From f2e09e98a7d48bd5653665adf48c4e77d435dfdb Mon Sep 17 00:00:00 2001
From: Xnoe <xnoe@xnoe.moe>
Date: Mon, 25 Oct 2021 01:13:29 +0100
Subject: [PATCH] Started work on Allocator class. Update PageMap

---
 src/kernel/kernel.cpp |  2 +-
 src/kernel/memory.cpp | 99 +++++++++++++++++++++++++++++++++++++++++++
 src/kernel/memory.h   | 36 +++++++++++-----
 3 files changed, 125 insertions(+), 12 deletions(-)

diff --git a/src/kernel/kernel.cpp b/src/kernel/kernel.cpp
index 63b945a..fcbc318 100644
--- a/src/kernel/kernel.cpp
+++ b/src/kernel/kernel.cpp
@@ -16,7 +16,7 @@ int main() {
   PageDirectory kernel_pd = PageDirectory(0xc0100000, 0x120000, 0xbffe0000);
   kernel_pd.select();
   kernel_pd.map(0x0, 0x400000);
-  //kernel_pd.unmap(0x8000);
+  kernel_pd.unmap(0x8000);
 
   init_idt();
   init_term();
diff --git a/src/kernel/memory.cpp b/src/kernel/memory.cpp
index 9fc62c8..bd03369 100644
--- a/src/kernel/memory.cpp
+++ b/src/kernel/memory.cpp
@@ -10,6 +10,67 @@ void memcpy(uint8_t* src, uint8_t* dst, uint32_t count) {
     dst[i] = src[i];
 }
 
+void PageMap::set_bit(uint32_t index) {
+  uint32_t offset = index % 8;
+  uint32_t i = index / 8;
+  
+  pagemap[i] |= 1<<(7-offset);
+}
+
+void PageMap::unset_bit(uint32_t index) {
+  uint32_t offset = index % 8;
+  uint32_t i = index / 8;
+  
+  pagemap[i] &= 255 - (1<<(7-offset));
+}
+
+bool PageMap::bit_set(uint32_t index) {
+  uint32_t offset = index % 8;
+  uint32_t i = index / 8;
+
+  return pagemap[i] & 1<<(7-offset);
+}
+
+void PageMap::mark_unavailable(uint32_t address) {
+  unset_bit(address >> 12);
+}
+
+void PageMap::mark_unavailable(uint32_t address, uint32_t count) {
+  for (int i=0; i<count; i++)
+    unset_bit((address >> 12) + i);
+}
+
+void PageMap::mark_available(uint32_t address) {
+  set_bit(address >> 12);
+}
+
+void PageMap::mark_available(uint32_t address, uint32_t count) {
+  for (int i=0; i<count; i++)
+    set_bit((address >> 12) + i);
+}
+
+bool PageMap::available(uint32_t address) {
+  return bit_set(address >> 4096);
+}
+
+uint32_t PageMap::find_next_available_from(uint32_t address) {
+  while (!available(address)) address += 4096;
+
+  return address;
+}
+
+uint32_t PageMap::find_next_available_from(uint32_t address, uint32_t count) {
+  while (1) {
+    while (!available(address)) address += 4096;
+
+    for (int a=address, i=0; i<count; i++, a+=4096)
+      if (!available(address))
+        continue;
+    
+    return address;
+  }
+}
+
 PageTable::PageTable(uint32_t phys, uint32_t virt) {
   phys_addr = phys;
   virt_addr = virt;
@@ -51,6 +112,10 @@ void PageTable::unmap_table(uint32_t index) {
   };
 }
 
+uint32_t PageTable::get_physical_address(uint32_t index) {
+  return page_table[index].address << 12;
+}
+
 PageDirectory::PageDirectory(PDE* page_directory, uint32_t phys_addr, uint32_t offset) {
   this->page_directory = page_directory;
   this->phys_addr = phys_addr;
@@ -86,6 +151,40 @@ void PageDirectory::unmap(uint32_t virt) {
   page_tables[split->pd_index].unmap_table(split->pt_index);
 }
 
+uint32_t PageDirectory::virtual_to_physical(uint32_t virt) {
+  split_addr* split = (split_addr*)&virt;
+  return page_tables[split->pd_index].get_physical_address(split->pt_index);
+}
+
 void PageDirectory::select() {
   asm volatile("mov %0, %%eax; mov %%eax, %%cr3" : : "m" (phys_addr));
+}
+
+PageMap* Allocator::phys;
+
+Allocator::Allocator(PageDirectory* page_directory, PageMap* phys, PageMap* virt) {
+  PD = page_directory;
+  phys = phys;
+  virt = virt;
+
+  remaining = 0;
+}
+
+void* Allocator::allocate() {
+  uint32_t phys_addr = phys->find_next_available_from(0);
+  uint32_t virt_addr = virt->find_next_available_from(virt_alloc_base);
+
+  phys->mark_unavailable(phys_addr);
+  virt->mark_unavailable(virt_addr);
+
+  PD->map(phys, virt);
+}
+
+void Allocator::deallocate(uint32_t virt_addr) {
+  uint32_t phys_addr = PD->virtual_to_physical(virt_addr);
+
+  PD->unmap(virt_addr);
+
+  phys->mark_available(phys_addr);
+  virt->mark_unavailable(virt_addr);
 }
\ No newline at end of file
diff --git a/src/kernel/memory.h b/src/kernel/memory.h
index b81c7e1..d3317f3 100644
--- a/src/kernel/memory.h
+++ b/src/kernel/memory.h
@@ -16,11 +16,21 @@ private:
   void set_bit(uint32_t index);
   void unset_bit(uint32_t index);
 
+  bool bit_set(uint32_t index);
+
 public:
   PageMap(uint8_t* map);
 
-  void mark_unavailble(uint32_t page);
-  void mark_available(uint32_t page);
+  void mark_unavailable(uint32_t address);
+  void mark_unavailable(uint32_t address, uint32_t count);
+
+  void mark_available(uint32_t address);
+  void mark_available(uint32_t address, uint32_t count);
+
+  bool available(uint32_t address);
+
+  uint32_t find_next_available_from(uint32_t address);
+  uint32_t find_next_available_from(uint32_t address, uint32_t count);
 };
 
 struct PageTable {
@@ -34,6 +44,8 @@ struct PageTable {
 
   void map_table(uint32_t index, uint32_t addr);
   void unmap_table(uint32_t index);
+
+  uint32_t get_physical_address(uint32_t index);
 };
 
 class PageDirectory {
@@ -47,26 +59,28 @@ public:
   PageDirectory(PDE* page_directories, uint32_t phys_addr, uint32_t offset);
 
   void map(uint32_t phys, uint32_t virt);
-
   void unmap(uint32_t virt);
 
+  uint32_t virtual_to_physical(uint32_t virt);
+
   void select();
 };
 
 class Allocator {
 protected:
-  static PageMap phys;
-  PageMap virt;
+  static PageMap* phys;
+  PageMap* virt;
 
-  PageDirectory PD;
+  PageDirectory* PD;
 
-  uint32_t current_page_index;
+  uint32_t current_alloc_address;
   uint32_t remaining;
+
+  uint32_t virt_alloc_base;
 public:
-  Allocator();
-  Allocator(PageDirectory page_directory, PageMap phys, PageMap virt);
-  void* allocate();
-  void deallocate();
+  Allocator(PageDirectory* page_directory, PageMap* phys, PageMap* virt);
+  virtual void* allocate();
+  virtual void deallocate(uint32_t virt_addr);
 };
 
 class Process : protected Allocator {