97 lines
3.2 KiB
Rust
97 lines
3.2 KiB
Rust
use core::sync::atomic::{AtomicBool, ATOMIC_BOOL_INIT, Ordering};
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/// This must be used by the kernel to ensure that context switches are done atomically
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/// Compare and exchange this to true when beginning a context switch on any CPU
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/// The Context::switch_to function will set it back to false, allowing other CPU's to switch
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/// This must be done, as no locks can be held on the stack during switch
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pub static CONTEXT_SWITCH_LOCK: AtomicBool = ATOMIC_BOOL_INIT;
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#[derive(Debug)]
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pub struct Context {
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/// RFLAGS register
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rflags: usize,
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/// RBX register
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rbx: usize,
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/// R12 register
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r12: usize,
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/// R13 register
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r13: usize,
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/// R14 register
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r14: usize,
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/// R15 register
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r15: usize,
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/// Base pointer
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rbp: usize,
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/// Stack pointer
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rsp: usize,
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/// Page table pointer
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cr3: usize
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}
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impl Context {
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pub fn new() -> Context {
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Context {
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rflags: 0,
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rbx: 0,
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r12: 0,
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r13: 0,
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r14: 0,
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r15: 0,
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rbp: 0,
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rsp: 0,
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cr3: 0
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}
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}
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pub fn set_stack(&mut self, address: usize) {
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self.rsp = address;
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}
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/// Switch to the next context by restoring its stack and registers
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#[inline(never)]
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#[naked]
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pub unsafe fn switch_to(&mut self, next: &mut Context) {
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/*
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asm!("fxsave [$0]" : : "r"(self.fx) : "memory" : "intel", "volatile");
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self.loadable = true;
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if next.loadable {
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asm!("fxrstor [$0]" : : "r"(next.fx) : "memory" : "intel", "volatile");
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}else{
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asm!("fninit" : : : "memory" : "intel", "volatile");
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}
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*/
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asm!("pushfq ; pop $0" : "=r"(self.rflags) : : "memory" : "intel", "volatile");
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asm!("push $0 ; popfq" : : "r"(next.rflags) : "memory" : "intel", "volatile");
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asm!("mov $0, rbx" : "=r"(self.rbx) : : "memory" : "intel", "volatile");
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asm!("mov rbx, $0" : : "r"(next.rbx) : "memory" : "intel", "volatile");
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asm!("mov $0, r12" : "=r"(self.r12) : : "memory" : "intel", "volatile");
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asm!("mov r12, $0" : : "r"(next.r12) : "memory" : "intel", "volatile");
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asm!("mov $0, r13" : "=r"(self.r13) : : "memory" : "intel", "volatile");
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asm!("mov r13, $0" : : "r"(next.r13) : "memory" : "intel", "volatile");
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asm!("mov $0, r14" : "=r"(self.r14) : : "memory" : "intel", "volatile");
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asm!("mov r14, $0" : : "r"(next.r14) : "memory" : "intel", "volatile");
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asm!("mov $0, r15" : "=r"(self.r15) : : "memory" : "intel", "volatile");
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asm!("mov r15, $0" : : "r"(next.r15) : "memory" : "intel", "volatile");
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asm!("mov $0, rsp" : "=r"(self.rsp) : : "memory" : "intel", "volatile");
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asm!("mov rsp, $0" : : "r"(next.rsp) : "memory" : "intel", "volatile");
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asm!("mov $0, rbp" : "=r"(self.rbp) : : "memory" : "intel", "volatile");
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asm!("mov rbp, $0" : : "r"(next.rbp) : "memory" : "intel", "volatile");
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/* TODO
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asm!("mov $0, cr3" : "=r"(self.cr3) : : "memory" : "intel", "volatile");
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asm!("mov cr3, $0" : : "r"(self.cr3) : "memory" : "intel", "volatile");
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*/
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// Unset global lock, set inside of kernel
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CONTEXT_SWITCH_LOCK.store(false, Ordering::SeqCst);
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}
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}
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