update kmalloc

1 files changed, 58 insertions, 7 deletions

diff --git a/kernel/mem.c b/kernel/mem.c
index 840a3b7..444436a 100644
--- a/kernel/mem.c
+++ b/kernel/mem.c
@@ -5,27 +5,76 @@
 
 static struct page *free_list;
 
+static void merge_freelist() {
+    struct page *list = free_list;
+
+    while (list && list->next) {
+        if ((void*)list + list->size == list->next) {
+            list->size += list->next->size;
+            list->next = list->next->next;
+            continue;
+        }
+        list = list->next;
+    }
+}
+
 void* kmalloc(size_t size) {
     struct page *page = free_list;
-    while (page != NULL && page->size < size && page->status != MEMPAGE_FREE) {
+    struct page *last = NULL;
+    while (page && page->size < size) {
+        last = page;
         page = page->next;
     }
     if (page == NULL)
         return NULL;
 
     size_t combined_size = size + sizeof(struct page);
-    struct page *next = (struct page *)((void *)page + combined_size);
-    next->next = page->next;
-    next->size = page->size - combined_size;
-    next->status = MEMPAGE_FREE;
+
+    if (page->size == combined_size) {
+        if (last)
+            last = page->next;
+        else
+            free_list = page->next;
+    } else if (page->size - combined_size < sizeof(struct page)) {
+        if (page->next) {
+            struct page *curr = (void *)page + combined_size;
+
+            size_t curr_size = page->size + page->next->size - combined_size;
+            struct page *next_page = page->next->next;
+
+            curr->next = next_page;
+            curr->size = curr_size;
+            curr->status = MEMPAGE_FREE;
+        }
+        // If page->next is undefined then there's nothing we can do except leak the last few bytes of memory.
+    } 
 
     page->status = MEMPAGE_USED;
-    next->size = combined_size;
-    next->next = NULL;
+    page->size = combined_size;
+    page->next = NULL;
 
     return (void *)page + sizeof(struct page);
 }
 
+void kfree(void *ptr) {
+    struct page *page_info = (struct page *)(ptr - sizeof(struct page));
+    struct page *iter = free_list;
+
+    if (!iter) {
+        free_list = page_info;
+        return;
+    }
+
+    while (iter->next && iter->next < page_info) {
+        iter = iter->next;
+    }
+
+    page_info->next = iter->next;
+    iter->next = page_info;
+
+    merge_freelist();
+}
+
 
 
 void* memcpy(void *to, const void *from, size_t size) {
@@ -47,3 +96,5 @@ void km_init(struct mem_info *info) {
 
     free_list = base;
 }
+
+