| // SPDX-License-Identifier: Apache-2.0 OR MIT |
| |
| // Refs: |
| // - https://five-embeddev.com/riscv-isa-manual/latest/machine.html#machine-status-registers-mstatus-and-mstatush |
| // - https://five-embeddev.com/riscv-isa-manual/latest/supervisor.html#sstatus |
| // |
| // Generated asm: |
| // - riscv64gc https://godbolt.org/z/osbzsT679 |
| |
| #[cfg(not(portable_atomic_no_asm))] |
| use core::arch::asm; |
| |
| pub(super) use super::super::riscv as atomic; |
| |
| // Status register |
| #[cfg(not(portable_atomic_s_mode))] |
| macro_rules! status { |
| () => { |
| "mstatus" |
| }; |
| } |
| #[cfg(portable_atomic_s_mode)] |
| macro_rules! status { |
| () => { |
| "sstatus" |
| }; |
| } |
| |
| // MIE (Machine Interrupt Enable) bit (1 << 3) |
| #[cfg(not(portable_atomic_s_mode))] |
| const MASK: State = 0x8; |
| #[cfg(not(portable_atomic_s_mode))] |
| macro_rules! mask { |
| () => { |
| "0x8" |
| }; |
| } |
| // SIE (Supervisor Interrupt Enable) bit (1 << 1) |
| #[cfg(portable_atomic_s_mode)] |
| const MASK: State = 0x2; |
| #[cfg(portable_atomic_s_mode)] |
| macro_rules! mask { |
| () => { |
| "0x2" |
| }; |
| } |
| |
| #[cfg(target_arch = "riscv32")] |
| pub(super) type State = u32; |
| #[cfg(target_arch = "riscv64")] |
| pub(super) type State = u64; |
| |
| /// Disables interrupts and returns the previous interrupt state. |
| #[inline] |
| pub(super) fn disable() -> State { |
| let r: State; |
| // SAFETY: reading mstatus and disabling interrupts is 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. |
| asm!(concat!("csrrci {0}, ", status!(), ", ", mask!()), out(reg) r, options(nostack, preserves_flags)); |
| } |
| r |
| } |
| |
| /// Restores the previous interrupt state. |
| /// |
| /// # Safety |
| /// |
| /// The state must be the one retrieved by the previous `disable`. |
| #[inline] |
| pub(super) unsafe fn restore(r: State) { |
| if r & MASK != 0 { |
| // SAFETY: the caller must guarantee that the state was retrieved by the previous `disable`, |
| // and we've checked that interrupts were enabled before disabling interrupts. |
| unsafe { |
| // Do not use `nomem` and `readonly` because prevent preceding memory accesses from being reordered after interrupts are enabled. |
| asm!(concat!("csrsi ", status!(), ", ", mask!()), options(nostack, preserves_flags)); |
| } |
| } |
| } |