Struct UserMode

pub struct UserMode {
    context: UserContext,
}

Code execution in the user mode.

This type enables executing the code in user space from a task in the kernel space safely.

Here is a sample code on how to use UserMode.

use ostd::task::Task;

let current = Task::current();
let user_ctx = current.user_ctx()
    .expect("the current task is not associated with a user context");
let mut user_mode = UserMode::new(UserContext::clone(user_ctx));
loop {
    // Execute in the user space until some interesting events occur.
    // Note: users should activate a suitable `VmSpace` before to support
    // user-mode execution.
    let return_reason = user_mode.execute(|| false);
    todo!("handle the event, e.g., syscall");
}

Fields

context: UserContext

Implementations

impl UserMode

pub fn new(context: UserContext) -> Self

Creates a new UserMode.

pub fn execute<F>(&mut self, has_kernel_event: F) -> ReturnReason

where F: FnMut() -> bool,

Starts executing in the user mode. Make sure current task is the task in UserMode.

The method returns for one of three possible reasons indicated by ReturnReason.

1. A system call is issued by the user space;
2. A CPU exception is triggered by the user space;
3. A kernel event is pending, as indicated by the given closure.

After handling whatever user or kernel events that cause the method to return and updating the user-mode CPU context, this method can be invoked again to go back to the user space.

pub fn context(&self) -> &UserContext

Returns an immutable reference the user-mode CPU context.

pub fn context_mut(&mut self) -> &mut UserContext

Returns a mutable reference the user-mode CPU context.

Trait Implementations

impl !Send for UserMode