From e6e156e2554fa3552bb2d1776585c4c93cc3145d Mon Sep 17 00:00:00 2001
From: Xnoe <xnoe@xnoe.moe>
Date: Mon, 25 Oct 2021 16:29:53 +0100
Subject: [PATCH] Implement Allocator. Add virtual page map. Fix PageMap class.

---
 src/boot_stage2/main.c | 31 ++++++++++++++++++++++++-------
 src/kernel/entry.asm   |  2 +-
 src/kernel/kernel.cpp  | 11 ++++++++++-
 src/kernel/memory.cpp  | 36 +++++++++++++++++++++++-------------
 src/kernel/memory.h    | 14 +++++++-------
 5 files changed, 65 insertions(+), 29 deletions(-)

diff --git a/src/boot_stage2/main.c b/src/boot_stage2/main.c
index 3181807..666aaff 100644
--- a/src/boot_stage2/main.c
+++ b/src/boot_stage2/main.c
@@ -33,7 +33,7 @@ void memset(uint8_t* base, uint32_t count, uint8_t to) {
   }
 }
 
-void mark_unavailble(uint32_t address, uint32_t size) {
+void mark_unavailble(uint32_t address, uint32_t size, uint8_t* buffer) {
   // This function takes an address and length and marks the corresponding pages as unavailable.
   address -= address % 4096; 
   if (size % 4096)
@@ -43,7 +43,7 @@ void mark_unavailble(uint32_t address, uint32_t size) {
   size /= 4096;
 
   for (int i=0; i<size; i++) {
-    unset_bit(address + i, bitmap);
+    unset_bit(address + i, buffer);
   }
 }
 
@@ -104,7 +104,7 @@ void main() {
     }
   }
 
-  mark_unavailble(bitmap, 0x20000);
+  mark_unavailble(bitmap, 0x20000, bitmap);
 
   // Page Directory
   PDE* kernel_page_directory = bitmap + 0x20000;
@@ -140,22 +140,39 @@ void main() {
   }
 
   // Mark unavailable bitmap to 0x522000
-  mark_unavailble(bitmap, 0x4000000);
+  mark_unavailble(bitmap, 0x4000000, bitmap);
 
   // Now we want to map some stuff.
   // But first, we should load the kernel somewhere
 
-  uint8_t* kernel_location = 0x522000; // Just load it at 0x522000 for now
-  mark_unavailble(0x522000, 32768); // Just treat the kernel as not growing beyong 32k for now.
 
-  map_many_4k_phys_to_virt(0x522000, 0xc0000000, kernel_page_directory, kernel_page_tables, 8); // Map 8 pages from 0x522000 to 0xc0000000;
+
+  uint8_t* kernel_location = 0x542000; // Just load it at 0x522000 for now
+  mark_unavailble(kernel_location, 32768, bitmap); // Just treat the kernel as not growing beyong 32k for now.
+
+  map_many_4k_phys_to_virt(kernel_location, 0xc0000000, kernel_page_directory, kernel_page_tables, 8); // Map 8 pages from 0x522000 to 0xc0000000;
   map_4k_phys_to_virt((uint32_t)kernel_page_directory, 0xc0100000, kernel_page_directory, kernel_page_tables); // Map the page directory to 0xc0100000
   map_many_4k_phys_to_virt(0x121000, 0xc0101000, kernel_page_directory, kernel_page_tables, 1024); // Map 1024 pages from 0x121000 to 0xc0101000
   map_4k_phys_to_virt(0xb8000, 0xc0501000, kernel_page_directory, kernel_page_tables); // Map 0xb8000 (video) to 0xc0501000
   map_4k_phys_to_virt(0x521000, 0xc0502000, kernel_page_directory, kernel_page_tables); // Map the PTE** data, we'll need to convert the pointers to point at kernel space at some point.
 
+  uint8_t* vm_bitmap = 0x522000;
+
+  memset(vm_bitmap, 0x20000, 0xff);
+
+  mark_unavailble(0xc0000000, 0x8000, vm_bitmap);
+  mark_unavailble(0xc0100000, 0x1000, vm_bitmap);
+  mark_unavailble(0xc0101000, 0x400000, vm_bitmap);
+  mark_unavailble(0xc0501000, 0x1000, vm_bitmap);
+  mark_unavailble(0xc0502000, 0x1000, vm_bitmap);
+  mark_unavailble(0xc0600000, 0x20000, vm_bitmap);
+  mark_unavailble(0xc0620000, 0x20000, vm_bitmap);
+  mark_unavailble(0x8a000, 0x6000, vm_bitmap);
+
   // Map the bitmap 
   map_many_4k_phys_to_virt(0x100000, 0xc0600000, kernel_page_directory, kernel_page_tables, 32);
+  // Map the virtual memory bitmap
+  map_many_4k_phys_to_virt(0x522000, 0xc0620000, kernel_page_directory, kernel_page_tables, 32);
 
   map_4k_phys_to_virt(0x8000, 0x8000, kernel_page_directory, kernel_page_tables);
   map_many_4k_phys_to_virt(0x8a000, 0x8a000, kernel_page_directory, kernel_page_tables, 6);
diff --git a/src/kernel/entry.asm b/src/kernel/entry.asm
index 7b8e693..446a4bc 100644
--- a/src/kernel/entry.asm
+++ b/src/kernel/entry.asm
@@ -1,6 +1,6 @@
 [BITS 32]
 
 _start:
-  call main
+  jmp main
 
 extern main
\ No newline at end of file
diff --git a/src/kernel/kernel.cpp b/src/kernel/kernel.cpp
index fcbc318..01c49f7 100644
--- a/src/kernel/kernel.cpp
+++ b/src/kernel/kernel.cpp
@@ -15,9 +15,16 @@ int main() {
 
   PageDirectory kernel_pd = PageDirectory(0xc0100000, 0x120000, 0xbffe0000);
   kernel_pd.select();
-  kernel_pd.map(0x0, 0x400000);
   kernel_pd.unmap(0x8000);
 
+  PageMap phys_pm(0xc0600000);
+  PageMap virt_pm(0xc0620000);
+
+  Allocator kernel_allocator = Allocator(&kernel_pd, &phys_pm, &virt_pm, 0xd0000000);
+
+  void* alloc = kernel_allocator.allocate(4096);
+  void* alloc2 = kernel_allocator.allocate(4096);
+
   init_idt();
   init_term();
 
@@ -25,6 +32,8 @@ int main() {
   
   printf("KERNEL OK!\n");
 
+  printf("Alloc: %x\nAlloc2: %x\n", alloc, alloc2);
+
   init_keyboard();
   
   enable_idt();
diff --git a/src/kernel/memory.cpp b/src/kernel/memory.cpp
index bd03369..7acfefa 100644
--- a/src/kernel/memory.cpp
+++ b/src/kernel/memory.cpp
@@ -1,4 +1,5 @@
 #include "memory.h"
+#include "screenstuff.h"
 
 void memset(uint8_t* address, uint32_t count, uint8_t value) {
   for (int i=0; i<count; i++)
@@ -10,6 +11,10 @@ void memcpy(uint8_t* src, uint8_t* dst, uint32_t count) {
     dst[i] = src[i];
 }
 
+PageMap::PageMap(uint32_t map) {
+  this->pagemap = (uint8_t*)map;
+}
+
 void PageMap::set_bit(uint32_t index) {
   uint32_t offset = index % 8;
   uint32_t i = index / 8;
@@ -50,7 +55,7 @@ void PageMap::mark_available(uint32_t address, uint32_t count) {
 }
 
 bool PageMap::available(uint32_t address) {
-  return bit_set(address >> 4096);
+  return bit_set(address >> 12);
 }
 
 uint32_t PageMap::find_next_available_from(uint32_t address) {
@@ -64,7 +69,7 @@ uint32_t PageMap::find_next_available_from(uint32_t address, uint32_t count) {
     while (!available(address)) address += 4096;
 
     for (int a=address, i=0; i<count; i++, a+=4096)
-      if (!available(address))
+      if (!available(a))
         continue;
     
     return address;
@@ -162,22 +167,27 @@ void PageDirectory::select() {
 
 PageMap* Allocator::phys;
 
-Allocator::Allocator(PageDirectory* page_directory, PageMap* phys, PageMap* virt) {
-  PD = page_directory;
-  phys = phys;
-  virt = virt;
+Allocator::Allocator(PageDirectory* page_directory, PageMap* phys, PageMap* virt, uint32_t virt_alloc_base) {
+  this->PD = page_directory;
+  this->phys = phys;
+  this->virt = virt;
 
-  remaining = 0;
+  this->virt_alloc_base = virt_alloc_base;
 }
 
-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);
+void* Allocator::allocate(uint32_t size) {
+  uint32_t count = (size + (4096%size)) / 4096;
 
-  phys->mark_unavailable(phys_addr);
-  virt->mark_unavailable(virt_addr);
+  uint32_t virt_addr = virt->find_next_available_from(this->virt_alloc_base, count);
+  this->virt->mark_unavailable(virt_addr, count);
 
-  PD->map(phys, virt);
+  for (int i=0; i<count; i++) {
+    uint32_t phys_addr = this->phys->find_next_available_from(0);
+    this->phys->mark_unavailable(phys_addr);
+    this->PD->map(phys_addr, virt_addr + 4096 * i);
+  }
+
+  return virt_addr;
 }
 
 void Allocator::deallocate(uint32_t virt_addr) {
diff --git a/src/kernel/memory.h b/src/kernel/memory.h
index d3317f3..d0a1a99 100644
--- a/src/kernel/memory.h
+++ b/src/kernel/memory.h
@@ -11,7 +11,7 @@ void memcpy(uint8_t* src, uint8_t* dst, uint32_t count);
 
 class __attribute__((packed)) PageMap {
 private:
-  uint8_t pagemap[1024^2 / 8];
+  uint8_t* pagemap;
 
   void set_bit(uint32_t index);
   void unset_bit(uint32_t index);
@@ -19,7 +19,7 @@ private:
   bool bit_set(uint32_t index);
 
 public:
-  PageMap(uint8_t* map);
+  PageMap(uint32_t map);
 
   void mark_unavailable(uint32_t address);
   void mark_unavailable(uint32_t address, uint32_t count);
@@ -73,16 +73,16 @@ protected:
 
   PageDirectory* PD;
 
-  uint32_t current_alloc_address;
-  uint32_t remaining;
-
   uint32_t virt_alloc_base;
 public:
-  Allocator(PageDirectory* page_directory, PageMap* phys, PageMap* virt);
-  virtual void* allocate();
+  Allocator(PageDirectory* page_directory, PageMap* phys, PageMap* virt, uint32_t virt_alloc_base);
+  virtual void* allocate(uint32_t size);
   virtual void deallocate(uint32_t virt_addr);
 };
 
+void* operator new (uint32_t size, Allocator* allocator);
+void operator delete (void* ptr, Allocator* allocator);
+
 class Process : protected Allocator {
 private:
   uint32_t PID;