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thomasarmelthomasarmel
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Add cooperative multitasking support
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9 files changed

+271
-7
lines changed

9 files changed

+271
-7
lines changed

‎src/dos.rs

+1
Original file line numberDiff line numberDiff line change
@@ -7,6 +7,7 @@ pub mod file;
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pub mod error_code;
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pub mod panic;
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pub mod math;
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pub mod cooperative_multitasking;
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use core::arch::asm;
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pub use alloc::string::String as String;

‎src/dos/cooperative_multitasking/cooperative_task_switching.S

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@@ -0,0 +1,60 @@
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# inspired from https://wiki.osdev.org/Cooperative_Multitasking
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; .section .text
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; .global cooperative_task_switching_assembly
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cooperative_task_switching_assembly:
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pushad # 32 bytes
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pushfd # 4 bytes # pushf
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mov eax, cr3 #Push CR3
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push eax
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mov eax, [44+esp] #The first argument, where to save
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mov [4+eax], ebx
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mov [8+eax], ecx
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mov [12+eax], edx
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mov [16+eax], esi
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mov [20+eax], edi
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mov ebx, [36+esp] # EAX
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mov ecx, [40+esp] # IP
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mov edx, [20+esp] # ESP
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add edx, 4 # Remove the return value
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mov esi, [16+esp] # EBP
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mov edi, [4+esp] # EFLAGS
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mov [eax], ebx
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mov [24+eax], edx
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mov [28+eax], esi
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mov [32+eax], ecx
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mov [36+eax], edi
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pop ebx # CR3
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mov [40+eax], ebx
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push ebx # Goodbye again
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mov eax, [48+esp] # The second argument, where to load
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mov ebx, [4+eax] # EBX
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mov ecx, [8+eax] # ECX
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mov edx, [12+eax] # EDX
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mov esi, [16+eax] # ESI
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mov edi, [20+eax] # EDI
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mov ebp, [28+eax] # EBP
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push eax
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mov eax, [36+eax] # EFLAGS
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push eax
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popfd
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pop eax
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mov esp, [24+eax] # ESP ## error ?
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push eax
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mov eax, [40+eax] # CR3
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mov cr3, eax
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pop eax
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push eax
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mov eax, [32+eax] # EIP
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xchg eax, [esp] # Cannot use a tmp storage
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mov eax, [eax] # EAX
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ret

‎src/dos/cooperative_multitasking/mod.rs

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@@ -0,0 +1,123 @@
1+
use alloc::collections::VecDeque;
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use core::arch::{asm, global_asm};
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use crate::dos::cooperative_multitasking::task::{Registers, Task};
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mod task;
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global_asm!(include_str!("cooperative_task_switching.S"));
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extern "C" {
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fn cooperative_task_switching_assembly(from: *mut Registers, to: *mut Registers) -> ();
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}
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pub struct Tasking{
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task_list: Option<VecDeque<Task>>,
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current_task_id: u8,
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eflags_register: u32,
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cr3_register: u32,
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initialized: bool,
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}
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impl Tasking {
22+
const MAX_TASKS: usize = 10;
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pub fn init(&mut self) {
25+
if self.task_list.is_some() {
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self.task_list = None;
27+
}
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let (eflags, cr3) = Self::get_eflags_and_cr3_registers();
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// Create main task
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self.task_list = Some(VecDeque::with_capacity(Self::MAX_TASKS));
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self.current_task_id = 0;
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self.eflags_register = eflags;
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self.cr3_register = cr3;
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self.initialized = true;
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self.task_list.as_mut().unwrap().push_back(Task {
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registers: Registers {
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eax: 0,
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ebx: 0,
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ecx: 0,
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edx: 0,
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esi: 0,
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edi: 0,
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esp: 0,
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ebp: 0,
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eip: 0,
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eflags,
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cr3,
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},
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});
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}
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pub fn add_task(&mut self, main_function: *mut fn()) -> Result<(), &'static str> {
54+
if !self.initialized {
55+
return Err("Cooperative tasking manager is not initialized");
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}
57+
if self.task_list.as_ref().unwrap().len() >= Self::MAX_TASKS {
58+
return Err("Maximum number of tasks reached");
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}
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let task_list = self.task_list.as_mut().unwrap();
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task_list.push_back(Task::new(main_function, self.eflags_register, self.cr3_register as *mut u32, task_list.len() as u8));
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Ok(())
63+
}
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pub fn yield_task(&mut self) {
66+
if !self.initialized {
67+
panic!("Cooperative tasking manager is not initialized");
68+
}
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let task_list = self.task_list.as_mut().unwrap();
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let current_task_registers_ptr = &mut task_list[self.current_task_id as usize].registers as *mut Registers;
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self.current_task_id += 1;
75+
if self.current_task_id >= task_list.len() as u8 {
76+
self.current_task_id = 0;
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}
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let next_task_registers_ptr = &mut task_list[self.current_task_id as usize].registers as *mut Registers;
80+
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unsafe {
82+
cooperative_task_switching_assembly(current_task_registers_ptr, next_task_registers_ptr);
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}
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}
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fn get_eflags_and_cr3_registers() -> (u32, u32) {
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let mut eflags: u32;
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let mut cr3: u32;
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unsafe {
90+
// Read CR3
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asm!("mov {}, cr3", out(reg) cr3);
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// Read EFLAGS
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asm!("pushfd; mov eax, [esp]; mov {}, eax; popfd;", out(reg) eflags);
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}
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(eflags, cr3)
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}
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}
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pub static mut TASKING: Tasking = Tasking {
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task_list: None,
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current_task_id: 0,
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eflags_register: 0,
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cr3_register: 0,
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initialized: false,
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};
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107+
#[macro_export]
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macro_rules! yield_cooperative_task {
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() => {
110+
unsafe {
111+
$crate::dos::cooperative_multitasking::TASKING.yield_task();
112+
}
113+
};
114+
}
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116+
#[macro_export]
117+
macro_rules! add_cooperative_task {
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($main_function: expr) => {
119+
unsafe {
120+
$crate::dos::cooperative_multitasking::TASKING.add_task($main_function as *mut fn())
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}
122+
};
123+
}

‎src/dos/cooperative_multitasking/task.rs

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@@ -0,0 +1,44 @@
1+
#[repr(C)] // To ensure that the struct is laid out in the same way as the assembly code expects
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#[derive(Copy, Clone, Debug)]
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pub(crate)struct Registers {
4+
pub eax: u32,
5+
pub ebx: u32,
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pub ecx: u32,
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pub edx: u32,
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pub esi: u32,
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pub edi: u32,
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pub esp: u32,
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pub ebp: u32,
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pub eip: u32,
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pub eflags: u32,
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pub cr3: u32,
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}
16+
17+
#[derive(Debug)]
18+
pub(crate) struct Task {
19+
pub(crate) registers: Registers,
20+
}
21+
22+
// In order to use heap as stack, we need to change ss stack segment register
23+
impl Task {
24+
const TASK_STACK_SIZE: usize = 4096;
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26+
/// Max stack for each task, including the main task, is 4KB
27+
pub fn new(main_function: *mut fn(), flags: u32, pagedir: *mut u32, task_index: u8) -> Task {
28+
Task {
29+
registers: Registers {
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eax: 0,
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ebx: 0,
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ecx: 0,
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edx: 0,
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esi: 0,
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edi: 0,
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esp: 0xffff as u32 - (Self::TASK_STACK_SIZE as u32 * task_index as u32),
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ebp: 0,
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eip: main_function as u32,
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eflags: flags,
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cr3: pagedir as u32,
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}
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}
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}
44+
}

‎src/dos_tests/allocator_test.rs

+1
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@@ -1,6 +1,7 @@
11
use rust_dos::*;
22
use dos::*;
33

4+
#[allow(dead_code)]
45
pub(crate) fn allocator_test() {
56
let mut box1 = Box::new(5);
67
assert_eq!(*box1, 5);

‎src/dos_tests/cooperative_multitasking_test.rs

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@@ -0,0 +1,31 @@
1+
use dos::*;
2+
use rust_dos::*;
3+
4+
#[allow(dead_code)]
5+
pub(crate) fn cooperative_multitasking_test() {
6+
add_cooperative_task!(task_2_main).unwrap();
7+
println!("Hello from main task!");
8+
yield_cooperative_task!();
9+
println!("Hello from main task! (bis)");
10+
yield_cooperative_task!();
11+
println!("Hello from main task! (tris)");
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}
13+
14+
fn task_2_main() {
15+
add_cooperative_task!(task_3_main).unwrap();
16+
for _ in 0..2 {
17+
let task_number = 2;
18+
let task2_string = String::from("Hello from task 2!");
19+
println!("Message from task{}: {}", task_number, task2_string);
20+
yield_cooperative_task!();
21+
}
22+
}
23+
24+
fn task_3_main() {
25+
for _ in 0..2 {
26+
let task_number = 3;
27+
let task2_string = String::from("Hello from task 3!");
28+
println!("Message from task{}: {}", task_number, task2_string);
29+
yield_cooperative_task!();
30+
}
31+
}

‎src/dos_tests/mod.rs

+2-1
Original file line numberDiff line numberDiff line change
@@ -1,2 +1,3 @@
11
pub(crate) mod file;
2-
pub(crate) mod allocator_test;
2+
pub(crate) mod allocator_test;
3+
pub(crate) mod cooperative_multitasking_test;

‎src/lib.rs

+2
Original file line numberDiff line numberDiff line change
@@ -8,12 +8,14 @@ extern crate rlibc;
88
extern crate alloc;
99

1010
use crate::dos::allocator::GLOBAL_ALLOCATOR;
11+
use crate::dos::cooperative_multitasking::TASKING;
1112

1213
#[link_section = ".startup"]
1314
#[no_mangle]
1415
fn _start() -> ! {
1516
unsafe {
1617
GLOBAL_ALLOCATOR.init();
18+
TASKING.init(); // Relies on the allocator
1719
}
1820
extern "Rust" {
1921
fn main() -> ();

‎src/main.rs

+7-6
Original file line numberDiff line numberDiff line change
@@ -1,18 +1,19 @@
11
#![no_std]
22
#![no_main]
33

4-
54
extern crate alloc;
65

76
mod dos_tests;
87

98
use rust_dos::*;
10-
use crate::dos_tests::allocator_test::allocator_test;
11-
use crate::dos_tests::file::file_read_test;
9+
use crate::dos_tests::cooperative_multitasking_test::cooperative_multitasking_test;
10+
//use crate::dos_tests::allocator_test::allocator_test;
11+
//use crate::dos_tests::file::file_read_test;
1212

1313
entry!(main);
1414

1515
fn main() {
16-
allocator_test();
17-
file_read_test();
18-
}
16+
/*allocator_test();
17+
file_read_test();*/
18+
cooperative_multitasking_test();
19+
}

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