feat(libkernel): accept a kevent read event on descriptor 0

[klosixgaming-arch]

What

EA SPORTS FC 27 (PPSA34015) creates a kqueue at start-up and registers EVFILT_READ for descriptor 0 in it. The code (eboot 0xba76b90) sets up an input console command, then calls kqueue() and kevent(kq, {ident 0, EVFILT_READ, EV_ADD}, 1, NULL, 0, NULL), stores the kqueue, and ignores kevent's result. With the PPSA34015 pull requests listed under Tested applied on main, the title then stops with:

terminate called after throwing an instance of 'std::runtime_error'
  what():  kevent: EVFILT_READ on a non-socket descriptor not implemented
FATAL: abort() (SIGABRT)

kevent now accepts a read event on the host stream on descriptor 0. The event never triggers, the same way select never reports descriptor 0 readable (libkernel debt, "console title with no input"). The change is limited to that case:

• Write events on descriptors 0 to 2 still throw.
• Read events on other non-socket descriptors still throw.
• A descriptor 0 that was not open when libkernel loaded still follows the existing path.

The debt entry for kqueue and kevent records the new case.

Tested

• Windows 11, WinLibs GCC 15.2.0, RTX 5090 (NVIDIA 610.47), Ryzen 9 9950X3D: PPSA34015 01.000.004 gets past the stop above and reaches the EA SPORTS FC 27 splash screen, which is still compiling shaders at 1–2 fps. Reaching this point also needs notaxeltv's open PPSA34015 pull requests (feat(libSceGameLiveStreaming): accept GetProgramInfo with no live stream #5352 feat(libSceLoginService): load Initialize/Terminate so PPSA34015 can start #6034 feat(libSceNpPartner001): answer sceNpHasEAAccessSubscription without an EA Access server #6049 feat(libSceNpManager): export two unknown NIDs so PPSA34015 can load #6056 feat(libScePlayerSelectionDialog): run common-dialog state machine without UI #6058 feat(libSceVdecsw): block on SyncDecodeInput/Output like TrySync #6062 feat(libc): raise logic_error::_Doraise and _Xruntime_error #6072 feat(libc): allocate through operator new with align_val_t #6074 feat(libc): throw bad_optional_access like bad_weak_ptr #6079 feat(libc): implement C11 timespec_get (PPSA34015) #6084 feat(libc): export _FDsign/_Dsign like MSVC CRT (PPSA34015) #6085 feat(libc): export std::thread::hardware_concurrency (PPSA34015) #6086 feat(libc): export locale::classic (PPSA34015) #6087 feat(libc): _Cnd_init_with_default_name_override (PPSA34015) #6088 feat(libSceSystemService): accept OpenTournamentOccurrence without system UI #6089 feat(libSceVoice): accept WriteToIPort on input ports (PPSA34015) #6090 feat(libSceWebBrowserDialog): finish PredeterminedContent without UI (PPSA34015) #6092), applied on main for this run.
• guest_kqueue has a new case for this and passes on Linux (GCC 13.3), run with descriptor 0 open and with it closed. On Windows, PPSA34015 runs the new path (above). On this Windows machine, guest_kqueue fails later in the existing DeniedParentWatch case (the vnode watch error lacks "parent"), which this change does not touch and test(libkernel): deny the kqueue parent listing to the token user's SID #6173 changes.

Checklist

• Based on current main; no other open PR implements the same functions (feat(libkernel): support EVFILT_READ on the read end of a pipe #5973 adds pipe read ends to the same function; descriptor 0 here is a console, not a pipe)
• One topic per PR; follow-ups go in a new PR
• No comments in code except technical debt
• Unimplemented paths throw (NotImplemented_nid_no_patch); silent stubs are listed under Silent stubs in their library's technical debt file
• No notes, investigation .md files or images added to the repository (attach them to this PR)
• New third-party code is a submodule built from source
• Generic behaviour, not specific to one title
• Depends on: none
• Unblocks: PPSA34015 EA SPORTS FC 27 (PPSA34015) #6344
• GPUs tested: RTX 5090
• AI-assisted: yes. Written with AI assistance and reviewed by me.

[github-actions]

Other open pull requests touch the same code. Merging one will break the other, or both implement the same thing. If this one builds on them, list them in Depends on.

Pull request	Conflicting files (lines on main)	Same exports	Same new files
PR 6542	docs/dev/debt/libkernel.md L112-113
PR 7075	docs/dev/debt/libkernel.md L113
PR 7121	docs/dev/debt/libkernel.md L113-114
PR 7129	core/libs/prx/libkernel/Equeue/src/Kqueue.cpp L142 docs/dev/debt/libkernel.md L113
PR 7653	core/libs/prx/libkernel/Equeue/src/Kqueue.cpp L2-3 docs/dev/debt/libkernel.md L113

Some comparisons could not be completed because a pull request conflicts with the base branch. Review these shared files manually before concluding that there is no overlap.

Pull request	Shared files not compared
PR 5021	docs/dev/debt/libkernel.md
PR 6044	core/libs/tests/GuestKqueue.cpp
PR 6446	docs/dev/debt/libkernel.md
PR 6510	core/libs/prx/libkernel/Equeue/src/Kqueue.cpp core/libs/tests/GuestKqueue.cpp docs/dev/debt/libkernel.md
PR 6519	docs/dev/debt/libkernel.md
PR 6534	docs/dev/debt/libkernel.md
PR 6908	docs/dev/debt/libkernel.md
PR 6936	docs/dev/debt/libkernel.md
PR 6977	docs/dev/debt/libkernel.md
PR 7039	docs/dev/debt/libkernel.md
PR 7049	core/libs/prx/libkernel/Equeue/src/Kqueue.cpp core/libs/tests/GuestKqueue.cpp docs/dev/debt/libkernel.md
PR 7088	core/libs/prx/libkernel/Equeue/src/Kqueue.cpp core/libs/tests/GuestKqueue.cpp docs/dev/debt/libkernel.md
PR 7105	docs/dev/debt/libkernel.md
PR 7149	docs/dev/debt/libkernel.md
PR 7192	docs/dev/debt/libkernel.md
PR 7332	docs/dev/debt/libkernel.md
PR 7509	docs/dev/debt/libkernel.md

[klosixgaming-arch]

No dependency — this PR builds on neither:

• feat(libkernel): support EVFILT_READ on the read end of a pipe #5973 adds EVFILT_READ for the read end of a pipe. Here descriptor 0 is the host console stream (PPSA34015 registers standard input in a kqueue at start-up), not a pipe. The two add separate branches to AddDescriptorKnote, so they can merge in either order.
• feat(libkernel): implement kevent EV_DISABLE, EV_DISPATCH and EV_FORCEONESHOT #5847 implements the event flags (EV_DISABLE, EV_DISPATCH, EV_FORCEONESHOT); that is a different code path from this descriptor-filter change. The only shared file is the debt doc, where both edit the same kqueue bullet at different parts (this PR adds the sentence about read events on descriptor 0; feat(libkernel): implement kevent EV_DISABLE, EV_DISPATCH and EV_FORCEONESHOT #5847 removes those flags from the throw list), so whichever merges second resolves it trivially.

[karimibrahim07]

Windows check of head 8078b7ef3, merged onto main 5d9dcc42d (clean merge). Windows 11 Pro (26300), WinLibs GCC 15.2.0 r7, Ninja Release.

• guest_kqueue passes on Windows here, including the new StandardInput case and DeniedParentWatch. So the failure you saw in DeniedParentWatch looks specific to that machine. guest_select, guest_select_wait, guest_poll and guest_equeue_events also pass.
• It does conflict with #5973, contrary to the comment above. With both heads, git merge-tree reports content conflicts in Kqueue.cpp and in the kqueue bullet of docs/dev/debt/libkernel.md. In Kqueue.cpp, #5973 rewrites the if (!GuestSockets::IsOpen(descriptor)) block that this PR's new branch sits directly above. The resolution is mechanical: keep this PR's descriptor-0 branch first, then #5973's socket-or-pipe block. The debt sentence needs both additions. Whichever merges second needs that resolution.
• One interaction for that resolution: with this branch first, a descriptor 0 that the host attached to a pipe (a run with stdin redirected) gets the never-triggering knote rather than #5973's pipe readiness, because File::IsHostStream(0) is true for any stream libkernel found at load. That seems the right choice for a console title, which has no input on descriptor 0. If it's intended, the debt sentence could say so.

AI-assisted: yes. I ran the build and tests above and the trial merge with #5973.

[hugodearaujo]

Another title needs this: Assassin's Creed Mirage (PPSA13960, 01.007.000). On main 0d078f7 it stops 7 s after start with kevent: EVFILT_READ on a descriptor that is neither a socket nor the read end of a pipe not implemented. With this PR's Kqueue.cpp change it passes that point; the next stop is a separate main-thread stack issue (#7532), and with #7532 and #7533 as well it runs through its start-up screens (#7534). EA SPORTS FC 25 (PPSA20049) also stops at this kevent read in my runs on main 66702f1.