49 lines
1.5 KiB
Rust
49 lines
1.5 KiB
Rust
// SPDX-License-Identifier: Apache-2.0 OR MIT
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// Adapted from https://github.com/rust-embedded/cortex-m.
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//
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// Generated asm:
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// - armv6-m https://godbolt.org/z/YxME38xcM
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#[cfg(not(portable_atomic_no_asm))]
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use core::arch::asm;
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pub(super) use core::sync::atomic;
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pub(super) type State = u32;
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/// Disables interrupts and returns the previous interrupt state.
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#[inline]
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pub(super) fn disable() -> State {
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let r: State;
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// SAFETY: reading the priority mask register and disabling interrupts are safe.
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// (see module-level comments of interrupt/mod.rs on the safety of using privileged instructions)
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unsafe {
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// Do not use `nomem` and `readonly` because prevent subsequent memory accesses from being reordered before interrupts are disabled.
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asm!(
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"mrs {0}, PRIMASK",
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"cpsid i",
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out(reg) r,
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options(nostack, preserves_flags),
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);
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}
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r
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}
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/// Restores the previous interrupt state.
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///
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/// # Safety
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///
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/// The state must be the one retrieved by the previous `disable`.
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#[inline]
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pub(super) unsafe fn restore(r: State) {
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if r & 0x1 == 0 {
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// SAFETY: the caller must guarantee that the state was retrieved by the previous `disable`,
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// and we've checked that interrupts were enabled before disabling interrupts.
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unsafe {
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// Do not use `nomem` and `readonly` because prevent preceding memory accesses from being reordered after interrupts are enabled.
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asm!("cpsie i", options(nostack, preserves_flags));
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}
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}
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}
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