kernel: add some basic features

+ feat list:
+ * gdt/idt
+ * brokie pmm

kernel/src/lib/log.h

@@ -0,0 +1,35 @@
+/*
+ *  The Soaplin Kernel
+ *  Copyright (C) 2025 The SILD Project
+ *
+ *  log.h - Kernel logging interface.
+ */
+
+#pragma once
+
+// Log levels in order of increasing severity
+#include <stdarg.h>
+#include <stdbool.h>
+
+#define LOGLEVEL_TRACE    7
+#define LOGLEVEL_DEBUG    6
+#define LOGLEVEL_INFO     5
+#define LOGLEVEL_NOTICE   4
+#define LOGLEVEL_WARNING  3
+#define LOGLEVEL_ERROR    2
+#define LOGLEVEL_FATAL    1
+
+typedef void(*log_output_func)(char *str, va_list *vl);
+
+void log_init(int max_loglevel);
+bool log_register_output(log_output_func fn);
+void log(int loglevel, char *str, ...);
+
+// Shortcuts to log
+#define trace(str, ...)   log(LOGLEVEL_TRACE,  str, ##__VA_ARGS__)
+#define debug(str, ...)   log(LOGLEVEL_DEBUG,  str, ##__VA_ARGS__)
+#define info(str, ...)    log(LOGLEVEL_INFO,   str, ##__VA_ARGS__)
+#define notice(str, ...)  log(LOGLEVEL_NOTICE, str, ##__VA_ARGS__)
+#define warn(str, ...)    log(LOGLEVEL_WARNING, str, ##__VA_ARGS__)
+#define error(str, ...)   log(LOGLEVEL_ERROR,  str, ##__VA_ARGS__)
+#define fatal(str, ...)   log(LOGLEVEL_FATAL,  str, ##__VA_ARGS__)