test: add integration test for instrumented Firecracker binary

Adds a new integration test that verifies Firecracker can be
built and run with `log_instrument` tracing instrumentation\
enabled.

Signed-off-by: DontPanicO <[email protected]>

Author: DontPanicO

tests/integration_tests/functional/test_instrumented_firecracker.py

@@ -0,0 +1,123 @@
+# Copyright 2025 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+"""
+Integration test verifying that Firecracker builds and runs correctly when instrumented
+with the `log_instrument::instrument` macro. Ensures that TRACE-level logs and entry/exit
+markers (ThreadId(...) >> / <<) are emitted when the binary is built with the `tracing`
+feature.
+"""
+
+import re
+import tempfile
+
+import pytest
+
+from framework import utils
+from framework.microvm import MicroVMFactory
+from host_tools.cargo_build import cargo, get_binary
+
+# Marker tipici emessi dalla macro log_instrument
+TRACE_LEVEL_HINT = "TRACE"
+MARKER_REGEX = re.compile(r"ThreadId\(\d+\).*?(?:>>|<<)")
+PATHS_TO_INSTRUMENT = [
+    "../src/firecracker/src/main.rs",
+    "../src/firecracker/src/api_server",
+    "../src/vmm/src/lib.rs",
+    "../src/vmm/src/builder.rs",
+]
+
+
+def build_instrumented_binary():
+    """Builds an instrumented Firecracker binary with tracing instrumentation."""
+    clippy_tracing = get_binary("clippy-tracing")
+    for p in PATHS_TO_INSTRUMENT:
+        utils.check_output(
+            f"{clippy_tracing} --action fix --suffix log_instrument:: --cfg-attr 'feature =\"tracing\"' --path {p}"
+        )
+    cargo(
+        "build",
+        "--workspace --target x86_64-unknown-linux-musl --no-default-features --release --features tracing --bin firecracker",
+    )
+    return get_binary("firecracker")
+
+
+def cleanup_instrumentation():
+    """Cleans up tracing instrumentation from the Firecracker binary."""
+    clippy_tracing = get_binary("clippy-tracing")
+    for p in PATHS_TO_INSTRUMENT:
+        utils.check_output(
+            f"{clippy_tracing} --action strip --suffix log_instrument:: --cfg-attr 'feature =\"tracing\"' --path {p}"
+        )
+
+
+@pytest.fixture(scope="module")
+def instrumented_binary():
+    """Build and provide the path to an instrumented Firecracker binary."""
+    binary_path = build_instrumented_binary()
+    yield binary_path
+    cleanup_instrumentation()
+
+
+@pytest.mark.timeout(120)
+def test_log_instrument_firecracker_basic_functionality(instrumented_binary):
+    """Test that instrumented Firecracker can start and handle basic API calls with trace logging."""
+    with tempfile.TemporaryDirectory() as _:
+        microvm_factory = MicroVMFactory(instrumented_binary.parent)
+        vm = microvm_factory.build()
+        vm.spawn(log_level="Trace", log_show_level=True, log_show_origin=True)
+
+        try:
+            vm._wait_for_api_socket()
+
+            # Generate some log traffic
+            resp = vm.api.describe.get()
+            assert resp.status_code == 200
+            resp = vm.api.machine_config.get()
+            assert resp.status_code == 200
+
+            # Ensure TRACE logs are being captured
+            logger_config = {
+                "level": "Trace",
+                "show_level": True,
+                "show_log_origin": True,
+            }
+            resp = vm.api.logger.put(**logger_config)
+            assert resp.status_code == 204
+
+            # Another API call after enabling TRACE
+            resp = vm.api.describe.get()
+            assert resp.status_code == 200
+
+        finally:
+            vm.kill()
+
+        log_data = vm.log_data
+        assert TRACE_LEVEL_HINT in log_data, "Expected TRACE level logs in output"
+
+        trace_matches = re.findall(MARKER_REGEX, log_data)
+
+        assert (
+            len(trace_matches) > 0
+        ), f"Expected to find log-instrument traces in logs, but found none. Log data: {log_data[:1000]}..."
+
+        entry_traces = [match for match in trace_matches if ">>" in match]
+        exit_traces = [match for match in trace_matches if "<<" in match]
+
+        assert len(entry_traces) > 0, "Expected to find function entry traces (>>)"
+        assert len(exit_traces) > 0, "Expected to find function exit traces (<<)"
+
+        meaningful_functions = ["main", "api", "vmm", "request", "response"]
+        found_meaningful = False
+
+        for trace in trace_matches:
+            for func in meaningful_functions:
+                if func.lower() in trace.lower():
+                    found_meaningful = True
+                    break
+            if found_meaningful:
+                break
+
+        assert (
+            found_meaningful
+        ), f"Expected to find traces from meaningful functions, but traces were: {trace_matches[:10]}"