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fix(memory): ignore CPU and DMA writes to unused I/O addresses

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Stores to I/O addresses with no register returned Unmapped and stopped the
machine. Hardware ignores them. Emulated writes there now pay their bus cost and
change nothing; host writes stay strict. The unmodeled internal memory control
register at 0x04xx0800 and all unused I/O reads remain diagnostics.

Rollback tests that used unused I/O as their failing word now run the block on
to a register that rejects the stored value: SIOMULTI2 outside multiplayer
mode, an RCNT GPIO serial IRQ, or 64-sample wave playback. Where no reachable
register can fail (JOYSTAT, POSTFLG/HALTCNT, IME, DMA3CNT), the test now checks
that the block commits and the unused word is ignored.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HhfHfHEuzv2AUTd6erW1gU
This commit is contained in:
0xrsydn 2026-10-14 11:38:51 +07:00
commit 20176716d9
16 changed files with 166 additions and 92 deletions
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38
crates/gba-core/tests/display.rs
View file

@ -375,26 +375,38 @@ fn display_sources_enter_an_original_irq_handler_acknowledge_and_return() {
#[test]
fn failed_block_store_does_not_change_window_controls_or_advance_display() {
let rom = [
0xe3a0_2301_u32, // MOV r2,#0x04000000
0xe282_2048, // ADD r2,r2,#0x48 (WININ/WINOUT)
0xe3a0_003f, // MOV r0,#0x3f
0xe3a0_1001, // MOV r1,#1
0xe8a2_001f, // STMIA r2!,{r0-r4}; last word is unmapped 0x04000058
]
.into_iter()
.flat_map(u32::to_le_bytes)
.collect();
let mut bus = Memory::new(rom).unwrap();
// STMIA r12!,{r0-r11} stores WININ/WINOUT through SOUND3CNT_X. Unused words are
// ignored. With 64-sample wave mode selected, r11 requests playback, a diagnostic.
let operands = [
(12, 0x0400_0048),
(0, 0x3f),
(1, 1),
(10, 0xa0),
(11, 0x8000),
];
let offset = (operands.len() as u32 - 1) * 4;
let mut code: Vec<u32> = operands
.iter()
.map(|&(register, _)| 0xe59f_0000 | (register as u32) << 12 | offset)
.collect();
code.push(0xe8ac_0fff);
code.extend(operands.iter().map(|&(_, value)| value));
let mut bus = Memory::new(code.into_iter().flat_map(u32::to_le_bytes).collect()).unwrap();
bus.write16(0x0400_0084, 0x80).unwrap(); // Master sound enable.
bus.write16(0x0400_0070, 0xa0).unwrap(); // Wave: 64-sample mode, DAC on.
let mut cpu = Cpu::new(ROM_START);
for _ in 0..4 {
for _ in operands {
cpu.step(&mut bus).unwrap();
}
bus.advance_cycles(7 * CYCLES_PER_LINE);
let before = cpu.clone();
let position = bus.display_position();
let mut machine = Machine::new(cpu, bus);
assert!(machine.step().is_err());
let error = machine.step().unwrap_err();
assert!(
error.to_string().contains("64-sample wave playback"),
"{error}"
);
assert_eq!(machine.cpu(), &before);
assert_eq!(machine.memory().display_position(), position);
assert_eq!(machine.memory().read32(gba_core::io::WININ).unwrap(), 0);