stos/amd64: cpu: Add HAL interrupt registration

Signed-off-by: Chloe M. <chloe@mensia.org>

paw/stos/arch/amd64/cpu/intr.c

@@ -0,0 +1,76 @@
+/*
+ * Copyright (c) 2026, Chloe M.
+ * Provided under the BSD-3 clause.
+ *
+ * Description:  Interrupt management
+ * Author:       Chloe M.
+ */
+
+#include <hal/intr.h>
+#include <machine/idt.h>
+#include <stdef.h>
+
+/* Interrupt priority level shift */
+#define IPL_SHIFT 4
+
+/* Globals */
+static INTR_HANDLER Handlers[256];
+
+ST_STATUS
+HalRegisterIntr(const INTR_HANDLER *Handler, BOOLEAN IsUser)
+{
+    UCHAR Vector, Idx;
+    INTR_HANDLER *HandlerSlot;
+
+    if (Handler == NULL) {
+        return STATUS_INVALID_PARAM;
+    }
+
+    /* Must have a valid handler */
+    if (Handler->Handler == NULL) {
+        return STATUS_INVALID_PARAM;
+    }
+
+    /* Ensure that the priority is valid */
+    switch (Handler->Irql) {
+    case IRQL_PASSIVE:
+    case IRQL_APC:
+    case IRQL_DEVICE:
+    case IRQL_HIGH:
+        break;
+    default:
+        return STATUS_INVALID_PARAM;
+    }
+
+    /*
+     * We have 16 priorities at every band as 4-bits makes up
+     * the interrupt priority level. Our job is to find a slot
+     * that is free for our interrupt handler at its given IRQL.
+     */
+    Vector = MAX(0x20, Handler->Irql << IPL_SHIFT);
+    for (Idx = Vector; Idx < Vector + 16; ++Idx) {
+        HandlerSlot = &Handlers[Idx];
+
+        /* This entry is present, don't overwrite */
+        if (HandlerSlot->Present) {
+            continue;
+        }
+
+        /* Fill the slot */
+        *HandlerSlot = *(INTR_HANDLER *)Handler;
+        HandlerSlot->Present = 1;
+
+        /* Register the interrupt */
+        MdIdtSetEntry(
+            Idx,
+            (UPTR)Handler->Handler,
+            (IsUser) ? IDT_USER_GATE : IDT_INT_GATE,
+            0
+        );
+
+        return STATUS_SUCCESS;
+    }
+
+    /* No entry found */
+    return STATUS_NOT_FOUND;
+}

paw/stos/head/hal/intr.h

@@ -9,6 +9,9 @@
 #ifndef _HAL_INTR_H_
 #define _HAL_INTR_H_ 1
 
+#include <stdef.h>
+#include <stapi/status.h>
+
 /*
  * Valid interrupt request levels
  *
@@ -23,4 +26,47 @@
 #define IRQL_DEVICE   3
 #define IRQL_HIGH     4
 
+/* IRQLs are of this type */
+typedef UCHAR IRQL;
+
+/*
+ * Interrupt data that is given to a service routine
+ *
+ * @Vector:  Interrupt vector that fired
+ * @Data:    Driver specific data
+ */
+typedef struct {
+    UCHAR Vector;
+    VOID *Data;
+} INTR_DATA;
+
+/*
+ * Interrupt handler descriptor
+ *
+ * @Irql:     Prioirty of handler
+ * @Present:  Must be 1 to be valid
+ * @Data:     Driver specific data
+ * @Handler:  Reference to interrupt handler
+ *
+ * XXX: There is no need to set the present bit when
+ *      creating an instance as it is set automatically.
+ */
+typedef struct {
+    IRQL Irql;
+    UCHAR Present : 1;
+    VOID *Data;
+    LONG(*Handler)(INTR_DATA *Data);
+} INTR_HANDLER;
+
+/*
+ * Register an interrupt handler
+ *
+ * @Handler: Interrupt handler to register
+ * @IsUser:  Should be set if user interrupt
+ *
+ * XXX: Most of the times, @IsUser should remain unset,
+ *      it is mostly there for the sake of scalability.
+ */
+ST_STATUS HalRegisterIntr(const INTR_HANDLER *Handler, BOOLEAN IsUser);
+
 #endif  /* !_HAL_INTR_H_ */