Add target experiment script. (#10544)

This launches a GCB build for a project, runs a specified fuzz target
with specified arguments, and uploads the output to a specified path.

e.g.

```
python infra/build/functions/target_experiment.py --project=libxml2 --target xml \
    --output_log gs://oss-fuzz-gcb-experiment-run-logs/output.log -- -max_total_time=30
```

infra/build/functions/build_lib.py

@@ -436,7 +436,12 @@ def get_project_image_steps(  # pylint: disable=too-many-arguments
 
   # TODO(metzman): Pass the URL to clone.
   clone_step = get_git_clone_step(repo_url=config.repo, branch=config.branch)
-  steps = [clone_step]
+  if experiment:
+    # Skip cloning if we're in an experiment. The source is submitted to GCB
+    # via gcloud builds submit.
+    steps = []
+  else:
+    steps = [clone_step]
   if config.test_image_suffix:
     steps.extend(get_pull_test_images_steps(config.test_image_suffix))
   src_root = 'oss-fuzz' if not experiment else '.'

infra/build/functions/target_experiment.py

@@ -0,0 +1,107 @@
+# Copyright 2023 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.
+#
+################################################################################
+"""Script to run target experiments on GCB."""
+
+import argparse
+import sys
+
+import google.auth
+
+import build_lib
+import build_project
+import trial_build
+
+
+def run_experiment(project_name, target_name, args, output_path):
+  config = build_project.Config(testing=True,
+                                test_image_suffix='',
+                                repo=build_project.DEFAULT_OSS_FUZZ_REPO,
+                                branch=None,
+                                parallel=False,
+                                upload=False,
+                                experiment=True)
+
+  try:
+    project_yaml, dockerfile_contents = (
+        build_project.get_project_data(project_name))
+  except FileNotFoundError:
+    logging.error('Couldn\'t get project data. Skipping %s.', project_name)
+    return
+
+  # Override sanitizers and engine because we only care about libFuzzer+ASan
+  # for benchmarking purposes.
+  build_project.set_yaml_defaults(project_yaml)
+  project_yaml['sanitizers'] = ['address']
+  project_yaml['fuzzing_engines'] = ['libfuzzer']
+
+  # Don't do bad build checks.
+  project_yaml['run_tests'] = False
+
+  steps = build_project.get_build_steps(project_name, project_yaml,
+                                        dockerfile_contents, config)
+
+  build = build_project.Build('libfuzzer', 'address', 'x86_64')
+  local_output_path = '/workspace/output.log'
+  fuzzer_args = ' '.join(args)
+
+  env = build_project.get_env(project_yaml['language'], build)
+  env.append('RUN_FUZZER_MODE=batch')
+
+  run_step = {
+      'name':
+          'gcr.io/oss-fuzz-base/base-runner',
+      'env':
+          env,
+      'args': [
+          'bash',
+          '-c',
+          f'run_fuzzer {target_name} {fuzzer_args} &> {local_output_path}',
+      ]
+  }
+  steps.append(build_lib.dockerify_run_step(run_step, build))
+
+  # TODO: Save corpus too.
+  steps.append({
+      'name': 'gcr.io/cloud-builders/gsutil',
+      'args': ['-m', 'cp', local_output_path, output_path]
+  })
+
+  credentials, _ = google.auth.default()
+  return build_project.run_build(project_name,
+                                 steps,
+                                 credentials,
+                                 'experiment',
+                                 experiment=True)
+
+
+def main():
+  parser = argparse.ArgumentParser(sys.argv[0], description='Test projects')
+  parser.add_argument('--project', required=True, help='Project name')
+  parser.add_argument('--target', required=True, help='Target name')
+  parser.add_argument('args',
+                      nargs='+',
+                      help='Additional arguments to pass to the target')
+  parser.add_argument('--output_log', required=True, help='GCS log location.')
+  args = parser.parse_args()
+
+  build_id = run_experiment(args.project, args.target, args.args,
+                            args.output_log)
+  #print('Link:', f'https://pantheon.corp.google.com/cloud-build/builds;region=us-central1/{build_id}?project=oss-fuzz'))
+  print(build_id)
+
+
+if __name__ == '__main__':
+  main()