Merge a1da3bfc12f77aacae9fb409df40d5151465dea4 into cd8089c20baaaee329cbf7951195953a9f86d7cf

Makes bitcoind spin during startup, waiting for a debugger to be attached.

Useful for debugging one or several bitcoind nodes running in the context of a functional test.

TODO: Confirm code works on Mac.

CMakeLists.txt

@@ -132,6 +132,7 @@ option(ENABLE_HARDENING "Attempt to harden the resulting executables." ON)
 option(REDUCE_EXPORTS "Attempt to reduce exported symbols in the resulting executables." OFF)
 option(WERROR "Treat compiler warnings as errors." OFF)
 option(WITH_CCACHE "Attempt to use ccache for compiling." ON)
+option(WAIT_FOR_DEBUGGER "Support for waiting during startup for debugger to be attached." OFF)
 
 option(WITH_ZMQ "Enable ZMQ notifications." OFF)
 if(WITH_ZMQ)
@@ -246,6 +247,10 @@ target_compile_definitions(core_interface_debug INTERFACE
   ABORT_ON_FAILED_ASSUME
 )
 
+if(WAIT_FOR_DEBUGGER)
+  add_compile_definitions(WAIT_FOR_DEBUGGER=1)
+endif()
+
 if(WIN32)
   #[=[
   This build system supports two ways to build binaries for Windows.

src/bitcoind.cpp

@@ -28,7 +28,19 @@
 #include <util/tokenpipe.h>
 #include <util/translation.h>
 
+#ifdef WIN32
+#include <windows.h>
+#include <debugapi.h>
+#elif defined(__APPLE__)
+#include <sys/sysctl.h>
+#elif defined(__linux__)
+#include <linux/prctl.h>
+#include <sys/prctl.h>
+#endif
+
 #include <any>
+#include <cstdlib>
+#include <fstream>
 #include <functional>
 #include <optional>
 
@@ -159,6 +171,60 @@ static bool ProcessInitCommands(ArgsManager& args)
     return false;
 }
 
+#ifdef WAIT_FOR_DEBUGGER
+static int HandleWaitForDebugger(int argc, char* argv[])
+{
+    for (int i = 0; i < argc; ++i) {
+        if (strcmp(argv[i], "-waitfordebugger") == 0) {
+            while (true) {
+                bool attached{false};
+#   if defined(__linux__)
+                // Allow any process to attach to us.
+                prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY);
+
+                std::ifstream sf{"/proc/self/status", std::ios::in};
+                if (!sf.good()) {
+                    return EXIT_FAILURE;
+                }
+
+                std::string s;
+                uint pid{0};
+                while (sf >> s) {
+                    if (s == "TracerPid:") {
+                        sf >> pid;
+                        break;
+                    }
+
+                    std::getline(sf, s);
+                }
+                attached = pid > 0;
+#   elif defined(__APPLE__)
+                const int mib[] = { CTL_KERN, KERN_PROC, KERN_PROC_PID, getpid() };
+                kinfo_proc info;
+                size_t size{sizeof(info)};
+                const int ret{sysctl(mib, sizeof(mib) / sizeof(*mib), &info, &size, nullptr, 0)};
+                if (ret != EXIT_SUCCESS) {
+                    return ret;
+                }
+                attached = info.kp_proc.p_flag & P_TRACED;
+#   elif defined(WIN32)
+                attached = IsDebuggerPresent();
+#   else
+#       error "Platform doesn't support -waitfordebugger.";
+#   endif // platform
+                if (attached) {
+                    break;
+                } else {
+                    std::this_thread::sleep_for(100ms);
+                }
+            }
+        }
+    }
+
+    return EXIT_SUCCESS;
+}
+#endif // WAIT_FOR_DEBUGGER
+
 static bool AppInit(NodeContext& node)
 {
     bool fRet = false;
@@ -254,6 +320,10 @@ static bool AppInit(NodeContext& node)
 
 MAIN_FUNCTION
 {
+#ifdef WAIT_FOR_DEBUGGER
+    if (int ret{HandleWaitForDebugger(argc, argv)}; ret != EXIT_SUCCESS) return ret;
+#endif
+
 #ifdef WIN32
     common::WinCmdLineArgs winArgs;
     std::tie(argc, argv) = winArgs.get();

src/init.cpp

@@ -681,6 +681,7 @@ void SetupServerArgs(ArgsManager& argsman, bool can_listen_ipc)
     hidden_args.emplace_back("-daemon");
     hidden_args.emplace_back("-daemonwait");
 #endif
+    argsman.AddArg("-waitfordebugger", "Spin until a debugger is attached", ArgsManager::ALLOW_ANY, OptionsCategory::DEBUG_TEST);
 
     // Add the hidden options
     argsman.AddHiddenArgs(hidden_args);
@@ -1119,6 +1120,12 @@ bool AppInitParameterInteraction(const ArgsManager& args)
         }
     }
 
+#ifndef WAIT_FOR_DEBUGGER
+    if (args.GetBoolArg("-waitfordebugger", false)) {
+        return InitError(Untranslated("-waitfordebugger support was not included as WAIT_FOR_DEBUGGER is not #defined."));
+    }
+#endif
+
     return true;
 }
 

test/functional/test_framework/test_framework.py

@@ -205,6 +205,8 @@ class BitcoinTestFramework(metaclass=BitcoinTestMetaClass):
                             help="Explicitly use v1 transport (can be used to overwrite global --v2transport option)")
         parser.add_argument("--test_methods", dest="test_methods", nargs='*',
                             help="Run specified test methods sequentially instead of the full test. Use only for methods that do not depend on any context set up in run_test or other methods.")
+        parser.add_argument("--debug_runs", dest="debug_runs", nargs="*", type=int, default=[],
+                            help="Node executions in the test to stall and wait for debugger, 0-based.")
 
         self.add_options(parser)
         # Running TestShell in a Jupyter notebook causes an additional -f argument
@@ -239,6 +241,8 @@ class BitcoinTestFramework(metaclass=BitcoinTestMetaClass):
 
         PortSeed.n = self.options.port_seed
 
+        TestNode.debug_runs = self.options.debug_runs
+
     def set_binary_paths(self):
         """Update self.options with the paths of all binaries from environment variables or their default values"""
 

test/functional/test_framework/test_node.py

@@ -76,6 +76,9 @@ class TestNode():
     To make things easier for the test writer, any unrecognised messages will
     be dispatched to the RPC connection."""
 
+    runs = 0
+    debug_runs = None
+
     def __init__(self, i, datadir_path, *, chain, rpchost, timewait, timeout_factor, bitcoind, bitcoin_cli, coverage_dir, cwd, extra_conf=None, extra_args=None, use_cli=False, start_perf=False, use_valgrind=False, version=None, descriptors=False, v2transport=False):
         """
         Kwargs:
@@ -253,10 +256,18 @@ class TestNode():
         if env is not None:
             subp_env.update(env)
 
+        wait_for_debugger = TestNode.debug_runs is not None and TestNode.runs in TestNode.debug_runs
+        if wait_for_debugger:
+            extra_args.append("-waitfordebugger")
+
         self.process = subprocess.Popen(self.args + extra_args, env=subp_env, stdout=stdout, stderr=stderr, cwd=cwd, **kwargs)
 
         self.running = True
-        self.log.debug("bitcoind started, waiting for RPC to come up")
+        if wait_for_debugger:
+            self.log.info(f"bitcoind started (run #{TestNode.runs}, node #{self.index}), waiting for debugger, PID: {self.process.pid}")
+        else:
+            self.log.debug(f"bitcoind started (run #{TestNode.runs}, node #{self.index}), waiting for RPC to come up")
+        TestNode.runs += 1
 
         if self.start_perf:
             self._start_perf()