Update Roadmap

README.md

@@ -2,17 +2,53 @@
 
 RISC-V Operating System.
 
-## Roadmap
-[x] Machine Mode initialization
+## Kernel Development Roadmap
 
-[x] UART Driver
+### Phase 1: Foundations & Memory Management (Current)
+- [x] **Bootstrapping**: RISC-V `entry.S` and kernel entry point.
+- [x] **UART Driver**: Basic serial communication for debugging.
+- [x] **Panic System**: Kernel panic mechanism for fatal errors.
+- [x] **Physical Memory**: Page-level allocator (free list based).
+- [x] **Kernel Heap**: `kmalloc`/`kfree` with:
+    - [x] Splitting of large blocks.
+    - [x] Doubly-linked list headers.
+    - [x] Bidirectional coalescing (Iterative).
+- [~] **String Library**: Complete `lib/string.c` (`memset`, `memcpy`, `strcmp`, `strlen`).
+- [~] **Formatted Printing**: Robust `kprintf` implementation for hex and decimal.
 
-[X] Trap / Panic
+### Phase 2: Hardware Interfacing & Traps
+- [ ] **Trap Handling**: 
+    - [~] Setup `mtvec` (Machine Trap Vector).
+    - [ ] Assembly "trampoline" to save/restore registers.
+    - [~] C dispatcher for exceptions and interrupts.
+- [ ] **Timer Interrupts**: 
+    - [ ] Interface with RISC-V CLINT (Core Local Interrupter).
+    - [ ] Implement a system heartbeat (ticks).
+- [ ] **External Interrupts**: Setup PLIC (Platform-Level Interrupt Controller).
 
-[x] Heap Allocator with coalescing
+### Phase 3: Multitasking & Scheduling
+- [ ] **Task Structure**: Define `task_struct` (PID, State, Stack Pointer, Priority).
+- [ ] **Context Switching**: Assembly logic to switch register sets between tasks.
+- [ ] **Scheduler**: 
+    - [ ] Implement a Round-Robin scheduling algorithm.
+    - [ ] Task lifecycle management (Create, Yield, Terminate).
+- [ ] **Synchronization**: Basic Spinlocks or Semaphores for resource protection.
 
-[ ] Context Switching / Multi-threading
+### Phase 4: Virtual Memory
+- [ ] **Sv39 Paging**: 
+    - [ ] Walk the 3-level page table structure.
+    - [ ] Map/Unmap functions for virtual addresses.
+- [ ] **Kernel/User Separation**: Isolate kernel memory from user processes.
+- [ ] **Higher Half Kernel**: Remap kernel to upper virtual memory.
 
-[ ] Timer Interrupts (Round Robin)
+### Phase 5: Userspace & System Calls
+- [ ] **User Mode Jump**: Switch CPU to User (U) mode.
+- [ ] **ECALL Interface**: 
+    - [ ] Implement system call dispatcher.
+    - [ ] Basic syscalls: `write`, `exit`, `getpid`, `fork`.
+- [ ] **ELF Loader**: Read and execute simple static binaries.
 
-[ ] User Mode (U-Mode) transition
+### Phase 6: Filesystem & Shell
+- [ ] **VFS Layer**: Abstract File System interface.
+- [ ] **Initial RAM Disk (initrd)**: Load basic files into memory.
+- [ ] **User Shell**: Interactive CLI to execute commands and scripts.