A shared mapping is a view of a file section created on the descriptor's
handle, read-write when the descriptor is, otherwise read-only. A private
mapping is a copy of the file read at mmap, as POSIX allows. Anonymous
shm_open objects and JIT shared memory descriptors are temporary files on
Windows, so mmap now maps them too (it failed with EOPNOTSUPP before).
mprotect of a mapped view above the view's protection fails with EACCES
before any bookkeeping changes. The cases Windows cannot represent are
listed in the libkernel debt.
Dusklight (PPSA99305) uses SQLite in WAL mode, which maps its -shm file.
On Windows main f0634088b every start logged "Failed to start
transaction: disk I/O error" for its Dawn and pipeline caches (3 of 3
runs); with this change the caches initialise and their WAL files fill
(4 of 4 runs). The title reaches its menu either way.
A shared mapping may end inside the 16 KiB page that holds the end of
the file, as POSIX mmap allows: the view ends with the file's last 4 KiB
host page, which Windows zero-fills past the end, the rest of the guest
page is private zero pages, and the file never grows. A mapping that
reaches a whole page past the end still fails with EOPNOTSUPP.
PS5LM Plus (PPSA99581) loads its model with llama.cpp, which maps the
whole GGUF file shared and read-only. With a 491,400,032-byte model,
Windows main 5de7a46e0 and this change without the last page logged
"llama_model_load: error loading model: mmap failed: Operation not
supported" (3 of 3 runs); now the model loads and the completion of
"The capital of France is" starts with " Paris" (3 of 3 runs).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
The three JIT shared memory exports (avvJ3J0H0EY, MR221Mwo0Pc,
YKT49TOLQWs) are absent imports of three homebrew titles that cannot
finish loading without them. Predicted next stops (registry order):
- VLC PPSA85300 after getdtablesize (idx 354):
"FAIL: unresolved ELF import YKT49TOLQWs from libkernel.prx"
(Map idx 452, Create idx 462)
- XPSemu PPSA97358 after tcsendbreak (idx 214):
"FAIL: unresolved ELF import avvJ3J0H0EY from libkernel.prx"
(Create idx 398, Map idx 399)
- RetroArch PPSA99169:
"FAIL: unresolved ELF import avvJ3J0H0EY from libkernel.prx"
(Create 476, Alias 477, Map 478)
XPSemu and VLC (ps5/compat/mmap.c, __wrap_mmap) create an object for
every anonymous PROT_EXEC mapping (QEMU's TCG buffer) and map it with
the same protection, falling back to flexible memory on any non-zero
return. RetroArch's eboot runs a probe: Create("ps5-platform-probe",
0x10000, 7, &fd), Alias(fd, 3, &alias), Map(fd, 5, &address), then logs
"jit create=0x%08x alias=0x%08x map=0x%08x".
Signatures from Orbital cc408367 tools/ida/db_types.json (name, len,
maxProt, fdOut; fd, maxProt, fdOut; fd, prot, startOut), matching
ps4sdk 4df9d001 include/sce/kernel.h, ps5-jar-loader 8034177e
LibKernel.java and the three titles' call sites. SharpProspero 5dfdb4b0
declares the alias as returning the descriptor; the RetroArch call site
passes an out pointer.
The object is a host anonymous file (memfd on Linux, a delete-on-close
temporary file mapped as a PAGE_EXECUTE_READWRITE section on Windows),
the alias a duplicate descriptor, and each map maps the whole object
through the direct memory placement path, so a write through one view
is visible through the others. Bad lengths and protection bits are
EINVAL, protection past the descriptor's maximum is EACCES (FreeBSD 11
vm_map_protect), unknown descriptors are EBADF; close, dup and dup2
keep the descriptor table in step. Unverified details are recorded in
TechnicalDebt.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
