rsnix/src/power.rs


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// ---------------------------------------------------------------------------
// Power — halt loop and ACPI shutdown via the UEFI ResetSystem runtime
// service.
//
// The firmware's runtime-services table is stashed before ExitBootServices
// (`init`).  Because we never call SetVirtualAddressMap, the service
// pointers keep working with physical (identity) addresses after EBS, so
// poweroff() can ask the firmware to shut the machine down (ACPI S5) — on
// QEMU this makes the VM exit, on real hardware the power drops.
// ---------------------------------------------------------------------------

use crate::uefi::{EFI_SUCCESS, RESET_SHUTDOWN, RuntimeServices};

static mut RUNTIME_SERVICES: *mut RuntimeServices = core::ptr::null_mut();

/// Stash the runtime-services table pointer (call in Phase 1, pre-EBS).
pub fn init(rt: *mut RuntimeServices) {
    unsafe {
        RUNTIME_SERVICES = rt;
    }
}

/// Halt the CPU forever (interrupts off, hlt loop).
pub fn halt() -> ! {
    loop {
        unsafe {
            core::arch::asm!("cli; hlt", options(nomem, nostack));
        }
    }
}

/// Shut the machine down through `ResetSystem(EfiResetShutdown)`.  Falls
/// back to `halt()` if no table was saved or the call failed.
pub fn poweroff() -> ! {
    unsafe {
        let rt = RUNTIME_SERVICES;
        if rt.is_null() {
            halt();
        }
        let reset = (*rt).reset_system;
        if reset as usize == 0 {
            halt();
        }
        (reset)(RESET_SHUTDOWN, EFI_SUCCESS, 0, core::ptr::null());
        // ResetSystem only returns on failure.
        halt()
    }
}