using crate semihosting on aarch64

This crate provides access to semihosting, a mechanism for
programs running on the real or virtual (e.g., QEMU) target
to communicate with I/O facilities on the host system.

Co-authored-by: Martin Kröning <martin.kroening@eonerc.rwth-aachen.de>

Cargo.toml

@@ -65,6 +65,7 @@ udp = ["smoltcp", "smoltcp/socket-udp"]
 trace = []
 vga = []
 common-os = []
+semihosting = ["dep:semihosting"]
 
 [dependencies]
 ahash = { version = "0.8", default-features = false }
@@ -85,7 +86,6 @@ num-traits = { version = "0.2", default-features = false }
 pci-ids = { version = "0.2", optional = true }
 pci_types = { version = "0.6" }
 pflock = "0.2"
-qemu-exit = "3.0"
 rand_chacha = { version = "0.3", default-features = false }
 shell-words = { version = "1.1", default-features = false }
 smallvec = { version = "1", features = ["const_new"] }
@@ -122,17 +122,20 @@ multiboot = "0.8"
 uart_16550 = "0.3"
 x86 = { version = "0.52", default-features = false }
 x86_64 = "0.14"
+qemu-exit = "3.0"
 
 [target.'cfg(target_arch = "aarch64")'.dependencies]
 aarch64 = { version = "0.0", default-features = false }
 arm-gic = { version = "0.1" }
 hermit-dtb = { version = "0.1" }
+semihosting = { version = "0.1", optional = true }
 
 [target.'cfg(target_arch = "riscv64")'.dependencies]
 fdt = "0.1"
 riscv = "0.11"
 sbi = "0.2"
 trapframe = "0.9"
+semihosting = { version = "0.1", optional = true }
 
 [dev-dependencies]
 float-cmp = "0.9"

src/arch/aarch64/kernel/processor.rs

@@ -4,7 +4,6 @@ use core::{fmt, str};
 use aarch64::regs::{Readable, CNTFRQ_EL0};
 use hermit_dtb::Dtb;
 use hermit_sync::{without_interrupts, Lazy};
-use qemu_exit::QEMUExit;
 
 use crate::arch::aarch64::kernel::boot_info;
 use crate::env;
@@ -119,8 +118,22 @@ pub fn halt() {
 pub fn shutdown() -> ! {
 	info!("Shutting down system");
 
-	let exit_handler = qemu_exit::AArch64::new();
-	exit_handler.exit_success();
+	cfg_if::cfg_if! {
+		if #[cfg(feature = "semihosting")] {
+			semihosting::process::exit(0)
+		} else {
+			unsafe {
+				const PSCI_SYSTEM_OFF: u64 = 0x84000008;
+				// call hypervisor to shut down the system
+				asm!("hvc #0", in("x0") PSCI_SYSTEM_OFF, options(nomem, nostack));
+
+				// we should never reach this point
+				loop {
+					asm!("wfe", options(nomem, nostack));
+				}
+			}
+		}
+	}
 }
 
 #[inline]

src/arch/riscv64/kernel/processor.rs

@@ -229,8 +229,15 @@ pub fn halt() {
 /// Shutdown the system
 pub fn shutdown() -> ! {
 	info!("Shutting down system");
-	//SBI shutdown
-	sbi::legacy::shutdown()
+
+	cfg_if::cfg_if! {
+		if #[cfg(feature = "semihosting")] {
+			semihosting::process::exit(0)
+		} else {
+			// use SBI shutdown
+			sbi::legacy::shutdown()
+		}
+	}
 }
 
 pub fn get_timer_ticks() -> u64 {