From 45f420a338ea02225bb8a98c9aca5eed8d6a23ae Mon Sep 17 00:00:00 2001
From: Steven Le Rouzic <steven.lerouzic@gmail.com>
Date: Sun, 2 Jun 2024 00:26:57 +0200
Subject: Initial commit

---
 kernel/kalloc.c | 87 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 87 insertions(+)
 create mode 100644 kernel/kalloc.c

(limited to 'kernel/kalloc.c')

diff --git a/kernel/kalloc.c b/kernel/kalloc.c
new file mode 100644
index 0000000..e197c0c
--- /dev/null
+++ b/kernel/kalloc.c
@@ -0,0 +1,87 @@
+#include "kernel/lib.h"
+#include "kernel/kalloc.h"
+#include "kernel/spinlock.h"
+
+extern uint32_t _heap_start;
+extern uint32_t _heap_end;
+
+union Page
+{
+    union Page* next;
+    char dummy[PAGE_SIZE];
+};
+typedef union Page Page;
+static_assert(sizeof(Page) == PAGE_SIZE);
+
+static inline void* align_page_down(void* p)
+{
+    return (void*)((uint32_t)p & ~(PAGE_SIZE - 1));
+}
+
+static inline void* align_page_up(void* p)
+{
+    return align_page_down((char*)p + PAGE_SIZE - 1);
+}
+
+static inline bool is_page_aligned(void* p)
+{
+    return ((uint32_t)p & (PAGE_SIZE - 1)) == 0;
+}
+
+static Page* g_page_start;
+static Page* g_page_end;
+static Page* g_free_list;
+static Spinlock g_lock;
+
+void kalloc_init()
+{
+    spinlock_init(&g_lock);
+    
+    g_free_list  = NULL;
+    g_page_start = (Page*)align_page_up(&_heap_start);
+    g_page_end   = (Page*)align_page_down(&_heap_end);
+
+    for (Page* p = g_page_end - 1; p >= g_page_start; --p)
+    {
+        p->next = g_free_list;
+        g_free_list = p;
+    }
+}
+
+void* kalloc()
+{
+    spinlock_acquire(&g_lock);
+    Page* page = g_free_list;
+    if (!page)
+    {
+        panic("kalloc: Out of memory");
+    }
+    g_free_list = page->next;
+    spinlock_release(&g_lock);
+    return page;
+}
+
+void* kzalloc()
+{
+    void* page = kalloc();
+    uint32_t* p = (uint32_t*)page;
+    for (uint32_t i = 0; i < PAGE_SIZE / 4; ++i)
+    {
+        *p++ = 0U;
+    }
+    return page;
+}
+
+void kfree(void* ptr)
+{
+    if (ptr < (void*)g_page_start || ptr >= (void*)g_page_end || !is_page_aligned(ptr))
+    {
+        panic("kfree: Invalid page");
+    }
+    
+    spinlock_acquire(&g_lock);
+    Page* page = (Page*)ptr;
+    page->next = g_free_list;
+    g_free_list = page;
+    spinlock_release(&g_lock);
+}
-- 
cgit