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feat(memory): protect CPU BIOS reads with retained ARM prefetch

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Retain the supplied image PC+8 snapshot after successful ARM BIOS instructions. CPU data reads from outside BIOS use its byte lanes; reads inside BIOS and host inspection remain mapped reads. Keep nominal timing and diagnostic atomicity. Unknown history, Thumb BIOS execution, and missing lookahead remain explicit limits rather than guessed values.

Add original regressions for ARM/Thumb callers, all CPU modes, widths and rotation, synthetic SWI/IRQ returns, original boot provenance, context isolation, history invalidation, and device progress. No Nintendo firmware or opcode constants are used to synthesize results.

Darwin arm64 validation: 861 workspace tests and 792 core/demo tests in debug and release; 39 Python tests; native ROM windows; all ten demo smoke tests; fmt, clippy, rustdoc, and docs links. Public ARM, Thumb, and memory ROMs still pass. The public BIOS ROM still fails firmware-specific test 1, now reading its actual replacement-BIOS prefetch rather than raw vector bytes.
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0xrsydn 2026-10-05 21:42:04 +07:00
commit c31a703db4
11 changed files with 399 additions and 16 deletions
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docs/testing.md
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@ -219,6 +219,11 @@ Status tests cover all modes, flag combinations, interrupt masks, field selectio
Exception tests cover vectors, ARM/Thumb return addresses, nested interrupts, mask priority, and return-state restoration.
User-bank transfers and failed returns are checked for unintended changes to active and hidden registers.
Integration tests execute original vector handlers and check optional BIOS mapping boundaries and write protection.
Original BIOS-access regressions check retained ARM PC+8 data for ARM/Thumb callers, all processor modes, load widths, lanes, and rotation.
They verify direct reads while executing inside BIOS, re-entry, SWI/IRQ returns, host-inspection isolation, and original-boot provenance.
Unknown history, Thumb BIOS execution, missing lookahead, and diagnostic-step retention have explicit checks.
Protected loads keep normal nominal costs and advance devices only through machine stepping.
The pinned public BIOS ROM remains a failed assertion, not a conformance pass.
Display tests cover color conversion, framebuffer bounds, cursor movement, pause behavior, and animation wraparound.
Input regression tests check focused arrow keys, focused Space presses, and ignored input when unfocused.
Command-line tests cover mode selection and invalid arguments.