mboot parsing

Makefile

@@ -8,7 +8,7 @@ ISO_NAME=os_image.iso
 CC=cc
 LD=ld
 
-CFLAGS=-std=c2x -ffreestanding -g -Wall -Wextra -pedantic -lgcc -isystem $(INCLUDE_DIR)
+CFLAGS=-std=c2x -ffreestanding -fno-stack-protector -g -Wall -Wextra -pedantic -lgcc -isystem $(INCLUDE_DIR)
 
 
 C_SRC=$(shell find $(SRC_DIR) -type f -name "*.c")

src/arch/amd64/mboot.c

@@ -0,0 +1,65 @@
+#include "mboot.h"
+
+#include <stddef.h>
+#include <lib.h>
+
+static void read_cmdline(struct mboot_info *info, struct mboot_tag *tag, char *data, uint8_t len) {
+    if (len >= CMDLINE_MAX)
+		len = CMDLINE_MAX; // truncate :(
+    memcpy(tag->data.cmdline, data, len);
+    tag->data.cmdline[len] = '\0';
+    info->tags[MBOOT_CMDLINE] = *tag;
+}
+
+static void read_xsdp(struct mboot_info *info, struct mboot_tag *tag, char *data) {
+	tag->data.rootsdp = (void *) data;
+    info->tags[MBOOT_XSDP] = *tag;
+}
+
+static uint32_t *read_tag(struct mboot_info *info, uint32_t *data) {
+    struct mboot_tag tag;
+    tag.type = ((uint16_t*)data)[0];
+    tag.size = data[1];
+    tag.valid = 1;
+
+    uint8_t data_len = tag.size - 2 * sizeof(uint32_t);
+
+    switch (tag.type) {
+        case MBOOT_CMDLINE:
+            read_cmdline(info, &tag, (char *)(data + 2), data_len);
+            break;
+        case MBOOT_XSDP:
+            read_xsdp(info, &tag, (char *) (data + 2));
+            break;
+        default:
+            break;
+    }
+
+    if(tag.size % 8 != 0) {
+		tag.size += 8 - (tag.size % 8);
+	}
+
+    return data + tag.size / sizeof(uint32_t);
+}
+
+struct mboot_info mboot_load_info(void *mboot_info) {
+	struct mboot_info info = {0};
+
+    uint32_t* data = (uint32_t*) mboot_info;
+    info.total_size = *data++;
+    info.reserved = *data++;
+
+    while((uint8_t*) data < (uint8_t*) mboot_info + info.total_size) {
+        data = read_tag(&info, data);
+    }
+	
+	return info;
+}
+
+struct mboot_tag *mboot_get_tag(struct mboot_info *info, enum mboot_tag_type type) {
+	if (info->tags[type].valid) {
+		return &info->tags[type];
+	} else {
+		return NULL;
+	}
+}

src/arch/amd64/mboot.h

@@ -0,0 +1,40 @@
+#pragma once
+
+#include <stdint.h>
+
+#define CMDLINE_MAX 32
+
+struct mboot_tag {
+	uint8_t valid; // if the tag at this location is set
+	uint32_t type;
+	uint32_t size;
+	union {
+		char cmdline[CMDLINE_MAX + 1];
+		void *rootsdp;
+	} data;
+};
+
+enum mboot_tag_type {
+	MBOOT_CMDLINE = 0,
+	MBOOT_XSDP = 14
+};
+
+struct mboot_info {
+	uint32_t total_size;
+	uint32_t reserved;
+	struct mboot_tag tags[21];
+};
+
+/**
+ * Loads the multi boot information
+ * @param mboot_info - the pointer passed from multiboot2
+ */
+struct mboot_info mboot_load_info(void *mboot_info);
+
+/**
+ * Gets a tag from multiboot
+ * @param type - the tag type
+ * @returns NULL - tag not loaded
+ * @returns tag - tag was loaded
+ */
+struct mboot_tag *mboot_get_tag(struct mboot_info *info, enum mboot_tag_type type);