git a/core/envsetup.rbc b/core/envsetup.rbc
new file mode 100644
index 0000000000..2924ee1525
--- /dev/null
+++ b/core/envsetup.rbc
@@ -0,0 +1,199 @@
+
+# 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
+#
+#      https://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.
+
+load(":build_id.rbc|init", _build_id_init="init")
+
+def _all_versions():
+    """Returns all known versions."""
+    versions = ["OPR1", "OPD1", "OPD2","OPM1", "OPM2", "PPR1", "PPD1", "PPD2", "PPM1",  "PPM2", "QPR1" ]
+    for v in ("Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"):
+        for e in ("P1A", "P1B", "P2A", "P2B", "D1A", "D1B", "D2A", "D2B", "Q1A", "Q1B", "Q2A", "Q2B", "Q3A",  "Q3B"):
+            versions.append(v+e)
+    return versions
+
+def _allowed_versions(all_versions, min_version, max_version, default_version):
+    """Checks that version range and default versions is valid, returns all versions in range."""
+    for v in (min_version, max_version, default_version):
+        if v not in all_versions:
+            fail("% is invalid" % v)
+
+    min_i = all_versions.index(min_version)
+    max_i = all_versions.index(max_version)
+    def_i = all_versions.index(default_version)
+    if min_i > max_i:
+        fail("%s should come before %s in the version list" % (min_version, max_version))
+    if def_i < min_i or def_i > max_i:
+        fail("%s should come between % and %s" % (default_version, min_version, max_version))
+    return all_versions[min_i:max_i+1]
+
+# This function is a manual conversion of the version_defaults.mk
+def _versions_default(g, all_versions):
+    """Handle various build version information.
+
+    Guarantees that the following are defined:
+     PLATFORM_VERSION
+     PLATFORM_SDK_VERSION
+     PLATFORM_VERSION_CODENAME
+     DEFAULT_APP_TARGET_SDK
+     BUILD_ID
+     BUILD_NUMBER
+     PLATFORM_SECURITY_PATCH
+     PLATFORM_VNDK_VERSION
+     PLATFORM_SYSTEMSDK_VERSIONS
+    """
+
+    # If build_id.rbc exists, it may override some of the defaults.
+    # Note that build.prop target also wants INTERNAL_BUILD_ID_MAKEFILE to be set if the file exists.
+    if _build_id_init != None:
+        _build_id_init(g)
+        g["INTERNAL_BUILD_ID_MAKEFILE"] = "build/make/core/build_id"
+
+    allowed_versions = _allowed_versions(all_versions, v_min, v_max, v_default)
+    g.setdefault("TARGET_PLATFORM_VERSION", v_default)
+    if g["TARGET_PLATFORM_VERSION"] not in allowed_versions:
+        fail("% is not valid, must be one of %s" % (g["TARGET_PLATFORM_VERSION"], allowed_versions))
+
+    g["DEFAULT_PLATFORM_VERSION"] = v_default
+    g["PLATFORM_VERSION_LAST_STABLE"] = 11
+    g.setdefault("PLATFORM_VERSION_CODENAME", g["TARGET_PLATFORM_VERSION"])
+    # TODO(asmundak): set PLATFORM_VERSION_ALL_CODENAMES
+
+    g.setdefault("PLATFORM_VERSION",
+        g["PLATFORM_VERSION_LAST_STABLE"] if g["PLATFORM_VERSION_CODENAME"] == "REL" else g["PLATFORM_VERSION_CODENAME"])
+    g.setdefault("PLATFORM_SDK_VERSION", 30)
+    if g["PLATFORM_VERSION_CODENAME"] == "REL":
+        g["PLATFORM_PREVIEW_SDK_VERSION"] = 0
+    else:
+        g.setdefault("PLATFORM_PREVIEW_SDK_VERSION", 1)
+
+    g.setdefault("DEFAULT_APP_TARGET_SDK",
+        g["PLATFORM_SDK_VERSION"] if g["PLATFORM_VERSION_CODENAME"] == "REL" else g["PLATFORM_VERSION_CODENAME"])
+    g.setdefault("PLATFORM_VNDK_VERSION",
+        g["PLATFORM_SDK_VERSION"] if g["PLATFORM_VERSION_CODENAME"] == "REL" else g["PLATFORM_VERSION_CODENAME"])
+    g.setdefault("PLATFORM_SYSTEMSDK_MIN_VERSION", 28)
+    versions = [str(i) for i in range(g["PLATFORM_SYSTEMSDK_MIN_VERSION"], g["PLATFORM_SDK_VERSION"] + 1)]
+    versions.append(g["PLATFORM_VERSION_CODENAME"])
+    g["PLATFORM_SYSTEMSDK_VERSIONS"] = sorted(versions)
+
+    #  Used to indicate the security patch that has been applied to the device.
+    #  It must signify that the build includes all security patches issued up through the designated Android Public Security Bulletin.
+    #  It must be of the form "YYYY-MM-DD" on production devices.
+    #  It must match one of the Android Security Patch Level strings of the Public Security Bulletins.
+    #  If there is no $PLATFORM_SECURITY_PATCH set, keep it empty.
+    g.setdefault("PLATFORM_SECURITY_PATCH", "2021-03-05")
+    dt = 'TZ="GMT" %s' % g["PLATFORM_SECURITY_PATCH"]
+    g.setdefault("PLATFORM_SECURITY_PATCH_TIMESTAMP", rblf_shell("date -d '%s' +%%s" % dt))
+
+    # Used to indicate the base os applied to the device. Can be an arbitrary string, but must be a single word.
+    # If there is no $PLATFORM_BASE_OS set, keep it empty.
+    g.setdefault("PLATFORM_BASE_OS", "")
+
+    # Used to signify special builds.  E.g., branches and/or releases, like "M5-RC7".  Can be an arbitrary string, but
+    # must be a single word and a valid file name. If there is no BUILD_ID set, make it obvious.
+    g.setdefault("BUILD_ID", "UNKNOWN")
+
+    # BUILD_NUMBER should be set to the source control value that represents the current state of the source code.
+    # E.g., a perforce changelist number or a git hash.  Can be an arbitrary string (to allow for source control that
+    # uses something other than numbers), but must be a single word and a valid file name.
+    #
+    # If no BUILD_NUMBER is set, create a useful "I am an engineering build from this date/time" value.  Make it start
+    # with a non-digit so that anyone trying to parse it as an integer will probably get "0".
+    g.setdefault("BUILD_NUMBER", "eng.%s.%s" % (g["USER"], "TIMESTAMP"))
+
+    # Used to set minimum supported target sdk version. Apps targeting SDK version lower than the set value will result
+    # in a warning being shown when any activity from the app is started.
+    g.setdefault("PLATFORM_MIN_SUPPORTED_TARGET_SDK_VERSION", 23)
+
+def init(g):
+    all_versions = _all_versions()
+    _versions_default(g, all_versions)
+    for v in all_versions:
+        g["IS_AT_LEAST" + v] = True
+        if v == g["TARGET_PLATFORM_VERSION"]:
+            break
+
+    # ---------------------------------------------------------------
+    # If you update the build system such that the environment setup or buildspec.mk need to be updated,
+    # increment this number, and people who haven't re-run those will have to do so before they can build.
+    # Make sure to also update the corresponding value in buildspec.mk.default and envsetup.sh.
+    g["CORRECT_BUILD_ENV_SEQUENCE_NUMBER"] = 13
+
+    g.setdefault("TARGET_PRODUCT", "aosp_arm")
+    g.setdefault("TARGET_BUILD_VARIANT", "eng")
+
+    g.setdefault("TARGET_BUILD_APPS", [])
+    g["TARGET_BUILD_UNBUNDLED"] = (g["TARGET_BUILD_APPS"] != []) or (getattr(g, "TARGET_BUILD_UNBUNDLED_IMAGE", "") != "")
+
+    # ---------------------------------------------------------------
+    # Set up configuration for host machine.  We don't do cross-compiles except for arm, so the HOST
+    # is whatever we are running on.
+    host = rblf_shell("uname -sm")
+    if host.find("Linux") >= 0:
+        g["HOST_OS"] = "linux"
+    elif host.find("Darwin") >= 0:
+        g["HOST_OS"] = "darwin"
+    else:
+        fail("Cannot run on %s OS" % host)
+
+    # TODO(asmundak): set g.HOST_OS_EXTRA
+
+    g["BUILD_OS"] = g["HOST_OS"]
+
+    # TODO(asmundak): check cross-OS build
+
+    if host.find("x86_64") >= 0:
+        g["HOST_ARCH"] = "x86_64"
+        g["HOST_2ND_ARCH"] = "x86"
+        g["HOST_IS_64_BIT"] = True
+    elif host.find("i686") >= 0 or host.find("x86") >= 0:
+        fail("Building on a 32-bit x86 host is not supported: %s" % host)
+    elif g["HOST_OS"] == "darwin":
+        g["HOST_2ND_ARCH"] = ""
+
+    g["HOST_2ND_ARCH_VAR_PREFIX"] = "2ND_"
+    g["HOST_2ND_ARCH_MODULE_SUFFIX"] = "_32"
+    g["HOST_CROSS_2ND_ARCH_VAR_PREFIX"] = "2ND_"
+    g["HOST_CROSS_2ND_ARCH_MODULE_SUFFIX"] = "_64"
+    g["TARGET_2ND_ARCH_VAR_PREFIX"] = "2ND_"
+
+    # TODO(asmundak): combo-related stuff
+
+    # on windows, the tools have .exe at the end, and we depend on the
+    # host config stuff being done first
+    g["BUILD_ARCH"] = g["HOST_ARCH"]
+    g["BUILD_2ND_ARCH"] = g["HOST_2ND_ARCH"]
+
+    # the host build defaults to release, and it must be release or debug
+    g.setdefault("HOST_BUILD_TYPE", "release")
+    if g["HOST_BUILD_TYPE"] != "release" and g["HOST_BUILD_TYPE"] != "debug":
+        fail("HOST_BUILD_TYPE must be either release or debug, not '%s'" % g["HOST_BUILD_TYPE"])
+
+    # TODO(asmundak): a lot more, but not needed for the product configuration
+
+    g["ART_APEX_JARS"] = [
+        "com.android.art:core-oj",
+        "com.android.art:core-libart",
+        "com.android.art:okhttp",
+        "com.android.art:bouncycastle",
+        "com.android.art:apache-xml"
+    ]
+
+    if g.get("TARGET_BUILD_TYPE", "") != "debug":
+        g["TARGET_BUILD_TYPE"] = "release"
+
+
+v_default = "SP1A"
+v_min = "SP1A"
+v_max = "SP1A"
diff --git a/core/product_config.rbc b/core/product_config.rbc
new file mode 100644
index 0000000000..6e968222d7
--- /dev/null
+++ b/core/product_config.rbc
@@ -0,0 +1,483 @@
+
+# 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
+#
+#      https://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.
+
+load("//build/make/core:envsetup.rbc", _envsetup_init="init")
+"""Runtime functions."""
+
+def _global_init():
+    """Returns dict created from the runtime environment."""
+    globals = dict()
+
+    # Environment variables
+    for k in dir(rblf_env):
+        globals[k] = getattr(rblf_env, k)
+
+    # Variables set as var=value command line arguments
+    for k in dir(rblf_cli):
+        globals[k] = getattr(rblf_cli, k)
+
+    globals.setdefault("PRODUCT_SOONG_NAMESPACES", [])
+    _envsetup_init(globals)
+
+    # Variables that should be defined.
+    mandatory_vars = [
+        "PLATFORM_VERSION_CODENAME", "PLATFORM_VERSION",
+        "PRODUCT_SOONG_NAMESPACES",
+        # TODO(asmundak): do we need TARGET_ARCH? AOSP does not reference it
+        "TARGET_BUILD_TYPE", "TARGET_BUILD_VARIANT", "TARGET_PRODUCT",
+    ]
+    for bv in mandatory_vars:
+        if not bv in globals:
+            fail(bv, " is not defined")
+
+    return globals
+
+_globals_base = _global_init()
+
+def __print_attr(attr, value):
+    if not value:
+        return
+    if type(value) == "list":
+        if _options.rearrange:
+            value = __printvars_rearrange_list(value)
+        if _options.format == "pretty":
+            print(attr, "=", repr(value))
+        elif _options.format == "make":
+            print(attr, ":=", " ".join(value))
+    else:
+        if _options.format == "pretty":
+            print(attr, "=", repr(value))
+        elif _options.format == "make":
+            print(attr, ":=", value)
+        else:
+            fail("bad output format", _options.format)
+
+
+def _printvars(globals, cfg):
+    """Prints known configuration variables."""
+    for attr, val in sorted(cfg.items()):
+        __print_attr(attr, val)
+    if _options.print_globals:
+        for attr, val in sorted(globals.items()):
+            print()
+            if attr not in _globals_base:
+                __print_attr(attr, val)
+
+
+def __printvars_rearrange_list(l):
+    """Rearrange value list: return only distinct elements, maybe sorted."""
+    seen = { item: 0 for item in l}
+    return sorted(seen.keys()) if _options.rearrange == "sort" else seen.keys()
+
+def _product_configuration(top_pcm_name, top_pcm):
+    """Creates configuration."""
+
+    # Product configuration is created by traversing product's inheritance
+    # tree. It is traversed twice.
+    # First, beginning with top-level module we execute a module and find
+    # its ancestors, repeating this recursively. At the end of this phase
+    # we get the full inheritance tree.
+    # Second, we traverse the tree in the postfix order (i.e., visiting a
+    # node after its ancestors) to calculate the product configuration.
+    #
+    # PCM means "Product Configuration Module", i.e., a Starlark file
+    # whose body consists of a single init function.
+
+    globals = dict(**_globals_base)
+
+    config_postfix = []     # Configs in postfix order
+    # Each PCM is represented by a quadruple of function, config, children names
+    # and readyness (that is, the configurations from inherited PCMs have been
+    # substituted).
+    configs = { top_pcm_name: (top_pcm, None, [], False)}  # All known PCMs
+
+    stash = []              # Configs to push once their descendants are done
+
+    # Stack maintaining PCMs to be processed. An item in the stack
+    # is a pair of PCMs name and its height in the product inheritance tree.
+    pcm_stack = []
+    pcm_stack.append((top_pcm_name, 0))
+    pcm_count = 0
+    # Run it until pcm_stack is exhausted, but no more than N times
+    for n in range(1000):
+        if not pcm_stack:
+            break
+        (name, height) = pcm_stack.pop()
+        pcm, cfg, c, _ = configs[name]
+        # each PCM is executed once
+        if cfg != None:
+            continue
+        # Push ancestors until we reach this node's height
+        config_postfix.extend([stash.pop() for i in range(len(stash) - height)])
+
+        # Run this one, obtaining its configuration and child PCMs.
+        if _options.trace_modules:
+            print("%s:" % n[0])
+
+        # The handle passed to the PCM consists of config and inheritance state.dict of inherited modules
+        # and a list containing the current default value of a list variable.
+        handle = __h_new()
+        pcm(globals, handle)
+        children = __h_inherited_modules(handle)
+        if _options.trace_modules:
+            print("   ", "    ".join(children.keys()))
+        configs[name] = (pcm, __h_cfg(handle), children.keys(), False)
+        pcm_count = pcm_count+1
+
+        if len(children) == 0:
+            # Leaf PCM goes straight to the config_postfix
+            config_postfix.append(name)
+            continue
+
+        # Stash this PCM, process children in the sorted order
+        stash.append(name)
+        for child_name in sorted(children, reverse=True):
+            if child_name not in configs:
+                configs[child_name] = (children[child_name], None, [], False)
+            pcm_stack.append((child_name, len(stash)))
+
+    # Flush the stash
+    config_postfix.extend([stash.pop() for i in range(len(stash))])
+    if len(config_postfix) != pcm_count:
+        fail("Ran %d modules but postfix tree has only %d entries" % (pcm_count, len(config_postfix)))
+
+
+    if _options.trace_modules:
+        print("\n---Postfix---")
+        for x in config_postfix:
+            print("   ", x)
+
+    # Traverse the tree from the bottom, evaluating inherited values
+    for pcm_name in config_postfix:
+        pcm, cfg, children_names, ready = configs[pcm_name]
+        # Should run
+        if cfg == None:
+            fail("%s: has not been run" % pcm_name)
+        # Ready once
+        if ready:
+            continue
+        # Children should be ready
+        for child_name in children_names:
+            if not configs[child_name][3]:
+                fail("%s: child is not ready" % child_name)
+
+        # if _options.trace_modules:
+        #     print(">%s: %s" % (pcm_name, cfg))
+
+        _substitute_inherited(configs, pcm_name, cfg)
+        _percolate_inherited(configs, pcm_name, cfg, children_names)
+        configs[pcm_name] = pcm, cfg, children_names, True
+        # if _options.trace_modules:
+        #     print("<%s: %s" % (pcm_name, cfg))
+
+    return globals, configs[top_pcm_name][1]
+
+
+def _substitute_inherited(configs, pcm_name, cfg):
+    """Substitutes inherited values in all the configuration settings."""
+    for attr, val in cfg.items():
+        trace_it = attr in _options.trace_variables
+        if trace_it:
+            old_val = val
+
+        # TODO(asmundak): should we handle single vars?
+        if type(val) != "list":
+            continue
+
+        if trace_it:
+            new_val = _value_expand(configs, attr, val)
+            if new_val != old_val:
+                print("%s(i): %s=%s (was %s)" % (pcm_name, attr, new_val, old_val))
+            cfg[attr] = new_val
+            continue
+
+        cfg[attr] = _value_expand(configs, attr, val)
+
+
+
+def _value_expand(configs, attr, values_list):
+    """Expands references to inherited values in a given list."""
+    result = []
+    expanded={}
+    for item in values_list:
+        # Inherited values are 1-tuples
+        if type(item) != "tuple":
+            result.append(item)
+            continue
+        child_name = item[0]
+        if child_name in expanded:
+            continue
+        expanded[child_name] = True
+        child = configs[child_name]
+        if not child[3]:
+            fail("%s should be ready" % child_name)
+        __move_items(result, child[1], attr)
+
+    return result
+
+
+def _percolate_inherited(configs, cfg_name, cfg, children_names):
+    """Percolates the settings that are present only in children."""
+    percolated_attrs = {}
+    for child_name in children_names:
+        child_cfg = configs[child_name][1]
+        for attr, value in child_cfg.items():
+            if type(value) != "list":
+                if attr in percolated_attrs or not attr in cfg:
+                    cfg[attr] = value
+                    percolated_attrs[attr] = True
+                continue
+            if attr in percolated_attrs:
+                # We already are percolating this one, just add this list
+                __move_items(cfg[attr], child_cfg, attr)
+            elif not attr in cfg:
+                percolated_attrs[attr] = True
+                cfg[attr] = []
+                __move_items(cfg[attr], child_cfg, attr)
+
+    for attr in _options.trace_variables:
+        if attr in percolated_attrs:
+            print("%s: %s^=%s" % (cfg_name, attr, cfg[attr]))
+
+
+def __move_items(to_list, from_cfg, attr):
+    l = from_cfg.get(attr, [])
+    if l:
+        to_list.extend(l)
+        from_cfg[attr] = []
+
+
+def _indirect(pcm_name):
+    """Returns configuration item for the inherited module."""
+    return (pcm_name,)
+
+
+def _addprefix(prefix, string_or_list):
+    """Adds prefix and returns a list.
+
+    If string_or_list is a list, prepends prefix to each element.
+    Otherwise, string_or_list is considered to be a string which
+    is split into words and then prefix is prepended to each one.
+
+    Args:
+        prefix
+        string_or_list
+
+    """
+    return [ prefix + x for x in __words(string_or_list)]
+
+
+def _addsuffix(suffix, string_or_list):
+    """Adds suffix and returns a list.
+
+    If string_or_list is a list, appends suffix to each element.
+    Otherwise, string_or_list is considered to be a string which
+    is split into words and then suffix is appended to each one.
+
+    Args:
+      suffix
+      string_or_list
+    """
+    return [ x + suffix for x in __words(string_or_list)]
+
+
+def __words(string_or_list):
+    if type(string_or_list) == "list":
+        return string_or_list
+    return string_or_list.split()
+
+
+def __h_new():
+    """Constructs a handle which is passed to PCM."""
+    return (dict(), dict(), list())
+
+def __h_inherited_modules(handle):
+    return handle[1]
+
+
+def __h_cfg(handle):
+    return handle[0]
+
+
+def _setdefault(handle, attr):
+    """Sets given attribute's value if it has not been set."""
+    cfg = handle[0]
+    if cfg.get(attr) == None:
+        cfg[attr] = list(handle[2])
+    return cfg[attr]
+
+def _inherit(handle, pcm_name, pcm):
+    """Records inheritance."""
+    cfg, inherited, default_lv = handle
+    inherited[pcm_name]=pcm
+    default_lv.append(_indirect(pcm_name))
+    # Add inherited module reference to all configuration values
+    for attr, val in cfg.items():
+        if type(val) == "list":
+            val.append(_indirect(pcm_name))
+
+
+def _copy_if_exists(path_pair):
+    """If from file exists, returns [from:to] pair."""
+    l = path_pair.split(":", 2)
+    # Check that l[0] exists
+    return [":".join(l)] if rblf_file_exists(l[0]) else []
+
+def _enforce_product_packages_exist(pkg_string_or_list):
+    """Makes including non-existent modules in PRODUCT_PACKAGES an error."""
+    #TODO(asmundak)
+    pass
+
+
+def _file_wildcard_exists(file_pattern):
+    """Return True if there are files matching given bash pattern."""
+    return len(rblf_wildcard(file_pattern)) > 0
+
+
+def _find_and_copy(pattern, from_dir, to_dir):
+    """Return a copy list for the files matching the pattern."""
+    return ["%s/%s:%s/%s" % (from_dir, f, to_dir, f) for f in rblf_wildcard(pattern, from_dir)]
+
+
+def _filter_out(pattern, text):
+    """Return all the words from `text' that do not match any word in `pattern'.
+
+    Args:
+        pattern: string or list of words. '%' stands for wildcard (in regex terms, '.*')
+        text: string or list of words
+    Return:
+        list of words
+    """
+    rex = __mk2regex(__words(pattern))
+    res = []
+    for w in __words(text):
+        if not _regex_match(rex, w):
+            res.append(w)
+    return res
+
+
+def _filter(pattern, text):
+    """Return all the words in `text` that match `pattern`.
+
+    Args:
+        pattern: strings of words or a list. A word can contain '%',
+         which stands for any sequence of characters.
+        text: string or list of words.
+    """
+    rex = __mk2regex(__words(pattern))
+    res = []
+    for w in __words(text):
+        if _regex_match(rex, w):
+            res.append(w)
+    return res
+
+
+def __mk2regex(words):
+    """Returns regular expression equivalent to Make pattern."""
+
+    # TODO(asmundak): this will mishandle '\%'
+    return "^(" + "|".join([w.replace("%", ".*", 1) for w in words]) + ")"
+
+
+def _regex_match(regex, w):
+    return rblf_regex(regex, w)
+
+
+def _require_artifacts_in_path(paths, allowed_paths):
+    """TODO."""
+    #print("require_artifacts_in_path(", __words(paths), ",", __words(allowed_paths), ")")
+    pass
+
+
+def _require_artifacts_in_path_relaxed(paths, allowed_paths):
+    """TODO."""
+    pass
+
+
+def _expand_wildcard(pattern):
+    """Expands shell wildcard pattern."""
+    return rblf_wildcard(pattern)
+
+
+def _mkerror(file, message=""):
+    """Prints error and stops."""
+    fail("%s: %s. Stop" % (file, message))
+
+
+def _mkwarning(file, message=""):
+    """Prints warning."""
+    print("%s: warning: %s" % (file, message))
+
+
+def _mkinfo(file, message=""):
+    """Prints info."""
+    print(message)
+
+
+def __get_options():
+    """Returns struct containing runtime global settings."""
+    settings = dict(
+        format = "pretty",
+        print_globals = False,
+        rearrange = "",
+        trace_modules = False,
+        trace_variables = [],
+    )
+    for x in getattr(rblf_cli, "RBC_OUT", "").split(","):
+        if x == "sort" or x == "unique":
+            if settings["rearrange"]:
+                fail("RBC_OUT: either sort or unique is allowed (and sort implies unique)")
+            settings["rearrange"] = x
+        elif x == "pretty" or x == "make":
+            settings["format"] = x
+        elif x == "global":
+            settings["print_globals"] = True
+        elif x != "":
+            fail("RBC_OUT: got %s, should be one of: [pretty|make] [sort|unique]" % x)
+    for x in getattr(rblf_cli, "RBC_DEBUG", "").split(","):
+        if x == "!trace":
+            settings["trace_modules"] = True
+        elif x != "":
+            settings["trace_variables"].append(x)
+    return struct(**settings)
+
+# Settings used during debugging.
+_options = __get_options()
+rblf = struct(addprefix=_addprefix,
+              addsuffix=_addsuffix,
+              copy_if_exists=_copy_if_exists,
+              cfg=__h_cfg,
+              enforce_product_packages_exist=_enforce_product_packages_exist,
+              expand_wildcard=_expand_wildcard,
+              file_exists=rblf_file_exists,
+              file_wildcard_exists=_file_wildcard_exists,
+              filter=_filter,
+              filter_out=_filter_out,
+              find_and_copy=_find_and_copy,
+              global_init=_global_init,
+              inherit=_inherit,
+              indirect=_indirect,
+              mkinfo=_mkinfo,
+              mkerror=_mkerror,
+              mkwarning=_mkwarning,
+              printvars=_printvars,
+              product_configuration=_product_configuration,
+              require_artifacts_in_path=_require_artifacts_in_path,
+              require_artifacts_in_path_relaxed=_require_artifacts_in_path_relaxed,
+              setdefault=_setdefault,
+              shell=rblf_shell,
+              warning=_mkwarning,
+              )
+
diff --git a/tests/device.rbc b/tests/device.rbc
new file mode 100644
index 0000000000..5d4e70c2b1
--- /dev/null
+++ b/tests/device.rbc
@@ -0,0 +1,42 @@
+
+# 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
+#
+#      https://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.
+
+# Top-level test configuration.
+# Converted from the following makefile
+### PRODUCT_PACKAGES += dev
+### PRODUCT_HOST_PACKAGES += host
+### $(call inherit-product, $(LOCAL_PATH)/part1.mk)
+### PRODUCT_COPY_FILES += device_from:device_to
+### include $(LOCAL_PATH)/include1.mk
+### PRODUCT_PACKAGES += dev_after
+### PRODUCT_COPY_FILES += $(call find-copy-subdir-files,audio_platform_info*.xml,device/google/redfin/audio,$(TARGET_COPY_OUT_VENDOR)/etc) xyz
+
+load("//build/make/core:product_config.rbc", "rblf")
+load(":part1.rbc", _part1_init = "init")
+load(":include1.rbc", _include1_init = "init")
+
+def init(g, handle):
+  cfg = rblf.cfg(handle)
+  rblf.setdefault(handle, "PRODUCT_PACKAGES")
+  cfg["PRODUCT_PACKAGES"] += ["dev"]
+  rblf.setdefault(handle, "PRODUCT_HOST_PACKAGES")
+  cfg["PRODUCT_HOST_PACKAGES"] += ["host"]
+  rblf.inherit(handle, "test/part1", _part1_init)
+  rblf.setdefault(handle, "PRODUCT_COPY_FILES")
+  cfg["PRODUCT_COPY_FILES"] += ["device_from:device_to"]
+  _include1_init(g, handle)
+  cfg["PRODUCT_PACKAGES"] += ["dev_after"]
+  cfg["PRODUCT_COPY_FILES"] += (rblf.find_and_copy("audio_platform_info*.xml", "device/google/redfin/audio", "||VENDOR-PATH-PH||/etc") +
+      ["xyz"])
diff --git a/tests/include1.rbc b/tests/include1.rbc
new file mode 100644
index 0000000000..c0c9b3ba9f
--- /dev/null
+++ b/tests/include1.rbc
@@ -0,0 +1,25 @@
+
+# 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
+#
+#      https://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.
+
+# Included file (not inherited)
+# Converted from makefile
+### PRODUCT_PACKAGES += inc
+
+load("//build/make/core:product_config.rbc", "rblf")
+
+def init(g, handle):
+  cfg = rblf.cfg(handle)
+  rblf.setdefault(handle, "PRODUCT_PACKAGES")
+  cfg["PRODUCT_PACKAGES"] += ["inc"]
diff --git a/tests/part1.rbc b/tests/part1.rbc
new file mode 100644
index 0000000000..3e50751026
--- /dev/null
+++ b/tests/part1.rbc
@@ -0,0 +1,28 @@
+
+# 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
+#
+#      https://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.
+
+# Part configuration
+# Converted from
+### PRODUCT_COPY_FILES += part_from:part_to
+### PRODUCT_PRODUCT_PROPERTIES += part_properties
+
+load("//build/make/core:product_config.rbc", "rblf")
+
+def init(g, handle):
+  cfg = rblf.cfg(handle)
+  rblf.setdefault(handle, "PRODUCT_COPY_FILES")
+  cfg["PRODUCT_COPY_FILES"] += ["part_from:part_to"]
+  rblf.setdefault(handle, "PRODUCT_PRODUCT_PROPERTIES")
+  cfg["PRODUCT_PRODUCT_PROPERTIES"] += ["part_properties"]
diff --git a/tests/run.rbc b/tests/run.rbc
new file mode 100644
index 0000000000..b13f835bc1
--- /dev/null
+++ b/tests/run.rbc
@@ -0,0 +1,50 @@
+
+# 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
+#
+#      https://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.
+
+
+# Run test configuration and verify its result.
+# The main configuration file is device.rbc.
+# It inherits part1.rbc and also includes include1.rbc
+# TODO(asmundak): more tests are needed to verify that:
+#  * multi-level inheritance works as expected
+#  * all runtime functions (wildcard, regex, etc.) work
+
+load("//build/make/core:product_config.rbc", "rblf")
+load(":device.rbc", "init")
+
+def assert_eq(expected, actual):
+    if expected != actual:
+        fail("Expected %s, got %s" % (expected, actual))
+
+
+globals, config = rblf.product_configuration("test/device", init)
+assert_eq(
+    {
+      "PRODUCT_COPY_FILES": [
+          "part_from:part_to",
+          "device_from:device_to",
+          "device/google/redfin/audio/audio_platform_info_noextcodec_snd.xml:||VENDOR-PATH-PH||/etc/audio_platform_info_noextcodec_snd.xml",
+          "xyz"
+      ],
+      "PRODUCT_HOST_PACKAGES": ["host"],
+      "PRODUCT_PACKAGES": [
+          "dev",
+          "inc",
+          "dev_after"
+      ],
+      "PRODUCT_PRODUCT_PROPERTIES": ["part_properties"]
+    },
+    { k:v for k, v in sorted(config.items()) }
+)
diff --git a/tools/rbcrun/Android.bp b/tools/rbcrun/Android.bp
new file mode 100644
index 0000000000..b5f71552a4
--- /dev/null
+++ b/tools/rbcrun/Android.bp
@@ -0,0 +1,36 @@
+//
+// Copyright (C) 2021 The Android Open Source Project
+//
+// 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.
+
+blueprint_go_binary {
+    name: "rbcrun",
+    srcs: ["cmd/rbcrun.go"],
+    deps: ["rbcrun-module"],
+}
+
+bootstrap_go_package {
+    name: "rbcrun-module",
+    srcs: [
+        "host.go",
+    ],
+    testSrcs: [
+        "host_test.go",
+    ],
+    pkgPath: "rbcrun",
+    deps: [
+        "go-starlark-starlark",
+        "go-starlark-starlarkstruct",
+        "go-starlark-starlarktest",
+    ],
+}
diff --git a/tools/rbcrun/README.md b/tools/rbcrun/README.md
new file mode 100644
index 0000000000..fb58c897aa
--- /dev/null
+++ b/tools/rbcrun/README.md
@@ -0,0 +1,84 @@
+# Roboleaf configuration files interpreter
+
+Reads and executes Roboleaf product configuration files.
+
+## Usage
+
+`rbcrun` *options* *VAR=value*... [ *file* ]
+
+A Roboleaf configuration file is a Starlark script. Usually it is read from *file*. The option `-c` allows to provide a
+script directly on the command line. The option `-f` is there to allow the name of a file script to contain (`=`).
+(i.e., `my=file.rbc` sets `my` to `file.rbc`, `-f my=file.rbc` runs the script from `my=file.rbc`).
+
+### Options
+
+`-d` *dir*\
+Root directory for load("//path",...)
+
+`-c` *text*\
+Read script from *text*
+
+`--perf` *file*\
+Gather performance statistics and save it to *file*. Use \
+`       go tool prof -top`*file*\
+to show top CPU users
+
+`-f` *file*\
+File to run.
+
+## Extensions
+
+The runner allows Starlark scripts to use the following features that Bazel's Starlark interpreter does not support:
+
+### Load statement URI
+
+Starlark does not define the format of the load statement's first argument.
+The Roboleaf configuration interpreter supports the format that Bazel uses
+(`":file"` or `"//path:file"`). In addition, it allows the URI to end with
+`"|symbol"` which defines a single variable `symbol` with `None` value if a
+module does not exist. Thus,
+
+```
+load(":mymodule.rbc|init", mymodule_init="init")
+```
+
+will load the module `mymodule.rbc` and export a symbol `init` in it as
+`mymodule_init` if `mymodule.rbc` exists. If `mymodule.rbc` is missing,
+`mymodule_init` will be set to `None`
+
+### Predefined Symbols
+
+#### rblf_env
+
+A `struct` containing environment variables. E.g., `rblf_env.USER` is the username when running on Unix.
+
+#### rblf_cli
+
+A `struct` containing the variable set by the interpreter's command line. That is, running
+
+```
+rbcrun FOO=bar myfile.rbc
+```
+
+will have the value of `rblf_cli.FOO` be `"bar"`
+
+### Predefined Functions
+
+#### rblf_file_exists(*file*)
+
+Returns `True`  if *file* exists
+
+#### rblf_wildcard(*glob*, *top* = None)
+
+Expands *glob*. If *top* is supplied, expands "*top*/*glob*", then removes
+"*top*/" prefix from the matching file names.
+
+#### rblf_regex(*pattern*, *text*)
+
+Returns *True* if *text* matches *pattern*.
+
+#### rblf_shell(*command*)
+
+Runs `sh -c "`*command*`"`, reads its output, converts all newlines into spaces, chops trailing newline returns this
+string. This is equivalent to Make's
+`shell` builtin function. *This function will be eventually removed*.
diff --git a/tools/rbcrun/cmd/rbcrun.go b/tools/rbcrun/cmd/rbcrun.go
new file mode 100644
index 0000000000..784856259b
--- /dev/null
+++ b/tools/rbcrun/cmd/rbcrun.go
@@ -0,0 +1,98 @@
+// 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 main
+
+import (
+	"flag"
+	"fmt"
+	"go.starlark.net/starlark"
+	"os"
+	"rbcrun"
+	"strings"
+)
+
+var (
+	execprog = flag.String("c", "", "execute program `prog`")
+	rootdir  = flag.String("d", ".", "the value of // for load paths")
+	file     = flag.String("f", "", "file to execute")
+	perfFile = flag.String("perf", "", "save performance data")
+)
+
+func main() {
+	flag.Parse()
+	filename := *file
+	var src interface{}
+	var env []string
+
+	rc := 0
+	for _, arg := range flag.Args() {
+		if strings.Contains(arg, "=") {
+			env = append(env, arg)
+		} else if filename == "" {
+			filename = arg
+		} else {
+			quit("only one file can be executed\n")
+		}
+	}
+	if *execprog != "" {
+		if filename != "" {
+			quit("either -c or file name should be present\n")
+		}
+		filename = "<cmdline>"
+		src = *execprog
+	}
+	if filename == "" {
+		if len(env) > 0 {
+			fmt.Fprintln(os.Stderr,
+				"no file to run -- if your file's name contains '=', use -f to specify it")
+		}
+		flag.Usage()
+		os.Exit(1)
+	}
+	if stat, err := os.Stat(*rootdir); os.IsNotExist(err) || !stat.IsDir() {
+		quit("%s is not a directory\n", *rootdir)
+	}
+	if *perfFile != "" {
+		pprof, err := os.Create(*perfFile)
+		if err != nil {
+			quit("%s: err", *perfFile)
+		}
+		defer pprof.Close()
+		if err := starlark.StartProfile(pprof); err != nil {
+			quit("%s\n", err)
+		}
+	}
+	rbcrun.LoadPathRoot = *rootdir
+	err := rbcrun.Run(filename, src, env)
+	if *perfFile != "" {
+		if err2 := starlark.StopProfile(); err2 != nil {
+			fmt.Fprintln(os.Stderr, err2)
+			rc = 1
+		}
+	}
+	if err != nil {
+		if evalErr, ok := err.(*starlark.EvalError); ok {
+			quit("%s\n", evalErr.Backtrace())
+		} else {
+			quit("%s\n", err)
+		}
+	}
+	os.Exit(rc)
+}
+
+func quit(format string, s ...interface{}) {
+	fmt.Fprintln(os.Stderr, format, s)
+	os.Exit(2)
+}
diff --git a/tools/rbcrun/go.mod b/tools/rbcrun/go.mod
new file mode 100644
index 0000000000..a029eb4ec2
--- /dev/null
+++ b/tools/rbcrun/go.mod
@@ -0,0 +1,10 @@
+module rbcrun
+
+require (
+	github.com/nbutton23/zxcvbn-go v0.0.0-20180912185939-ae427f1e4c1d // indirect
+	go.starlark.net v0.0.0-20201006213952-227f4aabceb5
+)
+
+replace go.starlark.net => ../../../../external/starlark-go
+
+go 1.15
diff --git a/tools/rbcrun/go.sum b/tools/rbcrun/go.sum
new file mode 100644
index 0000000000..db4d51e9dd
--- /dev/null
+++ b/tools/rbcrun/go.sum
@@ -0,0 +1,75 @@
+cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw=
+github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
+github.com/census-instrumentation/opencensus-proto v0.2.1/go.mod h1:f6KPmirojxKA12rnyqOA5BBL4O983OfeGPqjHWSTneU=
+github.com/chzyer/logex v1.1.10 h1:Swpa1K6QvQznwJRcfTfQJmTE72DqScAa40E+fbHEXEE=
+github.com/chzyer/logex v1.1.10/go.mod h1:+Ywpsq7O8HXn0nuIou7OrIPyXbp3wmkHB+jjWRnGsAI=
+github.com/chzyer/readline v0.0.0-20180603132655-2972be24d48e h1:fY5BOSpyZCqRo5OhCuC+XN+r/bBCmeuuJtjz+bCNIf8=
+github.com/chzyer/readline v0.0.0-20180603132655-2972be24d48e/go.mod h1:nSuG5e5PlCu98SY8svDHJxuZscDgtXS6KTTbou5AhLI=
+github.com/chzyer/test v0.0.0-20180213035817-a1ea475d72b1 h1:q763qf9huN11kDQavWsoZXJNW3xEE4JJyHa5Q25/sd8=
+github.com/chzyer/test v0.0.0-20180213035817-a1ea475d72b1/go.mod h1:Q3SI9o4m/ZMnBNeIyt5eFwwo7qiLfzFZmjNmxjkiQlU=
+github.com/client9/misspell v0.3.4/go.mod h1:qj6jICC3Q7zFZvVWo7KLAzC3yx5G7kyvSDkc90ppPyw=
+github.com/envoyproxy/go-control-plane v0.9.1-0.20191026205805-5f8ba28d4473/go.mod h1:YTl/9mNaCwkRvm6d1a2C3ymFceY/DCBVvsKhRF0iEA4=
+github.com/envoyproxy/protoc-gen-validate v0.1.0/go.mod h1:iSmxcyjqTsJpI2R4NaDN7+kN2VEUnK/pcBlmesArF7c=
+github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b/go.mod h1:SBH7ygxi8pfUlaOkMMuAQtPIUF8ecWP5IEl/CR7VP2Q=
+github.com/golang/mock v1.1.1/go.mod h1:oTYuIxOrZwtPieC+H1uAHpcLFnEyAGVDL/k47Jfbm0A=
+github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
+github.com/golang/protobuf v1.3.2/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
+github.com/golang/protobuf v1.4.0-rc.1/go.mod h1:ceaxUfeHdC40wWswd/P6IGgMaK3YpKi5j83Wpe3EHw8=
+github.com/golang/protobuf v1.4.0-rc.1.0.20200221234624-67d41d38c208/go.mod h1:xKAWHe0F5eneWXFV3EuXVDTCmh+JuBKY0li0aMyXATA=
+github.com/golang/protobuf v1.4.0-rc.2/go.mod h1:LlEzMj4AhA7rCAGe4KMBDvJI+AwstrUpVNzEA03Pprs=
+github.com/golang/protobuf v1.4.0-rc.4.0.20200313231945-b860323f09d0/go.mod h1:WU3c8KckQ9AFe+yFwt9sWVRKCVIyN9cPHBJSNnbL67w=
+github.com/golang/protobuf v1.4.0/go.mod h1:jodUvKwWbYaEsadDk5Fwe5c77LiNKVO9IDvqG2KuDX0=
+github.com/golang/protobuf v1.4.1/go.mod h1:U8fpvMrcmy5pZrNK1lt4xCsGvpyWQ/VVv6QDs8UjoX8=
+github.com/google/go-cmp v0.2.0/go.mod h1:oXzfMopK8JAjlY9xF4vHSVASa0yLyX7SntLO5aqRK0M=
+github.com/google/go-cmp v0.3.0/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
+github.com/google/go-cmp v0.3.1/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
+github.com/google/go-cmp v0.4.0/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
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diff --git a/tools/rbcrun/host.go b/tools/rbcrun/host.go
new file mode 100644
index 0000000000..f1697f1f3b
--- /dev/null
+++ b/tools/rbcrun/host.go
@@ -0,0 +1,263 @@
+// 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 rbcrun
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"regexp"
+	"strings"
+
+	"go.starlark.net/starlark"
+	"go.starlark.net/starlarkstruct"
+)
+
+const callerDirKey = "callerDir"
+
+var LoadPathRoot = "."
+var shellPath string
+
+type modentry struct {
+	globals starlark.StringDict
+	err     error
+}
+
+var moduleCache = make(map[string]*modentry)
+
+var builtins starlark.StringDict
+
+func moduleName2AbsPath(moduleName string, callerDir string) (string, error) {
+	path := moduleName
+	if ix := strings.LastIndex(path, ":"); ix >= 0 {
+		path = path[0:ix] + string(os.PathSeparator) + path[ix+1:]
+	}
+	if strings.HasPrefix(path, "//") {
+		return filepath.Abs(filepath.Join(LoadPathRoot, path[2:]))
+	} else if strings.HasPrefix(moduleName, ":") {
+		return filepath.Abs(filepath.Join(callerDir, path[1:]))
+	} else {
+		return filepath.Abs(path)
+	}
+}
+
+// loader implements load statement. The format of the loaded module URI is
+//  [//path]:base[|symbol]
+// The file path is $ROOT/path/base if path is present, <caller_dir>/base otherwise.
+// The presence of `|symbol` indicates that the loader should return a single 'symbol'
+// bound to None if file is missing.
+func loader(thread *starlark.Thread, module string) (starlark.StringDict, error) {
+	pipePos := strings.LastIndex(module, "|")
+	mustLoad := pipePos < 0
+	var defaultSymbol string
+	if !mustLoad {
+		defaultSymbol = module[pipePos+1:]
+		module = module[:pipePos]
+	}
+	modulePath, err := moduleName2AbsPath(module, thread.Local(callerDirKey).(string))
+	if err != nil {
+		return nil, err
+	}
+	e, ok := moduleCache[modulePath]
+	if e == nil {
+		if ok {
+			return nil, fmt.Errorf("cycle in load graph")
+		}
+
+		// Add a placeholder to indicate "load in progress".
+		moduleCache[modulePath] = nil
+
+		// Decide if we should load.
+		if !mustLoad {
+			if _, err := os.Stat(modulePath); err == nil {
+				mustLoad = true
+			}
+		}
+
+		// Load or return default
+		if mustLoad {
+			childThread := &starlark.Thread{Name: "exec " + module, Load: thread.Load}
+			// Cheating for the sake of testing:
+			// propagate starlarktest's Reporter key, otherwise testing
+			// the load function may cause panic in starlarktest code.
+			const testReporterKey = "Reporter"
+			if v := thread.Local(testReporterKey); v != nil {
+				childThread.SetLocal(testReporterKey, v)
+			}
+
+			childThread.SetLocal(callerDirKey, filepath.Dir(modulePath))
+			globals, err := starlark.ExecFile(childThread, modulePath, nil, builtins)
+			e = &modentry{globals, err}
+		} else {
+			e = &modentry{starlark.StringDict{defaultSymbol: starlark.None}, nil}
+		}
+
+		// Update the cache.
+		moduleCache[modulePath] = e
+	}
+	return e.globals, e.err
+}
+
+// fileExists returns True if file with given name exists.
+func fileExists(_ *starlark.Thread, b *starlark.Builtin, args starlark.Tuple,
+	kwargs []starlark.Tuple) (starlark.Value, error) {
+	var path string
+	if err := starlark.UnpackPositionalArgs(b.Name(), args, kwargs, 1, &path); err != nil {
+		return starlark.None, err
+	}
+	if stat, err := os.Stat(path); err != nil || stat.IsDir() {
+		return starlark.False, nil
+	}
+	return starlark.True, nil
+}
+
+// regexMatch(pattern, s) returns True if s matches pattern (a regex)
+func regexMatch(_ *starlark.Thread, b *starlark.Builtin, args starlark.Tuple,
+	kwargs []starlark.Tuple) (starlark.Value, error) {
+	var pattern, s string
+	if err := starlark.UnpackPositionalArgs(b.Name(), args, kwargs, 2, &pattern, &s); err != nil {
+		return starlark.None, err
+	}
+	match, err := regexp.MatchString(pattern, s)
+	if err != nil {
+		return starlark.None, err
+	}
+	if match {
+		return starlark.True, nil
+	}
+	return starlark.False, nil
+}
+
+// wildcard(pattern, top=None) expands shell's glob pattern. If 'top' is present,
+// the 'top/pattern' is globbed and then 'top/' prefix is removed.
+func wildcard(_ *starlark.Thread, b *starlark.Builtin, args starlark.Tuple,
+	kwargs []starlark.Tuple) (starlark.Value, error) {
+	var pattern string
+	var top string
+
+	if err := starlark.UnpackPositionalArgs(b.Name(), args, kwargs, 1, &pattern, &top); err != nil {
+		return starlark.None, err
+	}
+
+	var files []string
+	var err error
+	if top == "" {
+		if files, err = filepath.Glob(pattern); err != nil {
+			return starlark.None, err
+		}
+	} else {
+		prefix := top + string(filepath.Separator)
+		if files, err = filepath.Glob(prefix + pattern); err != nil {
+			return starlark.None, err
+		}
+		for i := range files {
+			files[i] = strings.TrimPrefix(files[i], prefix)
+		}
+	}
+	return makeStringList(files), nil
+}
+
+// shell(command) runs OS shell with given command and returns back
+// its output the same way as Make's $(shell ) function. The end-of-lines
+// ("\n" or "\r\n") are replaced with " " in the result, and the trailing
+// end-of-line is removed.
+func shell(_ *starlark.Thread, b *starlark.Builtin, args starlark.Tuple,
+	kwargs []starlark.Tuple) (starlark.Value, error) {
+	var command string
+	if err := starlark.UnpackPositionalArgs(b.Name(), args, kwargs, 1, &command); err != nil {
+		return starlark.None, err
+	}
+	if shellPath == "" {
+		return starlark.None,
+			fmt.Errorf("cannot run shell, SHELL environment variable is not set (running on Windows?)")
+	}
+	cmd := exec.Command(shellPath, "-c", command)
+	// We ignore command's status
+	bytes, _ := cmd.Output()
+	output := string(bytes)
+	if strings.HasSuffix(output, "\n") {
+		output = strings.TrimSuffix(output, "\n")
+	} else {
+		output = strings.TrimSuffix(output, "\r\n")
+	}
+
+	return starlark.String(
+		strings.ReplaceAll(
+			strings.ReplaceAll(output, "\r\n", " "),
+			"\n", " ")), nil
+}
+
+func makeStringList(items []string) *starlark.List {
+	elems := make([]starlark.Value, len(items))
+	for i, item := range items {
+		elems[i] = starlark.String(item)
+	}
+	return starlark.NewList(elems)
+}
+
+// propsetFromEnv constructs a propset from the array of KEY=value strings
+func structFromEnv(env []string) *starlarkstruct.Struct {
+	sd := make(map[string]starlark.Value, len(env))
+	for _, x := range env {
+		kv := strings.SplitN(x, "=", 2)
+		sd[kv[0]] = starlark.String(kv[1])
+	}
+	return starlarkstruct.FromStringDict(starlarkstruct.Default, sd)
+}
+
+func setup(env []string) {
+	// Create the symbols that aid makefile conversion. See README.md
+	builtins = starlark.StringDict{
+		"struct":   starlark.NewBuiltin("struct", starlarkstruct.Make),
+		"rblf_cli": structFromEnv(env),
+		"rblf_env": structFromEnv(os.Environ()),
+		// To convert makefile's $(wildcard foo)
+		"rblf_file_exists": starlark.NewBuiltin("rblf_file_exists", fileExists),
+		// To convert makefile's $(filter ...)/$(filter-out)
+		"rblf_regex": starlark.NewBuiltin("rblf_regex", regexMatch),
+		// To convert makefile's $(shell cmd)
+		"rblf_shell": starlark.NewBuiltin("rblf_shell", shell),
+		// To convert makefile's $(wildcard foo*)
+		"rblf_wildcard": starlark.NewBuiltin("rblf_wildcard", wildcard),
+	}
+
+	// NOTE(asmundak): OS-specific.
+	shellPath, _ = os.LookupEnv("SHELL")
+}
+
+// Parses, resolves, and executes a Starlark file.
+// filename and src parameters are as for starlark.ExecFile:
+// * filename is the name of the file to execute,
+//   and the name that appears in error messages;
+// * src is an optional source of bytes to use instead of filename
+//   (it can be a string, or a byte array, or an io.Reader instance)
+// * commandVars is an array of "VAR=value" items. They are accessible from
+//   the starlark script as members of the `rblf_cli` propset.
+func Run(filename string, src interface{}, commandVars []string) error {
+	setup(commandVars)
+
+	mainThread := &starlark.Thread{
+		Name:  "main",
+		Print: func(_ *starlark.Thread, msg string) { fmt.Println(msg) },
+		Load:  loader,
+	}
+	absPath, err := filepath.Abs(filename)
+	if err == nil {
+		mainThread.SetLocal(callerDirKey, filepath.Dir(absPath))
+		_, err = starlark.ExecFile(mainThread, absPath, src, builtins)
+	}
+	return err
+}
diff --git a/tools/rbcrun/host_test.go b/tools/rbcrun/host_test.go
new file mode 100644
index 0000000000..3be5ee67aa
--- /dev/null
+++ b/tools/rbcrun/host_test.go
@@ -0,0 +1,159 @@
+// 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 rbcrun
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"runtime"
+	"testing"
+
+	"go.starlark.net/resolve"
+	"go.starlark.net/starlark"
+	"go.starlark.net/starlarktest"
+)
+
+// In order to use "assert.star" from go/starlark.net/starlarktest in the tests,
+// provide:
+//  * load function that handles "assert.star"
+//  * starlarktest.DataFile function that finds its location
+
+func init() {
+	starlarktestSetup()
+}
+
+func starlarktestSetup() {
+	resolve.AllowLambda = true
+	starlarktest.DataFile = func(pkgdir, filename string) string {
+		// The caller expects this function to return the path to the
+		// data file. The implementation assumes that the source file
+		// containing the caller and the data file are in the same
+		// directory. It's ugly. Not sure what's the better way.
+		// TODO(asmundak): handle Bazel case
+		_, starlarktestSrcFile, _, _ := runtime.Caller(1)
+		if filepath.Base(starlarktestSrcFile) != "starlarktest.go" {
+			panic(fmt.Errorf("this function should be called from starlarktest.go, got %s",
+				starlarktestSrcFile))
+		}
+		return filepath.Join(filepath.Dir(starlarktestSrcFile), filename)
+	}
+}
+
+// Common setup for the tests: create thread, change to the test directory
+func testSetup(t *testing.T, env []string) *starlark.Thread {
+	setup(env)
+	thread := &starlark.Thread{
+		Load: func(thread *starlark.Thread, module string) (starlark.StringDict, error) {
+			if module == "assert.star" {
+				return starlarktest.LoadAssertModule()
+			}
+			return nil, fmt.Errorf("load not implemented")
+		}}
+	starlarktest.SetReporter(thread, t)
+	if err := os.Chdir(dataDir()); err != nil {
+		t.Fatal(err)
+	}
+	return thread
+}
+
+func dataDir() string {
+	_, thisSrcFile, _, _ := runtime.Caller(0)
+	return filepath.Join(filepath.Dir(thisSrcFile), "testdata")
+
+}
+
+func exerciseStarlarkTestFile(t *testing.T, starFile string) {
+	// In order to use "assert.star" from go/starlark.net/starlarktest in the tests, provide:
+	//  * load function that handles "assert.star"
+	//  * starlarktest.DataFile function that finds its location
+	setup(nil)
+	thread := &starlark.Thread{
+		Load: func(thread *starlark.Thread, module string) (starlark.StringDict, error) {
+			if module == "assert.star" {
+				return starlarktest.LoadAssertModule()
+			}
+			return nil, fmt.Errorf("load not implemented")
+		}}
+	starlarktest.SetReporter(thread, t)
+	_, thisSrcFile, _, _ := runtime.Caller(0)
+	filename := filepath.Join(filepath.Dir(thisSrcFile), starFile)
+	if _, err := starlark.ExecFile(thread, filename, nil, builtins); err != nil {
+		if err, ok := err.(*starlark.EvalError); ok {
+			t.Fatal(err.Backtrace())
+		}
+		t.Fatal(err)
+	}
+}
+
+func TestCliAndEnv(t *testing.T) {
+	// TODO(asmundak): convert this to use exerciseStarlarkTestFile
+	if err := os.Setenv("TEST_ENVIRONMENT_FOO", "test_environment_foo"); err != nil {
+		t.Fatal(err)
+	}
+	thread := testSetup(t, []string{"CLI_FOO=foo"})
+	if _, err := starlark.ExecFile(thread, "cli_and_env.star", nil, builtins); err != nil {
+		if err, ok := err.(*starlark.EvalError); ok {
+			t.Fatal(err.Backtrace())
+		}
+		t.Fatal(err)
+	}
+}
+
+func TestFileOps(t *testing.T) {
+	// TODO(asmundak): convert this to use exerciseStarlarkTestFile
+	if err := os.Setenv("TEST_DATA_DIR", dataDir()); err != nil {
+		t.Fatal(err)
+	}
+	thread := testSetup(t, nil)
+	if _, err := starlark.ExecFile(thread, "file_ops.star", nil, builtins); err != nil {
+		if err, ok := err.(*starlark.EvalError); ok {
+			t.Fatal(err.Backtrace())
+		}
+		t.Fatal(err)
+	}
+}
+
+func TestLoad(t *testing.T) {
+	// TODO(asmundak): convert this to use exerciseStarlarkTestFile
+	thread := testSetup(t, nil)
+	thread.Load = func(thread *starlark.Thread, module string) (starlark.StringDict, error) {
+		if module == "assert.star" {
+			return starlarktest.LoadAssertModule()
+		} else {
+			return loader(thread, module)
+		}
+	}
+	dir := dataDir()
+	thread.SetLocal(callerDirKey, dir)
+	LoadPathRoot = filepath.Dir(dir)
+	if _, err := starlark.ExecFile(thread, "load.star", nil, builtins); err != nil {
+		if err, ok := err.(*starlark.EvalError); ok {
+			t.Fatal(err.Backtrace())
+		}
+		t.Fatal(err)
+	}
+}
+
+func TestRegex(t *testing.T) {
+	exerciseStarlarkTestFile(t, "testdata/regex.star")
+}
+
+func TestShell(t *testing.T) {
+	if err := os.Setenv("TEST_DATA_DIR", dataDir()); err != nil {
+		t.Fatal(err)
+	}
+	exerciseStarlarkTestFile(t, "testdata/shell.star")
+}
diff --git a/tools/rbcrun/testdata/cli_and_env.star b/tools/rbcrun/testdata/cli_and_env.star
new file mode 100644
index 0000000000..d6f464aa79
--- /dev/null
+++ b/tools/rbcrun/testdata/cli_and_env.star
@@ -0,0 +1,11 @@
+# Tests rblf_env access
+load("assert.star", "assert")
+
+
+def test():
+    assert.eq(rblf_env.TEST_ENVIRONMENT_FOO, "test_environment_foo")
+    assert.fails(lambda: rblf_env.FOO_BAR_BAZ, ".*struct has no .FOO_BAR_BAZ attribute$")
+    assert.eq(rblf_cli.CLI_FOO, "foo")
+
+
+test()
diff --git a/tools/rbcrun/testdata/file_ops.star b/tools/rbcrun/testdata/file_ops.star
new file mode 100644
index 0000000000..e1f1ac27ea
--- /dev/null
+++ b/tools/rbcrun/testdata/file_ops.star
@@ -0,0 +1,18 @@
+# Tests file ops builtins
+load("assert.star", "assert")
+
+
+def test():
+    myname = "file_ops.star"
+    assert.true(rblf_file_exists(myname), "the file %s does exist" % myname)
+    assert.true(not rblf_file_exists("no_such_file"), "the file no_such_file does not exist")
+    files = rblf_wildcard("*.star")
+    assert.true(myname in files, "expected %s in  %s" % (myname, files))
+    # RBCDATADIR is set by the caller to the path where this file resides
+    files = rblf_wildcard("*.star", rblf_env.TEST_DATA_DIR)
+    assert.true(myname in files, "expected %s in %s" % (myname, files))
+    files = rblf_wildcard("*.xxx")
+    assert.true(len(files) == 0, "expansion should be empty but contains %s" % files)
+
+
+test()
diff --git a/tools/rbcrun/testdata/load.star b/tools/rbcrun/testdata/load.star
new file mode 100644
index 0000000000..b14f2bbef1
--- /dev/null
+++ b/tools/rbcrun/testdata/load.star
@@ -0,0 +1,14 @@
+# Test load, simple and conditional
+load("assert.star", "assert")
+load(":module1.star", test1="test")
+load("//testdata:module2.star", test2="test")
+load(":module3|test", test3="test")
+
+
+def test():
+    assert.eq(test1, "module1")
+    assert.eq(test2, "module2")
+    assert.eq(test3, None)
+
+
+test()
diff --git a/tools/rbcrun/testdata/module1.star b/tools/rbcrun/testdata/module1.star
new file mode 100644
index 0000000000..913fb7d7cb
--- /dev/null
+++ b/tools/rbcrun/testdata/module1.star
@@ -0,0 +1,7 @@
+# Module loaded my load.star
+load("assert.star", "assert")
+
+# Make sure that builtins are defined for the loaded module, too
+assert.true(rblf_file_exists("module1.star"))
+assert.true(not rblf_file_exists("no_such file"))
+test = "module1"
diff --git a/tools/rbcrun/testdata/module2.star b/tools/rbcrun/testdata/module2.star
new file mode 100644
index 0000000000..f6818a2915
--- /dev/null
+++ b/tools/rbcrun/testdata/module2.star
@@ -0,0 +1,2 @@
+# Module loaded my load.star
+test = "module2"
diff --git a/tools/rbcrun/testdata/regex.star b/tools/rbcrun/testdata/regex.star
new file mode 100644
index 0000000000..04e1d424e9
--- /dev/null
+++ b/tools/rbcrun/testdata/regex.star
@@ -0,0 +1,13 @@
+# Tests rblf_regex
+load("assert.star", "assert")
+
+
+def test():
+    pattern = "^(foo.*bar|abc.*d|1.*)$"
+    for w in ("foobar", "fooxbar", "abcxd", "123"):
+        assert.true(rblf_regex(pattern, w), "%s should match %s" % (w, pattern))
+    for w in ("afoobar", "abcde"):
+        assert.true(not rblf_regex(pattern, w), "%s should not match %s" % (w, pattern))
+
+
+test()
diff --git a/tools/rbcrun/testdata/shell.star b/tools/rbcrun/testdata/shell.star
new file mode 100644
index 0000000000..ad106974c4
--- /dev/null
+++ b/tools/rbcrun/testdata/shell.star
@@ -0,0 +1,5 @@
+# Tests "queue" data type
+load("assert.star", "assert")
+
+assert.eq("load.star shell.star", rblf_shell("cd %s && ls -1 shell.star load.star 2>&1" % rblf_env.TEST_DATA_DIR))
+assert.eq("shell.star", rblf_shell("cd %s && echo shell.sta*" % rblf_env.TEST_DATA_DIR))