Merge pull request #4 from Richard-Qin-001/dev/shell

Rebuilt the system's underlying structure; it is now stable enough to merge. 

The system now supports a read-only file system and has a simple shell implemented.

1 files changed, 42 insertions, 5 deletions

diff --git a/include/kernel/pmm.h b/include/kernel/pmm.h
index 3328450..d31473f 100644
--- a/include/kernel/pmm.h
+++ b/include/kernel/pmm.h
@@ -1,13 +1,50 @@
 #pragma once
 #include "common/types.h"
+#include "kernel/spinlock.h"
 
-#define PHYSTOP (0x80000000 + 128 * 1024 * 1024)
-#define PGSIZE 4096
+// Physical Memory Layout Definition
+#define KERNBASE 0x80000000
+// Set the memory size to 128MB
+#define PHYSIZE (128 * 1024 * 1024)
+#define PHYSTOP (KERNBASE + PHYSIZE)
 
-namespace PMM{
+// Buddy System Max Order
+// Order 10 => 2^10 pages = 1024 * 4KB = 4MB contiguous block
+// Order 11 => 2^11 pages = 8MB
+#define MAX_ORDER 11
+
+// Page flag
+#define PG_used 0x01     // This page is occupied
+#define PG_reserved 0x02 // This page is reserved (kernel code/data, DTB, MemMap)
+
+// Physical Page Metadata Structure
+struct Page
+{
+    uint8 flags;       // Page Status (PG_used, PG_reserved)
+    uint8 order;       // If it is the first page of a free block, record the order of the current block
+    uint16 refcnt;     // Reference Counting
+    struct Page *next; // Free list pointer (points to the next free block of the same size)
+    struct Page *prev; // Doubly linked list (easy to remove)
+};
+
+namespace PMM
+{
+    // Initialize physical memory management
     void init();
 
-    void* alloc_page();
+    // Core Allocation Interface (Buddy System)
+    // order: 0 ~ MAX_ORDER-1
+    void *alloc_pages(int order);
+    void free_pages(void *pa, int order);
+
+    // Compatible with old interface (allocate single page with order=0 and automatically reset to zero)
+    void *alloc_page();
+    void free_page(void *pa);
+
+    // Helper function
+    struct Page *pa_to_page(uint64 pa);
+    uint64 page_to_pa(struct Page *page);
 
-    void free_page(void* pa);
+    // Debug information
+    void print_free_lists();
 }
\ No newline at end of file