qemu-exit 3.0.2

// SPDX-License-Identifier: MIT OR Apache-2.0
//
// Copyright (c) 2020-2022 Esteban Blanc <estblcsk@gmail.com>

//! RISCV64.

use crate::QEMUExit;
use core::arch::asm;

const EXIT_SUCCESS: u32 = 0x5555; // Equals `exit(0)`.

const EXIT_FAILURE_FLAG: u32 = 0x3333;
const EXIT_FAILURE: u32 = exit_code_encode(1); // Equals `exit(1)`.
const EXIT_RESET: u32 = 0x7777;

/// RISCV64 configuration
pub struct RISCV64 {
    /// Address of the sifive_test mapped device.
    addr: u64,
}

/// Encode the exit code using EXIT_FAILURE_FLAG.
const fn exit_code_encode(code: u32) -> u32 {
    (code << 16) | EXIT_FAILURE_FLAG
}

impl RISCV64 {
    /// Create an instance.
    pub const fn new(addr: u64) -> Self {
        RISCV64 { addr }
    }
}

impl QEMUExit for RISCV64 {
    /// Exit qemu with specified exit code.
    fn exit(&self, code: u32) -> ! {
        // If code is not a special value, we need to encode it with EXIT_FAILURE_FLAG.
        let code_new = match code {
            EXIT_SUCCESS | EXIT_FAILURE | EXIT_RESET => code,
            _ => exit_code_encode(code),
        };

        unsafe {
            asm!(
                "sw {0}, 0({1})",
                in(reg)code_new, in(reg)self.addr
            );

            // For the case that the QEMU exit attempt did not work, transition into an infinite
            // loop. Calling `panic!()` here is unfeasible, since there is a good chance
            // this function here is the last expression in the `panic!()` handler
            // itself. This prevents a possible infinite loop.
            loop {
                asm!("wfi", options(nomem, nostack));
            }
        }
    }

    fn exit_success(&self) -> ! {
        self.exit(EXIT_SUCCESS);
    }

    fn exit_failure(&self) -> ! {
        self.exit(EXIT_FAILURE);
    }
}