fix(libkernel): give guest sockets ordinary descriptor numbers below FD_SETSIZE

libkernel numbered guest sockets from GuestSockets::FirstDescriptor
(0x10000000), so a title that puts a socket in a 1024-bit fd_set writes
fd / 8 bytes past it. The Epic Online Services SDK does this on its
RtcNetworkThread and three titles stop there (#1794):

Palworld PPSA23126 (queeeef, main a11c8f7f7):
  FATAL: unhandled exception 0xc0000005 on thread 37164 'RtcNetworkThread'
    rip 0x00007ffcdb1ea2be eossdk-ps5-shipping.prx.guest.prx+0xdea2be
    rcx 0000000010000005 rsi 0000000000400000 r12 0000000010000005
The Mound PPSA26223 (xXPBSXx, main 0a8b1d32b):
  FATAL: unhandled exception 0xc0000005 on thread 'RtcNetworkThread',
  rip eossdk-ps5-shipping.prx.guest.prx+0xefc6f4, rcx = 0x10000005,
  rsi = 0x400000
Dying Light 2 PPSA02262 (tv7):
  FATAL: unhandled exception 0xc0000005 on thread 'RtcNetworkThread'
    rcx 0000000010000005 ... rsi 0000000000400000 ... r12 0000000010000005

On FreeBSD 11.4 (8c639945) FD_SETSIZE is 1024 (sys/sys/select.h:58-59)
and sockets take the lowest free entry of the one process descriptor
table that files use (kern_descrip.c:1643-1660 fdalloc,
uipc_syscalls.c kern_socket through falloc).

Every socket number is now a real host descriptor: a zero-access NUL
handle registered with _open_osfhandle on Windows (as directory
descriptors already are) and an F_DUPFD_CLOEXEC duplicate of the host
socket on Linux. The socket table maps that number to the socket, so
"is this a socket" is a table lookup instead of a range check at the 31
former FirstDescriptor comparisons. close releases both the socket entry
and the number, dup and dup2 duplicate the number through the host table
and keep the socket shared, dup2 of a file onto a socket number drops the
socket entry, and sceKernelClose now closes sockets too. sceNetSocket and
sceNetAccept take their ids from the same table instead of a counter from
32, so libkernel and libSceNet numbers never collide.

select polls guest sockets alongside libSceNet sockets, the random device,
stdio and (on Linux) host descriptors; poll throws only for an open
descriptor that is not a guest socket and reports POLLNVAL otherwise.
File calls that used to fail with EBADF on the socket range return
FreeBSD's answer for a socket: lseek ESPIPE (kern_lseek), ftruncate and
getdirentries EINVAL (invfo_truncate, getvnode), flock EOPNOTSUPP;
fstat on a socket throws. pread on a closed descriptor returns EBADF.

title failing on host descriptor numbers; these three titles are that
case, and this change keeps host numbering for files and only moves
sockets into it.

Tests: guest_socket_descriptors (new: socket below 1024, select on a
socket and a file together, close frees the number for a file, dup of a
socket, sceKernelClose), guest_select (socket and pipe together, Linux),
guest_poll, guest_dup, guest_socket_pair, guest_fstatfs,
guest_posix_filesystem and guest_sce_net updated.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
(cherry picked from commit 20378375b31eb5db922db6e55f45e44a4dae6445)

docs/dev/debt/libkernel.md

@@ -57,7 +57,7 @@
 - [Map hints inside a reservation](../../../core/libs/prx/libkernel/DirectMemory/DirectMemory.cpp) (libkernel) - `sceKernelMapDirectMemory` and the flexible and anonymous maps place a mapping without `MAP_FIXED` at its hint address when the whole range lies in a range still reserved by `sceKernelReserveVirtualRange`, as if `MAP_FIXED` were set. Taken from PPSA01474, which reserves 64 GiB and then maps its heaps inside it with hints and no `MAP_FIXED`, and uses the hint addresses afterwards; not measured on the console. Hints outside a reservation, or over a range that is partly mapped, stay hints
 - [_sceKernelRtldThreadAtexitIncrement, _sceKernelRtldThreadAtexitDecrement](../../../core/libs/prx/libkernel/System/src/Rtld.cpp) (libkernel) - the argument is the `dso` address a title's `libc.prx` passes to `__cxa_thread_atexit` (PPSA14632), which fails when Increment returns nonzero. As in the [fpPS4](https://github.com/red-prig/fpPS4) reimplementation, Increment takes a reference on the loaded image containing the address and Decrement releases one; the variants without the leading underscore are assumed to match
 - [tcgetattr, tcsetattr](../../../core/libs/prx/libkernel/File/src/Terminal.cpp) (libkernel) - every file and pipe descriptor is taken as not a terminal (`ENOTTY`), and a socket gets `EADDRNOTAVAIL` for `AF_INET` and `EOPNOTSUPP` otherwise, as FreeBSD's `in_control` and `pru_control_notsupp` answer a termios ioctl; what descriptors 0 to 2 of a title are on the console, and whether any of them is a terminal there, is unknown
-- [select](../../../core/libs/prx/libkernel/Socket/src/Socket.cpp) (libkernel) - descriptor 0 is never reported readable and descriptors 1 and 2 are always writable, as for a console title with no input; reads from descriptor 0 still go to the host stdin. `/dev/random` and `/dev/urandom` are always readable and writable, as FreeBSD reports a seeded random device. Other descriptors that are not libSceNet sockets throw. Dungeons (PPSA16064) selects on descriptor 0
+- [select](../../../core/libs/prx/libkernel/Socket/src/Socket.cpp) (libkernel) - descriptor 0 is never reported readable and descriptors 1 and 2 are always writable, as for a console title with no input; reads from descriptor 0 still go to the host stdin. `/dev/random` and `/dev/urandom` are always readable and writable, as FreeBSD reports a seeded random device. Guest sockets and libSceNet sockets are polled; other descriptors throw on Windows and are polled through the host on Linux. Dungeons (PPSA16064) selects on descriptor 0
 - [select](../../../core/libs/prx/libkernel/Socket/src/Socket.cpp) (libkernel) - a descriptor the socket poller reports as unknown that is below `GuestSockets::FirstDescriptor` is polled on the host instead of throwing, except on Windows where it still throws; an invalid host descriptor fails with `EBADF`, and mixed host and socket sets are polled in short alternating slices so neither side waits out the full slice alone. Wobbly Life (PPSA29413) selects on file descriptors while streaming its bundles
 - [__progname](../../../core/libs/prx/libkernel/System/src/Process.cpp) (libkernel) - unknown data export
 - [environ](../../../core/libs/prx/libkernel/System/src/Process.cpp) (libkernel) - data export pointing to a fixed empty environment so titles that import it load; it is not the environment libc's `getenv` reads, so it lists none of those variables and `setenv`/`putenv` changes do not appear in it
@@ -128,7 +128,7 @@
 - [Thread cancellation](../../../core/libs/prx/libkernel/Pthread/src/Thread.cpp) (libkernel) follows FreeBSD libthr (states and types 0/1 and 0/2, `PTHREAD_CANCELED` 1, the `_pthread_cleanup_info` node layout), not measured on the console. A request is acted on only in `scePthreadTestcancel`, the condition variable, `sem` and `scePthreadSem` waits, `scePthreadJoin` and the sleeps, and their POSIX names; file and socket calls are not cancellation points. A sleep is not interrupted: the thread exits when it ends. The asynchronous type acts like the deferred one, except at the two set calls.
 - [cpuset_setaffinity](../../../core/libs/prx/libkernel/Pthread/Posix/Thread.cpp) (libkernel) - only the calling thread or the calling process is handled. Bits outside `sceKernelGetAvailableCpumask` are dropped, and a mask with none of those bits fails with `EDEADLK`, as FreeBSD does when the new set has no CPU in common with the parent set
 - [cpuset_getaffinity](../../../core/libs/prx/libkernel/Pthread/Posix/Thread.cpp) (libkernel) - only the calling thread or the calling process is handled. For the process the mask is the union of the affinities of the live guest threads, as [FreeBSD 11.4](https://github.com/freebsd/freebsd-src/blob/d106002967eff712894ab8b5337bbbff106ce5e0/sys/kern/kern_cpuset.c#L1150-L1156) ORs the mask of every thread in the process; threads the guest did not create through libkernel are not included, and the console result is unverified
-- [dup and dup2](../../../core/libs/prx/libkernel/File/src/Stdio.cpp) (libkernel) throw for the combinations they do not model: `dup2` between a guest socket and a host descriptor in either direction. Guest sockets share one socket object between the duplicates and the descriptor numbers come from the guest socket counter, not the lowest free number as in FreeBSD `kern_dup`. The errno values for descriptor exhaustion are not verified against the console.
+- [dup and dup2](../../../core/libs/prx/libkernel/File/src/Stdio.cpp) (libkernel) throw for the combinations they do not model: `dup2` of a guest socket onto descriptors 0 to 2, whose host streams libc writes without the socket table, and on Windows duplicating a directory descriptor. Guest sockets share one socket object between the duplicates; the numbers come from the host descriptor table like those of files. The errno values for descriptor exhaustion are not verified against the console.
 - [waitpid](../../../core/libs/prx/libkernel/System/src/Process.cpp) (libkernel) returns -1 with `ECHILD` (`EINVAL` for unknown options): nothing here creates a child process; child processes would need a real `waitpid`.
 - [execv](../../../core/libs/prx/libkernel/System/src/Process.cpp) (libkernel) throws: replacing the process image is not supported, the same as `execvp`. PPSA97358 imports it and fails to load without it.
 - [kern.proc.pathname](../../../core/libs/prx/libkernel/System/src/SystemConfiguration.cpp) (libkernel) returns `/app0/eboot.bin` for pid -1 and the calling process, following FreeBSD's `sysctl_kern_proc_pathname`; the exact pathname on retail consoles remains unverified.
@@ -139,9 +139,9 @@
 - [socketpair](../../../core/libs/prx/libkernel/Socket/src/Udp.cpp) (libkernel) - the pair is the host's `AF_UNIX` pair on Linux and, on Windows, a loopback TCP connection for `SOCK_STREAM` or two connected UDP sockets for `SOCK_DGRAM`; `SOCK_SEQPACKET` throws on Windows. A datagram sent to a full receiver gets `ENOBUFS` on the console, waits or gets `EAGAIN` on Linux and is dropped on Windows, and on Windows a datagram `recv` after the peer closed reports `ECONNRESET` instead of the console's `ENOTCONN`, and a stream `send` after the peer closed reports `ECONNABORTED` instead of the console's `EPIPE`. `read` and `write` on a pair end go to the host like on every guest socket. `getpeername` on a pair end succeeds after the peer closed, where the console returns `ENOTCONN`, and `connect`, `bind` and `sendto` with an address on a pair end report an address-family error instead of the console's `EISCONN`. On Windows `poll` on a stream end reports `POLLHUP` without `POLLIN` after the peer's `shutdown(SHUT_WR)` or `close`, where the console reports `POLLIN`, with `POLLHUP` only after `close`
 - [UDP recv/recvfrom](../../../core/libs/prx/libkernel/Socket/src/Udp.cpp) and [sceNetRecv/sceNetRecvfrom](../../../core/libs/prx/libSceNet/Export.cpp) translate Windows WSAEMSGSIZE into the copied byte count for datagram sockets, including MSG_PEEK, and retain the sender address. This follows FreeBSD 11.4 recv(2) and Winsock's documented truncated-datagram behavior; console behavior and existing title impact are unverified.
 - [send, sendto](../../../core/libs/prx/libkernel/Socket/src/Udp.cpp) (libkernel) - send and sendto without an address on an unconnected datagram socket map Windows `WSAENOTCONN` to FreeBSD's `EDESTADDRREQ` (39).
-- [read, write and vector I/O](../../../core/libs/prx/libkernel/File/src/Stdio.cpp) (libkernel) on a guest socket use `recv` and `send` without flags; `sceKernelReadv` and `sceKernelWritev` gather or scatter through one socket operation, preserving stream short reads and datagram boundaries. The positioned `pread`, `pwrite`, `preadv` and `pwritev` forms, and their `sceKernel` forms, return `ESPIPE` for an open guest socket and `EBADF` for a closed one. Guest socket descriptors start at `0x10000000` and are allocated upward, so the descriptor range selects the guest socket table or the host descriptor table. `EPIPE` from a write raises the host's `SIGPIPE` on Linux, which the guest can neither ignore nor suppress: `signal(SIGPIPE, SIG_IGN)` and `sigaction` record the disposition, as they do for every number from 1 to 128, but only the six signals with host equivalents (2, 4, 6, 8, 11 and 15) take effect on the host or are delivered, so the host `SIGPIPE` is not stopped; `SO_NOSIGPIPE` is not an option here, and raises nothing on Windows; a `write` longer than `INT_MAX` bytes is `EMSGSIZE` where the console sends it. AIO on a guest socket still goes to the host, which has no such descriptor
-- [poll](../../../core/libs/prx/libkernel/Socket/src/Udp.cpp) (libkernel) waits on guest sockets and pipes, through `WSAPoll` on Windows and `poll` on Linux; the `pollfd` layout and flag values are FreeBSD's. A pipe follows FreeBSD's `pipe_poll`: the read end is readable when data is buffered, either end reports `POLLHUP` once the other end is closed, with the requested `POLLIN` and `POLLRDNORM` bits and without `POLLOUT`, which `pollscan` clears, and the write end is writable when `PIPE_BUF` (512) bytes are free on Windows, or when the host kernel says so on Linux. `POLLOUT` on a read end throws: FreeBSD opens both ends for reading and writing and reports it writable, and host pipes are one-way. Windows pipes cannot be waited on, so while a pipe is polled `poll` checks it with `NtQueryInformationFile` and waits on the sockets in slices of 1 ms. A closed descriptor below the socket range reports `POLLNVAL`, and any other descriptor there (files, stdio) throws, as do event bits other than `POLLIN`, `POLLPRI`, `POLLOUT`, `POLLRDNORM`, `POLLRDBAND` and `POLLWRBAND` (the `POLLERR`, `POLLHUP` and `POLLNVAL` bits are ignored in `events`), `POLLPRI` on Windows, which `WSAPoll` rejects, and an infinite timeout with no socket or pipe to wait on. A closed socket descriptor reports `POLLNVAL`; the console's limit on the descriptor count is unknown and not checked
-- [Socket error numbers](../../../core/libs/prx/libkernel/Socket/include/SocketError.hpp) (libkernel) - a host socket error becomes the FreeBSD 11 `errno.h` number of the same name; the numbers are not checked on the console. Winsock `WSAESHUTDOWN` becomes `EPIPE`, as a send after `shutdown` does on FreeBSD, and a host error with no FreeBSD socket counterpart becomes `EIO`. A nonblocking `connect` in progress reports `EINPROGRESS` on Linux but `EAGAIN` on Windows (`WSAEWOULDBLOCK`), where FreeBSD reports `EINPROGRESS`. On Windows a refused nonblocking `connect` is never reported (`SO_ERROR` is unsupported), so a repeated one keeps reporting `EALREADY` where FreeBSD reports `ECONNREFUSED`. A receive after `shutdown(SHUT_RD)` reports `EPIPE` on Windows where FreeBSD returns 0
+- [read, write and vector I/O](../../../core/libs/prx/libkernel/File/src/Stdio.cpp) (libkernel) on a guest socket use `recv` and `send` without flags; `sceKernelReadv` and `sceKernelWritev` gather or scatter through one socket operation, preserving stream short reads and datagram boundaries. The positioned `pread`, `pwrite`, `preadv` and `pwritev` forms, and their `sceKernel` forms, return `ESPIPE` for an open guest socket and `EBADF` for a closed one. `EPIPE` from a write raises the host's `SIGPIPE` on Linux, which the guest can neither ignore nor suppress: `signal(SIGPIPE, SIG_IGN)` and `sigaction` record the disposition, as they do for every number from 1 to 128, but only the six signals with host equivalents (2, 4, 6, 8, 11 and 15) take effect on the host or are delivered, so the host `SIGPIPE` is not stopped; `SO_NOSIGPIPE` is not an option here, and raises nothing on Windows; a `write` longer than `INT_MAX` bytes is `EMSGSIZE` where the console sends it. AIO on a guest socket still goes to the host, which has no such descriptor
+- [Socket descriptor numbers](../../../core/libs/prx/libkernel/Socket/src/Udp.cpp) (libkernel, libSceNet) - `socket`, `accept`, `socketpair`, `dup`, `sceNetSocket` and `sceNetAccept` take the lowest free number of the host descriptor table that files use, as FreeBSD 11.4 `fdalloc` takes the lowest free entry of the one process table (`kern_descrip.c`), so every number stays below `FD_SETSIZE` (1024) while fewer than 1024 descriptors are open. The number holds a zero-access `NUL` handle on Windows and a duplicate of the host socket on Linux, and the socket tables map it to the socket. The host table also holds the runtime's own files, so the numbers differ from the console's; the first number `socket` and `sceNetSocket` return on a console and its `getdtablesize` are not measured. Paths that bypass the socket tables see the placeholder: libc `fdopen` on a socket opens it, libkernel `fstat` on a socket throws, and libkernel `close` of a libSceNet socket releases the number but leaves the libSceNet socket open. Palworld (PPSA23126), The Mound (PPSA26223) and Dying Light 2 (PPSA02262) set socket bits in a 1024-bit `fd_set`
+- [poll](../../../core/libs/prx/libkernel/Socket/src/Udp.cpp) (libkernel) waits on guest sockets and pipes, through `WSAPoll` on Windows and `poll` on Linux; the `pollfd` layout and flag values are FreeBSD's. An open descriptor that is neither a guest socket nor a pipe (files, stdio, libSceNet sockets) throws, as do event bits other than `POLLIN`, `POLLPRI`, `POLLOUT`, `POLLRDNORM`, `POLLRDBAND` and `POLLWRBAND` (the `POLLERR`, `POLLHUP` and `POLLNVAL` bits are ignored in `events`), `POLLPRI` on Windows, which `WSAPoll` rejects, and an infinite timeout with no socket to wait on. A closed socket descriptor reports `POLLNVAL`; the console's limit on the descriptor count is unknown and not checked- [Socket error numbers](../../../core/libs/prx/libkernel/Socket/include/SocketError.hpp) (libkernel) - a host socket error becomes the FreeBSD 11 `errno.h` number of the same name; the numbers are not checked on the console. Winsock `WSAESHUTDOWN` becomes `EPIPE`, as a send after `shutdown` does on FreeBSD, and a host error with no FreeBSD socket counterpart becomes `EIO`. A nonblocking `connect` in progress reports `EINPROGRESS` on Linux but `EAGAIN` on Windows (`WSAEWOULDBLOCK`), where FreeBSD reports `EINPROGRESS`. On Windows a refused nonblocking `connect` is never reported (`SO_ERROR` is unsupported), so a repeated one keeps reporting `EALREADY` where FreeBSD reports `ECONNREFUSED`. A receive after `shutdown(SHUT_RD)` reports `EPIPE` on Windows where FreeBSD returns 0
 - [connect to AF_UNSPEC](../../../core/libs/prx/libkernel/Socket/src/Udp.cpp) (libkernel) dissolves a datagram association as FreeBSD 11.4's `udp_disconnect()` does, which resets the local address to the wildcard address and keeps the port. On Linux a socket bound to an explicit port keeps its local address as well (`127.0.0.1:<port>` stays `127.0.0.1:<port>`), because a bound socket cannot be bound again; one bound to port 0 is bound again to the wildcard address with the port it had
 - [msync](../../../core/libs/prx/libkernel/DirectMemory/PosixMemory.cpp) (libkernel) follows FreeBSD 11's `kern_msync` and `vm_map_sync`, not measured on the console: the address is rounded down to the page, a range that wraps is `EINVAL`, as is `MS_ASYNC` with `MS_INVALIDATE`, and a range whose start or any page is not mapped (as `sceKernelVirtualQuery` reports it, reservations included) is `ENOMEM`; a page unmapped from inside a larger mapping still counts as mapped there, since `sceKernelVirtualQuery` keeps reporting the whole mapping. The guest has no file mappings, so a successful call writes nothing back. `MS_INVALIDATE` on a mapped range throws: FreeBSD returns `EBUSY` when the range holds `mlock`ed pages, and locked pages are not tracked
 - [sigtimedwait](../../../core/libs/prx/libkernel/System/src/Signals.cpp) (libkernel) waits on a process-wide pending set instead of throwing: a signal raised while blocked stays pending and is taken by `sigwait`, `sigwaitinfo` or `sigtimedwait`, delivered to the handler when `_sigprocmask` unblocks it, or delivered by `pause`. The set covers all 128 signals and the lowest number that is pending and in the set is selected (FreeBSD specifies the lowest number only among real-time signals). Selection, `EAGAIN` on timeout, `EINVAL` for a `tv_nsec` outside 0 to 1000000000 while nothing is pending and `NULL` timeout blocking indefinitely follow FreeBSD's [sigtimedwait(2)](https://man.freebsd.org/cgi/man.cgi?query=sigtimedwait). `sigwait` returns 0 with the number in its output, as POSIX specifies, and `sigwaitinfo` and `sigtimedwait` return the number, as FreeBSD does. The guest `siginfo_t` follows FreeBSD 11's `sys/sys/siginfo.h`: 80 bytes, `si_signo` at 0, `si_code` at 8, `si_pid` at 12, `si_uid` at 16, `si_addr` at 24, `si_value` at 32 and `si_band` at 40; only `si_signo`, `si_code` (`SI_USER`) and `si_pid` (the guest pid) are written, `si_uid` stays 0 because no uid is modelled, and the console's layout is not verified. PPSA85300 imports `sigtimedwait` and fails to load without it; its only call site is VLC's `vlc_writev` ([filesystem.c](https://github.com/videolan/vlc/blob/6de05adcbaf2e8b85fe86aad4169393098628119/src/posix/filesystem.c#L243-L278)), which polls with a zero timeout to drain a `SIGPIPE` only after `writev` fails with `EPIPE`. The waits are not cancellation points and an unblocked caught signal does not interrupt them with `EINTR`, where FreeBSD's `sigwaitinfo` and `sigtimedwait` may return it. `SIGPIPE` has no host equivalent and is never raised by a host write here (see `read, write and vector I/O`), so VLC's drain finds nothing