Martian OS

// Core kernel services in Rust
#[no_std]
#[no_main]
mod kernel {
    use crate::memory::MemoryManager;
    use crate::scheduler::RTScheduler;
    use crate::ipc::MessagePassing;
    
    pub struct MartianKernel {
        memory: MemoryManager,
        scheduler: RTScheduler,
        ipc: MessagePassing,
        interrupt_controller: InterruptController,
    }
    
    impl MartianKernel {
        pub const fn new() -> Self {
            Self {
                memory: MemoryManager::new(),
                scheduler: RTScheduler::new(),
                ipc: MessagePassing::new(),
                interrupt_controller: InterruptController::new(),
            }
        }
        
        pub fn boot(&mut self) -> ! {
            // Initialize hardware abstraction layer
            hal::init();
            
            // Setup memory protection
            self.memory.setup_protection_domains();
            
            // Start real-time scheduler
            self.scheduler.start_scheduling();
            
            // Enter user mode
            unsafe { self.enter_userspace() }
        }
    }
}

// Hardware memory protection
pub struct MemoryProtectionUnit {
    regions: [MpuRegion; 16],
    fault_handler: fn(FaultInfo),
}

impl MemoryProtectionUnit {
    pub fn protect_region(&mut self, 
        start: VirtAddr, size: usize, 
        perms: Permissions) -> Result<(), MpuError> {
        
        let region = MpuRegion::new(start, size, perms)?;
        self.configure_hardware(&region)?;
        Ok(())
    }
    
    pub fn handle_fault(&self, fault: FaultInfo) {
        match fault.fault_type {
            FaultType::AccessViolation => {
                // Immediate emergency stop
                emergency::trigger_safe_stop();
            }
            FaultType::StackOverflow => {
                // Graceful task termination
                scheduler::terminate_task(fault.task_id);
            }
        }
    }
}

// Real-time task scheduler
pub struct RTScheduler {
    ready_queues: [TaskQueue; 256], // 256 priority levels
    current_task: Option<TaskId>,
    timer: HighResTimer,
}

impl RTScheduler {
    pub fn schedule(&mut self) -> TaskId {
        // Rate-monotonic scheduling with deadline inheritance
        if let Some(highest_prio) = self.find_highest_priority() {
            if self.should_preempt(highest_prio) {
                self.context_switch(highest_prio)
            } else {
                self.current_task.unwrap()
            }
        } else {
            self.idle_task()
        }
    }
    
    pub fn add_periodic_task(&mut self, 
        task: Task, period: Duration, 
        deadline: Duration) -> Result<TaskId, SchedError> {
        
        // Verify schedulability using RMA analysis
        if !self.verify_schedulability(&task, period) {
            return Err(SchedError::NotSchedulable);
        }
        
        let priority = self.compute_priority(period);
        let task_id = self.allocate_task_id();
        
        self.ready_queues[priority as usize].push(task_id);
        Ok(task_id)
    }
}

// Ultra-low latency interrupt handling
#[naked]
#[no_mangle]
unsafe extern "C" fn irq_handler() {
    asm!(
        // Save minimal context (ARM64)
        "stp x0, x1, [sp, #-16]!",
        "stp x2, x3, [sp, #-16]!",
        
        // Read interrupt vector
        "mrs x0, #0x3000", // Read GICC_IAR
        
        // Branch to Rust handler
        "bl handle_interrupt_rust",
        
        // Restore context
        "ldp x2, x3, [sp], #16",
        "ldp x0, x1, [sp], #16",
        "eret",
        options(noreturn)
    );
}

#[no_mangle]
extern "C" fn handle_interrupt_rust(irq_num: u32) {
    // Sub-microsecond interrupt processing
    let handler = INTERRUPT_TABLE[irq_num as usize];
    handler.handle_fast();
    
    // Signal end of interrupt
    gic::end_interrupt(irq_num);
}