Bootloader: Locate the kernel's data segment and clear it.

This was a constant source of stupid bugs and I kept postponing it because I wasn't in the mood to write assembly code. Until now! :^)
luteresa · Feb 6, 2019 · a1b63bb · a1b63bb
1 parent 781f216
commit a1b63bb
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Showing 22 changed files with 54 additions and 83 deletions.
diff --git a/AK/StringImpl.cpp b/AK/StringImpl.cpp
@@ -21,15 +21,6 @@ namespace AK {
 
 static StringImpl* s_the_empty_stringimpl = nullptr;
 
-void StringImpl::initialize_globals()
-{
- s_the_empty_stringimpl = nullptr;
-#ifdef DEBUG_STRINGIMPL
- g_stringimpl_count = 0;
- g_all_live_stringimpls = new HashTable<StringImpl*>;
-#endif
-}
-
 StringImpl& StringImpl::the_empty_stringimpl()
 {
  if (!s_the_empty_stringimpl)

diff --git a/AK/StringImpl.h b/AK/StringImpl.h
@@ -17,7 +17,6 @@ class StringImpl : public Retainable<StringImpl> {
  RetainPtr<StringImpl> to_uppercase() const;
 
  static StringImpl& the_empty_stringimpl();
- static void initialize_globals();
 
  ~StringImpl();
 

diff --git a/Kernel/BochsVGADevice.cpp b/Kernel/BochsVGADevice.cpp
@@ -24,11 +24,6 @@ BochsVGADevice& BochsVGADevice::the()
  return *s_the;
 }
 
-void BochsVGADevice::initialize_statics()
-{
- s_the = nullptr;
-}
-
 BochsVGADevice::BochsVGADevice()
 {
  s_the = this;

diff --git a/Kernel/BochsVGADevice.h b/Kernel/BochsVGADevice.h
@@ -10,7 +10,6 @@ class BochsVGADevice {
  AK_MAKE_ETERNAL
 public:
  static BochsVGADevice& the();
- static void initialize_statics();
 
  BochsVGADevice();
 

diff --git a/Kernel/Boot/boot.asm b/Kernel/Boot/boot.asm
@@ -25,9 +25,13 @@ boot:
  mov ax, 0x2401
  int 0x15
 
- mov bx, 0x1000
+ ; HACK: Load the ELF kernel at 0xf000. Assuming that the first
+ ; LOAD header has a file offset of 0x1000, this puts _start
+ ; at 0x10000 which we jump to later.
+ ; This is all quite rickety.
+ mov bx, 0xf00
  mov es, bx
- xor bx, bx ; Load kernel @ 0x10000
+ xor bx, bx
 
  mov cx, word [cur_lba]
 .sector_loop:
@@ -65,6 +69,53 @@ boot:
  xor al, al
  out dx, al
 
+ ; Let's look at the ELF header.
+ mov bx, 0xf00
+ mov fs, bx
+ cmp [fs:0], dword 0x464c457f ; ELF magic: { 0x7f "ELF" }
+ jne fug
+
+ cmp [fs:24], dword 0x10000 ; Entry should be 0x10000
+ jne fug
+
+ mov ebx, dword [fs:28] ; EBX <- program header table
+ mov ecx, dword [fs:44] ; ECX <- program header count
+
+; Let's find the BSS and clear it.
+
+parse_program_header:
+ cmp [fs:ebx], dword 0x1 ; Is Load segment?
+ jne .next
+
+ cmp [fs:ebx+24], dword 0x6 ; Is read+write but not execute?
+ jne .next
+
+ mov edi, [fs:ebx+8] ; EDI <- p_vaddr
+ add edi, [fs:ebx+16] ; skip over 'p_filesz' bytes (leave them intact)
+
+ push ecx
+
+ sub edi, [fs:ebx+16] ; skip over 'p_filesz' bytes (see above)
+
+ ; Since we're in 16-bit real mode, create a segment address.
+ mov eax, edi
+ shr eax, 4
+ mov es, ax
+ and edi, 0xf
+
+ mov ecx, [fs:ebx+20] ; ECX <- p_memsz
+ xor al, al
+ rep stosb
+
+ pop ecx
+
+.next:
+ add ebx, 32
+ loop parse_program_header
+
+; Okay we're all set to go!
+
+lets_go:
  lgdt [cs:test_gdt_ptr]
 
  mov eax, cr0
@@ -182,7 +233,7 @@ convert_lba_to_chs:
  ret 
  
 cur_lba:
- dw 9
+ dw 1
 sectors_per_track:
  dw 18
 heads:

diff --git a/Kernel/FileSystem.cpp b/Kernel/FileSystem.cpp
@@ -23,13 +23,6 @@ HashTable<Inode*>& all_inodes()
  return *s_inode_set;
 }
 
-void FS::initialize_globals()
-{
- s_lastFileSystemID = 0;
- s_fs_map = nullptr;
- s_inode_set = nullptr;
-}
-
 FS::FS()
  : m_fsid(++s_lastFileSystemID)
 {

diff --git a/Kernel/FileSystem.h b/Kernel/FileSystem.h
@@ -23,7 +23,6 @@ class VMObject;
 
 class FS : public Retainable<FS> {
 public:
- static void initialize_globals();
  virtual ~FS();
 
  unsigned fsid() const { return m_fsid; }

diff --git a/Kernel/PTYMultiplexer.cpp b/Kernel/PTYMultiplexer.cpp
@@ -12,11 +12,6 @@ PTYMultiplexer& PTYMultiplexer::the()
  return *s_the;
 }
 
-void PTYMultiplexer::initialize_statics()
-{
- s_the = nullptr;
-}
-
 PTYMultiplexer::PTYMultiplexer()
  : CharacterDevice(5, 2)
 {

diff --git a/Kernel/PTYMultiplexer.h b/Kernel/PTYMultiplexer.h
@@ -13,7 +13,6 @@ class PTYMultiplexer final : public CharacterDevice {
  virtual ~PTYMultiplexer() override;
 
  static PTYMultiplexer& the();
- static void initialize_statics();
 
  // ^CharacterDevice
  virtual RetainPtr<FileDescriptor> open(int& error, int options) override;

diff --git a/Kernel/ProcessGUI.cpp b/Kernel/ProcessGUI.cpp
@@ -12,11 +12,6 @@
 
 void Process::initialize_gui_statics()
 {
- Font::initialize();
- WSMessageLoop::initialize();
- WSWindowManager::initialize();
- WSScreen::initialize();
-
  new WSMessageLoop;
 }
 

diff --git a/Kernel/VirtualFileSystem.cpp b/Kernel/VirtualFileSystem.cpp
@@ -19,12 +19,6 @@ VFS& VFS::the()
  return *s_the;
 }
 
-void VFS::initialize_globals()
-{
- s_the = nullptr;
- FS::initialize_globals();
-}
-
 VFS::VFS()
 {
 #ifdef VFS_DEBUG

diff --git a/Kernel/VirtualFileSystem.h b/Kernel/VirtualFileSystem.h
@@ -39,8 +39,6 @@ class VFS;
 class VFS {
  AK_MAKE_ETERNAL
 public:
- static void initialize_globals();
-
  class Mount {
  public:
  Mount(InodeIdentifier host, RetainPtr<FS>&&);

diff --git a/Kernel/init.cpp b/Kernel/init.cpp
@@ -151,8 +151,6 @@ void init()
  gdt_init();
  idt_init();
 
- PTYMultiplexer::initialize_statics();
- VFS::initialize_globals();
  vfs = new VFS;
 
  keyboard = new Keyboard;
@@ -169,10 +167,6 @@ void init()
  kprintf("Starting Serenity Operating System...\n");
 
  MemoryManager::initialize();
-
- StringImpl::initialize_globals();
- BochsVGADevice::initialize_statics();
-
  PIT::initialize();
 
  memset(&system, 0, sizeof(system));

diff --git a/LibC/entry.cpp b/LibC/entry.cpp
@@ -18,8 +18,6 @@ extern "C" int _start()
  __stdio_init();
  __malloc_init();
 
- StringImpl::initialize_globals();
-
  int status = 254;
  int argc;
  char** argv;

diff --git a/SharedGraphics/Font.cpp b/SharedGraphics/Font.cpp
@@ -50,12 +50,6 @@ static inline constexpr size_t font_file_size(unsigned glyph_height)
  return sizeof(FontFileHeader) + 256 * sizeof(dword) * glyph_height;
 }
 
-void Font::initialize()
-{
- s_default_font = nullptr;
- s_default_bold_font = nullptr;
-}
-
 Font& Font::default_font()
 {
  static const char* default_font_path = "/res/fonts/LizaRegular8x10.font";

diff --git a/SharedGraphics/Font.h b/SharedGraphics/Font.h
@@ -62,8 +62,6 @@ class Font : public Retainable<Font> {
  String name() const { return m_name; }
  void set_name(const String& name) { m_name = name; }
 
- static void initialize();
-
 private:
  Font(const String& name, unsigned* rows, byte glyph_width, byte glyph_height);
 

diff --git a/WindowServer/WSMessageLoop.cpp b/WindowServer/WSMessageLoop.cpp
@@ -12,11 +12,6 @@
 
 static WSMessageLoop* s_the;
 
-void WSMessageLoop::initialize()
-{
- s_the = nullptr;
-}
-
 WSMessageLoop::WSMessageLoop()
 {
  if (!s_the)

diff --git a/WindowServer/WSMessageLoop.h b/WindowServer/WSMessageLoop.h
@@ -19,8 +19,6 @@ class WSMessageLoop {
 
  static WSMessageLoop& the();
 
- static void initialize();
-
  bool running() const { return m_running; }
  Process& server_process() { return *m_server_process; }
 

diff --git a/WindowServer/WSScreen.cpp b/WindowServer/WSScreen.cpp
@@ -7,11 +7,6 @@
 
 static WSScreen* s_the;
 
-void WSScreen::initialize()
-{
- s_the = nullptr;
-}
-
 WSScreen& WSScreen::the()
 {
  ASSERT(s_the);

diff --git a/WindowServer/WSScreen.h b/WindowServer/WSScreen.h
@@ -21,8 +21,6 @@ class WSScreen {
  Size size() const { return { width(), height() }; }
  Rect rect() const { return { 0, 0, width(), height() }; }
 
- static void initialize();
-
  Point cursor_location() const { return m_cursor_location; }
  bool left_mouse_button_pressed() const { return m_left_mouse_button_pressed; }
  bool right_mouse_button_pressed() const { return m_right_mouse_button_pressed; }

diff --git a/WindowServer/WSWindowManager.cpp b/WindowServer/WSWindowManager.cpp
@@ -75,11 +75,6 @@ WSWindowManager& WSWindowManager::the()
  return *s_the;
 }
 
-void WSWindowManager::initialize()
-{
- s_the = nullptr;
-}
-
 static const char* cursor_bitmap_inner_ascii = {
  " # "
  " ## "

diff --git a/WindowServer/WSWindowManager.h b/WindowServer/WSWindowManager.h
@@ -29,8 +29,6 @@ class WSWindowManager : public WSMessageReceiver {
 
  void move_to_front(WSWindow&);
 
- static void initialize();
-
  void draw_cursor();
 
  void invalidate(const WSWindow&);