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93 lines
3.0 KiB
Rust
93 lines
3.0 KiB
Rust
// SPDX-License-Identifier: MIT OR Apache-2.0
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//
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// Copyright (c) 2020-2022 Andre Richter <andre.o.richter@gmail.com>
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//! State information about the kernel itself.
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use core::sync::atomic::{AtomicU8, Ordering};
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//--------------------------------------------------------------------------------------------------
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// Private Definitions
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//--------------------------------------------------------------------------------------------------
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/// Different stages in the kernel execution.
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#[derive(Copy, Clone, Eq, PartialEq)]
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enum State {
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/// The kernel starts booting in this state.
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Init,
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/// The kernel transitions to this state when jumping to `kernel_main()` (at the end of
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/// `kernel_init()`, after all init calls are done).
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SingleCoreMain,
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/// The kernel transitions to this state when it boots the secondary cores, aka switches
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/// exectution mode to symmetric multiprocessing (SMP).
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MultiCoreMain,
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}
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//--------------------------------------------------------------------------------------------------
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// Public Definitions
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//--------------------------------------------------------------------------------------------------
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/// Maintains the kernel state and state transitions.
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pub struct StateManager(AtomicU8);
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//--------------------------------------------------------------------------------------------------
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// Global instances
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//--------------------------------------------------------------------------------------------------
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static STATE_MANAGER: StateManager = StateManager::new();
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//--------------------------------------------------------------------------------------------------
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// Public Code
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//--------------------------------------------------------------------------------------------------
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/// Return a reference to the global StateManager.
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pub fn state_manager() -> &'static StateManager {
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&STATE_MANAGER
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}
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impl StateManager {
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const INIT: u8 = 0;
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const SINGLE_CORE_MAIN: u8 = 1;
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const MULTI_CORE_MAIN: u8 = 2;
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/// Create a new instance.
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pub const fn new() -> Self {
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Self(AtomicU8::new(Self::INIT))
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}
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/// Return the current state.
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fn state(&self) -> State {
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let state = self.0.load(Ordering::Acquire);
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match state {
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Self::INIT => State::Init,
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Self::SINGLE_CORE_MAIN => State::SingleCoreMain,
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Self::MULTI_CORE_MAIN => State::MultiCoreMain,
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_ => panic!("Invalid KERNEL_STATE"),
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}
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}
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/// Return if the kernel is init state.
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pub fn is_init(&self) -> bool {
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self.state() == State::Init
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}
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/// Transition from Init to SingleCoreMain.
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pub fn transition_to_single_core_main(&self) {
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if self
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.0
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.compare_exchange(
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Self::INIT,
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Self::SINGLE_CORE_MAIN,
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Ordering::Acquire,
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Ordering::Relaxed,
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)
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.is_err()
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{
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panic!("transition_to_single_core_main() called while state != Init");
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}
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}
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}
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