2 files changed, 62 insertions, 10 deletions

diff --git a/arch/x86_64/include/arch/boot/multiboot.hpp b/arch/x86_64/include/arch/boot/multiboot.hpp
index c6fed55..9a0757e 100644
--- a/arch/x86_64/include/arch/boot/multiboot.hpp
+++ b/arch/x86_64/include/arch/boot/multiboot.hpp
@@ -10,5 +10,39 @@ struct multiboot_info
 {
   uint32_t total_size;
   uint32_t reserved;
-  struct multiboot_tag tags[1];  // TODO: Size 0
-};
\ No newline at end of file
+  /*
+   * field "tags" is an array of multiboot_tags, however the array is never
+   * being accessed by index and using an array definition with size 0 produces a compiler
+   * error.
+   */
+  struct multiboot_tag tags;
+};
+
+/*
+ * Define all multiboot tag types to ther respective values
+ * The gnu boot information format is defined here:
+ * https://www.gnu.org/software/grub/manual/multiboot2/multiboot.html#Boot-information-format
+ */
+#define MULTIBOOT_TAG_ALIGN 8
+#define MULTIBOOT_TAG_TYPE_END 0
+#define MULTIBOOT_TAG_TYPE_CMDLINE 1
+#define MULTIBOOT_TAG_TYPE_BOOT_LOADER_NAME 2
+#define MULTIBOOT_TAG_TYPE_MODULE 3
+#define MULTIBOOT_TAG_TYPE_BASIC_MEMINFO 4
+#define MULTIBOOT_TAG_TYPE_BOOTDEV 5
+#define MULTIBOOT_TAG_TYPE_MMAP 6
+#define MULTIBOOT_TAG_TYPE_VBE 7
+#define MULTIBOOT_TAG_TYPE_FRAMEBUFFER 8
+#define MULTIBOOT_TAG_TYPE_ELF_SECTIONS 9
+#define MULTIBOOT_TAG_TYPE_APM 10
+#define MULTIBOOT_TAG_TYPE_EFI32 11
+#define MULTIBOOT_TAG_TYPE_EFI64 12
+#define MULTIBOOT_TAG_TYPE_SMBIOS 13
+#define MULTIBOOT_TAG_TYPE_ACPI_OLD 14
+#define MULTIBOOT_TAG_TYPE_ACPI_NEW 15
+#define MULTIBOOT_TAG_TYPE_NETWORK 16
+#define MULTIBOOT_TAG_TYPE_EFI_MMAP 17
+#define MULTIBOOT_TAG_TYPE_EFI_BS 18
+#define MULTIBOOT_TAG_TYPE_EFI32_IH 19
+#define MULTIBOOT_TAG_TYPE_EFI64_IH 20
+#define MULTIBOOT_TAG_TYPE_LOAD_BASE_ADDR 21
diff --git a/arch/x86_64/src/kernel/main.cpp b/arch/x86_64/src/kernel/main.cpp
index e77818e..8ca577a 100644
--- a/arch/x86_64/src/kernel/main.cpp
+++ b/arch/x86_64/src/kernel/main.cpp
@@ -10,16 +10,34 @@ namespace teachos::arch::kernel
   {
     using namespace video::vga;
 
-    auto t = arch::boot::multiboot_information_pointer;
-    // auto multiboot_tag = (struct multiboot_tag *) ((uint8_t) t + 8);
-    // for (auto tag = multiboot_tag; tag->type != )
-
-    if (t == 300)
-    {
-    }
-
     text::clear();
     text::cursor(false);
     text::write("TeachOS is starting up...", text::common_attributes::green_on_black);
+
+    auto mip = arch::boot::multiboot_information_pointer;
+
+    // Address of the first multiboot tag
+    auto multiboot_tag = (struct multiboot_tag *)((uint8_t *)mip + 8);
+
+    /*
+     * Loop over the multiboot2 tags to access the information needed.
+     * Tags are defined in the header.
+     */
+    for (auto tag = multiboot_tag; tag->type != MULTIBOOT_TAG_TYPE_END;
+         tag = (struct multiboot_tag *)((uint8_t *)tag + ((tag->size + 7) & ~7)))
+    {
+      switch (tag->type)
+      {
+        case MULTIBOOT_TAG_TYPE_BASIC_MEMINFO:
+          uint32_t size = tag->size;
+          uint32_t mem_lower = *(uint32_t *)(&size + 32);
+          uint32_t mem_upper = *(uint32_t *)(&size + 64);
+          if (mem_lower > mem_upper)
+          {
+          }
+          text::write("BUFFER IS HERE", text::common_attributes::green_on_black);
+          break;
+      }
+    }
   }
 }  // namespace teachos::arch::kernel