feat(kernel): Finalizing the first version of the user scheduler.

other:

 - Removed DmaPool into its own Kit.
 - ApplicationProcessor unit has been cleaned up.
 - Rename functions of MemoryMgr.
 - Use KIB instead of MIBs of stack.
 - Cleanup parts of the scheduler, and hw scheduler.
 - Use UD handler for INT 6.

Signed-off-by: Amlal El Mahrouss <amlal@nekernel.org>

8 files changed, 74 insertions, 125 deletions

diff --git a/dev/kernel/HALKit/AMD64/HalApplicationProcessor.cc b/dev/kernel/HALKit/AMD64/HalApplicationProcessor.cc
index dd9a36ed..84c52768 100644
--- a/dev/kernel/HALKit/AMD64/HalApplicationProcessor.cc
+++ b/dev/kernel/HALKit/AMD64/HalApplicationProcessor.cc
@@ -152,10 +152,13 @@ EXTERN_C BOOL mp_register_process(HAL::StackFramePtr stack_frame, ProcessID pid)
 
   kHWThread[process_index].mCoreID = kAPICLocales[0];
 
-  hal_send_sipi(kApicBaseAddress, kHWThread[process_index].mCoreID,
-                (UInt8) (((UIntPtr) stack_frame->BP) >> 12));
+  if (mp_is_smp()) {
+    /// TODO:
 
-  return YES;
+    return YES;
+  }
+
+  return NO;
 }
 
 /***********************************************************************************/
@@ -195,44 +198,36 @@ Void mp_init_cores(VoidPtr vendor_ptr) noexcept {
   kSMPAware  = NO;
 
   if (kMADTBlock) {
-    SizeT index = 1;
+    SizeT index = 0;
 
     kSMPInterrupt = 0;
     kSMPCount     = 0;
 
-    kout << "SMP: Starting APs...\r";
-
     kApicBaseAddress = kMADTBlock->Address;
 
+    constexpr const auto kSMPCountMax = kMaxAPInsideSched;
+
     while (Yes) {
       /// @note Anything bigger than x2APIC type doesn't exist.
-      if (kMADTBlock->List[index].Type > 9 || kSMPCount > kSchedProcessLimitPerTeam) break;
+      if (kSMPCount > kSMPCountMax) break;
 
-      switch (kMADTBlock->List[index].Type) {
-        case 0x00: {
-          if (kMADTBlock->List[kSMPCount].Apic.LAPIC.ProcessorID < 1) break;
+      if (kMADTBlock->List[index].Type > 9) {
+        ++index;
+        continue;
+      }
 
-          kAPICLocales[kSMPCount] = kMADTBlock->List[kSMPCount].Apic.LAPIC.ProcessorID;
-          (Void)(kout << "SMP: APIC ID: " << number(kAPICLocales[kSMPCount]) << kendl);
+      kAPICLocales[kSMPCount] = kMADTBlock->List[kSMPCount].Apic.LAPIC.ProcessorID;
+      (Void)(kout << "SMP: APIC ID: " << number(kAPICLocales[kSMPCount]) << kendl);
 
-          ++kSMPCount;
-          break;
-        }
-        default:
-          break;
-      }
+      ++kSMPCount;
 
       ++index;
     }
 
-    (Void)(kout << "SMP: Number of APs: " << number(kSMPCount) << kendl);
-
     // Kernel is now SMP aware.
     // That means that the scheduler is now available (on MP Kernels)
 
     kSMPAware = true;
-
-    /// TODO: Notify Boot AP that it must start.
   }
 }
 }  // namespace Kernel::HAL
diff --git a/dev/kernel/HALKit/AMD64/HalCoreInterruptHandlerAMD64.cc b/dev/kernel/HALKit/AMD64/HalCoreInterruptHandlerAMD64.cc
index 3a380a42..1e513e3f 100644
--- a/dev/kernel/HALKit/AMD64/HalCoreInterruptHandlerAMD64.cc
+++ b/dev/kernel/HALKit/AMD64/HalCoreInterruptHandlerAMD64.cc
@@ -16,10 +16,6 @@ STATIC BOOL kIsScheduling = NO;
 EXTERN_C void idt_handle_gpf(Kernel::UIntPtr rsp) {
   auto process = Kernel::UserProcessScheduler::The().CurrentProcess();
 
-  if (process.Leak().Status != Kernel::ProcessStatusKind::kRunning) {
-    MUST_PASS(NO);
-  }
-
   kIsScheduling = NO;
 
   Kernel::kout << "Kernel: General Protection Fault.\r";
@@ -40,10 +36,6 @@ EXTERN_C void idt_handle_gpf(Kernel::UIntPtr rsp) {
 EXTERN_C void idt_handle_pf(Kernel::UIntPtr rsp) {
   auto process = Kernel::UserProcessScheduler::The().CurrentProcess();
 
-  if (process.Leak().Status != Kernel::ProcessStatusKind::kRunning) {
-    MUST_PASS(NO);
-  }
-
   kIsScheduling = NO;
 
   Kernel::kout << "Kernel: Page Fault.\r";
@@ -58,27 +50,14 @@ EXTERN_C void idt_handle_pf(Kernel::UIntPtr rsp) {
   process.Leak().Crash();
 }
 
-namespace Kernel::Detail {
-constexpr static Int32 kTimeoutCount = 100000UL;
-}
-
 /// @brief Handle scheduler interrupt.
 EXTERN_C void idt_handle_scheduler(Kernel::UIntPtr rsp) {
   NE_UNUSED(rsp);
 
-  static Kernel::Int64 try_count_before_brute = Kernel::Detail::kTimeoutCount;
-
-  while (kIsScheduling) {
-    --try_count_before_brute;
-
-    if (try_count_before_brute < 1) break;
-  }
-
-  try_count_before_brute = Kernel::Detail::kTimeoutCount;
-  kIsScheduling          = YES;
+  Kernel::kout << "Kernel: Scheduler interrupt.\r";
 
+  kIsScheduling = YES;
   Kernel::UserProcessHelper::StartScheduling();
-
   kIsScheduling = NO;
 }
 
@@ -87,10 +66,6 @@ EXTERN_C void idt_handle_scheduler(Kernel::UIntPtr rsp) {
 EXTERN_C void idt_handle_math(Kernel::UIntPtr rsp) {
   auto process = Kernel::UserProcessScheduler::The().CurrentProcess();
 
-  if (process.Leak().Status != Kernel::ProcessStatusKind::kRunning) {
-    MUST_PASS(NO);
-  }
-
   kIsScheduling = NO;
 
   Kernel::kout << "Kernel: Math error (division by zero?).\r";
@@ -111,10 +86,6 @@ EXTERN_C void idt_handle_math(Kernel::UIntPtr rsp) {
 EXTERN_C void idt_handle_generic(Kernel::UIntPtr rsp) {
   auto process = Kernel::UserProcessScheduler::The().CurrentProcess();
 
-  if (process.Leak().Status != Kernel::ProcessStatusKind::kRunning) {
-    MUST_PASS(NO);
-  }
-
   kIsScheduling = NO;
 
   Kernel::kout << "Kernel: Generic Process Fault.\r";
@@ -163,10 +134,6 @@ EXTERN_C Kernel::Void idt_handle_breakpoint(Kernel::UIntPtr rip) {
 EXTERN_C void idt_handle_ud(Kernel::UIntPtr rsp) {
   auto process = Kernel::UserProcessScheduler::The().CurrentProcess();
 
-  if (process.Leak().Status != Kernel::ProcessStatusKind::kRunning) {
-    MUST_PASS(NO);
-  }
-
   kIsScheduling = NO;
 
   Kernel::kout << "Kernel: Undefined Opcode.\r";
diff --git a/dev/kernel/HALKit/AMD64/HalDescriptorLoader.cc b/dev/kernel/HALKit/AMD64/HalDescriptorLoader.cc
index 2fb6ad4c..b8eb8fe9 100644
--- a/dev/kernel/HALKit/AMD64/HalDescriptorLoader.cc
+++ b/dev/kernel/HALKit/AMD64/HalDescriptorLoader.cc
@@ -8,56 +8,10 @@
 #include <FSKit/NeFS.h>
 #include <HALKit/AMD64/Processor.h>
 
-#define kPITDefaultTicks (1000U)
-
 namespace Kernel::HAL {
 namespace Detail {
   STATIC ::Kernel::Detail::AMD64::InterruptDescriptorAMD64 kInterruptVectorTable[kKernelIdtSize] =
       {};
-
-  STATIC ATTRIBUTE(unused) void hal_set_irq_mask(UInt8 irql) [[maybe_unused]] {
-    UInt16 port;
-    UInt8  value;
-
-    if (irql < 8) {
-      port = kPICData;
-    } else {
-      port = kPIC2Data;
-      irql -= 8;
-    }
-
-    value = rt_in8(port) | (1 << irql);
-    rt_out8(port, value);
-  }
-
-  STATIC void hal_clear_irq_mask(UInt8 irql) [[maybe_unused]] {
-    UInt16 port;
-    UInt8  value;
-
-    if (irql < 8) {
-      port = kPICData;
-    } else {
-      port = kPIC2Data;
-      irql -= 8;
-    }
-
-    value = rt_in8(port) & ~(1 << irql);
-    rt_out8(port, value);
-  }
-
-  STATIC Void hal_enable_pit(UInt16 ticks) noexcept {
-    if (ticks == 0) ticks = kPITDefaultTicks;
-
-    // Configure PIT to receieve scheduler interrupts.
-
-    UInt16 kPITCommDivisor = kPITFrequency / ticks;  // 100 Hz.
-
-    HAL::rt_out8(kPITControlPort, 0x36);                            // Command to PIT
-    HAL::rt_out8(kPITChannel0Port, kPITCommDivisor & 0xFF);         // Send low byte
-    HAL::rt_out8(kPITChannel0Port, (kPITCommDivisor >> 8) & 0xFF);  // Send high byte
-
-    hal_clear_irq_mask(32);
-  }
 }  // namespace Detail
 
 /// @brief Loads the provided Global Descriptor Table.
@@ -72,8 +26,6 @@ Void GDTLoader::Load(Register64& gdt) {
 Void IDTLoader::Load(Register64& idt) {
   rt_cli();
 
-  const Int16 kPITTickForScheduler = kPITDefaultTicks;
-
   volatile ::Kernel::UIntPtr** ptr_ivt = (volatile ::Kernel::UIntPtr**) idt.Base;
 
   for (SizeT idt_indx = 0; idt_indx < kKernelIdtSize; ++idt_indx) {
@@ -92,12 +44,7 @@ Void IDTLoader::Load(Register64& idt) {
   idt.Base  = (UIntPtr) &Detail::kInterruptVectorTable[0];
   idt.Limit = sizeof(::Kernel::Detail::AMD64::InterruptDescriptorAMD64) * (kKernelIdtSize);
 
-  Detail::hal_enable_pit(kPITTickForScheduler);
-
-#ifndef __NE_MODULAR_KERNEL_COMPONENTS__
   hal_load_idt(idt);
-#endif  // __NE_MODULAR_KERNEL_COMPONENTS__
-
   rt_sti();
 }
 
diff --git a/dev/kernel/HALKit/AMD64/HalInterruptAPI.asm b/dev/kernel/HALKit/AMD64/HalInterruptAPI.asm
index a6c6bbb5..0634b0ea 100644
--- a/dev/kernel/HALKit/AMD64/HalInterruptAPI.asm
+++ b/dev/kernel/HALKit/AMD64/HalInterruptAPI.asm
@@ -138,7 +138,7 @@ __NE_INT_6:
     out 0x20, al
 
     push rcx
-    call idt_handle_generic
+    call idt_handle_ud
     pop rcx
 
     std
@@ -235,17 +235,14 @@ IntNormal 31
 
 __NE_INT_32:
     cld
-
-    mov al, 0x20
-    out 0xA0, al
-    out 0x20, al
     
     push rax
     mov rcx, rsp
     call idt_handle_scheduler
     pop rax
 
-    std
+    mov al, 0x20
+    out 0x20, al
 
     o64 iret
 
@@ -416,3 +413,12 @@ kInterruptVectorTable:
         dq __NE_INT_%+i
     %assign i i+1
     %endrep
+
+section .text
+
+global sched_jump_to_task
+
+;; Jump to the task from its stack frame.
+sched_jump_to_task:
+    mov rsp, rcx
+    ret
\ No newline at end of file
diff --git a/dev/kernel/HALKit/AMD64/HalKernelMain.cc b/dev/kernel/HALKit/AMD64/HalKernelMain.cc
index 2d213a9b..b0ac076d 100644
--- a/dev/kernel/HALKit/AMD64/HalKernelMain.cc
+++ b/dev/kernel/HALKit/AMD64/HalKernelMain.cc
@@ -27,6 +27,8 @@ EXTERN_C Int32 hal_init_platform(Kernel::HEL::BootInfoHeader* handover_hdr) {
     return kEfiFail;
   }
 
+  Kernel::HAL::rt_sti();
+
   kHandoverHeader = handover_hdr;
 
   FB::fb_clear_video();
@@ -54,7 +56,7 @@ EXTERN_C Int32 hal_init_platform(Kernel::HEL::BootInfoHeader* handover_hdr) {
 
   STATIC CONST auto kGDTEntriesCount = 6;
 
-  /* GDT, mostly descriptors for user and kernel segments. */
+  /* The GDT, mostly descriptors for user and kernel segments. */
   STATIC Kernel::HAL::Detail::NE_GDT_ENTRY ALIGN(0x08) kGDTArray[kGDTEntriesCount] = {
       {.fLimitLow   = 0,
        .fBaseLow    = 0,
@@ -101,6 +103,13 @@ EXTERN_C Int32 hal_init_platform(Kernel::HEL::BootInfoHeader* handover_hdr) {
   return kEfiFail;
 }
 
+EXTERN_C Kernel::Void rtl_ne_task(Kernel::Void) {
+  kout << "Hello, world!\r";
+  dbg_break_point();
+}
+
+EXTERN_C void idt_handle_scheduler(Kernel::UIntPtr rsp);
+
 EXTERN_C Kernel::Void hal_real_init(Kernel::Void) noexcept {
 #ifdef __FSKIT_INCLUDES_HEFS__
   if (!Kernel::HeFS::fs_init_hefs()) {
@@ -108,18 +117,24 @@ EXTERN_C Kernel::Void hal_real_init(Kernel::Void) noexcept {
     Kernel::NeFS::fs_init_nefs();
   }
 #elif defined(__FSKIT_INCLUDES_NEFS__)
-  Kernel::NeFS::fs_init_nefs();
+  if (!Kernel::NeFS::fs_init_nefs()) {
+    kout << "NeFS cannot be formated on the disk. Aborting\r";
+    dbg_break_point();
+  }
 #endif
 
+  Kernel::rtl_create_user_process(rtl_ne_task, "NeTask");
+
   Kernel::HAL::mp_init_cores(kHandoverHeader->f_HardwareTables.f_VendorPtr);
 
   Kernel::HAL::Register64 idt_reg;
-  idt_reg.Base = (Kernel::UIntPtr) kInterruptVectorTable;
+  idt_reg.Base = reinterpret_cast<Kernel::UIntPtr>(kInterruptVectorTable);
 
   Kernel::HAL::IDTLoader idt_loader;
 
   idt_loader.Load(idt_reg);
 
-  dbg_break_point();
+  while (YES)
+    ;
 }
 #endif  // ifndef __NE_MODULAR_KERNEL_COMPONENTS__
diff --git a/dev/kernel/HALKit/AMD64/Network/Generic+Basic+RTL8139.cc b/dev/kernel/HALKit/AMD64/Network/Generic+Basic+RTL8139.cc
index 06c18d8b..57f64712 100644
--- a/dev/kernel/HALKit/AMD64/Network/Generic+Basic+RTL8139.cc
+++ b/dev/kernel/HALKit/AMD64/Network/Generic+Basic+RTL8139.cc
@@ -4,8 +4,8 @@ Copyright (C) 2025, Amlal El Mahrouss, all rights reserved.
 
 ------------------------------------------- */
 
+#include <DmaKit/DmaPool.h>
 #include <HALKit/AMD64/Processor.h>
-#include <StorageKit/DmaPool.h>
 #include <modules/ACPI/ACPIFactoryInterface.h>
 
 using namespace Kernel;
@@ -14,7 +14,7 @@ using namespace Kernel::HAL;
 STATIC UInt16 kIOBase = 0xFFFF;
 
 STATIC UInt32                 kRXOffset     = 0UL;
-STATIC constexpr const UInt32 kRxBufferSize = 8192 + 16 + 1500;
+STATIC constexpr CONST UInt32 kRxBufferSize = 8192 + 16 + 1500;
 
 STATIC BOOL kTXEnabled = NO;
 
diff --git a/dev/kernel/HALKit/AMD64/Paging.h b/dev/kernel/HALKit/AMD64/Paging.h
index cfba232c..061bae45 100644
--- a/dev/kernel/HALKit/AMD64/Paging.h
+++ b/dev/kernel/HALKit/AMD64/Paging.h
@@ -63,6 +63,25 @@ auto mm_free_bitmap(VoidPtr page_ptr) -> Bool;
 }  // namespace Kernel::HAL
 
 namespace Kernel {
-typedef VoidPtr PTE;
-typedef VoidPtr PDE;
+struct PTE {
+  UInt64 Present : 1;
+  UInt64 Wr : 1;
+  UInt64 User : 1;
+  UInt64 Pwt : 1;  // Page-level Write-Through
+  UInt64 Pcd : 1;  // Page-level Cache Disable
+  UInt64 Accessed : 1;
+  UInt64 Dirty : 1;
+  UInt64 Pat : 1;  // Page Attribute Table (or PS for PDE)
+  UInt64 Global : 1;
+  UInt64 Ignored1 : 3;          // Available to software
+  UInt64 PhysicalAddress : 40;  // Physical page frame address (bits 12–51)
+  UInt64 Ignored2 : 7;          // More software bits / reserved
+  UInt64 ProtectionKey : 4;     // Optional (if PKU enabled)
+  UInt64 Reserved : 1;          // Usually reserved
+  UInt64 Nx : 1;                // No Execute
+};
+
+struct PDE {
+  ATTRIBUTE(aligned(kib_cast(4))) PTE fPTE[512];
+};
 }  // namespace Kernel
diff --git a/dev/kernel/HALKit/AMD64/Storage/AHCI+Generic.cc b/dev/kernel/HALKit/AMD64/Storage/AHCI+Generic.cc
index 21483560..57e77e77 100644
--- a/dev/kernel/HALKit/AMD64/Storage/AHCI+Generic.cc
+++ b/dev/kernel/HALKit/AMD64/Storage/AHCI+Generic.cc
@@ -15,6 +15,7 @@
  *
  */
 
+#include <DmaKit/DmaPool.h>
 #include <FirmwareKit/EPM.h>
 #include <KernelKit/DeviceMgr.h>
 #include <KernelKit/DriveMgr.h>
@@ -25,7 +26,6 @@
 #include <KernelKit/Timer.h>
 #include <NewKit/Utils.h>
 #include <StorageKit/AHCI.h>
-#include <StorageKit/DmaPool.h>
 #include <modules/AHCI/AHCI.h>
 #include <modules/ATA/ATA.h>