gn2bp: add copy of perfetto project gn to bp tooling

This will serve as a starting point to generate Android.bp files for
cronet.

Test: n/a
Change-Id: Ia5ccad48f705fd48cff212dbedbfb61b6e385468
diff --git a/tools/gn2bp/gen_android_bp b/tools/gn2bp/gen_android_bp
new file mode 100755
index 0000000..4cacf7c
--- /dev/null
+++ b/tools/gn2bp/gen_android_bp
@@ -0,0 +1,1129 @@
+#!/usr/bin/env python3
+# Copyright (C) 2022 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.
+
+# This tool translates a collection of BUILD.gn files into a mostly equivalent
+# Android.bp file for the Android Soong build system. The input to the tool is a
+# JSON description of the GN build definition generated with the following
+# command:
+#
+#   gn desc out --format=json --all-toolchains "//*" > desc.json
+#
+# The tool is then given a list of GN labels for which to generate Android.bp
+# build rules. The dependencies for the GN labels are squashed to the generated
+# Android.bp target, except for actions which get their own genrule. Some
+# libraries are also mapped to their Android equivalents -- see |builtin_deps|.
+
+import argparse
+import collections
+import json
+import os
+import re
+import sys
+
+import gn_utils
+
+from compat import itervalues
+
+ROOT_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+
+# Arguments for the GN output directory.
+gn_args = ' '.join([
+    'is_debug=false',
+    'is_perfetto_build_generator=true',
+    'perfetto_build_with_android=true',
+    'target_cpu="arm"',
+    'target_os="android"',
+])
+
+# Default targets to translate to the blueprint file.
+default_targets = [
+    '//:libperfetto_client_experimental',
+    '//:libperfetto',
+    '//:perfetto_integrationtests',
+    '//:perfetto_unittests',
+    '//protos/perfetto/trace:perfetto_trace_protos',
+    '//src/android_internal:libperfetto_android_internal',
+    '//src/perfetto_cmd:perfetto',
+    '//src/perfetto_cmd:trigger_perfetto',
+    '//src/profiling/memory:heapprofd_client',
+    '//src/profiling/memory:heapprofd_client_api',
+    '//src/profiling/memory:heapprofd_api_noop',
+    '//src/profiling/memory:heapprofd',
+    '//src/profiling/memory:heapprofd_standalone_client',
+    '//src/profiling/perf:traced_perf',
+    '//src/traced/probes:traced_probes',
+    '//src/traced/service:traced',
+    '//src/trace_processor:trace_processor_shell',
+    '//test/cts:perfetto_cts_deps',
+    '//test/cts:perfetto_cts_jni_deps',
+    '//test:perfetto_gtest_logcat_printer',
+    '//test/vts:perfetto_vts_deps',
+]
+
+# Host targets
+ipc_plugin = '//src/ipc/protoc_plugin:ipc_plugin(%s)' % gn_utils.HOST_TOOLCHAIN
+protozero_plugin = '//src/protozero/protoc_plugin:protozero_plugin(%s)' % (
+    gn_utils.HOST_TOOLCHAIN)
+cppgen_plugin = '//src/protozero/protoc_plugin:cppgen_plugin(%s)' % (
+    gn_utils.HOST_TOOLCHAIN)
+
+default_targets += [
+    '//src/traceconv:traceconv(%s)' % gn_utils.HOST_TOOLCHAIN,
+    protozero_plugin,
+    ipc_plugin,
+]
+
+# Defines a custom init_rc argument to be applied to the corresponding output
+# blueprint target.
+target_initrc = {
+    '//src/traced/service:traced': {'perfetto.rc'},
+    '//src/profiling/memory:heapprofd': {'heapprofd.rc'},
+    '//src/profiling/perf:traced_perf': {'traced_perf.rc'},
+}
+
+target_host_supported = [
+    '//:libperfetto',
+    '//:libperfetto_client_experimental',
+    '//protos/perfetto/trace:perfetto_trace_protos',
+    '//src/trace_processor:demangle',
+    '//src/trace_processor:trace_processor_shell',
+]
+
+target_vendor_available = [
+    '//:libperfetto_client_experimental',
+]
+
+# Proto target groups which will be made public.
+proto_groups = {
+    'trace': [
+        '//protos/perfetto/trace:non_minimal_source_set',
+        '//protos/perfetto/trace:minimal_source_set'
+    ],
+}
+
+# All module names are prefixed with this string to avoid collisions.
+module_prefix = 'perfetto_'
+
+# Shared libraries which are directly translated to Android system equivalents.
+shared_library_allowlist = [
+    'android',
+    'android.hardware.atrace@1.0',
+    'android.hardware.health@2.0',
+    'android.hardware.health-V1-ndk',
+    'android.hardware.power.stats@1.0',
+    "android.hardware.power.stats-V1-cpp",
+    'base',
+    'binder',
+    'binder_ndk',
+    'cutils',
+    'hidlbase',
+    'hidltransport',
+    'hwbinder',
+    'incident',
+    'log',
+    'services',
+    'statssocket',
+    "tracingproxy",
+    'utils',
+]
+
+# Static libraries which are directly translated to Android system equivalents.
+static_library_allowlist = [
+    'statslog_perfetto',
+]
+
+# Name of the module which settings such as compiler flags for all other
+# modules.
+defaults_module = module_prefix + 'defaults'
+
+# Location of the project in the Android source tree.
+tree_path = 'external/perfetto'
+
+# Path for the protobuf sources in the standalone build.
+buildtools_protobuf_src = '//buildtools/protobuf/src'
+
+# Location of the protobuf src dir in the Android source tree.
+android_protobuf_src = 'external/protobuf/src'
+
+# Compiler flags which are passed through to the blueprint.
+cflag_allowlist = r'^-DPERFETTO.*$'
+
+# Compiler defines which are passed through to the blueprint.
+define_allowlist = r'^(GOOGLE_PROTO.*)|(ZLIB_.*)|(USE_MMAP)|(HAVE_HIDDEN)$'
+
+# The directory where the generated perfetto_build_flags.h will be copied into.
+buildflags_dir = 'include/perfetto/base/build_configs/android_tree'
+
+
+def enumerate_data_deps():
+  with open(os.path.join(ROOT_DIR, 'tools', 'test_data.txt')) as f:
+    lines = f.readlines()
+  for line in (line.strip() for line in lines if not line.startswith('#')):
+    assert os.path.exists(line), 'file %s should exist' % line
+    if line.startswith('test/data/'):
+      # Skip test data files that require GCS. They are only for benchmarks.
+      # We don't run benchmarks in the android tree.
+      continue
+    if line.endswith('/.'):
+      yield line[:-1] + '**/*'
+    else:
+      yield line
+
+
+# Additional arguments to apply to Android.bp rules.
+additional_args = {
+    'heapprofd_client_api': [
+        ('static_libs', {'libasync_safe'}),
+        # heapprofd_client_api MUST NOT have global constructors. Because it
+        # is loaded in an __attribute__((constructor)) of libc, we cannot
+        # guarantee that the global constructors get run before it is used.
+        ('cflags', {'-Wglobal-constructors', '-Werror=global-constructors'}),
+        ('version_script', 'src/profiling/memory/heapprofd_client_api.map.txt'),
+        ('stubs', {
+            'versions': ['S'],
+            'symbol_file': 'src/profiling/memory/heapprofd_client_api.map.txt',
+        }),
+        ('export_include_dirs', {'src/profiling/memory/include'}),
+    ],
+    'heapprofd_api_noop': [
+        ('version_script', 'src/profiling/memory/heapprofd_client_api.map.txt'),
+        ('stubs', {
+            'versions': ['S'],
+            'symbol_file': 'src/profiling/memory/heapprofd_client_api.map.txt',
+        }),
+        ('export_include_dirs', {'src/profiling/memory/include'}),
+    ],
+    'heapprofd_client': [
+        ('include_dirs', {'bionic/libc'}),
+        ('static_libs', {'libasync_safe'}),
+    ],
+    'heapprofd_standalone_client': [
+        ('static_libs', {'libasync_safe'}),
+        ('version_script', 'src/profiling/memory/heapprofd_client_api.map.txt'),
+        ('export_include_dirs', {'src/profiling/memory/include'}),
+        ('stl', 'libc++_static'),
+    ],
+#    'perfetto_unittests': [
+#        ('data', set(enumerate_data_deps())),
+#        ('include_dirs', {'bionic/libc/kernel'}),
+#    ],
+    'perfetto_integrationtests': [
+        ('test_suites', {'general-tests'}),
+        ('test_config', 'PerfettoIntegrationTests.xml'),
+    ],
+    'traced_probes': [('required', {
+        'libperfetto_android_internal', 'trigger_perfetto', 'traced_perf',
+        'mm_events'
+    }),],
+    'libperfetto_android_internal': [('static_libs', {'libhealthhalutils'}),],
+    'trace_processor_shell': [
+        ('strip', {
+            'all': True
+        }),
+        ('host', {
+            'stl': 'libc++_static',
+            'dist': {
+                'targets': ['sdk_repo']
+            },
+        }),
+    ],
+    'libperfetto_client_experimental': [
+        ('apex_available', {
+            '//apex_available:platform', 'com.android.art',
+            'com.android.art.debug'
+        }),
+        ('min_sdk_version', 'S'),
+        ('shared_libs', {'liblog'}),
+        ('export_include_dirs', {'include', buildflags_dir}),
+    ],
+    'perfetto_trace_protos': [
+        ('apex_available', {
+            '//apex_available:platform', 'com.android.art',
+            'com.android.art.debug'
+        }),
+        ('min_sdk_version', 'S'),
+    ],
+    'libperfetto': [('export_include_dirs', {'include', buildflags_dir}),],
+}
+
+
+def enable_gtest_and_gmock(module):
+  module.static_libs.add('libgmock')
+  module.static_libs.add('libgtest')
+  if module.name != 'perfetto_gtest_logcat_printer':
+    module.whole_static_libs.add('perfetto_gtest_logcat_printer')
+
+
+def enable_protobuf_full(module):
+  if module.type == 'cc_binary_host':
+    module.static_libs.add('libprotobuf-cpp-full')
+  elif module.host_supported:
+    module.host.static_libs.add('libprotobuf-cpp-full')
+    module.android.shared_libs.add('libprotobuf-cpp-full')
+  else:
+    module.shared_libs.add('libprotobuf-cpp-full')
+
+
+def enable_protobuf_lite(module):
+  module.shared_libs.add('libprotobuf-cpp-lite')
+
+
+def enable_protoc_lib(module):
+  if module.type == 'cc_binary_host':
+    module.static_libs.add('libprotoc')
+  else:
+    module.shared_libs.add('libprotoc')
+
+
+def enable_libunwindstack(module):
+  if module.name != 'heapprofd_standalone_client':
+    module.shared_libs.add('libunwindstack')
+    module.shared_libs.add('libprocinfo')
+    module.shared_libs.add('libbase')
+  else:
+    module.static_libs.add('libunwindstack')
+    module.static_libs.add('libprocinfo')
+    module.static_libs.add('libbase')
+    module.static_libs.add('liblzma')
+    module.static_libs.add('libdexfile_support')
+    module.runtime_libs.add('libdexfile')  # libdexfile_support dependency
+
+
+def enable_libunwind(module):
+  # libunwind is disabled on Darwin so we cannot depend on it.
+  pass
+
+
+def enable_sqlite(module):
+  if module.type == 'cc_binary_host':
+    module.static_libs.add('libsqlite')
+    module.static_libs.add('sqlite_ext_percentile')
+  elif module.host_supported:
+    # Copy what the sqlite3 command line tool does.
+    module.android.shared_libs.add('libsqlite')
+    module.android.shared_libs.add('libicu')
+    module.android.shared_libs.add('liblog')
+    module.android.shared_libs.add('libutils')
+    module.android.static_libs.add('sqlite_ext_percentile')
+    module.host.static_libs.add('libsqlite')
+    module.host.static_libs.add('sqlite_ext_percentile')
+  else:
+    module.shared_libs.add('libsqlite')
+    module.shared_libs.add('libicu')
+    module.shared_libs.add('liblog')
+    module.shared_libs.add('libutils')
+    module.static_libs.add('sqlite_ext_percentile')
+
+
+def enable_zlib(module):
+  if module.type == 'cc_binary_host':
+    module.static_libs.add('libz')
+  elif module.host_supported:
+    module.android.shared_libs.add('libz')
+    module.host.static_libs.add('libz')
+  else:
+    module.shared_libs.add('libz')
+
+
+def enable_uapi_headers(module):
+  module.include_dirs.add('bionic/libc/kernel')
+
+
+def enable_bionic_libc_platform_headers_on_android(module):
+  module.header_libs.add('bionic_libc_platform_headers')
+
+
+# Android equivalents for third-party libraries that the upstream project
+# depends on.
+builtin_deps = {
+    '//gn:default_deps':
+        lambda x: None,
+    '//gn:gtest_main':
+        lambda x: None,
+    '//gn:protoc':
+        lambda x: None,
+    '//gn:gtest_and_gmock':
+        enable_gtest_and_gmock,
+    '//gn:libunwind':
+        enable_libunwind,
+    '//gn:protobuf_full':
+        enable_protobuf_full,
+    '//gn:protobuf_lite':
+        enable_protobuf_lite,
+    '//gn:protoc_lib':
+        enable_protoc_lib,
+    '//gn:libunwindstack':
+        enable_libunwindstack,
+    '//gn:sqlite':
+        enable_sqlite,
+    '//gn:zlib':
+        enable_zlib,
+    '//gn:bionic_kernel_uapi_headers':
+        enable_uapi_headers,
+    '//src/profiling/memory:bionic_libc_platform_headers_on_android':
+        enable_bionic_libc_platform_headers_on_android,
+}
+
+# ----------------------------------------------------------------------------
+# End of configuration.
+# ----------------------------------------------------------------------------
+
+
+class Error(Exception):
+  pass
+
+
+class ThrowingArgumentParser(argparse.ArgumentParser):
+
+  def __init__(self, context):
+    super(ThrowingArgumentParser, self).__init__()
+    self.context = context
+
+  def error(self, message):
+    raise Error('%s: %s' % (self.context, message))
+
+
+def write_blueprint_key_value(output, name, value, sort=True):
+  """Writes a Blueprint key-value pair to the output"""
+
+  if isinstance(value, bool):
+    if value:
+      output.append('    %s: true,' % name)
+    else:
+      output.append('    %s: false,' % name)
+    return
+  if not value:
+    return
+  if isinstance(value, set):
+    value = sorted(value)
+  if isinstance(value, list):
+    output.append('    %s: [' % name)
+    for item in sorted(value) if sort else value:
+      output.append('        "%s",' % item)
+    output.append('    ],')
+    return
+  if isinstance(value, Target):
+    value.to_string(output)
+    return
+  if isinstance(value, dict):
+    kv_output = []
+    for k, v in value.items():
+      write_blueprint_key_value(kv_output, k, v)
+
+    output.append('    %s: {' % name)
+    for line in kv_output:
+      output.append('    %s' % line)
+    output.append('    },')
+    return
+  output.append('    %s: "%s",' % (name, value))
+
+
+class Target(object):
+  """A target-scoped part of a module"""
+
+  def __init__(self, name):
+    self.name = name
+    self.shared_libs = set()
+    self.static_libs = set()
+    self.whole_static_libs = set()
+    self.cflags = set()
+    self.dist = dict()
+    self.strip = dict()
+    self.stl = None
+
+  def to_string(self, output):
+    nested_out = []
+    self._output_field(nested_out, 'shared_libs')
+    self._output_field(nested_out, 'static_libs')
+    self._output_field(nested_out, 'whole_static_libs')
+    self._output_field(nested_out, 'cflags')
+    self._output_field(nested_out, 'stl')
+    self._output_field(nested_out, 'dist')
+    self._output_field(nested_out, 'strip')
+
+    if nested_out:
+      output.append('    %s: {' % self.name)
+      for line in nested_out:
+        output.append('    %s' % line)
+      output.append('    },')
+
+  def _output_field(self, output, name, sort=True):
+    value = getattr(self, name)
+    return write_blueprint_key_value(output, name, value, sort)
+
+
+class Module(object):
+  """A single module (e.g., cc_binary, cc_test) in a blueprint."""
+
+  def __init__(self, mod_type, name, gn_target):
+    self.type = mod_type
+    self.gn_target = gn_target
+    self.name = name
+    self.srcs = set()
+    self.comment = 'GN: ' + gn_utils.label_without_toolchain(gn_target)
+    self.shared_libs = set()
+    self.static_libs = set()
+    self.whole_static_libs = set()
+    self.runtime_libs = set()
+    self.tools = set()
+    self.cmd = None
+    self.host_supported = False
+    self.vendor_available = False
+    self.init_rc = set()
+    self.out = set()
+    self.export_include_dirs = set()
+    self.generated_headers = set()
+    self.export_generated_headers = set()
+    self.defaults = set()
+    self.cflags = set()
+    self.include_dirs = set()
+    self.header_libs = set()
+    self.required = set()
+    self.user_debug_flag = False
+    self.tool_files = None
+    self.android = Target('android')
+    self.host = Target('host')
+    self.lto = None
+    self.stl = None
+    self.dist = dict()
+    self.strip = dict()
+    self.data = set()
+    self.apex_available = set()
+    self.min_sdk_version = None
+    self.proto = dict()
+    # The genrule_XXX below are properties that must to be propagated back
+    # on the module(s) that depend on the genrule.
+    self.genrule_headers = set()
+    self.genrule_srcs = set()
+    self.genrule_shared_libs = set()
+    self.version_script = None
+    self.test_suites = set()
+    self.test_config = None
+    self.stubs = {}
+
+  def to_string(self, output):
+    if self.comment:
+      output.append('// %s' % self.comment)
+    output.append('%s {' % self.type)
+    self._output_field(output, 'name')
+    self._output_field(output, 'srcs')
+    self._output_field(output, 'shared_libs')
+    self._output_field(output, 'static_libs')
+    self._output_field(output, 'whole_static_libs')
+    self._output_field(output, 'runtime_libs')
+    self._output_field(output, 'tools')
+    self._output_field(output, 'cmd', sort=False)
+    if self.host_supported:
+      self._output_field(output, 'host_supported')
+    if self.vendor_available:
+      self._output_field(output, 'vendor_available')
+    self._output_field(output, 'init_rc')
+    self._output_field(output, 'out')
+    self._output_field(output, 'export_include_dirs')
+    self._output_field(output, 'generated_headers')
+    self._output_field(output, 'export_generated_headers')
+    self._output_field(output, 'defaults')
+    self._output_field(output, 'cflags')
+    self._output_field(output, 'include_dirs')
+    self._output_field(output, 'header_libs')
+    self._output_field(output, 'required')
+    self._output_field(output, 'dist')
+    self._output_field(output, 'strip')
+    self._output_field(output, 'tool_files')
+    self._output_field(output, 'data')
+    self._output_field(output, 'stl')
+    self._output_field(output, 'apex_available')
+    self._output_field(output, 'min_sdk_version')
+    self._output_field(output, 'version_script')
+    self._output_field(output, 'test_suites')
+    self._output_field(output, 'test_config')
+    self._output_field(output, 'stubs')
+    self._output_field(output, 'proto')
+
+    target_out = []
+    self._output_field(target_out, 'android')
+    self._output_field(target_out, 'host')
+    if target_out:
+      output.append('    target: {')
+      for line in target_out:
+        output.append('    %s' % line)
+      output.append('    },')
+
+    if self.user_debug_flag:
+      output.append('    product_variables: {')
+      output.append('        debuggable: {')
+      output.append(
+          '            cflags: ["-DPERFETTO_BUILD_WITH_ANDROID_USERDEBUG"],')
+      output.append('        },')
+      output.append('    },')
+    if self.lto is not None:
+      output.append('    target: {')
+      output.append('        android: {')
+      output.append('            lto: {')
+      output.append('                thin: %s,' %
+                    'true' if self.lto else 'false')
+      output.append('            },')
+      output.append('        },')
+      output.append('    },')
+    output.append('}')
+    output.append('')
+
+  def add_android_static_lib(self, lib):
+    if self.type == 'cc_binary_host':
+      raise Exception('Adding Android static lib for host tool is unsupported')
+    elif self.host_supported:
+      self.android.static_libs.add(lib)
+    else:
+      self.static_libs.add(lib)
+
+  def add_android_shared_lib(self, lib):
+    if self.type == 'cc_binary_host':
+      raise Exception('Adding Android shared lib for host tool is unsupported')
+    elif self.host_supported:
+      self.android.shared_libs.add(lib)
+    else:
+      self.shared_libs.add(lib)
+
+  def _output_field(self, output, name, sort=True):
+    value = getattr(self, name)
+    return write_blueprint_key_value(output, name, value, sort)
+
+
+class Blueprint(object):
+  """In-memory representation of an Android.bp file."""
+
+  def __init__(self):
+    self.modules = {}
+
+  def add_module(self, module):
+    """Adds a new module to the blueprint, replacing any existing module
+        with the same name.
+
+        Args:
+            module: Module instance.
+        """
+    self.modules[module.name] = module
+
+  def to_string(self, output):
+    for m in sorted(itervalues(self.modules), key=lambda m: m.name):
+      m.to_string(output)
+
+
+def label_to_module_name(label):
+  """Turn a GN label (e.g., //:perfetto_tests) into a module name."""
+  # If the label is explicibly listed in the default target list, don't prefix
+  # its name and return just the target name. This is so tools like
+  # "traceconv" stay as such in the Android tree.
+  label_without_toolchain = gn_utils.label_without_toolchain(label)
+  if label in default_targets or label_without_toolchain in default_targets:
+    return label_without_toolchain.split(':')[-1]
+
+  module = re.sub(r'^//:?', '', label_without_toolchain)
+  module = re.sub(r'[^a-zA-Z0-9_]', '_', module)
+  if not module.startswith(module_prefix):
+    return module_prefix + module
+  return module
+
+
+def is_supported_source_file(name):
+  """Returns True if |name| can appear in a 'srcs' list."""
+  return os.path.splitext(name)[1] in ['.c', '.cc', '.proto']
+
+
+def create_proto_modules(blueprint, gn, target):
+  """Generate genrules for a proto GN target.
+
+    GN actions are used to dynamically generate files during the build. The
+    Soong equivalent is a genrule. This function turns a specific kind of
+    genrule which turns .proto files into source and header files into a pair
+    equivalent genrules.
+
+    Args:
+        blueprint: Blueprint instance which is being generated.
+        target: gn_utils.Target object.
+
+    Returns:
+        The source_genrule module.
+    """
+  assert (target.type == 'proto_library')
+
+  tools = {'aprotoc'}
+  cpp_out_dir = '$(genDir)/%s/' % tree_path
+  target_module_name = label_to_module_name(target.name)
+
+  # In GN builds the proto path is always relative to the output directory
+  # (out/tmp.xxx).
+  cmd = ['mkdir -p %s &&' % cpp_out_dir, '$(location aprotoc)']
+  cmd += ['--proto_path=%s' % tree_path]
+
+  if buildtools_protobuf_src in target.proto_paths:
+    cmd += ['--proto_path=%s' % android_protobuf_src]
+
+  # We don't generate any targets for source_set proto modules because
+  # they will be inlined into other modules if required.
+  if target.proto_plugin == 'source_set':
+    return None
+
+  # Descriptor targets only generate a single target.
+  if target.proto_plugin == 'descriptor':
+    out = '{}.bin'.format(target_module_name)
+
+    cmd += ['--descriptor_set_out=$(out)']
+    cmd += ['$(in)']
+
+    descriptor_module = Module('genrule', target_module_name, target.name)
+    descriptor_module.cmd = ' '.join(cmd)
+    descriptor_module.out = [out]
+    descriptor_module.tools = tools
+    blueprint.add_module(descriptor_module)
+
+    # Recursively extract the .proto files of all the dependencies and
+    # add them to srcs.
+    descriptor_module.srcs.update(
+        gn_utils.label_to_path(src) for src in target.sources)
+    for dep in target.transitive_proto_deps:
+      current_target = gn.get_target(dep)
+      descriptor_module.srcs.update(
+          gn_utils.label_to_path(src) for src in current_target.sources)
+
+    return descriptor_module
+
+  # We create two genrules for each proto target: one for the headers and
+  # another for the sources. This is because the module that depends on the
+  # generated files needs to declare two different types of dependencies --
+  # source files in 'srcs' and headers in 'generated_headers' -- and it's not
+  # valid to generate .h files from a source dependency and vice versa.
+  source_module_name = target_module_name + '_gen'
+  source_module = Module('genrule', source_module_name, target.name)
+  blueprint.add_module(source_module)
+  source_module.srcs.update(
+      gn_utils.label_to_path(src) for src in target.sources)
+
+  header_module = Module('genrule', source_module_name + '_headers',
+                         target.name)
+  blueprint.add_module(header_module)
+  header_module.srcs = set(source_module.srcs)
+
+  # TODO(primiano): at some point we should remove this. This was introduced
+  # by aosp/1108421 when adding "protos/" to .proto include paths, in order to
+  # avoid doing multi-repo changes and allow old clients in the android tree
+  # to still do the old #include "perfetto/..." rather than
+  # #include "protos/perfetto/...".
+  header_module.export_include_dirs = {'.', 'protos'}
+
+  source_module.genrule_srcs.add(':' + source_module.name)
+  source_module.genrule_headers.add(header_module.name)
+
+  if target.proto_plugin == 'proto':
+    suffixes = ['pb']
+    source_module.genrule_shared_libs.add('libprotobuf-cpp-lite')
+    cmd += ['--cpp_out=lite=true:' + cpp_out_dir]
+  elif target.proto_plugin == 'protozero':
+    suffixes = ['pbzero']
+    plugin = create_modules_from_target(blueprint, gn, protozero_plugin)
+    tools.add(plugin.name)
+    cmd += ['--plugin=protoc-gen-plugin=$(location %s)' % plugin.name]
+    cmd += ['--plugin_out=wrapper_namespace=pbzero:' + cpp_out_dir]
+  elif target.proto_plugin == 'cppgen':
+    suffixes = ['gen']
+    plugin = create_modules_from_target(blueprint, gn, cppgen_plugin)
+    tools.add(plugin.name)
+    cmd += ['--plugin=protoc-gen-plugin=$(location %s)' % plugin.name]
+    cmd += ['--plugin_out=wrapper_namespace=gen:' + cpp_out_dir]
+  elif target.proto_plugin == 'ipc':
+    suffixes = ['ipc']
+    plugin = create_modules_from_target(blueprint, gn, ipc_plugin)
+    tools.add(plugin.name)
+    cmd += ['--plugin=protoc-gen-plugin=$(location %s)' % plugin.name]
+    cmd += ['--plugin_out=wrapper_namespace=gen:' + cpp_out_dir]
+  else:
+    raise Error('Unsupported proto plugin: %s' % target.proto_plugin)
+
+  cmd += ['$(in)']
+  source_module.cmd = ' '.join(cmd)
+  header_module.cmd = source_module.cmd
+  source_module.tools = tools
+  header_module.tools = tools
+
+  for sfx in suffixes:
+    source_module.out.update('%s/%s' %
+                             (tree_path, src.replace('.proto', '.%s.cc' % sfx))
+                             for src in source_module.srcs)
+    header_module.out.update('%s/%s' %
+                             (tree_path, src.replace('.proto', '.%s.h' % sfx))
+                             for src in header_module.srcs)
+  return source_module
+
+
+def create_amalgamated_sql_metrics_module(blueprint, target):
+  bp_module_name = label_to_module_name(target.name)
+  module = Module('genrule', bp_module_name, target.name)
+  module.tool_files = [
+      'tools/gen_amalgamated_sql_metrics.py',
+  ]
+  module.cmd = ' '.join([
+      '$(location tools/gen_amalgamated_sql_metrics.py)',
+      '--cpp_out=$(out)',
+      '$(in)',
+  ])
+  module.genrule_headers.add(module.name)
+  module.out.update(target.outputs)
+  module.srcs.update(gn_utils.label_to_path(src) for src in target.inputs)
+  blueprint.add_module(module)
+  return module
+
+
+def create_cc_proto_descriptor_module(blueprint, target):
+  bp_module_name = label_to_module_name(target.name)
+  module = Module('genrule', bp_module_name, target.name)
+  module.tool_files = [
+      'tools/gen_cc_proto_descriptor.py',
+  ]
+  module.cmd = ' '.join([
+      '$(location tools/gen_cc_proto_descriptor.py)', '--gen_dir=$(genDir)',
+      '--cpp_out=$(out)', '$(in)'
+  ])
+  module.genrule_headers.add(module.name)
+  module.srcs.update(
+      ':' + label_to_module_name(dep) for dep in target.proto_deps)
+  module.srcs.update(
+      gn_utils.label_to_path(src)
+      for src in target.inputs
+      if "tmp.gn_utils" not in src)
+  module.out.update(target.outputs)
+  blueprint.add_module(module)
+  return module
+
+
+def create_gen_version_module(blueprint, target, bp_module_name):
+  module = Module('genrule', bp_module_name, gn_utils.GEN_VERSION_TARGET)
+  script_path = gn_utils.label_to_path(target.script)
+  module.genrule_headers.add(bp_module_name)
+  module.tool_files = [script_path]
+  module.out.update(target.outputs)
+  module.srcs.update(gn_utils.label_to_path(src) for src in target.inputs)
+  module.cmd = ' '.join([
+      'python3 $(location %s)' % script_path, '--no_git',
+      '--changelog=$(location CHANGELOG)', '--cpp_out=$(out)'
+  ])
+  blueprint.add_module(module)
+  return module
+
+
+def create_proto_group_modules(blueprint, gn, module_name, target_names):
+  # TODO(lalitm): today, we're only adding a Java lite module because that's
+  # the only one used in practice. In the future, if we need other target types
+  # (e.g. C++, Java full etc.) add them here.
+  bp_module_name = label_to_module_name(module_name) + '_java_protos'
+  module = Module('java_library', bp_module_name, bp_module_name)
+  module.comment = f'''GN: [{', '.join(target_names)}]'''
+  module.proto = {'type': 'lite', 'canonical_path_from_root': False}
+
+  for name in target_names:
+    target = gn.get_target(name)
+    module.srcs.update(gn_utils.label_to_path(src) for src in target.sources)
+    for dep_label in target.transitive_proto_deps:
+      dep = gn.get_target(dep_label)
+      module.srcs.update(gn_utils.label_to_path(src) for src in dep.sources)
+
+  blueprint.add_module(module)
+
+
+def _get_cflags(target):
+  cflags = {flag for flag in target.cflags if re.match(cflag_allowlist, flag)}
+  cflags |= set("-D%s" % define
+                for define in target.defines
+                if re.match(define_allowlist, define))
+  return cflags
+
+
+def create_modules_from_target(blueprint, gn, gn_target_name):
+  """Generate module(s) for a given GN target.
+
+    Given a GN target name, generate one or more corresponding modules into a
+    blueprint. The only case when this generates >1 module is proto libraries.
+
+    Args:
+        blueprint: Blueprint instance which is being generated.
+        gn: gn_utils.GnParser object.
+        gn_target_name: GN target for module generation.
+    """
+  bp_module_name = label_to_module_name(gn_target_name)
+  if bp_module_name in blueprint.modules:
+    return blueprint.modules[bp_module_name]
+  target = gn.get_target(gn_target_name)
+
+  name_without_toolchain = gn_utils.label_without_toolchain(target.name)
+  if target.type == 'executable':
+    if target.toolchain == gn_utils.HOST_TOOLCHAIN:
+      module_type = 'cc_binary_host'
+    elif target.testonly:
+      module_type = 'cc_test'
+    else:
+      module_type = 'cc_binary'
+    module = Module(module_type, bp_module_name, gn_target_name)
+  elif target.type == 'static_library':
+    module = Module('cc_library_static', bp_module_name, gn_target_name)
+  elif target.type == 'shared_library':
+    module = Module('cc_library_shared', bp_module_name, gn_target_name)
+  elif target.type == 'source_set':
+    module = Module('filegroup', bp_module_name, gn_target_name)
+  elif target.type == 'group':
+    # "group" targets are resolved recursively by gn_utils.get_target().
+    # There's nothing we need to do at this level for them.
+    return None
+  elif target.type == 'proto_library':
+    module = create_proto_modules(blueprint, gn, target)
+    if module is None:
+      return None
+  elif target.type == 'action':
+    if 'gen_amalgamated_sql_metrics' in target.name:
+      module = create_amalgamated_sql_metrics_module(blueprint, target)
+    elif re.match('.*gen_cc_.*_descriptor$', name_without_toolchain):
+      module = create_cc_proto_descriptor_module(blueprint, target)
+    elif target.type == 'action' and \
+        name_without_toolchain == gn_utils.GEN_VERSION_TARGET:
+      module = create_gen_version_module(blueprint, target, bp_module_name)
+    else:
+      raise Error('Unhandled action: {}'.format(target.name))
+  else:
+    raise Error('Unknown target %s (%s)' % (target.name, target.type))
+
+  blueprint.add_module(module)
+  module.host_supported = (name_without_toolchain in target_host_supported)
+  module.vendor_available = (name_without_toolchain in target_vendor_available)
+  module.init_rc = target_initrc.get(target.name, [])
+  module.srcs.update(
+      gn_utils.label_to_path(src)
+      for src in target.sources
+      if is_supported_source_file(src))
+
+  if target.type in gn_utils.LINKER_UNIT_TYPES:
+    module.cflags.update(_get_cflags(target))
+
+  module_is_compiled = module.type not in ('genrule', 'filegroup')
+  if module_is_compiled:
+    # Don't try to inject library/source dependencies into genrules or
+    # filegroups because they are not compiled in the traditional sense.
+    module.defaults = [defaults_module]
+    for lib in target.libs:
+      # Generally library names should be mangled as 'libXXX', unless they
+      # are HAL libraries (e.g., android.hardware.health@2.0) or AIDL c++ / NDK
+      # libraries (e.g. "android.hardware.power.stats-V1-cpp")
+      android_lib = lib if '@' in lib or "-cpp" in lib or "-ndk" in lib \
+        else 'lib' + lib
+      if lib in shared_library_allowlist:
+        module.add_android_shared_lib(android_lib)
+      if lib in static_library_allowlist:
+        module.add_android_static_lib(android_lib)
+
+  # If the module is a static library, export all the generated headers.
+  if module.type == 'cc_library_static':
+    module.export_generated_headers = module.generated_headers
+
+  # Merge in additional hardcoded arguments.
+  for key, add_val in additional_args.get(module.name, []):
+    curr = getattr(module, key)
+    if add_val and isinstance(add_val, set) and isinstance(curr, set):
+      curr.update(add_val)
+    elif isinstance(add_val, str) and (not curr or isinstance(curr, str)):
+      setattr(module, key, add_val)
+    elif isinstance(add_val, bool) and (not curr or isinstance(curr, bool)):
+      setattr(module, key, add_val)
+    elif isinstance(add_val, dict) and isinstance(curr, dict):
+      curr.update(add_val)
+    elif isinstance(add_val, dict) and isinstance(curr, Target):
+      curr.__dict__.update(add_val)
+    else:
+      raise Error('Unimplemented type %r of additional_args: %r' %
+                  (type(add_val), key))
+
+  # dep_name is an unmangled GN target name (e.g. //foo:bar(toolchain)).
+  all_deps = target.deps | target.source_set_deps | target.transitive_proto_deps
+  for dep_name in all_deps:
+    # If the dependency refers to a library which we can replace with an
+    # Android equivalent, stop recursing and patch the dependency in.
+    # Don't recurse into //buildtools, builtin_deps are intercepted at
+    # the //gn:xxx level.
+    if dep_name.startswith('//buildtools'):
+      continue
+
+    # Ignore the dependency on the gen_buildflags genrule. That is run
+    # separately in this generator and the generated file is copied over
+    # into the repo (see usage of |buildflags_dir| in this script).
+    if dep_name.startswith(gn_utils.BUILDFLAGS_TARGET):
+      continue
+
+    dep_module = create_modules_from_target(blueprint, gn, dep_name)
+
+    # For filegroups and genrule, recurse but don't apply the deps.
+    if not module_is_compiled:
+      continue
+
+    # |builtin_deps| override GN deps with Android-specific ones. See the
+    # config in the top of this file.
+    if gn_utils.label_without_toolchain(dep_name) in builtin_deps:
+      builtin_deps[gn_utils.label_without_toolchain(dep_name)](module)
+      continue
+
+    # Don't recurse in any other //gn dep if not handled by builtin_deps.
+    if dep_name.startswith('//gn:'):
+      continue
+
+    if dep_module is None:
+      continue
+    if dep_module.type == 'cc_library_shared':
+      module.shared_libs.add(dep_module.name)
+    elif dep_module.type == 'cc_library_static':
+      module.static_libs.add(dep_module.name)
+    elif dep_module.type == 'filegroup':
+      module.srcs.add(':' + dep_module.name)
+    elif dep_module.type == 'genrule':
+      module.generated_headers.update(dep_module.genrule_headers)
+      module.srcs.update(dep_module.genrule_srcs)
+      module.shared_libs.update(dep_module.genrule_shared_libs)
+    elif dep_module.type == 'cc_binary':
+      continue  # Ignore executables deps (used by cmdline integration tests).
+    else:
+      raise Error('Unknown dep %s (%s) for target %s' %
+                  (dep_module.name, dep_module.type, module.name))
+
+  return module
+
+
+def create_blueprint_for_targets(gn, desc, targets):
+  """Generate a blueprint for a list of GN targets."""
+  blueprint = Blueprint()
+
+  # Default settings used by all modules.
+  defaults = Module('cc_defaults', defaults_module, '//gn:default_deps')
+
+  # We have to use include_dirs passing the path relative to the android tree.
+  # This is because: (i) perfetto_cc_defaults is used also by
+  # test/**/Android.bp; (ii) if we use local_include_dirs instead, paths
+  # become relative to the Android.bp that *uses* cc_defaults (not the one
+  # that defines it).s
+  defaults.include_dirs = {
+      tree_path, tree_path + '/include', tree_path + '/' + buildflags_dir,
+      tree_path + '/src/profiling/memory/include'
+  }
+  defaults.cflags = [
+      '-Wno-error=return-type',
+      '-Wno-sign-compare',
+      '-Wno-sign-promo',
+      '-Wno-unused-parameter',
+      '-fvisibility=hidden',
+      '-O2',
+  ]
+  defaults.user_debug_flag = True
+  defaults.lto = True
+
+  blueprint.add_module(defaults)
+  for target in targets:
+    create_modules_from_target(blueprint, gn, target)
+  return blueprint
+
+
+def main():
+  parser = argparse.ArgumentParser(
+      description='Generate Android.bp from a GN description.')
+  parser.add_argument(
+      '--check-only',
+      help='Don\'t keep the generated files',
+      action='store_true')
+  parser.add_argument(
+      '--desc',
+      help='GN description (e.g., gn desc out --format=json --all-toolchains "//*"'
+  )
+  parser.add_argument(
+      '--extras',
+      help='Extra targets to include at the end of the Blueprint file',
+      default=os.path.join(gn_utils.repo_root(), 'Android.bp.extras'),
+  )
+  parser.add_argument(
+      '--output',
+      help='Blueprint file to create',
+      default=os.path.join(gn_utils.repo_root(), 'Android.bp'),
+  )
+  parser.add_argument(
+      'targets',
+      nargs=argparse.REMAINDER,
+      help='Targets to include in the blueprint (e.g., "//:perfetto_tests")')
+  args = parser.parse_args()
+
+  if args.desc:
+    with open(args.desc) as f:
+      desc = json.load(f)
+  else:
+    desc = gn_utils.create_build_description(gn_args)
+
+  gn = gn_utils.GnParser(desc)
+  blueprint = create_blueprint_for_targets(gn, desc, args.targets or
+                                           default_targets)
+  project_root = os.path.abspath(os.path.dirname(os.path.dirname(__file__)))
+  tool_name = os.path.relpath(os.path.abspath(__file__), project_root)
+
+  # TODO(primiano): enable this on Android after the TODO in
+  # perfetto_component.gni is fixed.
+  # Check for ODR violations
+  # for target_name in default_targets:
+  # checker = gn_utils.ODRChecker(gn, target_name)
+
+  # Add any proto groups to the blueprint.
+  for l_name, t_names in proto_groups.items():
+    create_proto_group_modules(blueprint, gn, l_name, t_names)
+
+  output = [
+      """// Copyright (C) 2017 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.
+//
+// This file is automatically generated by %s. Do not edit.
+""" % (tool_name)
+  ]
+  blueprint.to_string(output)
+  with open(args.extras, 'r') as r:
+    for line in r:
+      output.append(line.rstrip("\n\r"))
+
+  out_files = []
+
+  # Generate the Android.bp file.
+  out_files.append(args.output + '.swp')
+  with open(out_files[-1], 'w') as f:
+    f.write('\n'.join(output))
+    # Text files should have a trailing EOL.
+    f.write('\n')
+
+  # Generate the perfetto_build_flags.h file.
+  out_files.append(os.path.join(buildflags_dir, 'perfetto_build_flags.h.swp'))
+  gn_utils.gen_buildflags(gn_args, out_files[-1])
+
+  # Either check the contents or move the files to their final destination.
+  return gn_utils.check_or_commit_generated_files(out_files, args.check_only)
+
+
+if __name__ == '__main__':
+  sys.exit(main())