alarm() and setitimer() stored a countdown nothing counted down, so no
timer has ever fired; setitimer and getitimer were also registered with
no Linux number. alarmd now posts SIGALRM on the tick, while any process
has a timer armed. busybox's ping, /bin/ping on the Alpine root, sends
every request after the first from its SIGALRM handler.
It also opens SOCK_RAW, which was EPROTOTYPE. A raw ICMP socket is now a
ping socket whose reads start at the IP header. And a blocked socket
call gives up for a signal with a handler, not only for a kill: the
alarm woke recvfrom, and the wait put it straight back to sleep.
For Xorg: AF_UNIX abstract names, which read as the empty path and so as
EADDRINUSE ("server already running"); and getsockname and getpeername,
which did not exist, so libxcb sent no cookie and the server refused
every client.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4
Found by running Alpine's apk on SchOS, one failure at a time:
- chroot(2) was a stub returning EPERM. Each process now has a root:
where an absolute path starts and where .. stops. Mounts remember
whose root they were made under, and a walk leaves a mount by the way
it came in, so one filesystem can be mounted twice.
- devtmpfs and proc mounted only on /dev and /proc, whatever the target;
a chroot got "already mounted".
- mmap never reused freed address space, so musl's malloc used up the
256 mapping records while 780 MB were free. A mergeable mapping now
goes straight after an anonymous one whose end has room.
- unlinkat returned -1 (EPERM) where apk expects ENOENT, and renameat
was an old copy of rename: no replacing the target, and v1 dirents
written into SchFS. Both now share rename's implementation.
- execve runs #! scripts, and says ENOEXEC for what it cannot run.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4
Sixty-five headers sat side by side in include/, so `#include "irq.h"`
said nothing about where irq.h was or what it belonged to, and errno.h,
stat.h and fcntl.h at the top shadowed the system's for any host tool
built with -I./include. They are in folders now -- arch/ core/ fs/
dev/ gfx/ net/ uapi/ (and ldls/ for the Linux driver layer) -- and
every include names the folder, as Linux's do: "core/proc.h".
Done mechanically and checked the hard way: the kernel built from this
tree disassembles identically to the one built from the tree before
it. The full image boots, and userland is the same set of programs.
Paths in docs and comments follow; docs/guides/layout.md has a table
of what is where, and tools/fix-includes.py rewrites old-style
includes from the folders in the tree, for code written before this.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4
