Files
Syplheed-Reborn/tools/re-capture/diff_words.py
Claude (auto-RE) faa7b3d611 re(challenge): the part id is never persisted -- differential search says stack only
No literal 26 exists anywhere, so the GamePart id is computed. That does not stop
it being found: the id is KNOWN at each screen from the GamePart table (EXTRAS = 5,
MISSION SELECT = 7), so snapshot both and intersect. New tool diff_words.py does
the classic differential search over the sparse guest image, and find_partslot.sh
drives the two screens and runs it.

Result: 171 MB scanned, exactly 4 addresses read 5 then 7 -- 0x708FFBEC,
0x708FFCBC, 0x708FFDAC, 0x708FFE20 -- and all four are guest STACK (the same run's
log puts thread stacks at 0x709...). So the requested part id exists only as a
stack argument in flight; there is no persistent field, which is consistent with
finding no literal store, and means there is nothing stable to poke.

That closes the last memory-and-menu route to the challenge missions. Reaching
them needs either the genuine in-game unlock (an in-mission attainment, per
AVSCRIPT_COMMAND_ATTAINMENT_CHALLENGE_MISSION_CARGO_SCORE) or an emulator-side
hook that forces the transition -- a code change, not a poke.

diff_words.py is worth keeping well beyond this question: it locates any field
whose address is unknown but whose value is known at two moments.
2026-08-13 21:31:47 +00:00

75 lines
2.3 KiB
Python
Executable File

#!/usr/bin/env python3
"""Find guest addresses holding one value in snapshot A and another in snapshot B.
The classic differential search, which is how you locate a field whose ADDRESS is
unknown but whose VALUE is known at two moments. Used here for the GamePart slot:
`GP_EXTRAS` = 5 on the extras screen, `GP_MISSION_SELECT` = 7 on the next one, so
the slot is a word that reads 5 then 7.
Both snapshots are sparse copies of `/dev/shm/xenia_memory_*`, so the ~4.6 GB of
holes cost nothing: walk A's allocated extents with SEEK_DATA and only look at B
where A already matched.
diff_words.py <snapA> <valA> <snapB> <valB> [--near <va> <span>]
"""
import os
import struct
import sys
sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
from gmem import off_to_vas # noqa: E402
def main():
if len(sys.argv) < 5:
print(__doc__)
return 1
pa, va_, pb, vb_ = sys.argv[1], int(sys.argv[2], 0), sys.argv[3], int(sys.argv[4], 0)
pat_a = struct.pack(">I", va_)
fa, fb = open(pa, "rb"), open(pb, "rb")
size = min(os.path.getsize(pa), os.path.getsize(pb))
hits, scanned = [], 0
off = 0
while off < size:
try:
off = os.lseek(fa.fileno(), off, os.SEEK_DATA)
except OSError:
break
if off >= size:
break
try:
end = min(os.lseek(fa.fileno(), off, os.SEEK_HOLE), size)
except OSError:
end = size
while off < end:
n = min(1 << 22, end - off)
fa.seek(off)
buf = fa.read(n)
scanned += len(buf)
i = 0
while True:
i = buf.find(pat_a, i)
if i < 0:
break
p = off + i
if p % 4 == 0:
fb.seek(p)
if fb.read(4) == struct.pack(">I", vb_):
hits.append(p)
i += 1
off += n
print(f"scanned {scanned/1e6:.0f} MB of allocated guest memory")
print(f"addresses reading {va_} in A and {vb_} in B: {len(hits)}")
for h in hits[:40]:
vas = off_to_vas(h)
print(f" file off {h:#012x} guest VA {[hex(v) for v in vas][:2]}")
if len(hits) > 40:
print(f" … and {len(hits)-40} more")
return 0
if __name__ == "__main__":
raise SystemExit(main())