systemless 0.34.0

//! Concrete 68K execution ownership and Mixed Mode transitions.
//!
//! This owner is deliberately not Clone: live CPU caches and memory bindings
//! must move with their context. The task store remains the process authority.

use crate::cpu::{M68kCpu, Register};
use crate::execution_kernel::ExecutionContextBank;
use crate::guest_call::{PendingM68kExecution, SharedGuestCallStack};
use crate::memory::GuestAddressSpace as PpcSectionMem;
use ppc::PpcMemory;

pub(crate) struct M68kExecution {
    pub(crate) cpu: M68kCpu,
    pub(crate) parked: ExecutionContextBank<M68kCpu>,
    calls: SharedGuestCallStack,
}

impl M68kExecution {
    pub(crate) fn new(calls: &SharedGuestCallStack) -> Self {
        Self {
            cpu: M68kCpu::new(),
            parked: ExecutionContextBank::default(),
            calls: calls.shared_handle(),
        }
    }

    /// A launch cannot discard contexts still associated with live calls.
    pub(crate) fn can_relaunch(&self) -> bool {
        self.parked.is_empty() && self.calls.is_empty()
    }

    /// Validate and park the outgoing context before installing the callback.
    pub(crate) fn activate_pending(&mut self) -> Option<PendingM68kExecution> {
        if let Some(active) = self.calls.active_m68k() {
            return Some(active);
        }
        let pending = self
            .calls
            .activate_m68k_parking(&mut self.parked, &mut self.cpu)?;
        for (index, value) in pending.registers.data.into_iter().enumerate() {
            self.cpu.core.set_d(index, value);
        }
        for (index, value) in pending.registers.address.into_iter().enumerate() {
            self.cpu.core.set_a(index, value);
        }
        self.cpu.write_reg(Register::A7, pending.initial_sp);
        self.cpu.write_reg(Register::PC, pending.entry);
        Some(pending)
    }

    /// Apply a completed native result to its actual caller, then restore it.
    pub(crate) fn resume_after_powerpc(&mut self, memory: &mut PpcSectionMem) -> bool {
        let Some(parked) = self
            .calls
            .commit_m68k_resume(&mut self.parked, |resume, parked| {
                let cpu = parked.unwrap_or(&mut self.cpu);
                if !Self::apply_m68k_resume_result(cpu, memory, resume) {
                    return false;
                }
                cpu.write_reg(Register::PC, resume.return_pc);
                cpu.write_reg(Register::A7, resume.final_sp);
                true
            })
        else {
            return false;
        };
        if let Some(parked) = parked {
            self.cpu = parked;
        }
        true
    }

    pub(crate) fn apply_m68k_resume_result(
        cpu: &mut M68kCpu,
        memory: &mut PpcSectionMem,
        resume: crate::guest_call::M68kResume,
    ) -> bool {
        use crate::guest_call::M68kResultTarget;

        let mask_value = |value: u32, size: u8| match size {
            1 => Some(value & 0xff),
            2 => Some(value & 0xffff),
            4 => Some(value),
            _ => None,
        };
        match resume.result {
            None => true,
            Some(M68kResultTarget::Data { index, size }) if index < 8 => {
                mask_value(resume.powerpc.gpr3, size).is_some_and(|value| {
                    cpu.core.set_d(usize::from(index), value);
                    true
                })
            }
            Some(M68kResultTarget::Address { index, size }) if index < 8 => {
                mask_value(resume.powerpc.gpr3, size).is_some_and(|value| {
                    cpu.core.set_a(usize::from(index), value);
                    true
                })
            }
            Some(M68kResultTarget::Ccr { mask }) => {
                // Native return values always arrive in R3; Mixed Mode then
                // copies that value to the ProcInfo-selected 68k destination,
                // including a CCR bit. Inside Macintosh: PowerPC System
                // Software (1994), pp. 2-10--2-12.
                let set = resume.powerpc.gpr3 != 0;
                let ccr = (cpu.core.get_ccr() & !mask) | if set { mask } else { 0 };
                cpu.core.set_ccr(ccr);
                true
            }
            Some(M68kResultTarget::Memory { address, size }) => {
                mask_value(resume.powerpc.gpr3, size).is_some_and(|value| match size {
                    1 => memory.write_u8(address, value as u8).is_some(),
                    2 => memory.write_u16_be(address, value as u16).is_some(),
                    4 => memory.write_u32_be(address, value).is_some(),
                    _ => false,
                })
            }
            Some(M68kResultTarget::SpecialCase { selector, scratch }) => {
                Self::apply_m68k_special_case_result(
                    cpu,
                    memory,
                    selector,
                    scratch,
                    resume.powerpc.gpr3,
                )
            }
            _ => false,
        }
    }

    pub(crate) fn apply_m68k_special_case_result(
        cpu: &mut M68kCpu,
        memory: &mut PpcSectionMem,
        selector: u8,
        scratch: u32,
        native_result: u32,
    ) -> bool {
        use crate::mixed_mode::special_case;

        let set_data_word = |cpu: &mut crate::cpu::M68kCpu, index: usize, value: u32| {
            let preserved = cpu.core.d(index) & 0xffff_0000;
            cpu.core.set_d(index, preserved | (value & 0xffff));
        };
        let set_z = |cpu: &mut crate::cpu::M68kCpu, value: bool| {
            let ccr = (cpu.core.get_ccr() & !0x04) | if value { 0x04 } else { 0 };
            cpu.core.set_ccr(ccr);
        };

        match u32::from(selector) {
            special_case::EOL_HOOK
            | special_case::PROTOCOL_HANDLER
            | special_case::SOCKET_LISTENER => {
                set_z(cpu, native_result & 0xff != 0);
                true
            }
            special_case::WIDTH_HOOK | special_case::NWIDTH_HOOK => {
                set_data_word(cpu, 1, native_result);
                true
            }
            special_case::HIT_TEST_HOOK => {
                let Some(pixel_width) = memory.read_u16_be(scratch) else {
                    return false;
                };
                let Some(char_offset) = scratch
                    .checked_add(2)
                    .and_then(|address| memory.read_u16_be(address))
                else {
                    return false;
                };
                let Some(pixel_in_char) = scratch
                    .checked_add(4)
                    .and_then(|address| memory.read_u8(address))
                else {
                    return false;
                };
                cpu.core
                    .set_d(0, ((native_result & 0xff) << 16) | u32::from(pixel_width));
                set_data_word(cpu, 1, u32::from(char_offset));
                set_data_word(cpu, 2, u32::from(pixel_in_char));
                true
            }
            special_case::TE_FIND_WORD => {
                let Some(word_start) = memory.read_u16_be(scratch) else {
                    return false;
                };
                let Some(word_end) = scratch
                    .checked_add(2)
                    .and_then(|address| memory.read_u16_be(address))
                else {
                    return false;
                };
                set_data_word(cpu, 0, u32::from(word_start));
                set_data_word(cpu, 1, u32::from(word_end));
                true
            }
            special_case::TE_RECALC => {
                let Some(line_start) = memory.read_u16_be(scratch) else {
                    return false;
                };
                let Some(first_char) = scratch
                    .checked_add(2)
                    .and_then(|address| memory.read_u16_be(address))
                else {
                    return false;
                };
                let Some(last_char) = scratch
                    .checked_add(4)
                    .and_then(|address| memory.read_u16_be(address))
                else {
                    return false;
                };
                set_data_word(cpu, 2, u32::from(line_start));
                set_data_word(cpu, 3, u32::from(first_char));
                set_data_word(cpu, 4, u32::from(last_char));
                true
            }
            special_case::TE_DO_TEXT => {
                let Some(current_graf_port) = memory.read_u32_be(scratch) else {
                    return false;
                };
                let Some(char_position) = scratch
                    .checked_add(4)
                    .and_then(|address| memory.read_u16_be(address))
                else {
                    return false;
                };
                cpu.core.set_a(0, current_graf_port);
                set_data_word(cpu, 0, u32::from(char_position));
                true
            }
            special_case::MBAR_HOOK => {
                set_data_word(cpu, 0, native_result);
                true
            }
            _ => false,
        }
    }

    pub(crate) fn complete_pending(
        &mut self,
        memory: &mut PpcSectionMem,
        native: &mut ppc::PpcCpu,
        pending: crate::guest_call::PendingM68kExecution,
    ) -> bool {
        use crate::guest_call::M68kResultSource;

        let result = match pending.result {
            None => None,
            Some(M68kResultSource::Data(index)) => Some(self.cpu.core.d(usize::from(index))),
            Some(M68kResultSource::Address(index)) => Some(self.cpu.core.a(usize::from(index))),
            Some(M68kResultSource::Memory { address, size }) => {
                let value = match size {
                    1 => memory.read_u8(address).map(u32::from),
                    2 => memory.read_u16_be(address).map(u32::from),
                    4 => memory.read_u32_be(address),
                    _ => None,
                };
                let Some(value) = value else {
                    return false;
                };
                Some(value)
            }
            Some(M68kResultSource::SpecialCase {
                selector,
                arguments,
                stack_result,
            }) => {
                let Ok(value) = self.complete_m68k_special_case_result(
                    memory,
                    selector,
                    arguments,
                    stack_result,
                ) else {
                    return false;
                };
                value
            }
        };
        self.calls.complete_m68k_for_powerpc(
            pending.return_pc,
            self.cpu.read_reg(Register::A7),
            result,
            native,
        )
    }

    pub(crate) fn complete_m68k_special_case_result(
        &mut self,
        memory: &mut PpcSectionMem,
        selector: u8,
        arguments: crate::guest_call::PowerPcArguments,
        stack_result: Option<u32>,
    ) -> std::result::Result<Option<u32>, ()> {
        use crate::mixed_mode::special_case;

        let arguments = arguments.as_slice();
        let proc_info = crate::mixed_mode::proc_info::SPECIAL_CASE
            | (u32::from(selector) << special_case::SELECTOR_PHASE);
        let signature = crate::mixed_mode::native_special_case_signature(proc_info).ok_or(())?;
        if arguments.len() != signature.argument_count {
            return Err(());
        }
        let z = u32::from(self.cpu.core.get_ccr() & 0x04 != 0);
        match u32::from(selector) {
            // A void callback has no native return value. Preserve the
            // caller's PPC R3 rather than manufacturing zero and treating it
            // as a result to copy back through the cross-ISA frame.
            special_case::HIGH_HOOK | special_case::DRAW_HOOK => Ok(None),
            special_case::EOL_HOOK
            | special_case::PROTOCOL_HANDLER
            | special_case::SOCKET_LISTENER => Ok(Some(z)),
            special_case::WIDTH_HOOK | special_case::NWIDTH_HOOK => {
                Ok(Some(self.cpu.core.d(1) & 0xffff))
            }
            special_case::HIT_TEST_HOOK => {
                if ![(arguments[6], 2), (arguments[7], 2), (arguments[8], 1)]
                    .into_iter()
                    .all(|(address, size)| memory.preflight_writable_range(address, size))
                {
                    return Err(());
                }
                memory
                    .write_u16_be(arguments[6], self.cpu.core.d(0) as u16)
                    .ok_or(())?;
                memory
                    .write_u16_be(arguments[7], self.cpu.core.d(1) as u16)
                    .ok_or(())?;
                memory
                    .write_u8(arguments[8], self.cpu.core.d(2) as u8)
                    .ok_or(())?;
                Ok(Some((self.cpu.core.d(0) >> 16) & 0xff))
            }
            special_case::TE_FIND_WORD => {
                if ![(arguments[4], 2), (arguments[5], 2)]
                    .into_iter()
                    .all(|(address, size)| memory.preflight_writable_range(address, size))
                {
                    return Err(());
                }
                memory
                    .write_u16_be(arguments[4], self.cpu.core.d(0) as u16)
                    .ok_or(())?;
                memory
                    .write_u16_be(arguments[5], self.cpu.core.d(1) as u16)
                    .ok_or(())?;
                Ok(None)
            }
            special_case::TE_RECALC => {
                if !arguments[2..5]
                    .iter()
                    .copied()
                    .all(|address| memory.preflight_writable_range(address, 2))
                {
                    return Err(());
                }
                for (argument, register) in arguments[2..5].iter().copied().zip(2..=4) {
                    memory
                        .write_u16_be(argument, self.cpu.core.d(register) as u16)
                        .ok_or(())?;
                }
                Ok(None)
            }
            special_case::TE_DO_TEXT => {
                if ![(arguments[4], 4), (arguments[5], 2)]
                    .into_iter()
                    .all(|(address, size)| memory.preflight_writable_range(address, size))
                {
                    return Err(());
                }
                memory
                    .write_u32_be(arguments[4], self.cpu.core.a(0))
                    .ok_or(())?;
                memory
                    .write_u16_be(arguments[5], self.cpu.core.d(0) as u16)
                    .ok_or(())?;
                Ok(None)
            }
            special_case::GNE_FILTER_PROC => {
                let result = memory.read_u16_be(stack_result.ok_or(())?).ok_or(())?;
                if !memory.preflight_writable_range(arguments[1], 1) {
                    return Err(());
                }
                memory.write_u8(arguments[1], result as u8).ok_or(())?;
                Ok(None)
            }
            special_case::MBAR_HOOK => Ok(Some(self.cpu.core.d(0) & 0xffff)),
            _ => Err(()),
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::guest_call::GuestCallTarget;
    use crate::guest_procedure::GuestIsa;

    #[test]
    fn relaunch_waits_for_the_bound_process_calls_to_finish() {
        let calls = SharedGuestCallStack::default();
        let mut engine = M68kExecution::new(&calls);
        engine.cpu.core.set_d(0, 42);
        assert!(engine.can_relaunch());
        assert!(calls.begin_m68k(
            GuestCallTarget {
                isa: GuestIsa::M68k,
                entry: 0x1000,
                rtoc: 0,
            },
            0x2000,
            0x3000
        ));
        assert!(!engine.can_relaunch());
        assert_eq!(engine.cpu.core.d(0), 42);
        assert!(calls.complete_m68k(0x2002, 0x3000));
        assert!(engine.can_relaunch());
        assert_eq!(engine.cpu.core.d(0), 42);
    }
}