Cashing in the io/stat and io/shortname recordings.
__IoGetStat began with memset(stat, 0xfe, sizeof(SceIoStat)), which destroyed 24 bytes of the
caller's buffer that a real PSP never touches - it writes only as far as the timestamps and
leaves all six st_private words exactly as it found them. It also wrote a made-up sector number
into st_private[0] on the memory stick. That word carries the LBN on a UMD, which games read to
build disc0:/sce_lbn paths, so it stays for non-FAT and is left alone otherwise.
FAT has no permissions of its own and everything reads back as 0777. We were passing the host's
idea of the file through instead. The existing "all files look executable on FAT" hack for Beats
(issue #14812) was right in substance but lived only in sceIoDread, so sceIoGetstat and
sceIoDread disagreed about the same file where hardware has them agree. Both now go through one
path, which also gets the read-only case right: no write bits means mode 0555 and attr 0x21.
sceIoGetstat on the root of a volume is refused, as on hardware.
sceIoChstat was a logging stub. It now applies the read-only flag, which is what st_mode's write
bits and st_attr's 0x01 both mean on FAT - setting either produces both, and it's reversible.
That needs a new IFileSystem::SetFileWritable, defaulting to "can't" so read-only filesystems and
hosts that can't express it (Android content URIs) are unaffected; the call still succeeds there,
since hardware would have.
GenerateFatShortNames now accounts for capitalisation. FAT keeps a lowercase flag for the base and
another for the extension, but the PSP only honours the base one, so "shrt" becomes SHRT while
"readme.txt" becomes README~1.TXT. We were only adding a counter on collision. The unit test
carries the whole recorded set, including the corrected README~1.MD.
io/shortname stays in tests_next: its d_name column can't match while SimulateVFATBug is
uppercasing lowercase 8.3 names, which is deliberate and load-bearing for homebrew.
sceIoDread hands back a dirent whose d_private holds the 8.3 short name
ahead of the long name, and we never wrote the short name at all - the game
got whatever was on the stack there. Crazy Taxi: Fare Wars reads it rather
than d_name, so it rejected every file in ms0:/MUSIC, ended up with an empty
playlist and never even reserved an mp3 handle: custom soundtracks were
silently dead, with the game spinning on InitResource/SetLoopNum forever.
Generate the names from the directory listing, and resolve them back in
DirectoryFileSystem so a game can open a file by the short name it was given.
Both sides come from the same function, so they agree.
We can't lean on the host for any of this. Linux, macOS and Android have no
8.3 names at all, and while Windows does keep aliases it generates them by a
different rule - it counts to ~4 and then switches to a hash - so resolution
runs before the literal path is tried rather than as a fallback, or on
Windows we'd quietly open a different file than the one we handed the game.
The exact names a real PSP produces are still unverified - no pspautotest
covers d_private - so this implements the ordinary FAT rule and the new
FatShortNames unit test pins that down until hardware can settle it.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Henrik Rydgård