From 5dc4e27392aaab78f3be45be8f485d37eb362818 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20Lov=C3=A9n?= <thomasloven@gmail.com>
Date: Thu, 4 Jan 2018 00:10:27 +0100
Subject: [PATCH] Map all free memory pages and add to page stack

---
 src/kernel/Link.ld          |  2 ++
 src/kernel/boot/kmain.c     | 15 +++++++++++++++
 src/kernel/include/memory.h |  3 +++
 3 files changed, 20 insertions(+)

diff --git a/src/kernel/Link.ld b/src/kernel/Link.ld
index 2fa7802..767844d 100644
--- a/src/kernel/Link.ld
+++ b/src/kernel/Link.ld
@@ -6,6 +6,7 @@ KERNEL_START = 0x10000;
 SECTIONS
 {
   . = KERNEL_START + KERNEL_OFFSET;
+  kernel_start = .;
   .text : AT(ADDR(.text) - KERNEL_OFFSET)
   {
     *(.multiboot)
@@ -24,4 +25,5 @@ SECTIONS
     *(.COMMON)
     *(.bss)
   }
+  kernel_end = .;
 }
diff --git a/src/kernel/boot/kmain.c b/src/kernel/boot/kmain.c
index ebdbd03..b2e01fd 100644
--- a/src/kernel/boot/kmain.c
+++ b/src/kernel/boot/kmain.c
@@ -22,7 +22,22 @@ void kmain(uint64_t multiboot_magic, void *multiboot_data)
   uintptr_t start, end;
   uint32_t type, i=0;
   while(!multiboot_get_memory_area(i++, &start, &end, &type))
+  {
+    if(type != 1)
+      continue;
     debug_printf("Mem %d 0x%x-0x%x\n", type, start, end);
+    for(uintptr_t p = start; p < end; p += PAGE_SIZE)
+    {
+      if(p >= V2P(&kernel_start) && p < V2P(&kernel_end))
+        continue;
+      if(!(p & 0x1FFFFF))
+      {
+        touch_page(&BootP4, (uintptr_t)P2V(p), PAGE_HUGE);
+        vmm_set_page(&BootP4, (uintptr_t)P2V(p), p, PAGE_HUGE | PAGE_WRITE | PAGE_PRESENT);
+      }
+      pmm_free(p);
+    }
+  }
 
   debug_ok("Boot \"Complete\"\n");
 
diff --git a/src/kernel/include/memory.h b/src/kernel/include/memory.h
index 498cf3a..e22f554 100644
--- a/src/kernel/include/memory.h
+++ b/src/kernel/include/memory.h
@@ -38,4 +38,7 @@ uintptr_t vmm_get_page(void *P4, uintptr_t addr);
 int vmm_set_page(void *P4, uintptr_t addr, uintptr_t page, uint16_t flags);
 int touch_page(void *P4, uintptr_t addr, uint16_t flags);
 void free_page(void *P4, uintptr_t addr, int free);
+
+extern union PTE BootP4;
+extern int kernel_start, kernel_end;
 #endif