Struct TaskContext 

#[repr(C)]
pub struct TaskContext {

    pub ra: usize,
    pub sp: usize,
    pub s0: usize,
    pub s1: usize,
    pub s2: usize,
    pub s3: usize,
    pub s4: usize,
    pub s5: usize,
    pub s6: usize,
    pub s7: usize,
    pub s8: usize,
    pub s9: usize,
    pub s10: usize,
    pub s11: usize,
    pub tp: usize,
    pub satp: PhysAddr,
    pub fp_state: FpState,
}

Saved hardware states of a task.

The context usually includes:

• Callee-saved registers
• Stack pointer register
• Thread pointer register (for kernel-space thread-local storage)
• 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.

Fields

ra: usize

sp: usize

s0: usize

s1: usize

s2: usize

s3: usize

s4: usize

s5: usize

s6: usize

s7: usize

s8: usize

s9: usize

s10: usize

s11: usize

tp: usize

Thread Pointer

satp: PhysAddr

Available on crate feature uspace only.

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

fp_state: FpState

Available on crate feature fp-simd only.

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, satp: PhysAddr)

Available on crate feature uspace only.

Changes the page table root in this context.

The hardware register for page table root (satp for riscv64) 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.

impl Default for TaskContext

fn default() -> TaskContext

Returns the “default value” for a type.