feat: Initial PMM implementation

Introduce the foundational Physical Memory Manager (PMM) and restructure the project for modularity.
Implemented basic PMM and related memory management headers (mm/pmm.h, mm/vm.h).
Updated Makefile and build process to support new modular structure.

1 files changed, 53 insertions, 3 deletions

diff --git a/src/kernel/main.cc b/src/kernel/main.cc
index 49adf2b..beda9dc 100644
--- a/src/kernel/main.cc
+++ b/src/kernel/main.cc
@@ -1,17 +1,67 @@
 #include "drivers/uart.h"
+#include "kernel/pmm.h"
+#include "kernel/mm.h"
+
+void print_hex(uint64_t val)
+{
+    char buf[17];
+    buf[16] = 0;
+    const char *digits = "0123456789ABCDEF";
+    for (int i = 15; i >= 0; i--)
+    {
+        buf[i] = digits[val & 0xf];
+        val >>= 4;
+    }
+    Drivers::uart_puts("0x");
+    Drivers::uart_puts(buf);
+}
 
 extern "C" void kernel_main()
 {
 
     Drivers::uart_init();
+    Drivers::uart_puts("\n[Modern DOS Kernel] Booted in S-Mode.\n");
+    Drivers::uart_puts("2025 Richard Qin\n");
+    Drivers::uart_puts("\n");
+
+    Drivers::uart_puts("[Kernel] Initializing PMM...\n");
+    PMM::init();
+    Drivers::uart_puts("[Kernel] PMM initialized.\n");
 
+    Drivers::uart_puts("[Kernel] Testing alloc_page...\n");
+    void *p1 = PMM::alloc_page();
+    void *p2 = PMM::alloc_page();
+
+    Drivers::uart_puts("Allocated Page 1: ");
+    print_hex((uint64_t)p1);
     Drivers::uart_puts("\n");
-    Drivers::uart_puts("Modern DOS v1.0 [RISC-V 64]\n");
-    Drivers::uart_puts("2025 Richard Qin\n");
+
+    Drivers::uart_puts("Allocated Page 2: ");
+    print_hex((uint64_t)p2);
     Drivers::uart_puts("\n");
 
-    Drivers::uart_puts("A:\\> ");
+    Drivers::uart_puts("[Kernel] Freeing Page 1...\n");
+    PMM::free_page(p1);
+
+    void *p3 = PMM::alloc_page();
+    Drivers::uart_puts("Allocated Page 3: ");
+    print_hex((uint64_t)p3);
+    Drivers::uart_puts("\n");
+
+    if (p3 == p1)
+    {
+        Drivers::uart_puts("[Test Passed] Reuse freed memory successfully.\n");
+    }
+    else
+    {
+        Drivers::uart_puts("[Test Failed] Memory leak or logic error.\n");
+    }
+
+    VM::kvminit();
+    Drivers::uart_puts("[Boot] Kernel page table created.\n");
 
+    VM::kvminithart();
+    Drivers::uart_puts("[Boot] MMU ENABLED! We are now using virtual addresses.\n");
 
     while (1)
     {