- SIGSTOP/SIGTSTP/SIGTTIN/SIGTTOU stop, SIGCONT resumes; the parent gets
SIGCHLD and wait4 reports WUNTRACED/WCONTINUED; ps shows T. Ctrl-Z works,
and mc no longer hangs waiting for its subshell to stop.
- Blocking reads (console, pty, pipe) and sleeps take a pending stop and
carry on after SIGCONT; a caught signal without SA_RESTART ends them
with EINTR.
- nanosleep reads tv_nsec (sleep 0.5 used to return at once), writes the
remainder, and clock_nanosleep understands TIMER_ABSTIME.
- rt_sigaction uses the k_sigaction layout for Linux-ABI processes: the old
action's restorer was written 112 bytes past the caller's struct. Flags
are kept; SIGKILL and SIGSTOP cannot be caught.
- F1..F12 reach programs, as the Linux console sends them (PS/2, USB, I2C).
- TIOCLINUX subcode 6 answers "no modifiers" instead of echoing the 6 back.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4
- /dev/ptmx and /dev/pts/N: Unix98 pairs with a full line discipline,
window sizes, job control and hangup (kernel/dev/pty.c).
- The console speaks scroll regions, insert/delete line, SU/SD, RI/IND/NEL,
DECSC/DECRC; swallows charset designations and private CSI sequences;
and LF only returns the carriage under ONLCR.
- setsid() drops the controlling terminal, so a pane's pty becomes its ctty.
- pipe2() honours O_NONBLOCK and O_CLOEXEC (libevent's signal pipe).
- File modes are stored and enforced: chmod, fchmod(at), umask, creation
modes; /tmp is 1777.
- /proc/stat has real user/system/idle; /proc/<pid>/task; kthread flag.
- SO_PEERCRED, IOV_MAX 1024.
- /proc/strace: name a program and its syscalls go to the kernel log.
- World gains htop, btop, tmux, mc, ncdu, fastfetch, games, X toys, NetSurf.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4
The second micro driver: i2c_hid.c with everything but reading a
keyboard's input reports taken out. No ACPI -- AML cannot run on a dead
kernel -- so the live driver hands over what it found at boot
(i2c_hid_keyboards): the DesignWare controller, the address, the report
size, the AMD GPIO pin if there is one, and the parsed report descriptor.
No power commands, no reset, a read-only transfer.
usb_hid.c's report-protocol rewrite is split out as hid_boot_report(),
which does nothing but rewrite, and kernel/gmmos/hidkeys.c turns boot
reports into keys for this and the USB micro drivers to come.
GMMOS now probes every micro driver and polls all that answer.
Not run: QEMU has no DesignWare I2C, and the laptops at hand have PS/2
keyboards.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4
The touchpad driver crashed the ASUS TUF A15 at boot. Its thread runs the
firmware's AML -- _DSM, _PS0, _CRS -- through uACPI at -O0, on an 8 KB
kernel stack, and kernel stacks are one array: running off the end lands
in the next thread's stack, and the machine dies a moment later in some
other code. The thread now runs on a 64 KB stack of its own, through
SCFF's call_on_stack().
And a crashed laptop sat with its fans up until somebody held the power
button, since the other processors keep running. On an ordinary boot the
PSOGM now says it will power off, and does, after three minutes: SLP_TYP
from \_S5, read at boot, written straight to PM1 control with no AML, which
could sleep or wait on a lock a dead processor holds. A verbose boot keeps
the screen up for ever.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4
A laptop's touchpad is on the chipset's I2C bus, found only through ACPI
(PNP0C50 / ACPI0C50), and SchOS had no I2C at all, so the touchpad of
every recent laptop did nothing.
kernel/acpi/i2c_hid.c drives the DesignWare I2C controller every x86
chipset uses (AMDI0010 on Ryzen) by polling, speaks HID over I2C to the
device the _DSM points at, and feeds the reports through the USB HID
parser. On AMD the interrupt pin's level is read every tick, so a report
is read exactly when one is waiting; elsewhere the input register is polled.
The touchpad is driven in mouse mode, which it starts in after a reset:
motion, clicks and taps become /dev/input/event1 like any mouse. The HID
parser now prefers a descriptor's relative pointer over an absolute one
for this, and takes descriptors from transports other than USB.
Untested on hardware: QEMU emulates no I2C touchpad.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4
Xorg on a framebuffer -- the fbdev video driver, the evdev input driver,
libpciaccess -- asks the kernel a fixed set of questions before it draws
anything, and gives up on the first wrong answer. These are those
answers.
evdev: EVIOCGVERSION, GID, GNAME, GPHYS, GUNIQ, GPROP, GBIT, GKEY, GABS,
GREP and the accepted setters. Xorg and libinput decide what a device
*is* from the capability bitmaps; /dev/input/eventN answered only
EVIOCGRAB, which reads as no device at all. Each device's bitmaps are
its defaults plus whatever it has reported, so a USB tablet makes the
pointer absolute.
fbdev: FBIOPUT_VSCREENINFO succeeds for the mode already set, as on
Linux -- the fbdev driver sets it every time it starts -- and still
refuses any other. FBIOPAN_DISPLAY to the origin; FBIOBLANK.
The console: KDSETMODE(KD_GRAPHICS) stops it drawing on a terminal,
KDSKBMODE(K_OFF) stops keys reaching its tty, and VT_PROCESS now does
the switch handshake: leaving the terminal sends relsig and waits for
VT_RELDISP, arriving sends acqsig. A terminal whose owner has died goes
back to the kernel whole, so a crashed X cannot leave the console dead.
/sys: boot_vga, a writable enable, and graphics/fb0 under the display
device, which is how the fbdev driver pairs a card with /dev/fb0.
ports/linux-headers: <linux/*.h> into musl's prefix, from sabotage-
linux's kernel-headers 4.19.88-2. Its checksum is recorded from the
first download; upstream publishes none.
cmd/xready makes each call and checks the answer, including the switch
handshake on tty2 and an owner that dies holding it.
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
