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docs: architecture describes what is built now

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kernel (threads, demand paging, TLB shootdowns, dynamic linking, RAM direct map), syscalls, filesystem (/proc, /sys,
/dev), terminals (12, VT handshake, ptys), networking (r8169 through LDLS), LDLS (module sets; Linux code may ship),
devices (what stays in the kernel; hybrid.md's lasting content), boot (the loader's placement of the kernel),
graphics (fbdev, GMMOS, QR 1-40), audio (ALSA over OSS), debugging, usb. New: packages.md (the apk root) and
desktop.md (Xorg on the framebuffer).

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EVRhxi9zpdW2uDUN4FVcao
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Nexoniarz 2026-10-26 07:57:25 +01:00
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41
docs/architecture/syscalls.md
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@ -74,19 +74,19 @@ machine off, and Linux number 48 is the socket call. Two syscalls cannot share a
## What is implemented
Roughly 190 native numbers covering:
About 215 native numbers (193 of them with a Linux number) covering:
| Area | |
|---|---|
| Process | fork, exec, exit, wait/waitpid/wait4/waitid, clone, kill, sessions, process groups |
| Process | fork, exec, exit, exit_group, wait/waitpid/wait4/waitid, clone (processes and threads), futex, kill, tgkill, sessions, process groups |
| 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 |
| Memory | mmap, munmap, mremap, mprotect, brk/sbrk, madvise, System V shared memory, memfd |
| 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 (create, create1, ctl, wait, pwait), ioctl, fcntl |
| Sockets | socket, bind, listen, accept, connect, sendto, recvfrom, socketpair, setsockopt, getsockopt |
| Sockets | socket, bind, listen, accept/accept4, connect, sendto/recvfrom, sendmsg/recvmsg, socketpair, getsockname/getpeername, setsockopt/getsockopt, over AF_UNIX, AF_INET and AF_NETLINK |
| Signals | rt_sigaction, rt_sigreturn, rt_sigsuspend, rt_sigpending, rt_sigtimedwait, sigaltstack |
| Time | gettimeofday, clock_gettime, clock_getres, nanosleep, clock_nanosleep, alarm, timers |
| Notification | eventfd, eventfd2, timerfd_create/settime/gettime, signalfd, signalfd4 -- see `kernel/sys/sys_event.c` |
| Notification | eventfd, timerfd, signalfd, inotify -- see `kernel/sys/sys_event.c` |
### Argument fetching
@ -113,20 +113,19 @@ field by field, each through its own translation, or use `copyin`/`copyout`.
## What it does not do
- **`sendmsg`/`recvmsg` carry `SCM_RIGHTS` and nothing else.**
`SCM_CREDENTIALS` is refused rather than ignored. See
[networking.md](networking.md#descriptor-passing).
- **No `memfd_create`.**
- **No `getsockname` or `getpeername`**, and `accept()` does not report an
AF_INET peer's address.
- **`setsockopt` handles six options** and answers `ENOPROTOOPT` for everything
else. `SO_RCVTIMEO`/`SO_SNDTIMEO` are among the refused.
- **`clone` does not share an address space**, so it is `fork` with extra steps.
- **`sendmsg`/`recvmsg` carry `SCM_RIGHTS` and `SCM_CREDENTIALS`**, and nothing
else. Credentials are delivered only to a socket that asked with `SO_PASSCRED`
(D-Bus and WebKit do); other control messages are refused rather than ignored.
See [networking.md](networking.md#descriptor-passing).
- **`setsockopt` applies the options it understands** — they reach lwIP's pcb or
the Unix socket — and answers `ENOPROTOOPT` for everything else, never a
success that did nothing. The options that take a `struct` (`SO_RCVTIMEO`,
`SO_SNDTIMEO`) are among the refused.
- **`sched_setaffinity` is accepted and ignored.**
- **`getrusage` does not distinguish `RUSAGE_CHILDREN`** from `RUSAGE_SELF`, and
fills in only the calling process's own tick count.
- **The ABI is chosen by link address.** It works, and it is a heuristic rather
than a fact about the binary.
- **`/proc/<pid>/exe` is a regular file, not a symlink**, so `readlink()` on it
fails and `ps -o comm` prints `[init]` rather than `init`. Default `ps` and
`top` output is unaffected.
- **The ABI is chosen by link address.** Anything linked at `0x100000` or above
— musl's programs, and every dynamically linked one, whose interpreter is
placed at `0x40000000` — gets the Linux map; a first-party program linked at
`0x4000` gets the native one. It works, and it is a heuristic rather than a
fact about the binary.
- **`ptrace` and `seccomp`** are not implemented; a program that needs them
gets `ENOSYS`.