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feat(hal_x86_64): be less stupid about ISR tracing #496

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merged 1 commit into from
Dec 30, 2024
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feat(hal_x86_64): be less stupid about ISR tracing #496

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61 changes: 39 additions & 22 deletions hal-x86_64/src/interrupt.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -523,11 +523,10 @@ impl hal_core::interrupt::Control for Idt {
code: u64,
) {
unsafe {
// Safety: who cares!
crate::vga::writer().force_unlock();
if let Some(com1) = crate::serial::com1() {
com1.force_unlock();
}
// Safety: An invalid TSS exception is always an oops. Since we're
// not coming back from this, it's okay to forcefully unlock the
// tracing outputs.
force_unlock_tracing();
}
let selector = SelectorErrorCode(code as u16);
tracing::error!(?selector, "invalid task-state segment!");
Expand All @@ -548,11 +547,10 @@ impl hal_core::interrupt::Control for Idt {
code: u64,
) {
unsafe {
// Safety: who cares!
crate::vga::writer().force_unlock();
if let Some(com1) = crate::serial::com1() {
com1.force_unlock();
}
// Safety: An segment not present exception is always an oops.
// Since we're not coming back from this, it's okay to
// forcefully unlock the tracing outputs.
force_unlock_tracing();
}
let selector = SelectorErrorCode(code as u16);
tracing::error!(?selector, "a segment was not present!");
Expand All @@ -573,11 +571,10 @@ impl hal_core::interrupt::Control for Idt {
code: u64,
) {
unsafe {
// Safety: who cares!
crate::vga::writer().force_unlock();
if let Some(com1) = crate::serial::com1() {
com1.force_unlock();
}
// Safety: An stack-segment fault exeption is always an oops.
// Since we're not coming back from this, it's okay to
// forcefully unlock the tracing outputs.
force_unlock_tracing();
}
let selector = SelectorErrorCode(code as u16);
tracing::error!(?selector, "a stack-segment fault is happening");
Expand All @@ -598,12 +595,17 @@ impl hal_core::interrupt::Control for Idt {
code: u64,
) {
unsafe {
// Safety: who cares!

crate::vga::writer().force_unlock();
if let Some(com1) = crate::serial::com1() {
com1.force_unlock();
}
// Safety: A general protection fault is (currently) always an
// oops. Since we're not coming back from this, it's okay to
// forcefully unlock the tracing outputs.
//
// TODO(eliza): in the future, if we allow the kernel to
// recover from general protection faults in user mode programs,
// rather than treating them as invariably fatal, we should
// probably not always do this. Instead, we should just handle
// the user-mode GPF non-fatally, and only unlock the tracing
// stuff if we know we're going to do a kernel oops...
force_unlock_tracing();
}

let segment = if code > 0 {
Expand All @@ -625,7 +627,7 @@ impl hal_core::interrupt::Control for Idt {
}

extern "x86-interrupt" fn spurious_isr() {
tracing::trace!("spurious");
// TODO(eliza): do we need to actually do something here?
}

// === exceptions ===
Expand Down Expand Up @@ -675,6 +677,21 @@ impl hal_core::interrupt::Control for Idt {
}
}

/// Forcefully unlock the VGA port and COM1 serial port (used by tracing), so
/// that an ISR can log stuff without deadlocking.
///
/// # Safety
///
/// This forcefully unlocks a mutex, which is probably bad to do. Only do this
/// in ISRs that definitely represent real actual faults, and not just because
/// "you wanted to log something".
unsafe fn force_unlock_tracing() {
crate::vga::writer().force_unlock();
if let Some(com1) = crate::serial::com1() {
com1.force_unlock();
}
}

impl fmt::Debug for Registers {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let Self {
Expand Down
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