epoll, eventfd, timerfd, signalfd

The set libwayland's event loop is made of, in kernel/sys/sys_event.c:
four kinds of descriptor with no inode, FD_EVENT, that read() drains
and poll() reports on. They were table entries returning ENOSYS that
read as done.

epoll registers (descriptor, file) pairs, so a closed descriptor
leaves the set; level- and edge-triggered, EPOLLONESHOT. Waiting is
poll()'s, a tick at a time. The old eventfd and signalfd numbers (284,
282) were aliased to the new calls and read flags from a garbage
register; they are their own entries now, with epoll_create and
epoll_pwait.

cmd/evtest checks each, then all four in one set. The plans are
brought up to date: everything Wayland was waiting on is built except
setsockopt.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4

docs/architecture/syscalls.md

@@ -82,11 +82,11 @@ Roughly 190 native numbers covering:
 | Identity | the full real/effective/saved set for both uid and gid, groups, umask |
 | Memory | mmap, munmap, mprotect, brk/sbrk, madvise, System V shared memory |
 | Filesystem | the ordinary set, the whole `*at()` family, statfs, xattr, mount/umount2 |
-| I/O | read/write, readv/writev, pread/pwrite, sendfile, poll/select/ppoll/pselect6, epoll, ioctl, fcntl |
+| I/O | read/write, readv/writev, pread/pwrite, sendfile, poll/select/ppoll/pselect6, epoll (create, create1, ctl, wait, pwait), ioctl, fcntl |
 | Sockets | socket, bind, listen, accept, connect, sendto, recvfrom, socketpair, setsockopt, getsockopt |
 | Signals | rt_sigaction, rt_sigreturn, rt_sigsuspend, rt_sigpending, rt_sigtimedwait, sigaltstack |
 | Time | gettimeofday, clock_gettime, clock_getres, nanosleep, clock_nanosleep, alarm, timers |
-| Notification | eventfd2, timerfd_create/settime/gettime, signalfd4 |
+| Notification | eventfd, eventfd2, timerfd_create/settime/gettime, signalfd, signalfd4 -- see `kernel/sys/sys_event.c` |
 
 ### Argument fetching
 

docs/plan/1.0.md

@@ -512,7 +512,7 @@ attention. Nothing here is cancelled.
 | | Why it waits |
 |---|---|
 | **The rest of the hybrid kernel** ([hybrid.md](hybrid.md)) | Still not a completeness requirement — but the mechanisms and the first eviction happened early, because the alternative to a driver compatibility layer is writing a driver for every device that exists, and that is not a plan. What is deferred is the foreign driver host, not the interface it needs. |
-| **Dynamic linking, Mesa, SDL3** | Everything at 1.0 is statically linked. This is the single biggest post-1.0 unlock and it is a whole project. |
+| **Mesa, SDL3** | The kernel and musl do dynamic linking now (`cmd/dynhello`), but every shipped program is still static. Mesa is the single biggest post-1.0 unlock and it is a whole project. |
 | **A page cache** | `memfd` covers the desktop's needs. General writable `MAP_SHARED` of a file is a real project with no 1.0 consumer. |
 | **`.sip` and the installer** | 1.0 installs by writing a USB stick. That is how most systems start and it is honest. |
 | **SchFS snapshots, FUSE, Linux module, sparse files, online fsck** | The format version (Gate 0) is the prerequisite for all of them, and it is the only part on a clock. |

docs/plan/foundations.md

@@ -37,10 +37,10 @@ same lie in a new place.
 
 ---
 
-## The five items
+## The six items
 
 In dependency order. The first three are what Wayland cannot start without.
-Item 1 is built; items 2 and 3 are what a buffer still cannot cross on.
+All but item 4 are built.
 
 ### 1. `sendmsg` / `recvmsg` with `SCM_RIGHTS` — **done**
 
@@ -128,13 +128,41 @@ strength of the lie.
 Small, and grouped here because it is in the same file as item 3 and will be
 found by the same testing.
 
-### 5. Dynamic linking
+### 5. Dynamic linking — **done**
 
-`PT_INTERP` and `ET_DYN` in `kernel/fs/exec.c`.
+`PT_INTERP` and `ET_DYN` in `kernel/fs/exec.c`. A program that names an
+interpreter gets it loaded at the bottom of the mmap area and started instead,
+with `AT_PHDR`, `AT_PHENT`, `AT_PHNUM`, `AT_BASE` and `AT_ENTRY` to find the
+program by; a PIE program is placed where a fixed one would be. The interpreter
+is musl's own: `ports/musl` now builds `libc.so` as well, shipped as
+`/lib/ld-musl-x86_64.so.1`, which is libc and loader in one file.
 
-**Deferrable, and deferred.** Static binaries are enough to reach a working
-desktop with software rendering. This becomes necessary when Mesa does — EGL
-means `dlopen` means a loader — and that is a separate decision made later.
+The kernel half that was missing besides `exec` was `mmap(MAP_FIXED)` of a
+file. It handed back zeroed pages whatever the descriptor said, and kept no
+record of them for `fork` — and a dynamic linker maps every library segment
+after the first exactly that way.
+
+Every port still links `-static`, on purpose: this makes the other kind
+possible, it does not convert anything. `cmd/dynhello` is the test — a
+program against `libc.so` and a library of its own, checking TLS, the heap and
+a forked child that still has its libraries.
+
+`mprotect` is accepted and not enforced, so RELRO is not read-only yet.
+
+### 6. The event descriptors — **done**
+
+`epoll`, `eventfd`, `timerfd` and `signalfd`, in `kernel/sys/sys_event.c`.
+libwayland's event loop is all four in one epoll set, which is why they arrive
+together; not in the original list because they were stubs that looked like
+syscalls, returning `ENOSYS` from `table.inc` entries that read as done.
+
+They wait the way `poll()` does, a tick at a time, so the latency is 10 ms.
+`cmd/evtest` checks each one, then all four in one set, level- and
+edge-triggered.
+
+Building it found a signal bug: a default-fatal signal killed on arrival even
+when it was blocked. A blocked signal now stays pending, which is the contract
+`signalfd` is built on.
 
 ---
 

docs/plan/wayland.md

@@ -3,9 +3,10 @@
 Schcom survives and changes its wire format. SchWM and SchDE are deleted. What
 follows is why that is not a retreat, and what it costs.
 
-Blocked on [foundations.md](foundations.md), items 1–4. **Item 1 is built** —
-descriptor passing, without which no Wayland client can hand over a buffer. Item
-2, a shareable memory object, is the next thing it stops at.
+Blocked on [foundations.md](foundations.md). Everything there is built except
+item 4, `setsockopt` that does not lie: descriptor passing, shareable memory,
+sockets in the filesystem, dynamic linking, and the epoll/eventfd/timerfd/
+signalfd set libwayland's event loop is made of.
 
 ---
 
@@ -106,9 +107,10 @@ through `display_ops`, which already exists.
 ### Software rendering first, and probably for a long time
 
 `pixman` for composition, `wl_shm` for buffers. Mesa means EGL means `dlopen`
-means a dynamic loader, and that is a large kernel project that does not have to
-be on this path. Static binaries are enough to reach a working desktop; keep it
-that way until something concrete demands otherwise.
+means a dynamic loader -- which now exists (see [foundations.md](foundations.md)
+item 5), so it is no longer what stands in the way of Mesa; a GPU driver is.
+Static binaries are still enough to reach a working desktop, and the desktop's
+own programs can stay static until something concrete demands otherwise.
 
 ### One sharp edge
 
@@ -160,8 +162,8 @@ something proves nothing.
 
 ## What it will still not do
 
-- **No hardware acceleration.** Software rendering only, until dynamic linking
-  and Mesa, neither of which is on this plan.
+- **No hardware acceleration.** Software rendering only, until Mesa, which is
+  not on this plan. Dynamic linking, which it also needs, is in.
 - **No XWayland**, so no X11 clients, ever, unless someone ports it.
 - **No mode setting.** Resolution stays whatever the loader asked for — see
   [hybrid.md](hybrid.md), where the GPU driver's eviction is also where a modeset