1 files changed, 48 insertions, 0 deletions

diff --git a/rsnix/src/power.rs b/rsnix/src/power.rs
new file mode 100644
index 0000000..cb5d296
--- /dev/null
+++ b/rsnix/src/power.rs
@@ -0,0 +1,48 @@
+// ---------------------------------------------------------------------------
+// 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::{RuntimeServices, EFI_SUCCESS, RESET_SHUTDOWN};
+
+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()
+    }
+}