Add SIGTERM handling logic that properly shuts down the EE.

Author: adityamandaleeka

src/pal/inc/pal.h

@@ -480,9 +480,10 @@ typedef long time_t;
 #define PAL_INITIALIZE_SYNC_THREAD     0x01
 #define PAL_INITIALIZE_EXEC_ALLOCATOR  0x02
 #define PAL_INITIALIZE_STD_HANDLES     0x04
+#define PAL_INITIALIZE_SIGNAL_THREAD   0x08
 
 // PAL_Initialize() flags
-#define PAL_INITIALIZE                 (PAL_INITIALIZE_SYNC_THREAD | PAL_INITIALIZE_STD_HANDLES)
+#define PAL_INITIALIZE                 (PAL_INITIALIZE_SYNC_THREAD | PAL_INITIALIZE_STD_HANDLES | PAL_INITIALIZE_SIGNAL_THREAD)
 
 // PAL_InitializeDLL() flags - don't start any of the helper threads
 #define PAL_INITIALIZE_DLL             PAL_INITIALIZE_NONE       
@@ -6487,6 +6488,7 @@ struct PAL_SEHException
 };
 
 typedef VOID (PALAPI *PHARDWARE_EXCEPTION_HANDLER)(PAL_SEHException* ex);
+typedef VOID (PALAPI *PTERMINATION_REQUEST_HANDLER)();
 typedef DWORD (PALAPI *PGET_GCMARKER_EXCEPTION_CODE)(LPVOID ip);
 
 PALIMPORT
@@ -6508,6 +6510,12 @@ PAL_ThrowExceptionFromContext(
     IN CONTEXT* context,
     IN PAL_SEHException* ex);
 
+PALIMPORT
+VOID
+PALAPI
+PAL_SetTerminationRequestHandler(
+    IN PTERMINATION_REQUEST_HANDLER terminationRequestHandler);
+
 //
 // This holder is used to indicate that a hardware
 // exception should be raised as a C++ exception

src/pal/src/exception/seh.cpp

@@ -51,8 +51,18 @@ const UINT RESERVED_SEH_BIT = 0x800000;
 
 /* Internal variables definitions **********************************************/
 
-PHARDWARE_EXCEPTION_HANDLER g_hardwareExceptionHandler = NULL;
-PGET_GCMARKER_EXCEPTION_CODE g_getGcMarkerExceptionCode = NULL;
+PHARDWARE_EXCEPTION_HANDLER g_hardwareExceptionHandler = nullptr;
+PGET_GCMARKER_EXCEPTION_CODE g_getGcMarkerExceptionCode = nullptr;
+PTERMINATION_REQUEST_HANDLER g_terminationRequestHandler = nullptr;
+
+/* Internal function declarations *********************************************/
+
+#if !HAVE_MACH_EXCEPTIONS
+PAL_ERROR
+StartExternalSignalHandlerThread(
+    CPalThread *pthr);
+#endif // !HAVE_MACH_EXCEPTIONS
+
 
 /* Internal function definitions **********************************************/
 
@@ -80,6 +90,17 @@ SEHInitialize (CPalThread *pthrCurrent, DWORD flags)
         SEHCleanup();
         return FALSE;
     }
+
+    if (flags & PAL_INITIALIZE_SIGNAL_THREAD)
+    {
+        PAL_ERROR palError = StartExternalSignalHandlerThread(pthrCurrent);
+        if (palError != NO_ERROR)
+        {
+            ERROR("StartExternalSignalHandlerThread returned %d\n", palError);
+            SEHCleanup();
+            return FALSE;
+        }
+    }
 #endif
 
     return TRUE;
@@ -129,6 +150,26 @@ PAL_SetHardwareExceptionHandler(
     g_hardwareExceptionHandler = exceptionHandler;
 }
 
+/*++
+Function:
+    PAL_SetTerminationRequestHandler
+
+    Register a termination request handler.
+
+Parameters:
+    terminationHandler - handler for termination request
+
+Return value:
+    None
+--*/
+VOID
+PALAPI 
+PAL_SetTerminationRequestHandler(
+    IN PTERMINATION_REQUEST_HANDLER terminationHandler)
+{
+    g_terminationRequestHandler = terminationHandler;
+}
+
 /*++
 Function:
     PAL_SetGetGcMarkerExceptionCode
@@ -225,6 +266,15 @@ SEHProcessException(PEXCEPTION_POINTERS pointers)
         pointers->ExceptionRecord->ExceptionCode, pointers->ExceptionRecord->ExceptionAddress);
 }
 
+VOID
+SEHHandleTerminationRequest()
+{
+    if (g_terminationRequestHandler != NULL)
+    {
+        g_terminationRequestHandler();
+    }
+}
+
 /*++
 Function :
     SEHEnable

src/pal/src/exception/signal.cpp

@@ -72,6 +72,7 @@ static void sigtrap_handler(int code, siginfo_t *siginfo, void *context);
 static void sigbus_handler(int code, siginfo_t *siginfo, void *context);
 static void sigint_handler(int code, siginfo_t *siginfo, void *context);
 static void sigquit_handler(int code, siginfo_t *siginfo, void *context);
+static void sigterm_handler(int code, siginfo_t *siginfo, void *context);
 
 static void common_signal_handler(PEXCEPTION_POINTERS pointers, int code, 
                                   native_context_t *ucontext);
@@ -92,7 +93,12 @@ struct sigaction g_previous_sigbus;
 struct sigaction g_previous_sigsegv;
 struct sigaction g_previous_sigint;
 struct sigaction g_previous_sigquit;
+struct sigaction g_previous_sigterm;
 
+// Pipe used for sending signal notifications to a helper thread
+int g_signalPipe[2] = { 0, 0 };
+
+DWORD g_dwExternalSignalHandlerThreadId = 0;
 
 /* public function definitions ************************************************/
 
@@ -179,6 +185,13 @@ void SEHCleanupSignals()
     restore_signal(SIGSEGV, &g_previous_sigsegv);
     restore_signal(SIGINT, &g_previous_sigint);
     restore_signal(SIGQUIT, &g_previous_sigquit);
+
+    // Only restore if the signal handler thread was started and
+    // the previous handler was saved.
+    if (g_dwExternalSignalHandlerThreadId != 0)
+    {
+        restore_signal(SIGTERM, &g_previous_sigterm);
+    }
 }
 
 /* internal function definitions **********************************************/
@@ -494,6 +507,60 @@ static void sigquit_handler(int code, siginfo_t *siginfo, void *context)
     kill(gPID, code);
 }
 
+/*++
+ Function :
+    HandleExternalSignal
+
+    Write to a pipe to kick off handling of the signal.
+
+ Parameters :
+    signalCode - code of the external signal
+
+    (no return value)
+--*/
+static void HandleExternalSignal(int signalCode)
+{
+    BYTE signalCodeByte = (BYTE)signalCode;
+    ssize_t writtenBytes;
+    do
+    {
+        writtenBytes = write(g_signalPipe[1], &signalCodeByte, 1);
+    }
+    while ((writtenBytes == -1) && (errno == EINTR));
+
+    if (writtenBytes == -1)
+    {
+        // Fatal error
+        PROCAbort();
+    }
+}
+
+/*++
+Function :
+    sigterm_handler
+
+    handle SIGTERM signal
+
+Parameters :
+    POSIX signal handler parameter list ("man sigaction" for details)
+
+    (no return value)
+--*/
+static void sigterm_handler(int code, siginfo_t *siginfo, void *context)
+{
+    if (PALIsInitialized())
+    {
+        HandleExternalSignal(code);
+    }
+    else
+    {
+        if (g_previous_sigterm.sa_sigaction != NULL)
+        {
+            g_previous_sigterm.sa_sigaction(code, siginfo, context);
+        }
+    }
+}
+
 #ifdef INJECT_ACTIVATION_SIGNAL
 /*++
 Function :
@@ -714,4 +781,111 @@ void restore_signal(int signal_id, struct sigaction *previousAction)
     }
 }
 
+static
+DWORD
+PALAPI
+ExternalSignalHandlerThreadRoutine(
+    PVOID
+    );
+
+PAL_ERROR
+StartExternalSignalHandlerThread(
+    CPalThread *pthr)
+{
+    PAL_ERROR palError = NO_ERROR;
+    
+#ifndef DO_NOT_USE_SIGNAL_HANDLING_THREAD
+    HANDLE hThread;
+
+    if (pipe(g_signalPipe) != 0)
+    {
+        palError = ERROR_CANNOT_MAKE;
+        goto done;
+    }
+
+    palError = InternalCreateThread(
+        pthr,
+        NULL,
+        0,
+        ExternalSignalHandlerThreadRoutine,
+        NULL,
+        0,
+        SignalHandlerThread, // Want no_suspend variant
+        &g_dwExternalSignalHandlerThreadId,
+        &hThread
+        );
+
+    if (palError != NO_ERROR)
+    {
+        ERROR("Failure creating external signal handler thread (%d)\n", palError);
+        goto done;
+    }
+
+    InternalCloseHandle(pthr, hThread);
+
+    handle_signal(SIGTERM, sigterm_handler, &g_previous_sigterm);
+#endif // DO_NOT_USE_SIGNAL_HANDLING_THREAD
+
+done:
+
+    return palError;
+}
+
+static
+DWORD
+PALAPI
+ExternalSignalHandlerThreadRoutine(
+    PVOID
+    )
+{
+    DWORD dwThreadId;
+    bool fContinue = TRUE;
+    HANDLE hThread;
+    PAL_ERROR palError = NO_ERROR;
+    CPalThread *pthr = InternalGetCurrentThread();
+
+    //
+    // Wait for a signal to occur
+    //
+
+    while (fContinue)
+    {
+        BYTE signalCode;
+        ssize_t bytesRead;
+
+        do
+        {
+            bytesRead = read(g_signalPipe[0], &signalCode, 1);
+        }
+        while ((bytesRead == -1) && (errno == EINTR));
+
+        if (bytesRead == -1)
+        {
+            // Fatal error 
+            PROCAbort();
+        }
+
+        switch (signalCode)
+        {
+            case SIGTERM:
+            {
+                SEHHandleTerminationRequest();
+            }
+
+            default:
+                ASSERT("Unexpected signal %d in signal thread\n", signalCode);
+                PROCAbort();
+                break;
+        }
+    }
+
+    //
+    // Perform an immediate (non-graceful) shutdown
+    //
+
+    _exit(EXIT_FAILURE);
+
+    return 0;
+}
+
 #endif // !HAVE_MACH_EXCEPTIONS

src/pal/src/include/pal/process.h

@@ -134,7 +134,7 @@ void PROCAbort();
 Function:
   PROCNotifyProcessShutdown
   
-  Calls the abort handler to do any shutdown cleanup. Call be
+  Calls the abort handler to do any shutdown cleanup. Can be
   called from the unhandled native exception handler.
 
 (no return value)

src/pal/src/include/pal/seh.hpp

@@ -74,6 +74,18 @@ Return value:
 VOID 
 SEHProcessException(PEXCEPTION_POINTERS pointers);
 
+/*++
+Function:
+    SEHHandleTerminationRequest
+
+    Send a process termination request to a registered handler.
+
+Parameters:
+    None
+--*/
+VOID 
+SEHHandleTerminationRequest();
+
 #if !HAVE_MACH_EXCEPTIONS
 // TODO: Implement for Mach exceptions.  Not in CoreCLR surface area.
 /*++

src/pal/src/thread/process.cpp

@@ -2673,7 +2673,7 @@ DestroyProcessModules(IN ProcessModules *listHead)
 Function:
   PROCNotifyProcessShutdown
   
-  Calls the abort handler to do any shutdown cleanup. Call be called 
+  Calls the abort handler to do any shutdown cleanup. Can be called 
   from the unhandled native exception handler.
 
 (no return value)

src/vm/exceptionhandling.cpp

@@ -139,6 +139,11 @@ static inline void UpdatePerformanceMetrics(CrawlFrame *pcfThisFrame, BOOL bIsRe
     ETW::ExceptionLog::ExceptionThrown(pcfThisFrame, bIsRethrownException, bIsNewException);
 }
 
+void ShutdownEEAndExitProcess()
+{
+    ForceEEShutdown(SCA_ExitProcessWhenShutdownComplete);
+}
+
 void InitializeExceptionHandling()
 {
     EH_LOG((LL_INFO100, "InitializeExceptionHandling(): ExceptionTracker size: 0x%x bytes\n", sizeof(ExceptionTracker)));
@@ -158,6 +163,9 @@ void InitializeExceptionHandling()
 
     // Register handler for determining whether the specified IP has code that is a GC marker for GCCover
     PAL_SetGetGcMarkerExceptionCode(GetGcMarkerExceptionCode);
+
+    // Register handler for termination requests (e.g. SIGTERM)
+    PAL_SetTerminationRequestHandler(ShutdownEEAndExitProcess);
 #endif // FEATURE_PAL
 }