Function dispatch_syscall

kernel/src/syscalls.rs:275–313

(context_ptr: *mut Context, syscall_id: u64,
                               arg1: u64, arg2: u64, arg3: u64)

}

extern "C" fn dispatch_syscall(context_ptr: *mut Context, syscall_id: u64,
                               arg1: u64, arg2: u64, arg3: u64) {

    let context = unsafe{&mut *context_ptr};

    // Set the CS and SS segment selectors
    let (code_selector, data_selector) =
        if context.rip < process::USER_CODE_START as usize {
            // Called from kernel code
            gdt::get_kernel_segments()
        } else {
            gdt::get_user_segments()
        };
    context.cs = code_selector.0 as usize;
    context.ss = data_selector.0 as usize;

    match syscall_id & SYSCALL_MASK {
        SYSCALL_FORK_THREAD => process::fork_current_thread(context),
        SYSCALL_EXIT_THREAD => process::exit_current_thread(context),
        SYSCALL_DEBUG_WRITE => sys_debug_write(arg1 as *const u8, arg2 as usize),
        SYSCALL_RECEIVE => sys_receive(context_ptr, arg1),
        SYSCALL_SEND => sys_send(context_ptr, syscall_id, arg1, arg2, arg3),
        SYSCALL_SENDRECEIVE => sys_send(context_ptr, syscall_id, arg1, arg2, arg3), // sys_sendreceive
        SYSCALL_OPEN => sys_open(context_ptr, arg1 as *const u8, arg2 as usize),
        SYSCALL_MALLOC => sys_malloc(context_ptr, arg1, arg2),
        SYSCALL_FREE => sys_free(context_ptr, arg1),
        SYSCALL_YIELD => sys_yield(context_ptr),
        SYSCALL_NEW_RENDEZVOUS => sys_new_rendezvous(context_ptr),
        SYSCALL_COPY_RENDEZVOUS => sys_copy_rendezvous(context_ptr, arg1),
        SYSCALL_EXEC => sys_exec(context_ptr, syscall_id, arg1 as *const u8, arg2, arg3 as *const u8),
        SYSCALL_MOUNT => sys_mount(context_ptr, syscall_id, arg1 as *const u8, arg2),
        SYSCALL_LISTMOUNTS => sys_listmounts(context_ptr),
        SYSCALL_UMOUNT => sys_umount(context_ptr, arg1 as *const u8, arg2),
        SYSCALL_CLOSE => sys_close(context_ptr, arg1),
        SYSCALL_AWAIT_INTERRUPT => sys_await_interrupt(context_ptr, arg1),
        _ => println!("Unknown syscall {:?} {} {} {}",
                      context_ptr, syscall_id, arg1, arg2)
    }
}

fn sys_debug_write(ptr: *const u8, len:usize) {
    // Check all inputs: Does ptr -> ptr+len lie entirely in user address space?