feat/kernel: Added First-Fit algorithm for kernel heap

kernel/src/mm/heap.h

@@ -0,0 +1,11 @@
+/* EMK 1.0 Copyright (c) 2025 Piraterna */
+#ifndef HEAP_H
+#define HEAP_H
+
+#include <stddef.h>
+
+void heap_init();
+void *kmalloc(size_t size);
+void kfree(void *ptr);
+
+#endif // HEAP_H

kernel/src/mm/heap/ff.c

@@ -0,0 +1,82 @@
+/* EMK 1.0 Copyright (c) 2025 Piraterna */
+#include <mm/heap/ff.h>
+#include <mm/heap.h>
+#include <mm/vmm.h>
+#include <mm/pmm.h>
+#include <boot/emk.h>
+#include <util/align.h>
+#include <sys/kpanic.h>
+
+void *pool;
+block_t *freelist = NULL;
+
+void heap_init()
+{
+    pool = valloc(kvm_ctx, FF_POOL_SIZE, VALLOC_RW);
+    if (!pool)
+        kpanic(NULL, "Failed to alloc memory for the heap pool");
+    freelist = (block_t *)pool;
+    freelist->size = (FF_POOL_SIZE * PAGE_SIZE) - sizeof(block_t);
+    freelist->next = NULL;
+}
+
+void *kmalloc(size_t size)
+{
+    if (size == 0)
+        return NULL;
+
+    size = ALIGN_UP(size, 8);
+
+    block_t *prev = NULL;
+    block_t *cur = freelist;
+
+    while (cur)
+    {
+        if (cur->size >= size)
+        {
+            size_t tot_size = sizeof(block_t) + size;
+
+            if (cur->size >= ALIGN_UP(tot_size + sizeof(block_t), 8))
+            {
+                /* do splitting */
+                block_t *new_block = (block_t *)((uint8_t *)cur + tot_size);
+                new_block->size = cur->size - tot_size;
+                new_block->next = cur->next;
+
+                cur->size = size;
+
+                if (prev)
+                    prev->next = new_block;
+                else
+                    freelist = new_block;
+            }
+            else
+            {
+                /* use entire block */
+                if (prev)
+                    prev->next = cur->next;
+                else
+                    freelist = cur->next;
+            }
+
+            return (void *)((uint8_t *)cur + sizeof(block_t));
+        }
+        prev = cur;
+        cur = cur->next;
+    }
+
+    return NULL;
+}
+
+void kfree(void *ptr)
+{
+    if (!ptr)
+        return;
+
+    /* get block header */
+    block_t *block = (block_t *)((uint8_t *)ptr - sizeof(block_t));
+
+    /* insert freed block at head of freelist */
+    block->next = freelist;
+    freelist = block;
+}

kernel/src/mm/heap/ff.h

@@ -0,0 +1,18 @@
+/* EMK 1.0 Copyright (c) 2025 Piraterna */
+#ifndef FF_H
+#define FF_H
+
+/* Kevin's simple First-Fit allocator */
+
+#include <stdint.h>
+#include <stddef.h>
+
+#define FF_POOL_SIZE 512 // 2MB, in pages
+
+typedef struct block
+{
+    size_t size;
+    struct block *next;
+} block_t;
+
+#endif // FF_H