From fbe59c8ffc9e57c449f0ad5f5614e53f621b9f33 Mon Sep 17 00:00:00 2001
From: DualFroz <me@dualfroz.com>
Date: Sun, 23 Aug 2026 16:23:33 +0200
Subject: [PATCH] feat(boot): parse multiboot2 boot information structure

---
 include/multiboot2.h | 42 ++++++++++++++++++++++++++++++++++++++++++
 src/multiboot.c      | 28 ++++++++++++++++++++++++++++
 2 files changed, 70 insertions(+)
 create mode 100644 include/multiboot2.h
 create mode 100644 src/multiboot.c

diff --git a/include/multiboot2.h b/include/multiboot2.h
new file mode 100644
index 0000000..edf7e8c
--- /dev/null
+++ b/include/multiboot2.h
@@ -0,0 +1,42 @@
+#ifndef FROSTBYTE_MULTIBOOT2_H
+#define FROSTBYTE_MULTIBOOT2_H
+
+#include "types.h"
+
+#define multibootTagTypeEnd 0
+#define multibootTagTypeModule 3
+#define multibootTagTypeMmap 6
+
+#define multibootMemoryAvailable 1
+
+typedef struct MultibootTag {
+    uint32 type;
+    uint32 size;
+} __attribute__((packed)) MultibootTag;
+
+typedef struct MultibootTagModule {
+    uint32 type;
+    uint32 size;
+    uint32 moduleStart;
+    uint32 moduleEnd;
+    char string[];
+} __attribute__((packed)) MultibootTagModule;
+
+typedef struct MultibootMmapEntry {
+    uint64 baseAddr;
+    uint64 length;
+    uint32 type;
+    uint32 reserved;
+} __attribute__((packed)) MultibootMmapEntry;
+
+typedef struct MultibootTagMmap {
+    uint32 type;
+    uint32 size;
+    uint32 entrySize;
+    uint32 entryVersion;
+    MultibootMmapEntry entries[];
+} __attribute__((packed)) MultibootTagMmap;
+
+bool multibootFindModule(uint64 multibootInfo, uint64* start, uint64* end);
+
+#endif
diff --git a/src/multiboot.c b/src/multiboot.c
new file mode 100644
index 0000000..ba84a8b
--- /dev/null
+++ b/src/multiboot.c
@@ -0,0 +1,28 @@
+#include "multiboot2.h"
+
+static uint64 alignUp(uint64 value, uint64 alignment)
+{
+    return (value + alignment - 1) & ~(alignment - 1);
+}
+
+bool multibootFindModule(uint64 multibootInfo, uint64* start, uint64* end)
+{
+    uint32 totalSize = *(uint32*)multibootInfo;
+    uint64 tagAddr = multibootInfo + 8;
+    uint64 endAddr = multibootInfo + totalSize;
+
+    while (tagAddr < endAddr) {
+        MultibootTag* tag = (MultibootTag*)tagAddr;
+        if (tag->type == multibootTagTypeEnd)
+            break;
+        if (tag->type == multibootTagTypeModule) {
+            MultibootTagModule* module = (MultibootTagModule*)tag;
+            *start = module->moduleStart;
+            *end = module->moduleEnd;
+            return true;
+        }
+        tagAddr = alignUp(tagAddr + tag->size, 8);
+    }
+
+    return false;
+}