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//! Context and ring switching
use super::gdt::SegmentSelector;
/// Prepare for return from interrupt to user,
/// the expected current stack layout is:
///
/// ```text
/// _____________________________
/// | User Data Segment Selector |
/// | User Stack Pointer |
/// | EFLAGS (Interrupts enabled) |
/// | User Code Segment Selector |
/// | Target Instruction Pointer |
/// ```
pub extern "C" fn switch_to_user(
ds: SegmentSelector,
sp: *mut u32,
cs: SegmentSelector,
ip: *mut (),
syscall_ret: u32,
) -> ! {
unsafe {
todo!("BST B1 - Implement ring switch")
}
}
/// Starts the thread for the first time
#[inline(never)]
pub unsafe extern "C" fn launch(thread: &Registers) {
todo!("BSB A4")
}
/// Switches between two threads
#[inline(never)]
pub unsafe extern "C" fn switch(current: &mut Registers, next: &Registers) {
todo!("BSB A4")
}
/// Non-volatile registers that have to survive function calls.
///
/// See <https://wiki.osdev.org/Calling_Conventions>
#[derive(Copy, Clone, Debug)]
#[repr(C)]
pub struct Registers {
pub ebx: u32,
pub esi: u32,
pub edi: u32,
pub ebp: u32,
pub esp: u32,
}
impl Registers {
pub const fn new() -> Self {
Self {
ebx: 0,
esi: 0,
edi: 0,
ebp: 0,
esp: 0,
}
}
}