test: validation:block_connected tracepoint test

This adds a test for the validation:block_connected tracepoint.

test/functional/interface_usdt_validation.py

@@ -0,0 +1,136 @@
+#!/usr/bin/env python3
+# Copyright (c) 2022 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+""" Tests the validation:* tracepoint API interface.
+    See https://github.com/bitcoin/bitcoin/blob/master/doc/tracing.md#context-validation
+"""
+
+import ctypes
+
+# Test will be skipped if we don't have bcc installed
+try:
+    from bcc import BPF, USDT # type: ignore[import]
+except ImportError:
+    pass
+
+from test_framework.address import ADDRESS_BCRT1_UNSPENDABLE
+from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import assert_equal
+
+
+validation_blockconnected_program = """
+#include <uapi/linux/ptrace.h>
+
+typedef signed long long i64;
+
+struct connected_block
+{
+    char        hash[32];
+    int         height;
+    i64         transactions;
+    int         inputs;
+    i64         sigops;
+    u64         duration;
+};
+
+BPF_PERF_OUTPUT(block_connected);
+int trace_block_connected(struct pt_regs *ctx) {
+    struct connected_block block = {};
+    bpf_usdt_readarg_p(1, ctx, &block.hash, 32);
+    bpf_usdt_readarg(2, ctx, &block.height);
+    bpf_usdt_readarg(3, ctx, &block.transactions);
+    bpf_usdt_readarg(4, ctx, &block.inputs);
+    bpf_usdt_readarg(5, ctx, &block.sigops);
+    bpf_usdt_readarg(6, ctx, &block.duration);
+    block_connected.perf_submit(ctx, &block, sizeof(block));
+    return 0;
+}
+"""
+
+
+class ValidationTracepointTest(BitcoinTestFramework):
+    def set_test_params(self):
+        self.num_nodes = 1
+
+    def skip_test_if_missing_module(self):
+        self.skip_if_platform_not_linux()
+        self.skip_if_no_bitcoind_tracepoints()
+        self.skip_if_no_python_bcc()
+        self.skip_if_no_bpf_permissions()
+
+    def run_test(self):
+        # Tests the validation:block_connected tracepoint by generating blocks
+        # and comparing the values passed in the tracepoint arguments with the
+        # blocks.
+        # See https://github.com/bitcoin/bitcoin/blob/master/doc/tracing.md#tracepoint-validationblock_connected
+
+        class Block(ctypes.Structure):
+            _fields_ = [
+                ("hash", ctypes.c_ubyte * 32),
+                ("height", ctypes.c_int),
+                ("transactions", ctypes.c_int64),
+                ("inputs", ctypes.c_int),
+                ("sigops", ctypes.c_int64),
+                ("duration", ctypes.c_uint64),
+            ]
+
+            def __repr__(self):
+                return "ConnectedBlock(hash=%s height=%d, transactions=%d, inputs=%d, sigops=%d, duration=%d)" % (
+                    bytes(self.hash[::-1]).hex(),
+                    self.height,
+                    self.transactions,
+                    self.inputs,
+                    self.sigops,
+                    self.duration)
+
+        # The handle_* function is a ctypes callback function called from C. When
+        # we assert in the handle_* function, the AssertError doesn't propagate
+        # back to Python. The exception is ignored. We manually count and assert
+        # that the handle_* functions succeeded.
+        BLOCKS_EXPECTED = 2
+        blocks_checked = 0
+        expected_blocks = list()
+
+        self.log.info("hook into the validation:block_connected tracepoint")
+        ctx = USDT(path=str(self.options.bitcoind))
+        ctx.enable_probe(probe="validation:block_connected",
+                         fn_name="trace_block_connected")
+        bpf = BPF(text=validation_blockconnected_program,
+                  usdt_contexts=[ctx], debug=0)
+
+        def handle_blockconnected(_, data, __):
+            nonlocal expected_blocks, blocks_checked
+            event = ctypes.cast(data, ctypes.POINTER(Block)).contents
+            self.log.info(f"handle_blockconnected(): {event}")
+            block = expected_blocks.pop(0)
+            assert_equal(block["hash"], bytes(event.hash[::-1]).hex())
+            assert_equal(block["height"], event.height)
+            assert_equal(len(block["tx"]), event.transactions)
+            assert_equal(len([tx["vin"] for tx in block["tx"]]), event.inputs)
+            assert_equal(0, event.sigops)  # no sigops in coinbase tx
+            # only plausibility checks
+            assert(event.duration > 0)
+
+            blocks_checked += 1
+
+        bpf["block_connected"].open_perf_buffer(
+            handle_blockconnected)
+
+        self.log.info(f"mine {BLOCKS_EXPECTED} blocks")
+        block_hashes = self.generatetoaddress(
+            self.nodes[0], BLOCKS_EXPECTED, ADDRESS_BCRT1_UNSPENDABLE)
+        for block_hash in block_hashes:
+            expected_blocks.append(self.nodes[0].getblock(block_hash, 2))
+
+        bpf.perf_buffer_poll(timeout=200)
+        bpf.cleanup()
+
+        self.log.info(f"check that we traced {BLOCKS_EXPECTED} blocks")
+        assert_equal(BLOCKS_EXPECTED, blocks_checked)
+        assert_equal(0, len(expected_blocks))
+
+
+if __name__ == '__main__':
+    ValidationTracepointTest().main()

test/functional/test_runner.py

@@ -170,6 +170,7 @@ BASE_SCRIPTS = [
     'interface_rpc.py',
     'interface_usdt_net.py',
     'interface_usdt_utxocache.py',
+    'interface_usdt_validation.py',
     'rpc_psbt.py --legacy-wallet',
     'rpc_psbt.py --descriptors',
     'rpc_users.py',