Function fork_current_thread

kernel/src/process.rs:634–679

Fork the current user thread

(current_context: &mut Context)

///
///
pub fn fork_current_thread(current_context: &mut Context) {

    if let Some(current_thread) = CURRENT_THREAD.read().as_ref() {

        // Allocate user stack
        let page_table_ptr = memory::active_pagetable_ptr();
        if let Ok((user_stack_start, user_stack_end)) = memory::allocate_user_stack(page_table_ptr) {
            let new_thread = {
                // Create a new kernel stack
                let kernel_stack = Vec::with_capacity(KERNEL_STACK_SIZE);
                let kernel_stack_start = VirtAddr::from_ptr(kernel_stack.as_ptr());
                let kernel_stack_end = (kernel_stack_start + KERNEL_STACK_SIZE).as_u64();

                Box::new(Thread {
                    tid: unique_id(),
                    process: current_thread.process.clone(), // Shared state
                    page_table_physaddr: current_thread.page_table_physaddr, // Shared page table
                    kernel_stack,
                    kernel_stack_end,
                    user_stack_end,
                    context: kernel_stack_end - INTERRUPT_CONTEXT_SIZE as u64,
                })
            };

            let new_context = unsafe {&mut *(new_thread.context as *mut Context)};
            *new_context = current_context.clone();

            // Set new stack pointer
            new_context.rsp = new_thread.user_stack_end as usize;

            // Set return values in rax
            new_context.rax = 0; // No error
            new_context.rdi = 0; // Indicates that this is the new thread
            current_context.rax = 0; // No error
            current_context.rdi = new_thread.tid as usize;

            RUNNING_QUEUE.write().push_back(new_thread);
        } else {
            // Failed to allocate user stack
            current_context.rax = syscalls::SYSCALL_ERROR_MEMALLOC; // Error code
        }
    } else {
        // Somehow no current thread
        current_context.rax = 2; // Error code
    }
}

/// This function is called via syscall (and maybe other mechanism)
/// to remove the current thread.