sched: thread: add cpu context pointer usable during interrupts and syscalls

arch/x86_64/irq.c

@@ -8,6 +8,7 @@
 #include <kernel/panic.h>
 #include <kernel/sched.h>
 #include <kernel/syscall.h>
+#include <kernel/thread.h>
 #include <stddef.h>
 
 #define MAX_ISR_HANDLERS  16
@@ -166,6 +167,12 @@ int idt_load(struct idt_ptr *ptr)
 
 void isr_dispatch(struct ml_cpu_context *regs)
 {
+	struct thread *thr = get_current_thread();
+	if (thr) {
+		thr->tr_irqctx = regs;
+		put_current_thread(thr);
+	}
+
 	int_hook h = isr_handlers[regs->int_no];
 	if (h) {
 		h(regs);
@@ -188,6 +195,13 @@ void irq_dispatch(struct ml_cpu_context *regs)
 	end_charge_period();
 
 	irq_ack(regs->int_no);
+
+	struct thread *thr = get_current_thread();
+	if (thr) {
+		thr->tr_irqctx = regs;
+		put_current_thread(thr);
+	}
+
 	struct queue *hooks = &irq_hooks[regs->int_no - IRQ0];
 	queue_foreach(struct irq_hook, hook, hooks, irq_entry)
 	{

include/kernel/thread.h

@@ -8,6 +8,8 @@
 
 #define THREAD_KSTACK_ORDER VM_PAGE_4K
 
+struct ml_cpu_context;
+
 enum thread_state {
 	THREAD_READY = 1,
 	THREAD_SLEEPING = 2,
@@ -39,6 +41,9 @@ struct thread {
 	virt_addr_t tr_ip, tr_sp, tr_bp;
 	virt_addr_t tr_cpu_user_sp, tr_cpu_kernel_sp;
 
+	/* only valid within an interrupt or syscall context */
+	struct ml_cpu_context *tr_irqctx;
+
 	struct ml_thread tr_ml;
 	struct runqueue *tr_rq;