include/setup.sh

1 files changed, 46 insertions, 0 deletions

diff --git a/include/09.paging/paging.c b/include/09.paging/paging.c
new file mode 100644
index 0000000..f08530d
--- /dev/null
+++ b/include/09.paging/paging.c
@@ -0,0 +1,46 @@
+#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 page_table[1024][1024] __attribute__((aligned(4096)));
+
+void set_pt(size_t num,uint32_t address)
+{
+    // 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.
+
+    //we will fill all 1024 entries in the table, mapping 4 megabytes
+    for(size_t 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 ;)
+        page_table[num][i] = (address + i * 0x1000) | 3; // attributes: supervisor level, read/write, present.
+    }
+
+    page_directory[num] = ((uint32_t)page_table[num]) | 3;
+    // attributes: supervisor level, read/write, present
+}
+
+void set_paging()
+{
+    set_pd();
+    for(size_t i=0;i<1024;i++) set_pt(i,0x00400000 * i); // all 4GB mapped
+    loadPageDirectory(page_directory);
+    enablePaging();
+}