From 2d0f539e233943d6db4149f0b6369dab7396de2f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20Lov=C3=A9n?= <thomasloven@gmail.com>
Date: Tue, 20 Feb 2018 13:41:32 +0100
Subject: [PATCH] Create and load new page directories

---
 src/kernel/boot/kmain.c     | 2 ++
 src/kernel/cpu/registers.S  | 4 ++++
 src/kernel/include/cpu.h    | 1 +
 src/kernel/include/memory.h | 1 +
 src/kernel/memory/vmm.c     | 7 +++++++
 src/kernel/memory/vmm.tt    | 8 +++++++-
 6 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/src/kernel/boot/kmain.c b/src/kernel/boot/kmain.c
index 7805c58..c0c27e5 100644
--- a/src/kernel/boot/kmain.c
+++ b/src/kernel/boot/kmain.c
@@ -35,6 +35,8 @@ void kmain(uint64_t multiboot_magic, void *multiboot_data)
 
   cpu_init();
 
+  uintptr_t P4 = new_P4();
+  write_cr3(P4);
 
   debug_ok("Boot \"Complete\"\n");
 
diff --git a/src/kernel/cpu/registers.S b/src/kernel/cpu/registers.S
index fa5a1da..09e1eec 100644
--- a/src/kernel/cpu/registers.S
+++ b/src/kernel/cpu/registers.S
@@ -17,6 +17,10 @@ read_cr2:
 read_cr3:
   mov rax, cr3
   ret
+.global write_cr3
+write_cr3:
+  mov cr3, rdi
+  ret
 .global read_cr4
 read_cr4:
   mov rax, cr4
diff --git a/src/kernel/include/cpu.h b/src/kernel/include/cpu.h
index f1d0dcd..7b93617 100644
--- a/src/kernel/include/cpu.h
+++ b/src/kernel/include/cpu.h
@@ -9,4 +9,5 @@ void load_idt(void *);
 uint64_t read_cr0();
 uint64_t read_cr2();
 uint64_t read_cr3();
+void write_cr3(uint64_t);
 uint64_t read_cr4();
diff --git a/src/kernel/include/memory.h b/src/kernel/include/memory.h
index 8c9414f..e4ae958 100644
--- a/src/kernel/include/memory.h
+++ b/src/kernel/include/memory.h
@@ -39,6 +39,7 @@ void pmm_free(uint64_t page);
 uint64_t pmm_alloc();
 uint64_t pmm_calloc();
 
+uint64_t new_P4();
 uint64_t vmm_get_page(uint64_t P4, uint64_t addr);
 #define PAGE_EXIST(p) ((p) != (uint64_t)-1)
 int vmm_set_page(uint64_t P4, uint64_t addr, uint64_t page, uint16_t flags);
diff --git a/src/kernel/memory/vmm.c b/src/kernel/memory/vmm.c
index e8cb79e..eae6c17 100644
--- a/src/kernel/memory/vmm.c
+++ b/src/kernel/memory/vmm.c
@@ -14,6 +14,13 @@
 #define P2E PT(P3E)[P2_OFFSET(addr)]
 #define P1E PT(P2E)[P1_OFFSET(addr)]
 
+uint64_t new_P4()
+{
+  uint64_t p4 = pmm_alloc();
+  memcpy(P2V(p4), (void *)kernel_P4, PAGE_SIZE);
+  return p4;
+}
+
 static int page_exists(uint64_t P4, uint64_t addr)
 {
   if(P4 && PRESENT(P4E) && PRESENT(P3E) && PRESENT(P2E))
diff --git a/src/kernel/memory/vmm.tt b/src/kernel/memory/vmm.tt
index 15d3283..b0b31a6 100644
--- a/src/kernel/memory/vmm.tt
+++ b/src/kernel/memory/vmm.tt
@@ -3,7 +3,13 @@
 
 #include <memory.h>
 #undef P2V
-#define P2V(p) (p)
+#define P2V(p) ((void *)(p))
+
+uint64_t kernel_P4;
+uint64_t pmm_alloc()
+{
+  return 0;
+}
 
 #include "vmm.c"