Implement debug console device

kernel/device/debugconsole.c

@@ -0,0 +1,33 @@
+#include <device/debugconsole.h>
+#include <device/device.h>
+#include <libk/std.h>
+#include <proc/proc.h>
+#include <proc/reschedule.h>
+#include <status.h>
+#include <sys/debug.h>
+
+bool debugconsole_init (struct device* device, void* arg) {
+  (void)device, (void)arg;
+  return true;
+}
+
+void debugconsole_fini (struct device* device) { (void)device; }
+
+int debugconsole_putstr (struct device* device, struct proc* proc, struct reschedule_ctx* rctx,
+                         void* a1, void* a2, void* a3, void* a4) {
+  (void)a2, (void)a3, (void)a4, (void)device, (void)rctx;
+
+  char* string = (char*)a1;
+  size_t* len = (size_t*)a2;
+
+  if (string == NULL || len == NULL)
+    return -ST_BAD_ADDRESS_SPACE;
+
+  spin_lock (&proc->lock);
+  int pid = proc->pid;
+  spin_unlock (&proc->lock);
+
+  debugprintf ("(CPU %d; PID %d) %.*s\n", thiscpu->id, pid, (int)*len, string);
+
+  return ST_OK;
+}