D175 - The filesystem is exonerated, and four walls are not one wall
decided ยท 2026-08-21
Two questions asked in order after image+0x43c4 resisted
eight attempts.
Is the data the guest loaded actually correct?
Verifying content would double every read - re-reading each file to compare. Verifying completeness costs a counter and catches the failure that matters: a title that silently receives a truncated asset then faults inside its own parser, which is exactly the shape of wall that cannot be attributed.
Short reads are counted, with one distinction that makes the count mean something: reading to the end of a file is a short read, and counting it would bury the case that matters. A read cut short before the end is the defect, and the two are separated by whether the file had already finished.
files 10 reads, 11328 KiB, none cut shortThe guest receives every byte it asks for. The filesystem is exonerated, and the fault is downstream of it - which is worth as much as finding a bug would have been, because it removes a whole layer from suspicion.
Printed on every run that reads anything, including when clean, for the same reason the stack-conformance line is: a line that only appears on failure cannot be told apart from one nobody wired up.
The corpus says the wall was never singular
| title | result |
|---|---|
| PPSA28061 | 47 imports, 933 calls, image+0x43c4 |
| PPSA25872 | 14 imports, 1735 calls,
image+0x7b591e |
| PPSA04263 | spins on sceKernelDirectMemoryQuery, hits the time
limit |
| PPSA03416 | illegal instruction at image+0x1595bc9,
rax holding our error code |
| PPSA02664 | does not parse - previous-generation wrapper |
| PPSA21564 | does not parse - previous-generation wrapper |
Four distinct walls in four different places.
image+0x43c4 had begun to feel like the blocker,
and optimising against one title is how that happens. The loop is meant
to be run across the corpus.
PPSA03416 is the more tractable lead: three frames from the entry
point, rax holding 0x7FFF0001, and execution
at an offset twenty-two megabytes into the image - which reads as the
guest calling through a pointer a stub handed it. Far closer to the
surface than Earthion's wall.
And two of six titles do not parse at all. That is the only item here that changes the denominator rather than one numerator.