File indexing completed on 2024-04-21 11:27:33

 /*
     This file is part of the KDE Libraries
     SPDX-FileCopyrightText: 2000 Timo Hummel <timo.hummel@sap.com>
     SPDX-FileCopyrightText: 2000 Tom Braun <braunt@fh-konstanz.de>
     SPDX-FileCopyrightText: 2010 George Kiagiadakis <kiagiadakis.george@gmail.com>
     SPDX-FileCopyrightText: 2009 KDE e.V. <kde-ev-board@kde.org>
     SPDX-FileCopyrightText: 2021 Harald Sitter <sitter@kde.org>
     SPDX-FileContributor: 2009 Adriaan de Groot <groot@kde.org>
 
     SPDX-License-Identifier: LGPL-2.0-or-later
 */
 
 #include "kcrash.h"
 
 #include <config-kcrash.h>
 
 #include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
 #include <qplatformdefs.h>
 #ifndef Q_OS_WIN
 #include <cerrno>
 #include <sys/resource.h>
 #include <sys/un.h>
 #else
 #include <qt_windows.h>
 #endif
 #ifdef Q_OS_LINUX
 #include <sys/poll.h>
 #include <sys/prctl.h>
 #endif
 
 #include <KAboutData>
 
 #include <algorithm>
 #include <array>
 #include <memory>
 
 #include <QDebug>
 #include <QDir>
 #include <QFile>
 #include <QGuiApplication>
 #include <QLibraryInfo>
 #include <QStandardPaths>
 #include <QThread>
 
 #include <QLoggingCategory>
 Q_DECLARE_LOGGING_CATEGORY(LOG_KCRASH)
 
 // logging category for this framework, default: log stuff >= info
 Q_LOGGING_CATEGORY(LOG_KCRASH, "kf.crash", QtInfoMsg)
 
 #if HAVE_X11
 #include <X11/Xlib.h>
 #if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
 #include <QX11Info>
 #endif
 #endif
 
 #include "coreconfig_p.h"
 #include "metadata_p.h"
 
 // Copy from klauncher_cmds
 typedef struct {
     long cmd;
     long arg_length;
 } kcrash_launcher_header;
 
 #define LAUNCHER_OK 4
 #define LAUNCHER_EXEC_NEW 12
 
 namespace KCrash
 {
 KCRASH_EXPORT bool loadedByKdeinit = false;
 void setApplicationFilePath(const QString &filePath);
 // Create socket path to transfer ptrace scope and open connection
 }
 #ifdef Q_OS_LINUX
 static QByteArray s_socketpath;
 #endif
 
 struct Args {
     ~Args()
     {
         clear();
     }
 
     void clear()
     {
         if (!argc) {
             return;
         }
 
         for (int i = 0; i < argc; ++i) {
             delete[] argv[i];
         }
         delete[] argv;
 
         argv = nullptr;
         argc = 0;
     }
 
     void resize(int size)
     {
         clear();
         argc = size;
         argv = new char *[argc + 1];
         for (int i = 0; i < argc + 1; ++i) {
             argv[i] = nullptr;
         }
     }
 
     explicit operator bool() const
     {
         return argc > 0;
     }
 
     int argc = 0;
     // null-terminated array of null-terminated strings
     char **argv = nullptr;
 };
 
 static KCrash::HandlerType s_emergencySaveFunction = nullptr;
 static KCrash::HandlerType s_crashHandler = nullptr;
 static std::unique_ptr<char[]> s_appFilePath; // this is the actual QCoreApplication::applicationFilePath
 static std::unique_ptr<char[]> s_appName; // the binary name (may be altered by the application)
 static std::unique_ptr<char[]> s_appPath; // the binary dir path (may be altered by the application)
 static Args s_autoRestartCommandLine;
 static std::unique_ptr<char[]> s_drkonqiPath;
 static KCrash::CrashFlags s_flags = KCrash::CrashFlags();
 static int s_launchDrKonqi = -1; // -1=initial value 0=disabled 1=enabled
 static int s_originalSignal = -1;
 static QByteArray s_metadataPath;
 
 static std::unique_ptr<char[]> s_kcrashErrorMessage;
 Q_GLOBAL_STATIC(KCrash::CoreConfig, s_coreConfig)
 
 static void kcrashInitialize()
 {
     // Static because in some cases this is called multiple times
     // but if an application had any of the bad cases we always want
     // to skip the check
     static bool doAutoInitKCrash = true;
 
     if (!doAutoInitKCrash) {
         return;
     }
 
     QCoreApplication *app = QCoreApplication::instance();
     if (!app) {
         doAutoInitKCrash = false;
         return;
     }
 
     if (!QCoreApplication::startingUp()) {
         // If the app has already started, this means we're not being run as part of
         // qt_call_pre_routines, which most probably means that we're being run as part
         // of KCrash being loaded as part of some plugin of the app, so don't
         // do any magic
         doAutoInitKCrash = false;
         return;
     }
 
     if (!QCoreApplication::eventDispatcher()) {
         // We are called with event dispatcher being null when KCrash is being loaded
         // through plasma-integration instead of being linked to the app (i.e. QtCreator vs Okular)
         // For apps that don't link directly to KCrash do not do the magic
         doAutoInitKCrash = false;
         return;
     }
 
     KCrash::initialize();
 }
 Q_COREAPP_STARTUP_FUNCTION(kcrashInitialize)
 
 static QStringList libexecPaths()
 {
     // Static since we only need to evaluate once.
     static QStringList list = QFile::decodeName(qgetenv("LIBEXEC_PATH")).split(QLatin1Char(':'), Qt::SkipEmptyParts) // env var is used first
         + QStringList{
             QCoreApplication::applicationDirPath(), // then look where our application binary is located
             QLibraryInfo::location(QLibraryInfo::LibraryExecutablesPath), // look where libexec path is (can be set in qt.conf)
             QFile::decodeName(KDE_INSTALL_FULL_LIBEXECDIR) // look at our installation location
         };
     return list;
 }
 
 namespace KCrash
 {
 void setApplicationFilePath(const QString &filePath);
 void startProcess(int argc, const char *argv[], bool waitAndExit);
 
 #if defined(Q_OS_WIN)
 LONG WINAPI win32UnhandledExceptionFilter(_EXCEPTION_POINTERS *exceptionInfo);
 #endif
 }
 
 static bool shouldWriteMetadataToDisk()
 {
 #ifdef Q_OS_LINUX
     // NB: The daemon being currently running must not be a condition here. If something crashes during logout
     // the daemon may already be gone but we'll still want to deal with the crash on next login!
     // Similar reasoning applies to not checking the presence of the launcher socket.
     const bool drkonqiCoredumpHelper = !QStandardPaths::findExecutable(QStringLiteral("drkonqi-coredump-processor"), libexecPaths()).isEmpty();
     return s_coreConfig()->isCoredumpd() && drkonqiCoredumpHelper && !qEnvironmentVariableIsSet("KCRASH_NO_METADATA");
 #else
     return false;
 #endif
 }
 
 void KCrash::initialize()
 {
     if (s_launchDrKonqi == 0) { // disabled by the program itself
         return;
     }
     const QStringList args = QCoreApplication::arguments();
     if (!qEnvironmentVariableIsSet("KDE_DEBUG") //
         && !qEnvironmentVariableIsSet("KCRASH_AUTO_RESTARTED") //
         && !qEnvironmentVariableIntValue("RUNNING_UNDER_RR") //
         && qEnvironmentVariableIntValue("KCRASH_DUMP_ONLY") == 0) {
         // enable drkonqi
         KCrash::setDrKonqiEnabled(true);
     } else {
         // This loads qtlogging.ini very early which prevents unittests from doing QStandardPaths::setTestModeEnabled(true) in initTestCase()
         // qCDebug(LOG_KCRASH) << "KCrash disabled through environment.";
     }
 
     if (QCoreApplication::instance()) {
         const QString path = QCoreApplication::applicationFilePath();
         s_appFilePath.reset(qstrdup(qPrintable(path))); // This intentionally cannot be changed by the application!
         KCrash::setApplicationFilePath(path);
     } else {
         qWarning() << "This process needs a QCoreApplication instance in order to use KCrash";
     }
 
 #ifdef Q_OS_LINUX
     // Create socket path to transfer ptrace scope and open connection
     s_socketpath = QFile::encodeName(QStringLiteral("%1/kcrash_%2").arg(QStandardPaths::writableLocation(QStandardPaths::RuntimeLocation)).arg(getpid()));
 #endif
 
     if (shouldWriteMetadataToDisk()) {
         // We do not actively clean up metadata via KCrash but some other service. This potentially means we litter
         // a lot -> put the metadata in a subdir.
         const QString metadataDir = QStandardPaths::writableLocation(QStandardPaths::GenericCacheLocation) + QStringLiteral("/kcrash-metadata");
         if (QDir().mkpath(metadataDir)) {
             s_metadataPath = QFile::encodeName(metadataDir + QStringLiteral("/%1.ini").arg(QCoreApplication::applicationPid()));
         }
         if (!s_crashHandler) {
             // Always enable the default handler. We cannot create the metadata ahead of time since we do not know
             // when the application metadata is "complete".
             // TODO: kf6 maybe change the way init works and have the users run it when their done with kaboutdata etc.?
             //    the problem with delayed writing is that our crash handler (or any crash handler really) introduces a delay
             //    in dumping and this in turn increases the risk of another stepping into a puddle (SEGV only runs on the
             //    faulting thread; all other threads continue running!). therefore it'd be greatly preferred if we
             //    were able to write the metadata during initial app setup instead of when a crash occurs
             setCrashHandler(defaultCrashHandler);
         }
     } // empty s_metadataPath disables writing
 
     s_coreConfig(); // Initialize.
 }
 
 void KCrash::setEmergencySaveFunction(HandlerType saveFunction)
 {
     s_emergencySaveFunction = saveFunction;
 
     /*
      * We need at least the default crash handler for
      * emergencySaveFunction to be called
      */
     if (s_emergencySaveFunction && !s_crashHandler) {
         setCrashHandler(defaultCrashHandler);
     }
 }
 
 KCrash::HandlerType KCrash::emergencySaveFunction()
 {
     return s_emergencySaveFunction;
 }
 
 // Set the default crash handler in 10 seconds
 // This is used after an autorestart, the second instance of the application
 // is started with KCRASH_AUTO_RESTARTED=1, and we
 // set the defaultCrashHandler (to handle autorestart) after 10s.
 // The delay is to see if we stay up for more than 10s time, to avoid infinite
 // respawning if the app crashes on startup.
 class KCrashDelaySetHandler : public QObject
 {
 public:
     KCrashDelaySetHandler()
     {
         startTimer(10000); // 10 s
     }
 
 protected:
     void timerEvent(QTimerEvent *event) override
     {
         if (!s_crashHandler) { // not set meanwhile
             KCrash::setCrashHandler(KCrash::defaultCrashHandler);
         }
         killTimer(event->timerId());
         this->deleteLater();
     }
 };
 
 void KCrash::setFlags(KCrash::CrashFlags flags)
 {
     s_flags = flags;
     if (s_flags & AutoRestart) {
         // We need at least the default crash handler for autorestart to work.
         if (!s_crashHandler) {
             if (qEnvironmentVariableIsSet("KCRASH_AUTO_RESTARTED")) {
                 new KCrashDelaySetHandler;
             } else {
                 setCrashHandler(defaultCrashHandler);
             }
         }
     }
 }
 
 void KCrash::setApplicationFilePath(const QString &filePath)
 {
     const int pos = filePath.lastIndexOf(QLatin1Char('/'));
     const QString appName = filePath.mid(pos + 1);
     const QString appPath = filePath.left(pos); // could be empty, in theory
 
     s_appName.reset(qstrdup(QFile::encodeName(appName).constData()));
     s_appPath.reset(qstrdup(QFile::encodeName(appPath).constData()));
 
     // Prepare the auto-restart command
     QStringList args = QCoreApplication::arguments();
     if (args.isEmpty()) { // edge case: tst_QX11Info::startupId does QApplication app(argc, nullptr)...
         args.append(filePath);
     } else {
         args[0] = filePath; // replace argv[0] with full path above
     }
 
     s_autoRestartCommandLine.resize(args.count());
     for (int i = 0; i < args.count(); ++i) {
         s_autoRestartCommandLine.argv[i] = qstrdup(QFile::encodeName(args.at(i)).constData());
     }
 }
 
 void KCrash::setDrKonqiEnabled(bool enabled)
 {
     const int launchDrKonqi = enabled ? 1 : 0;
     if (s_launchDrKonqi == launchDrKonqi) {
         return;
     }
     s_launchDrKonqi = launchDrKonqi;
     if (s_launchDrKonqi && !s_drkonqiPath) {
 #ifdef Q_OS_WINDOWS
         static const QString drkonqi = QStringLiteral("drkonqi.exe");
 #else
         static const QString drkonqi = QStringLiteral("drkonqi");
 #endif
         const QString exec = QStandardPaths::findExecutable(drkonqi, libexecPaths());
         if (exec.isEmpty()) {
             qCDebug(LOG_KCRASH) << "Could not find drkonqi in search paths:" << libexecPaths();
             s_launchDrKonqi = 0;
         } else {
             s_drkonqiPath.reset(qstrdup(qPrintable(exec)));
         }
     }
 
     // we need at least the default crash handler to launch drkonqi
     if (s_launchDrKonqi && !s_crashHandler) {
         setCrashHandler(defaultCrashHandler);
     }
 }
 
 bool KCrash::isDrKonqiEnabled()
 {
     return s_launchDrKonqi == 1;
 }
 
 void KCrash::setCrashHandler(HandlerType handler)
 {
 #if defined(Q_OS_WIN)
     static LPTOP_LEVEL_EXCEPTION_FILTER s_previousExceptionFilter = NULL;
 
     if (handler && !s_previousExceptionFilter) {
         s_previousExceptionFilter = SetUnhandledExceptionFilter(KCrash::win32UnhandledExceptionFilter);
     } else if (!handler && s_previousExceptionFilter) {
         SetUnhandledExceptionFilter(s_previousExceptionFilter);
         s_previousExceptionFilter = NULL;
     }
 #else
     if (!handler) {
         handler = SIG_DFL;
     }
 
     sigset_t mask;
     sigemptyset(&mask);
 
 #ifdef SIGSEGV
     signal(SIGSEGV, handler);
     sigaddset(&mask, SIGSEGV);
 #endif
 #ifdef SIGBUS
     signal(SIGBUS, handler);
     sigaddset(&mask, SIGBUS);
 #endif
 #ifdef SIGFPE
     signal(SIGFPE, handler);
     sigaddset(&mask, SIGFPE);
 #endif
 #ifdef SIGILL
     signal(SIGILL, handler);
     sigaddset(&mask, SIGILL);
 #endif
 #ifdef SIGABRT
     signal(SIGABRT, handler);
     sigaddset(&mask, SIGABRT);
 #endif
 
     sigprocmask(SIG_UNBLOCK, &mask, nullptr);
 #endif
 
     s_crashHandler = handler;
 }
 
 KCrash::HandlerType KCrash::crashHandler()
 {
     return s_crashHandler;
 }
 
 #if !defined(Q_OS_WIN) && !defined(Q_OS_OSX)
 static void closeAllFDs()
 {
     // Close all remaining file descriptors except for stdin/stdout/stderr
     struct rlimit rlp = {};
     getrlimit(RLIMIT_NOFILE, &rlp);
     for (rlim_t i = 3; i < rlp.rlim_cur; i++) {
         close(i);
     }
 }
 #endif
 
 void crashOnSigTerm(int sig)
 {
     Q_UNUSED(sig)
     raise(s_originalSignal);
 }
 
 void KCrash::defaultCrashHandler(int sig)
 {
     // WABA: Do NOT use qDebug() in this function because it is much too risky!
     // Handle possible recursions
     static int crashRecursionCounter = 0;
     crashRecursionCounter++; // Nothing before this, please !
     s_originalSignal = sig;
 
 #if !defined(Q_OS_WIN)
     signal(SIGALRM, SIG_DFL);
     alarm(3); // Kill me... (in case we deadlock in malloc)
 #endif
 
     if (crashRecursionCounter < 2) {
         if (s_emergencySaveFunction) {
             s_emergencySaveFunction(sig);
         }
         if ((s_flags & AutoRestart) && s_autoRestartCommandLine) {
             QThread::sleep(1);
             startProcess(s_autoRestartCommandLine.argc, const_cast<const char **>(s_autoRestartCommandLine.argv), false);
         }
         crashRecursionCounter++;
     }
 
     if (crashRecursionCounter < 3) {
         // If someone is telling me to stop while I'm already crashing, then I should resume crashing
         signal(SIGTERM, &crashOnSigTerm);
 
         // NB: all metadata writing ought to happen before closing FDs to reduce synchronization problems with dbus.
 
         // WARNING: do not forget to increase Metadata::argv's size when adding more potential arguments!
         Metadata data(s_drkonqiPath.get());
 #ifdef Q_OS_LINUX
         // The ini is required to be scoped here, as opposed to the conditional scope, so its lifetime is the same as
         // the regular data instance!
         MetadataINIWriter ini(s_metadataPath);
         if (ini.isWritable()) {
             // Add the canonical exe path so the coredump daemon has more data points to map metadata to journald entry.
             ini.add("--exe", s_appFilePath.get(), MetadataWriter::BoolValue::No);
             data.setAdditionalWriter(&ini);
         }
 #endif
 
         const QByteArray platformName = QGuiApplication::platformName().toUtf8();
         if (!platformName.isEmpty()) {
             data.add("--platform", platformName.constData());
         }
 
 #if HAVE_X11
         if (platformName == QByteArrayLiteral("xcb")) {
             // start up on the correct display
             char *display = nullptr;
 #if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
             if (QX11Info::display()) {
                 display = XDisplayString(QX11Info::display());
 #else
             if (auto disp = qGuiApp->nativeInterface<QNativeInterface::QX11Application>()->display()) {
                 display = XDisplayString(disp);
 #endif
             } else {
                 display = getenv("DISPLAY");
             }
             data.add("--display", display);
         }
 #endif
 
         data.add("--appname", s_appName ? s_appName.get() : "<unknown>");
 
         if (loadedByKdeinit) {
             data.addBool("--kdeinit");
         }
 
         // only add apppath if it's not NULL
         if (s_appPath && s_appPath[0]) {
             data.add("--apppath", s_appPath.get());
         }
 
         // signal number -- will never be NULL
         char sigtxt[10];
         sprintf(sigtxt, "%d", sig);
         data.add("--signal", sigtxt);
 
         char pidtxt[20];
         sprintf(pidtxt, "%lld", QCoreApplication::applicationPid());
         data.add("--pid", pidtxt);
 
         const KAboutData *about = KAboutData::applicationDataPointer();
         if (about) {
             if (about->internalVersion()) {
                 data.add("--appversion", about->internalVersion());
             }
 
             if (about->internalProgramName()) {
                 data.add("--programname", about->internalProgramName());
             }
 
             if (about->internalBugAddress()) {
                 data.add("--bugaddress", about->internalBugAddress());
             }
 
             if (about->internalProductName()) {
                 data.add("--productname", about->internalProductName());
             }
         }
 
         if (s_flags & SaferDialog) {
             data.addBool("--safer");
         }
 
         if ((s_flags & AutoRestart) && s_autoRestartCommandLine) {
             data.addBool("--restarted");
         }
 
 #if defined(Q_OS_WIN)
         char threadId[8] = {0};
         sprintf(threadId, "%d", GetCurrentThreadId());
         data.add("--thread", threadId);
 #endif
 
         data.close();
         const int argc = data.argc;
         const char **argv = data.argv.data();
 
 #ifndef NDEBUG
         fprintf(stderr, "KCrash: crashing... crashRecursionCounter = %d\n", crashRecursionCounter);
         fprintf(stderr,
                 "KCrash: Application Name = %s path = %s pid = %lld\n",
                 s_appName ? s_appName.get() : "<unknown>",
                 s_appPath ? s_appPath.get() : "<unknown>",
                 QCoreApplication::applicationPid());
         fprintf(stderr, "KCrash: Arguments: ");
         for (int i = 0; i < s_autoRestartCommandLine.argc; ++i) {
             fprintf(stderr, "%s ", s_autoRestartCommandLine.argv[i]);
         }
         fprintf(stderr, "\n");
 #else
         fprintf(stderr, "KCrash: Application '%s' crashing...\n", s_appName ? s_appName.get() : "<unknown>");
 #endif
 
 #if !defined(Q_OS_WIN) && !defined(Q_OS_OSX)
         if (!(s_flags & KeepFDs)) {
             // This tries to prevent problems where applications fail to release resources that drkonqi might need.
             // Specifically this was introduced to ensure that an application that had grabbed the X11 cursor would
             // forcefully have it removed upon crash to ensure it is ungrabbed by the time drkonqi makes an appearance.
             // This is also the point in time when, for example, dbus services are lost. Closing the socket indicates
             // to dbus-daemon that the process has disappeared and it will forcefully reclaim the registered service names.
             //
             // Once we close our socket we lose potential dbus names and if we were running as a systemd service anchored to a name,
             // the daemon may decide to jump at us with a TERM signal. We'll want to have finished the metadata by now and
             // be near our tracing/raise().
             closeAllFDs();
         }
 #if HAVE_X11
 #if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
         else if (QX11Info::display()) {
             close(ConnectionNumber(QX11Info::display()));
         }
 #else
         else if (auto display = qGuiApp->nativeInterface<QNativeInterface::QX11Application>()->display()) {
             close(ConnectionNumber(display));
         }
 #endif
 #endif
 #endif
 
         if (s_launchDrKonqi != 1) {
             setCrashHandler(nullptr);
 #if !defined(Q_OS_WIN)
             raise(sig); // dump core, or whatever is the default action for this signal.
 #endif
             return;
         }
 
         startProcess(argc, argv, true);
     }
 
     if (crashRecursionCounter < 4) {
         fprintf(stderr, "Unable to start Dr. Konqi\n");
     }
 
     if (s_coreConfig->isProcess()) {
         fprintf(stderr, "Re-raising signal for core dump handling.\n");
         KCrash::setCrashHandler(nullptr);
         raise(sig);
         // not getting here
     }
 
     _exit(255);
 }
 
 #if defined(Q_OS_WIN)
 
 void KCrash::startProcess(int argc, const char *argv[], bool waitAndExit)
 {
     QString cmdLine;
     for (int i = 0; i < argc; ++i) {
         cmdLine.append(QLatin1Char('\"'));
         cmdLine.append(QFile::decodeName(argv[i]));
         cmdLine.append(QStringLiteral("\" "));
     }
 
     PROCESS_INFORMATION procInfo;
     STARTUPINFOW startupInfo =
         {sizeof(STARTUPINFO), 0, 0, 0, (ulong)CW_USEDEFAULT, (ulong)CW_USEDEFAULT, (ulong)CW_USEDEFAULT, (ulong)CW_USEDEFAULT, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
 
     bool success = CreateProcess(0, (wchar_t *)cmdLine.utf16(), NULL, NULL, false, CREATE_UNICODE_ENVIRONMENT, NULL, NULL, &startupInfo, &procInfo);
 
     if (success && waitAndExit) {
         // wait for child to exit
         WaitForSingleObject(procInfo.hProcess, INFINITE);
         _exit(253);
     }
 }
 
 // glue function for calling the unix signal handler from the windows unhandled exception filter
 LONG WINAPI KCrash::win32UnhandledExceptionFilter(_EXCEPTION_POINTERS *exceptionInfo)
 {
     // kdbgwin needs the context inside exceptionInfo because if getting the context after the
     // exception happened, it will walk down the stack and will stop at KiUserEventDispatch in
     // ntdll.dll, which is supposed to dispatch the exception from kernel mode back to user mode
     // so... let's create some shared memory
     HANDLE hMapFile = NULL;
     hMapFile = CreateFileMapping(INVALID_HANDLE_VALUE, NULL, PAGE_READWRITE, 0, sizeof(CONTEXT), TEXT("Local\\KCrashShared"));
 
     LPCTSTR pBuf = NULL;
     pBuf = (LPCTSTR)MapViewOfFile(hMapFile, FILE_MAP_ALL_ACCESS, 0, 0, sizeof(CONTEXT));
     CopyMemory((PVOID)pBuf, exceptionInfo->ContextRecord, sizeof(CONTEXT));
 
     if (s_crashHandler) {
         s_crashHandler(exceptionInfo->ExceptionRecord->ExceptionCode);
     }
 
     CloseHandle(hMapFile);
     return EXCEPTION_EXECUTE_HANDLER; // allow windows to do the default action (terminate)
 }
 #else
 
 static pid_t startDirectly(const char *argv[]);
 
 #ifdef Q_OS_LINUX
 static int write_socket(int sock, char *buffer, int len);
 static int read_socket(int sock, char *buffer, int len);
 
 static int openDrKonqiSocket(const QByteArray &socketpath);
 static int pollDrKonqiSocket(pid_t pid, int sockfd);
 #endif
 
 void KCrash::startProcess(int argc, const char *argv[], bool waitAndExit)
 {
     Q_UNUSED(argc);
     fprintf(stderr, "KCrash: Attempting to start %s\n", argv[0]);
 
     pid_t pid = startDirectly(argv);
 
     if (pid > 0 && waitAndExit) {
         // Seems we made it....
         alarm(0); // Stop the pending alarm that was set at the top of the defaultCrashHandler
 
         bool running = true;
         // Wait forever until the started process exits. This code path is executed
         // when launching drkonqi. Note that DrKonqi will SIGSTOP this process in the meantime
         // and only send SIGCONT when it is about to attach a debugger.
 #ifdef Q_OS_LINUX
         // Declare the process that will be debugging the crashed KDE app (#245529).
         // For now that will be DrKonqi, which may ask to transfer the ptrace scope to
         // a debugger it is not an ancestor of (because it was started via kdeinit or
         // KProcess::startDetached()) using a socket.
 #ifndef PR_SET_PTRACER
 #define PR_SET_PTRACER 0x59616d61
 #endif
         prctl(PR_SET_PTRACER, pid, 0, 0, 0);
 
         int sockfd = openDrKonqiSocket(s_socketpath);
 
         if (sockfd >= 0) {
             // Wait while DrKonqi is running and the socket connection exists
             // If the process was started directly, use waitpid(), as it's a child...
             while ((running = waitpid(pid, nullptr, WNOHANG) != pid) && pollDrKonqiSocket(pid, sockfd) >= 0) { }
             close(sockfd);
             unlink(s_socketpath.constData());
         }
 #endif
         if (running) {
             // If the process was started directly, use waitpid(), as it's a child...
             while (waitpid(pid, nullptr, 0) != pid) { }
         }
         if (!s_coreConfig->isProcess()) {
             // Only exit if we don't forward to core dumps
             _exit(253);
         }
     }
 }
 
 extern "C" char **environ;
 static pid_t startDirectly(const char *argv[])
 {
     char **environ_end;
     for (environ_end = environ; *environ_end; ++environ_end) { }
 
     std::array<const char *, 1024> environ_data; // hope it's big enough
     if ((unsigned)(environ_end - environ) + 2 >= environ_data.size()) {
         fprintf(stderr, "environ_data in KCrash not big enough!\n");
         return 0;
     }
     auto end = std::copy_if(environ, environ_end, environ_data.begin(), [](const char *s) {
         static const char envvar[] = "KCRASH_AUTO_RESTARTED=";
         return strncmp(envvar, s, sizeof(envvar) - 1) != 0;
     });
     *end++ = "KCRASH_AUTO_RESTARTED=1";
     *end++ = nullptr;
     pid_t pid = fork();
     switch (pid) {
     case -1:
         fprintf(stderr, "KCrash failed to fork(), errno = %d\n", errno);
         return 0;
     case 0:
         setgroups(0, nullptr); // Remove any extraneous groups
         if (setgid(getgid()) < 0 || setuid(getuid()) < 0) {
             _exit(253); // This cannot happen. Theoretically.
         }
 #ifndef Q_OS_OSX
         closeAllFDs(); // We are in the child now. Close FDs unconditionally.
 #endif
         execve(argv[0], const_cast<char **>(argv), const_cast<char **>(environ_data.data()));
         fprintf(stderr, "KCrash failed to exec(), errno = %d\n", errno);
         _exit(253);
     default:
         return pid;
     }
 }
 
 #ifdef Q_OS_LINUX
 
 /*
  * Write 'len' bytes from 'buffer' into 'sock'.
  * returns 0 on success, -1 on failure.
  */
 static int write_socket(int sock, char *buffer, int len)
 {
     ssize_t result;
     int bytes_left = len;
     while (bytes_left > 0) {
         result = write(sock, buffer, bytes_left);
         if (result > 0) {
             buffer += result;
             bytes_left -= result;
         } else if (result == 0) {
             return -1;
         } else if ((result == -1) && (errno != EINTR) && (errno != EAGAIN)) {
             return -1;
         }
     }
     return 0;
 }
 
 /*
  * Read 'len' bytes from 'sock' into 'buffer'.
  * returns 0 on success, -1 on failure.
  */
 static int read_socket(int sock, char *buffer, int len)
 {
     ssize_t result;
     int bytes_left = len;
     while (bytes_left > 0) {
         result = read(sock, buffer, bytes_left);
         if (result > 0) {
             buffer += result;
             bytes_left -= result;
         } else if (result == 0) {
             return -1;
         } else if ((result == -1) && (errno != EINTR) && (errno != EAGAIN)) {
             return -1;
         }
     }
     return 0;
 }
 
 static int openDrKonqiSocket(const QByteArray &socketpath)
 {
     int sockfd = socket(PF_UNIX, SOCK_STREAM, 0);
     if (sockfd < 0) {
         perror("Warning: socket() for communication with DrKonqi failed");
         return -1;
     }
 
     struct sockaddr_un drkonqi_server;
     drkonqi_server.sun_family = AF_UNIX;
 
     if (socketpath.size() >= static_cast<int>(sizeof(drkonqi_server.sun_path))) {
         fprintf(stderr, "Warning: socket path is too long\n");
         close(sockfd);
         return -1;
     }
     strcpy(drkonqi_server.sun_path, socketpath.constData());
 
     unlink(drkonqi_server.sun_path); // remove potential stale socket
     if (bind(sockfd, (struct sockaddr *)&drkonqi_server, sizeof(drkonqi_server)) < 0) {
         perror("Warning: bind() for communication with DrKonqi failed");
         close(sockfd);
         unlink(drkonqi_server.sun_path);
         return -1;
     }
 
     listen(sockfd, 1);
 
     return sockfd;
 }
 
 static int pollDrKonqiSocket(pid_t pid, int sockfd)
 {
     struct pollfd fd;
     fd.fd = sockfd;
     fd.events = POLLIN;
     int r;
     do {
         r = poll(&fd, 1, 1000); // wait for 1 second for a request by DrKonqi
     } while (r == -1 && errno == EINTR);
     // only continue if POLLIN event returned
     if (r == 0) { // timeout
         return 0;
     } else if (r == -1 || !(fd.revents & POLLIN)) { // some error
         return -1;
     }
 
     static struct sockaddr_un drkonqi_client;
     static socklen_t cllength = sizeof(drkonqi_client);
     int clsockfd;
     do {
         clsockfd = accept(sockfd, (struct sockaddr *)&drkonqi_client, &cllength);
     } while (clsockfd == -1 && errno == EINTR);
     if (clsockfd < 0) {
         return -1;
     }
 
     // check whether the message is coming from DrKonqi
     static struct ucred ucred;
     static socklen_t credlen = sizeof(struct ucred);
     if (getsockopt(clsockfd, SOL_SOCKET, SO_PEERCRED, &ucred, &credlen) < 0) {
         return -1;
     }
 
     if (ucred.pid != pid) {
         fprintf(stderr, "Warning: peer pid does not match DrKonqi pid\n");
         return -1;
     }
 
     // read PID to change ptrace scope
     static const int msize = 21; // most digits in a 64bit int (+sign +'\0')
     char msg[msize];
     if (read_socket(clsockfd, msg, msize) == 0) {
         int dpid = atoi(msg);
         prctl(PR_SET_PTRACER, dpid, 0, 0, 0);
         // confirm change to DrKonqi
         if (write_socket(clsockfd, msg, msize) == 0) {
             fprintf(stderr, "KCrash: ptrace access transferred to %s\n", msg);
         }
     }
     close(clsockfd);
 
     return 1;
 }
 
 #endif
 
 #endif // Q_OS_UNIX
 
 void KCrash::setErrorMessage(const QString &message)
 {
     s_kcrashErrorMessage.reset(qstrdup(message.toUtf8().constData()));
 }