add windows exception handling in C (#175)

lib/win-exception-handler/exception_handling/exception_handling.c

@@ -0,0 +1,74 @@
+#include <windows.h>
+#include <setjmp.h>
+#include "exception_handling.h"
+
+#define CALL_FIRST 1
+
+__declspec(thread) jmp_buf jmpBuf;
+__declspec(thread) PVOID caughtExceptionAddress;
+__declspec(thread) DWORD64 caughtInstructionPointer;
+__declspec(thread) PVOID savedStackPointer;
+__declspec(thread) BOOL exceptionHandlerInstalled = FALSE;
+__declspec(thread) BOOL alreadyHandlingException = FALSE;
+
+void longjmpOutOfHere() {
+    longjmp(jmpBuf, 1);
+}
+
+/// Get the current address that we use to jmp, the no inline is important
+static __declspec(noinline) void *get_callee_frame_address(void) {
+    return _AddressOfReturnAddress();
+}
+
+static LONG WINAPI
+exceptionHandler(struct _EXCEPTION_POINTERS *ExceptionInfo) {
+    EXCEPTION_RECORD* pExceptionRecord = ExceptionInfo->ExceptionRecord;
+    PCONTEXT pCONTEXT = ExceptionInfo->ContextRecord;
+    caughtExceptionAddress = pExceptionRecord->ExceptionAddress;
+    caughtInstructionPointer = pCONTEXT->Rip;
+    if (alreadyHandlingException == TRUE) {
+        return EXCEPTION_CONTINUE_SEARCH;
+    }
+    alreadyHandlingException = TRUE;
+
+    // Basically, here, we coerce the os to resume us into a context that calls `longjmp` instead of just continuing.
+    // Presumably, we cannot `longjmp` out of the signal/exception context, like we can on unix.
+    pCONTEXT->Rip = (uintptr_t)(&longjmpOutOfHere);
+    pCONTEXT->Rsp = (uintptr_t)(savedStackPointer);
+    return EXCEPTION_CONTINUE_EXECUTION;
+}
+
+uint8_t callProtected(trampoline_t trampoline,
+        const struct wasmer_instance_context_t* ctx,
+        const struct func_t* func,
+        const uint64_t* param_vec,
+        uint64_t* return_vec,
+        struct call_protected_result_t* out_result) {
+
+    // install exception handler
+    if (exceptionHandlerInstalled == FALSE) {
+        exceptionHandlerInstalled = TRUE;
+        AddVectoredExceptionHandler(CALL_FIRST, exceptionHandler);
+    }
+
+    // jmp jmp jmp!
+    int signum = setjmp(jmpBuf);
+    if (signum == 0) {
+        // save the stack pointer
+        savedStackPointer = get_callee_frame_address();
+        trampoline(ctx, func, param_vec, return_vec);
+        out_result->code = 0;
+        out_result->exceptionAddress = 0;
+        out_result->instructionPointer = 0;
+        return TRUE;
+    }
+
+    out_result->code = (uint64_t)signum;
+    out_result->exceptionAddress = (uint64_t)caughtExceptionAddress;
+    out_result->instructionPointer = caughtInstructionPointer;
+
+    caughtExceptionAddress = 0;
+    caughtInstructionPointer = 0;
+
+    return FALSE;
+}