blob: 76d99c142c4110d16a8c656fd03ce0eaf20e5700 (
plain) (
blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
|
// SPDX-License-Identifier: Apache-2.0 OR MIT
// Adapted from https://github.com/Rahix/avr-device.
//
// Refs:
// - AVR Instruction Set Manual https://ww1.microchip.com/downloads/en/DeviceDoc/AVR-InstructionSet-Manual-DS40002198.pdf
#[cfg(not(portable_atomic_no_asm))]
use core::arch::asm;
pub(super) type State = u8;
/// Disables interrupts and returns the previous interrupt state.
#[inline]
pub(super) fn disable() -> State {
let sreg: State;
// SAFETY: reading the status register (SREG) and disabling interrupts are safe.
// (see module-level comments of interrupt/mod.rs on the safety of using privileged instructions)
unsafe {
// Do not use `nomem` and `readonly` because prevent subsequent memory accesses from being reordered before interrupts are disabled.
// Do not use `preserves_flags` because CLI modifies the I bit of the status register (SREG).
// Refs: https://ww1.microchip.com/downloads/en/DeviceDoc/AVR-InstructionSet-Manual-DS40002198.pdf#page=58
#[cfg(not(portable_atomic_no_asm))]
asm!(
"in {0}, 0x3F",
"cli",
out(reg) sreg,
options(nostack),
);
#[cfg(portable_atomic_no_asm)]
{
llvm_asm!("in $0, 0x3F" : "=r"(sreg) ::: "volatile");
llvm_asm!("cli" ::: "memory" : "volatile");
}
}
sreg
}
/// Restores the previous interrupt state.
///
/// # Safety
///
/// The state must be the one retrieved by the previous `disable`.
#[inline]
pub(super) unsafe fn restore(sreg: State) {
// SAFETY: the caller must guarantee that the state was retrieved by the previous `disable`,
unsafe {
// This clobbers the entire status register. See msp430.rs to safety on this.
//
// Do not use `nomem` and `readonly` because prevent preceding memory accesses from being reordered after interrupts are enabled.
// Do not use `preserves_flags` because OUT modifies the status register (SREG).
#[cfg(not(portable_atomic_no_asm))]
asm!("out 0x3F, {0}", in(reg) sreg, options(nostack));
#[cfg(portable_atomic_no_asm)]
llvm_asm!("out 0x3F, $0" :: "r"(sreg) : "memory" : "volatile");
}
}
|
