1 files changed, 101 insertions, 3 deletions
diff --git a/kernel/mm/virtual_mm/virtual_mm.c b/kernel/mm/virtual_mm/virtual_mm.c
index 6350c11..0f55950 100644
--- a/kernel/mm/virtual_mm/virtual_mm.c
+++ b/kernel/mm/virtual_mm/virtual_mm.c
@@ -18,6 +18,8 @@
 
 #include <stdint.h>
 
+#include <kernel/halt.h>
+
 #include <libk/stdio.h>
 
 #include <mm/physical_mm.h>
@@ -26,8 +28,7 @@
 extern uint32_t kernel_start;
 extern uint32_t kernel_end;
 
-uint32_t initial_page_directory[PAGE_DIRECTORY_SIZE];
-uint32_t initial_page_table[PAGE_TABLE_SIZE];
+uint32_t *current_page_directory = 0;
 
 bool
 virtual_mm_allocate_page(uint32_t *pt_entry)
@@ -75,5 +76,102 @@ virtual_mm_lookup_directory(uint32_t *page_directory, uint32_t virtual_addr)
 ALWAYS_INLINE void
 virtual_mm_load_page_directory(uint32_t *page_directory)
 {
-  __asm__("movl %0, %%cr0" ::"r"(page_directory));
+  __asm__("movl %0, %%eax" ::"r"(page_directory) : "%eax");
+  /* For some reason, that colon is required; else the assembler thinks that
+   * %eax doesn't exist :^) */
+  __asm__("movl %%eax, %%cr3" ::: "%eax");
+}
+
+bool
+virtual_mm_switch_page_directory(uint32_t *page_directory)
+{
+  if (!page_directory)
+    return false;
+  current_page_directory = page_directory;
+  virtual_mm_load_page_directory(page_directory);
+
+  return true;
+}
+
+/* TODO: I have absolutely _no_ idea if this works */
+void
+virtual_mm_flush_tlb_entry(uint32_t *virtual_addr)
+{
+  __asm__("cli;"
+          "invlpg (%0);"
+          "sti" ::"r"(virtual_addr));
+}
+
+bool
+virtual_mm_map_page(uint32_t *physical_addr, uint32_t *virtual_addr)
+{
+  uint32_t *pd_entry
+      = &current_page_directory[PAGE_DIRECTORY_INDEX((uint32_t) virtual_addr)];
+
+  /* If the page directory entry isn't present */
+  if (!PTE_IS_PRESENT(*pd_entry)) {
+    uint32_t *page_table = physical_mm_allocate_block();
+    if (!page_table)
+      return false;
+
+    *pd_entry = 0;
+    ADD_ATTRIB(pd_entry, SET_PDE_PRESENT(1));
+    ADD_ATTRIB(pd_entry, SET_PDE_WRITABLE(1));
+    ADD_ATTRIB(pd_entry, SET_PDE_FRAME((uint32_t) page_table));
+  }
+
+  uint32_t *page_table = (uint32_t *) GET_PDE_FRAME(pd_entry);
+  uint32_t *pt_entry = &page_table[PAGE_TABLE_INDEX((uint32_t) virtual_addr)];
+  *pt_entry = 0;
+
+  ADD_ATTRIB(pt_entry, SET_PTE_PRESENT(1));
+  ADD_ATTRIB(pt_entry, SET_PTE_FRAME((uint32_t) physical_addr));
+
+  return true;
+}
+
+ALWAYS_INLINE static void
+virtual_mm_enable_paging(void)
+{
+  __asm__("movl %%cr0, %%eax;"
+          "orl $0x80000000, %%eax;"
+          "movl %%eax, %%cr0" ::
+              : "eax");
+}
+
+void
+virtual_mm_initialize(void)
+{
+  uint32_t *table = physical_mm_allocate_block();
+  if (!table)
+    ASSERT_NOT_REACHED();
+
+  for (uint32_t i = 0; i < 1024; i++)
+    table[i] = 0;
+
+  /* Identity map the first 4MiB (maps 4KiB 1024 times) */
+  for (uint32_t i = 0, physical_addr = 0, virtual_addr = 0; i < 1024;
+       i++, physical_addr += 4096, virtual_addr += 4096) {
+    uint32_t page = 0;
+    ADD_ATTRIB(&page, SET_PTE_PRESENT(1));
+    ADD_ATTRIB(&page, SET_PTE_FRAME(physical_addr));
+
+    table[PAGE_TABLE_INDEX(virtual_addr)] = page;
+  }
+
+  uint32_t *page_directory = physical_mm_allocate_block();
+  if (!page_directory)
+    ASSERT_NOT_REACHED();
+
+  for (uint32_t i = 0; i < 1024; i++)
+    page_directory[i] = 0;
+
+  uint32_t *pd_entry = &page_directory[PAGE_DIRECTORY_INDEX(0)];
+  ADD_ATTRIB(pd_entry, SET_PDE_PRESENT(1));
+  ADD_ATTRIB(pd_entry, SET_PDE_WRITABLE(1));
+  ADD_ATTRIB(pd_entry, SET_PDE_FRAME((uint32_t) table));
+
+  current_page_directory = page_directory;
+  virtual_mm_switch_page_directory(current_page_directory);
+  virtual_mm_enable_paging();
 }