Added paging

1 files changed, 51 insertions, 0 deletions

diff --git a/src/c/paging.c b/src/c/paging.c
new file mode 100644
index 0000000..b256b74
--- /dev/null
+++ b/src/c/paging.c
@@ -0,0 +1,51 @@
+#include"../include/types.h"
+
+extern void loadPageDirectory(uint32_t*);
+extern void enablePaging();
+
+uint32_t page_directory[1024] __attribute__((aligned(4096)));
+
+void set_pd()
+{
+    //set each entry to not present
+    for(size_t i=0;i<1024;i++)
+    {
+	// This sets the following flags to the pages:
+	//   Supervisor: Only kernel-mode can access them
+	//   Write Enabled: It can be both read from and written to
+	//   Not Present: The page table is not present
+	page_directory[i] = 0x00000002;
+    }
+}
+
+uint32_t first_page_table[1024] __attribute__((aligned(4096)));
+
+void set_pt()
+{
+    // holds the physical address where we want to start mapping these pages to.
+    // in this case, we want to map these pages to the very beginning of memory.
+    unsigned int i;
+     
+    //we will fill all 1024 entries in the table, mapping 4 megabytes
+    for(i = 0; i < 1024; i++)
+    {
+	// As the address is page aligned, it will always leave 12 bits zeroed.
+	// Those bits are used by the attributes ;)
+	first_page_table[i] = (i * 0x1000) | 3; // attributes: supervisor level, read/write, present.
+    }
+}
+
+void put_pt()
+{
+    // attributes: supervisor level, read/write, present
+    page_directory[0] = ((uint32_t)first_page_table) | 3;
+}
+
+void set_paging()
+{
+    set_pd();
+    set_pt();
+    put_pt();
+    loadPageDirectory(page_directory);
+    enablePaging();
+}