Added an array for unary multiboot tags to be able to fetch them in constant-time

kernel/include/3rd/multiboot2.h

@@ -42,6 +42,8 @@
 /*  Flags set in the ’flags’ member of the multiboot header. */
 
 #define MULTIBOOT_TAG_ALIGN 8
+#define MULTIBOOT_TAG_TOTAL 22
+
 #define MULTIBOOT_TAG_TYPE_END 0
 #define MULTIBOOT_TAG_TYPE_CMDLINE 1
 #define MULTIBOOT_TAG_TYPE_BOOT_LOADER_NAME 2

kernel/include/kreflock.h

@@ -34,11 +34,11 @@ typedef struct {
 } reflock_t;
 
 #define NEW_REFLOCK(_on_lock, _on_unlock, _strict, _allow_force)               \
-	{ _on_lock,                                                                \
-	  _on_unlock,                                                              \
-	  _strict,                                                                 \
-	  _allow_force,                                                            \
-	  { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 } }
+	{                                                                          \
+		_on_lock, _on_unlock, _strict, _allow_force, {                         \
+			0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0                                 \
+		}                                                                      \
+	}
 
 void reflock_make(reflock_t *lock);
 bool reflock_validate_magic(reflock_t *lock);

kernel/include/multiboot2.h

@@ -0,0 +1,23 @@
+#ifndef __K_MULTIBOOT2
+#define __K_MULTIBOOT2
+
+#include "3rd/multiboot2.h"
+#include <stdint.h>
+
+// STUB!
+typedef int list_head;
+
+// make it tag-like to fit better with get_multiboot_tag
+struct multiboot_module_list_tag {
+	multiboot_uint16_t type;  // will be MULTIBOOT_TAG_MODULE
+	multiboot_uint16_t flags; // will be 0
+	multiboot_uint32_t size; // will be sizeof(struct multiboot_module_list_tag)
+
+	struct multiboot_tag_module *module;
+	list_head list;
+};
+
+struct multiboot_tag *get_multiboot_tag(uint8_t tag_id);
+int multiboot2_init(uint64_t *addr, uint32_t magic);
+
+#endif

kernel/multiboot2.c

@@ -1,10 +1,23 @@
+#include "multiboot2.h"
+#include "3rd/multiboot2.h"
 #include "khal.h"
 #include "kstdlib.h"
-#include <3rd/multiboot2.h>
+#include "kstring.h"
+#include "sys/panic.h"
 #include <stdint.h>
 
+static struct multiboot_tag *unary_tags[MULTIBOOT_TAG_TOTAL];
+
 #define CHECK_FLAG(flags, bit) ((flags) & (1 << (bit)))
 
+struct multiboot_tag *get_multiboot_tag(uint8_t tag_id) {
+	if (tag_id < 0 || tag_id >= MULTIBOOT_TAG_TOTAL) {
+		return NULL;
+	}
+
+	return unary_tags[tag_id];
+}
+
 void handle_cmdline_tag(struct multiboot_tag *tag);
 void handle_module_tag(struct multiboot_tag *tag);
 void handle_basic_load_base_addr(struct multiboot_tag *tag);
@@ -28,6 +41,10 @@ int multiboot2_init(uint64_t *addr, uint32_t magic) {
 	uint64_t size = *addr;
 	serial_printf("Announced mbi size 0x%x\n", size);
 
+	// set all tags to NULL
+	memset(unary_tags, 0x00,
+	       sizeof(struct multiboot_tag *) * MULTIBOOT_TAG_TOTAL);
+
 	tag = (struct multiboot_tag *)(mbi_addr + sizeof(uint64_t));
 
 	while (tag->type != MULTIBOOT_TAG_TYPE_END) {
@@ -52,6 +69,14 @@ int multiboot2_init(uint64_t *addr, uint32_t magic) {
 				break;
 		}
 
+		// In case I'm just stupid
+		if (unary_tags[tag->type])
+			PANIC("Duplicate multiboot tag during initialization");
+
+		// there can be more than one of those
+		// module tags will be handled separately after heap init
+		if (tag->type != MULTIBOOT_TAG_TYPE_MODULE) unary_tags[tag->type] = tag;
+
 		// Move to the next tag
 		tag = (struct multiboot_tag *)((uintptr_t)tag) + ((tag->size + 7) & ~7);
 	}