Struct TaskContext 

pub struct TaskContext {
    pub kstack_top: VirtAddr,
    pub rsp: u64,
    pub fs_base: usize,
    pub gs_base: usize,
    pub ext_state: ExtendedState,
    pub cr3: PhysAddr,
}

Saved hardware states of a task.

The context usually includes:

• Callee-saved registers
• Stack pointer register
• Thread pointer register (for thread-local storage, currently unsupported)
• FP/SIMD registers

On context switch, current task saves its context from CPU to memory, and the next task restores its context from memory to CPU.

On x86_64, callee-saved registers are saved to the kernel stack by the PUSH instruction. So that rsp is the RSP after callee-saved registers are pushed, and kstack_top is the top of the kernel stack (RSP before any push).

Fields

kstack_top: VirtAddr

The kernel stack top of the task.

rsp: u64

RSP after all callee-saved registers are pushed.

fs_base: usize

Thread Local Storage (TLS).

gs_base: usize

Available on crate feature uspace only.

The gs_base register value.

ext_state: ExtendedState

Available on crate feature fp-simd only.

Extended states, i.e., FP/SIMD states.

cr3: PhysAddr

Available on crate feature uspace only.

The CR3 register value, i.e., the page table root.

Implementations

impl TaskContext

pub fn new() -> Self

Creates a dummy context for a new task.

Note the context is not initialized, it will be filled by switch_to (for initial tasks) and init (for regular tasks) methods.

pub fn init(&mut self, entry: usize, kstack_top: VirtAddr, tls_area: VirtAddr)

Initializes the context for a new task, with the given entry point and kernel stack.

pub fn set_page_table_root(&mut self, cr3: PhysAddr)

Available on crate feature uspace only.

Changes the page table root in this context.

The hardware register for page table root (CR3 for x86) will be updated to the next task’s after Self::switch_to.

pub fn switch_to(&mut self, next_ctx: &Self)

Switches to another task.

It first saves the current task’s context from CPU to this place, and then restores the next task’s context from next_ctx to CPU.

Trait Implementations

impl Debug for TaskContext

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.