[RTL/x64] Implement RtlRaiseException in asm

This fixes invalid contexts being passed to RtlDispatchException. Also update the ExceptionAddress field in the EXCEPTION_FRAME, to match the Rip value in the CONTEXT, which is required for proper unwinding.

sdk/lib/rtl/amd64/except.c

@@ -13,50 +13,6 @@
 
 /* PUBLIC FUNCTIONS **********************************************************/
 
-VOID
-NTAPI
-RtlRaiseException(IN PEXCEPTION_RECORD ExceptionRecord)
-{
-    CONTEXT Context;
-    NTSTATUS Status = STATUS_INVALID_DISPOSITION;
-
-    /* Capture the current context */
-    RtlCaptureContext(&Context);
-
-    /* Fix up Context.Rip for the caller */
-    Context.Rip = (ULONG64)_ReturnAddress();
-
-    /* Fix up Context.Rsp for the caller */
-    Context.Rsp = (ULONG64)_AddressOfReturnAddress() + 8;
-
-    /* Save the exception address */
-    ExceptionRecord->ExceptionAddress = (PVOID)Context.Rip;
-
-    /* Check if user mode debugger is active */
-    if (RtlpCheckForActiveDebugger())
-    {
-        /* Raise an exception immediately */
-        Status = ZwRaiseException(ExceptionRecord, &Context, TRUE);
-    }
-    else
-    {
-        /* Dispatch the exception and check if we should continue */
-        if (!RtlDispatchException(ExceptionRecord, &Context))
-        {
-            /* Raise the exception */
-            Status = ZwRaiseException(ExceptionRecord, &Context, FALSE);
-        }
-        else
-        {
-            /* Continue, go back to previous context */
-            Status = ZwContinue(&Context, FALSE);
-        }
-    }
-
-    /* If we returned, raise a status */
-    RtlRaiseStatus(Status);
-}
-
 /*
 * @unimplemented
 */

sdk/lib/rtl/amd64/except_asm.S

@@ -233,6 +233,81 @@ ReturnFar:
 
 .ENDP
 
+EXTERN RtlpCheckForActiveDebugger:PROC
+EXTERN RtlDispatchException:PROC
+EXTERN ZwContinue:PROC
+EXTERN ZwRaiseException:PROC
+EXTERN RtlRaiseStatus:PROC
+
+/*
+ * VOID
+ * RtlRaiseException (
+ *     _In_ PEXCEPTION_RECORD ExceptionRecord);
+ */
+PUBLIC RtlRaiseException
+.PROC RtlRaiseException
+
+    /* Allocate stack space for a CONTEXT record */
+    sub rsp, CONTEXT_FRAME_LENGTH + 8
+    .allocstack CONTEXT_FRAME_LENGTH + 8
+
+    /* Save the ExceptionRecord pointer */
+    mov [rsp + CONTEXT_FRAME_LENGTH + 8 + P1Home], rcx
+
+    .endprolog
+
+    /* Save the return address in EXCEPTION_RECORD.ExceptionAddress */
+    mov rdx, [rsp + CONTEXT_FRAME_LENGTH + 8]
+    mov [rcx + ErExceptionAddress], rdx
+
+    /* Capture the current context */
+    mov rcx, rsp
+    call RtlCaptureContext
+
+    /* Fix up CONTEXT.Rip for the caller (RtlCaptureContext doesn't change rdx!) */
+    mov [rsp + CxRip], rdx
+
+    /* Fix up CONTEXT.Rsp for the caller (+8 for the return address) */
+    lea rdx, [rsp + CONTEXT_FRAME_LENGTH + 8 + 8]
+    mov [rsp + CxRsp], rdx
+
+    /* Check if a user mode debugger is active */
+    call RtlpCheckForActiveDebugger
+    test al, al
+    mov r8b, 1
+    jnz RaiseException
+
+    /* Dispatch the exception */
+    mov rcx, [rsp + CONTEXT_FRAME_LENGTH + 8 + P1Home]
+    mov rdx, rsp
+    call RtlDispatchException
+
+    /* Check if it was handled */
+    test al, al
+    mov r8b, 0
+    jz RaiseException
+
+    /* It was handled, continue with the updated context */
+    mov rcx, rsp
+    mov dl, 0
+    call  ZwContinue
+    jmp RaiseStatus
+
+RaiseException:
+
+    mov rcx, [rsp + CxP1Home]
+    mov rdx, rsp
+    call ZwRaiseException
+
+RaiseStatus:
+
+    mov rcx, rax
+    mov rdx, rsp
+    call RtlRaiseStatus
+
+.ENDP
+
+
 END