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Interrupt soundness (#408)

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Makes interrupt sound, albeit unsafe.
Also makes allocator not pause interrupts (and therefore not interrupt
safe!!!)

- [x] Changelog updated
This commit is contained in:
Corwin 2023-04-11 21:09:36 +01:00 committed by GitHub
parent 7d9e7318a3 aea64e974f
commit 79e43ccb8b
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GPG key ID: 4AEE18F83AFDEB23
7 changed files with 143 additions and 152 deletions
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2
CHANGELOG.md
View file

@ -14,6 +14,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
- The template now uses rust 2021 edition by default.
- All objects which should only be created once now have the correct lifetimes to only allow one to exist.
- Template now uses codegen-units=1 to workaround bug in nightly.
- Allocator is no longer interrupt safe.
- Soundness issues with interrupts resolved which makes them unsafe and require the closure to be static (breaking change).
### Fixed
- Alpha channel is now considered by `include_gfx!()` even when `transparent_colour` is absent.

13
agb/examples/output.rs
View file

@ -3,13 +3,16 @@
use agb::sync::Static;
static COUNT: Static<u32> = Static::new(0);
#[agb::entry]
fn main(_gba: agb::Gba) -> ! {
let count = Static::new(0);
let _a = agb::interrupt::add_interrupt_handler(agb::interrupt::Interrupt::VBlank, |_| {
let cur_count = count.read();
let _a = unsafe {
agb::interrupt::add_interrupt_handler(agb::interrupt::Interrupt::VBlank, |_| {
let cur_count = COUNT.read();
agb::println!("Hello, world, frame = {}", cur_count);
count.write(cur_count + 1);
});
COUNT.write(cur_count + 1);
})
};
loop {}
}

23
agb/examples/wave.rs
View file

@ -18,6 +18,11 @@ struct BackCosines {
row: usize,
}
static BACK: Mutex<RefCell<BackCosines>> = Mutex::new(RefCell::new(BackCosines {
cosines: [0; 32],
row: 0,
}));
#[agb::entry]
fn main(mut gba: agb::Gba) -> ! {
let (gfx, mut vram) = gba.display.video.tiled0();
@ -30,24 +35,22 @@ fn main(mut gba: agb::Gba) -> ! {
example_logo::display_logo(&mut background, &mut vram);
let mut time = 0;
let cosines = [0_u16; 32];
let back = Mutex::new(RefCell::new(BackCosines { cosines, row: 0 }));
let _a = agb::interrupt::add_interrupt_handler(Interrupt::HBlank, |key: CriticalSection| {
let mut back = back.borrow(key).borrow_mut();
let _a = unsafe {
agb::interrupt::add_interrupt_handler(Interrupt::HBlank, |key: CriticalSection| {
let mut back = BACK.borrow(key).borrow_mut();
let deflection = back.cosines[back.row % 32];
unsafe { ((0x0400_0010) as *mut u16).write_volatile(deflection) }
((0x0400_0010) as *mut u16).write_volatile(deflection);
back.row += 1;
});
})
};
let vblank = agb::interrupt::VBlank::get();
let mut time = 0;
loop {
vblank.wait_for_vblank();
free(|key| {
let mut back = back.borrow(key).borrow_mut();
let mut back = BACK.borrow(key).borrow_mut();
back.row = 0;
time += 1;
for (r, a) in back.cosines.iter_mut().enumerate() {

41
agb/src/agb_alloc/block_allocator.rs
View file

@ -5,13 +5,10 @@
use core::alloc::{Allocator, GlobalAlloc, Layout};
use core::cell::RefCell;
use core::cell::UnsafeCell;
use core::convert::TryInto;
use core::ptr::NonNull;
use crate::interrupt::free;
use bare_metal::Mutex;
use super::bump_allocator::{BumpAllocatorInner, StartEnd};
use super::SendNonNull;
@ -53,36 +50,45 @@ struct BlockAllocatorInner {
}
pub struct BlockAllocator {
inner: Mutex<RefCell<BlockAllocatorInner>>,
inner: UnsafeCell<BlockAllocatorInner>,
}
unsafe impl Sync for BlockAllocator {}
impl BlockAllocator {
pub(crate) const unsafe fn new(start: StartEnd) -> Self {
Self {
inner: Mutex::new(RefCell::new(BlockAllocatorInner::new(start))),
inner: UnsafeCell::new(BlockAllocatorInner::new(start)),
}
}
#[inline(always)]
unsafe fn with_inner<F, T>(&self, f: F) -> T
where
F: Fn(&mut BlockAllocatorInner) -> T,
{
let inner = &mut *self.inner.get();
f(inner)
}
#[doc(hidden)]
#[cfg(any(test, feature = "testing"))]
pub unsafe fn number_of_blocks(&self) -> u32 {
free(|key| self.inner.borrow(key).borrow_mut().number_of_blocks())
self.with_inner(|inner| inner.number_of_blocks())
}
pub unsafe fn alloc(&self, layout: Layout) -> Option<NonNull<u8>> {
free(|key| self.inner.borrow(key).borrow_mut().alloc(layout))
self.with_inner(|inner| inner.alloc(layout))
}
pub unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
free(|key| self.inner.borrow(key).borrow_mut().dealloc(ptr, layout));
self.with_inner(|inner| inner.dealloc(ptr, layout));
}
pub unsafe fn dealloc_no_normalise(&self, ptr: *mut u8, layout: Layout) {
free(|key| {
self.inner
.borrow(key)
.borrow_mut()
.dealloc_no_normalise(ptr, layout);
self.with_inner(|inner| {
inner.dealloc_no_normalise(ptr, layout);
});
}
@ -92,12 +98,7 @@ impl BlockAllocator {
layout: Layout,
new_layout: Layout,
) -> Option<NonNull<u8>> {
free(|key| {
self.inner
.borrow(key)
.borrow_mut()
.grow(ptr, layout, new_layout)
})
self.with_inner(|inner| inner.grow(ptr, layout, new_layout))
}
}

84
agb/src/interrupt.rs
View file

@ -1,8 +1,4 @@
use core::{
cell::Cell,
marker::{PhantomData, PhantomPinned},
pin::Pin,
};
use core::{cell::Cell, marker::PhantomPinned, pin::Pin};
use alloc::boxed::Box;
use bare_metal::CriticalSection;
@ -206,9 +202,8 @@ impl Drop for InterruptInner {
}
}
pub struct InterruptHandler<'a> {
pub struct InterruptHandler {
_inner: Pin<Box<InterruptInner>>,
_lifetime: PhantomData<&'a ()>,
}
impl InterruptRoot {
@ -231,6 +226,14 @@ fn interrupt_to_root(interrupt: Interrupt) -> &'static InterruptRoot {
/// Adds an interrupt handler as long as the returned value is alive. The
/// closure takes a [`CriticalSection`] which can be used for mutexes.
///
/// # Safety
/// * You *must not* allocate in an interrupt.
/// - Many functions in agb allocate and it isn't always clear.
///
/// # Staticness
/// * The closure must be static because forgetting the interrupt handler would
/// cause a use after free.
///
/// [`CriticalSection`]: bare_metal::CriticalSection
///
/// # Examples
@ -238,23 +241,22 @@ fn interrupt_to_root(interrupt: Interrupt) -> &'static InterruptRoot {
/// ```rust,no_run
/// # #![no_std]
/// # #![no_main]
/// use bare_metal::CriticalSection;
///
/// # fn foo() {
/// # use agb::interrupt::{add_interrupt_handler, Interrupt};
/// let _a = add_interrupt_handler(Interrupt::VBlank, |_: CriticalSection| {
/// use bare_metal::CriticalSection;
/// use agb::interrupt::{add_interrupt_handler, Interrupt};
/// // Safety: doesn't allocate
/// let _a = unsafe {
/// add_interrupt_handler(Interrupt::VBlank, |_: CriticalSection| {
/// agb::println!("Woah there! There's been a vblank!");
/// });
/// })
/// };
/// # }
/// ```
pub fn add_interrupt_handler<'a>(
pub unsafe fn add_interrupt_handler(
interrupt: Interrupt,
handler: impl Fn(CriticalSection) + Send + Sync + 'a,
) -> InterruptHandler<'a> {
fn do_with_inner<'a>(
interrupt: Interrupt,
inner: Pin<Box<InterruptInner>>,
) -> InterruptHandler<'a> {
handler: impl Fn(CriticalSection) + Send + Sync + 'static,
) -> InterruptHandler {
fn do_with_inner(interrupt: Interrupt, inner: Pin<Box<InterruptInner>>) -> InterruptHandler {
free(|_| {
let root = interrupt_to_root(interrupt);
root.add();
@ -274,10 +276,7 @@ pub fn add_interrupt_handler<'a>(
}
});
InterruptHandler {
_inner: inner,
_lifetime: PhantomData,
}
InterruptHandler { _inner: inner }
}
let root = interrupt_to_root(interrupt) as *const _;
let inner = unsafe { create_interrupt_inner(handler, root) };
@ -322,9 +321,12 @@ impl VBlank {
#[must_use]
pub fn get() -> Self {
if !HAS_CREATED_INTERRUPT.read() {
let handler = add_interrupt_handler(Interrupt::VBlank, |_| {
// safety: we don't allocate in the interrupt
let handler = unsafe {
add_interrupt_handler(Interrupt::VBlank, |_| {
NUM_VBLANKS.write(NUM_VBLANKS.read() + 1);
});
})
};
core::mem::forget(handler);
HAS_CREATED_INTERRUPT.write(true);
@ -351,36 +353,6 @@ impl VBlank {
#[cfg(test)]
mod tests {
use super::*;
use bare_metal::Mutex;
use core::cell::RefCell;
#[test_case]
fn test_can_create_and_destroy_interrupt_handlers(_gba: &mut crate::Gba) {
let mut counter = Mutex::new(RefCell::new(0));
let counter_2 = Mutex::new(RefCell::new(0));
let vblank = VBlank::get();
{
let _a = add_interrupt_handler(Interrupt::VBlank, |key: CriticalSection| {
*counter.borrow(key).borrow_mut() += 1;
});
let _b = add_interrupt_handler(Interrupt::VBlank, |key: CriticalSection| {
*counter_2.borrow(key).borrow_mut() += 1;
});
while free(|key| {
*counter.borrow(key).borrow() < 100 || *counter_2.borrow(key).borrow() < 100
}) {
vblank.wait_for_vblank();
}
}
vblank.wait_for_vblank();
vblank.wait_for_vblank();
assert_eq!(*counter.get_mut().get_mut(), 100);
}
#[test_case]
fn test_interrupt_table_length(_gba: &mut crate::Gba) {
@ -406,7 +378,9 @@ pub fn profiler(timer: &mut crate::timer::Timer, period: u16) -> InterruptHandle
timer.set_overflow_amount(period);
timer.set_enabled(true);
unsafe {
add_interrupt_handler(timer.interrupt(), |_key: CriticalSection| {
crate::println!("{:#010x}", crate::program_counter_before_interrupt());
})
}
}

8
agb/src/sound/mixer/sw_mixer.rs
View file

@ -82,7 +82,7 @@ extern "C" {
pub struct Mixer<'gba> {
interrupt_timer: Timer,
// SAFETY: Has to go before buffer because it holds a reference to it
_interrupt_handler: InterruptHandler<'static>,
_interrupt_handler: InterruptHandler,
buffer: Pin<Box<MixerBuffer, InternalAllocator>>,
channels: [Option<SoundChannel>; 8],
@ -140,9 +140,11 @@ impl Mixer<'_> {
// In the case of the mixer being forgotten, both stay alive so okay
let buffer_pointer_for_interrupt_handler: &MixerBuffer =
unsafe { core::mem::transmute(buffer_pointer_for_interrupt_handler) };
let interrupt_handler = add_interrupt_handler(interrupt_timer.interrupt(), |cs| {
let interrupt_handler = unsafe {
add_interrupt_handler(interrupt_timer.interrupt(), |cs| {
buffer_pointer_for_interrupt_handler.swap(cs);
});
})
};
set_asm_buffer_size(frequency);

48
agb/src/sync/statics.rs
View file

@ -267,9 +267,11 @@ mod test {
use crate::timer::Divider;
use crate::Gba;
fn write_read_concurrency_test_impl<const COUNT: usize>(gba: &mut Gba) {
let sentinel = [0x12345678; COUNT];
let value: Static<[u32; COUNT]> = Static::new(sentinel);
macro_rules! generate_concurrency_test {
($count:literal, $gba:ident) => {{
(|gba: &mut Gba| {
const SENTINEL: [u32; $count] = [0x12345678; $count];
static VALUE: Static<[u32; $count]> = Static::new(SENTINEL);
// set up a timer and an interrupt that uses the timer
let mut timer = gba.timers.timers().timer2;
@ -279,23 +281,25 @@ mod test {
timer.set_interrupt(true);
timer.set_enabled(true);
let _int = crate::interrupt::add_interrupt_handler(Interrupt::Timer2, |_| {
value.write(sentinel);
});
let _int = unsafe {
crate::interrupt::add_interrupt_handler(Interrupt::Timer2, |_| {
VALUE.write(SENTINEL);
})
};
// the actual main test loop
let mut interrupt_seen = false;
let mut no_interrupt_seen = false;
for i in 0..250000 {
// write to the static
let new_value = [i; COUNT];
value.write(new_value);
let new_value = [i; $count];
VALUE.write(new_value);
// check the current value
let current = value.read();
let current = VALUE.read();
if current == new_value {
no_interrupt_seen = true;
} else if current == sentinel {
} else if current == SENTINEL {
interrupt_seen = true;
} else {
panic!("Unexpected value found in `Static`.");
@ -312,20 +316,22 @@ mod test {
timer.set_overflow_amount(1049 + (i / 64) as u16);
}
}
panic!("Concurrency test timed out: {}", COUNT)
panic!("Concurrency test timed out: {}", $count)
})($gba);
}};
}
#[test_case]
fn write_read_concurrency_test(gba: &mut Gba) {
write_read_concurrency_test_impl::<1>(gba);
write_read_concurrency_test_impl::<2>(gba);
write_read_concurrency_test_impl::<3>(gba);
write_read_concurrency_test_impl::<4>(gba);
write_read_concurrency_test_impl::<5>(gba);
write_read_concurrency_test_impl::<6>(gba);
write_read_concurrency_test_impl::<7>(gba);
write_read_concurrency_test_impl::<8>(gba);
write_read_concurrency_test_impl::<9>(gba);
write_read_concurrency_test_impl::<10>(gba);
generate_concurrency_test!(1, gba);
generate_concurrency_test!(2, gba);
generate_concurrency_test!(3, gba);
generate_concurrency_test!(4, gba);
generate_concurrency_test!(5, gba);
generate_concurrency_test!(6, gba);
generate_concurrency_test!(7, gba);
generate_concurrency_test!(8, gba);
generate_concurrency_test!(9, gba);
generate_concurrency_test!(10, gba);
}
}