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Nexoniarz 182cc76588 gfx: the second head shows the boot, not just what comes after it 
Two things, both asked for.

**The crash report no longer says which monitors it reached.** "The report is
on the virtio-gpu display too" was a line about the crash screen printed on the
crash screen. The report says what happened and where to read it again; that is
not part of it.

**And the second head now shows the F8 menu and the boot.** It used to be black
until vgpud started several seconds into userspace -- through the splash,
through the menu, through every boot message -- which from the outside is
indistinguishable from a display that does not work. Three stages now cover the
whole boot and hand over to each other without coordinating:

*The loader.* LocateProtocol() answers with the first GOP and offers no way to
ask for the rest, so the rest are found by handle and fed the primary's
framebuffer as a Blt source at the points where a screen is finished: the menu,
the resolution chooser, system information, the splash, each segment of the
kernel load. Blt rather than a second framebuffer to draw into, because a
virtio GOP does not have one -- the same fact that made a virtio-only machine
reboot-loop two commits ago.

*The kernel.* gfx remembers which rows were drawn, as one span rather than a
list of rectangles, because console output is lines and a span is what lines
make. display_mirror_console() copies that span across: a line of boot text is
one cell-row transfer, not a screen. Primed once after pci_init(), because a
display that has just appeared has a black scanout and the console it should be
showing was drawn by the loader into a framebuffer it knows nothing about.

*Then vgpud*, from the same console framebuffer, unchanged.

**Two bugs found building it, both worth the retelling.**

The mirror ran per character from inside vt_feed -- which is inside the console
lock -- and vga_disp_acquire() announces its back buffer with a cprintf. A CPU
taking a lock it already holds, with a call chain that said exactly that. It
runs at the end of consolewrite() and cprintf() now, outside the lock, which is
also the better batching: one transfer per write instead of one per character.

And "is this the console's own screen" was asked of the pointer acquire()
returned. vga_fb hands back a back buffer it copies onto the console's
framebuffer afterwards, so on a one-screen machine the answer was "a different
screen" -- and the console was mirrored onto itself through two megabytes of
intermediate, allocated for the purpose. display_ops grew scanout_phys, which
is a fact about the hardware rather than a policy a driver can get subtly
wrong, and it is asked first: it has no side effects and acquire() has two.

Verified with two heads under QEMU, screendumping the virtio head every 400 ms
from power-on: splash, splash, splash, then the console, and it stays. The F8
menu appears on it; choosing 1024x768 there brings both heads up at 1024x768
byte-identical. A panic still reaches both. Both supported configurations: one
boot each, no traps, no panics, socktest and memfdtest green.

One gap remains and is documented rather than hidden: while the kernel's driver
resets the device during probe, QEMU shows "Display output is not active" for a
fraction of a second. A device being taken over has no scanout until the new
driver sets one.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
2026-09-22 21:47:35 +02:00

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SchOS
Copyright 2026 Nexoniarz
This product includes software developed as part of the SchOS project,
licensed under the Apache License, Version 2.0. See LICENSE.
================================================================================
Third-party software
================================================================================
SchOS incorporates and redistributes software written by others. Their
licences apply to their code and are NOT superseded by the SchOS licence.
A built SchOS image contains binaries derived from all of the following.
--------------------------------------------------------------------------------
xv6-x86_64 / xv6 MIT License
--------------------------------------------------------------------------------
Copyright (c) 2006-2019 Frans Kaashoek, Robert Morris, Russ Cox,
Massachusetts Institute of Technology CSAIL
The SchIFT kernel is a derivative work of xv6. Substantial portions of
kernel/ -- notably the process, trap, virtual memory, buffer cache and v1
filesystem code -- descend from it, however heavily rewritten. The MIT licence
requires that this notice be preserved in all copies; see LICENSE.MIT.
--------------------------------------------------------------------------------
musl libc 1.2.5 MIT License
--------------------------------------------------------------------------------
Copyright (c) 2005-2020 Rich Felker and contributors
Built from ports/musl. Provides the C library every userland program links
against. See the extracted source's COPYRIGHT file for the full contributor
list, which the MIT terms require be carried along with binaries.
--------------------------------------------------------------------------------
toybox 0.8.12 Zero-Clause BSD (0BSD)
--------------------------------------------------------------------------------
Copyright (c) 2006-2024 Rob Landley and contributors
Built from ports/toybox. Supplies the standard command set in /bin -- 268
applets, which is defconfig's 236 plus a curated set from toys/pending/ (awk,
bc, diff and the rest); see ports/toybox/Makefile. 0BSD imposes no attribution
requirement at all; this entry is courtesy, not obligation.
--------------------------------------------------------------------------------
kilo (commit 323d93b) BSD 2-Clause
--------------------------------------------------------------------------------
Copyright (c) 2016 Salvatore Sanfilippo <antirez@gmail.com>
Built from ports/kilo. Supplies /bin/kilo and /bin/edit, the text editor. The
BSD 2-Clause terms require the copyright notice and disclaimer be retained in
binary distributions; the full text is installed at
/usr/share/licenses/kilo/LICENSE in every image.
--------------------------------------------------------------------------------
mksh R59c MirOS Licence
--------------------------------------------------------------------------------
Copyright (c) 2002-2023 Thorsten Glaser and contributors
Portions derived from the Public Domain Korn Shell (pdksh)
Built from ports/mksh. Supplies /bin/sh. The MirOS Licence is permissive and
requires the copyright notice be retained.
--------------------------------------------------------------------------------
zsh 5.9 MIT-like
--------------------------------------------------------------------------------
Copyright (c) 1992-2017 Paul Falstad, Richard Coleman, Zoltan Hidvegi,
Andrew Main, Peter Stephenson, Sven Wischnowsky, and others
Built from ports/zsh. Installed as /bin/zsh and used as the interactive shell;
/bin/sh remains mksh.
zsh's LICENCE notes that a few shell functions are licensed under the GNU
General Public Licence and states that, since no core function is affected,
those files may simply be omitted. They are. ports/zsh/Makefile removes four
files after extraction -- completions for darcs, qdbus, osc and zypper -- and
refuses to install if any of them is still present. No GPL-licensed file is
shipped in a SchOS image.
--------------------------------------------------------------------------------
ncurses 6.4 MIT License
--------------------------------------------------------------------------------
Copyright 2018-2022 Thomas E. Dickey
Copyright 1998-2018 Free Software Foundation, Inc.
Built from ports/ncurses. Linked into zsh so that its line editor can drive a
terminal, and into sysroot/bin/tinfotest. Built with --disable-database and
compiled-in fallbacks, so no terminfo files are installed.
--------------------------------------------------------------------------------
lwIP 2.2.0 BSD 3-Clause
--------------------------------------------------------------------------------
Copyright (c) 2001, 2002 Swedish Institute of Computer Science
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
1. Redistributions of source code must retain the above copyright notice,
this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice,
this list of conditions and the following disclaimer in the documentation
and/or other materials provided with the distribution.
3. The name of the author may not be used to endorse or promote products
derived from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
Fetched by ports/lwip and compiled into the kernel -- it is the TCP/IP stack,
not a userland library, so it is present in every built kernel image rather
than in a binary under /bin. The port layer written for SchOS
(kernel/net/lwip/) is Apache-2.0 and is not part of lwIP; lwIP's own sources
are unmodified. Clause 3 is a no-endorsement term, not the four-clause
advertising requirement, so it combines with Apache-2.0 without difficulty.
--------------------------------------------------------------------------------
Intel 8254x device identifiers BSD 3-Clause
--------------------------------------------------------------------------------
Copyright (c) 2001-2020, Intel Corporation
All rights reserved.
The PCI device IDs in include/e1000.h are transcribed from FreeBSD's
sys/dev/e1000/e1000_hw.h, which carries the Intel 3-clause BSD licence above
(verified: no advertising clause). Only the identifier constants are used --
data, not implementation. kernel/drivers/net/e1000/e1000.c is written from
Intel's public manual 317453 and contains no FreeBSD or Intel driver code.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the conditions of the 3-clause BSD
licence are met, including retention of this notice and the disclaimer, and
that neither the name of Intel Corporation nor the names of its contributors
are used to endorse or promote products derived from this software without
specific prior written permission.
--------------------------------------------------------------------------------
usb.ids -- USB vendor and product database BSD 3-Clause (dual-licensed)
--------------------------------------------------------------------------------
Maintained by Stephen J. Gowdy <linux.usb.ids@gmail.com>
http://www.linux-usb.org/usb.ids
Distributed by its maintainer under the terms of *either* the GNU General
Public License version 2 or later, *or* the 3-clause BSD Licence. SchOS takes
the BSD option; the GPL option is not exercised and could not be, since
Apache-2.0 and GPL-2.0-only cannot be combined (see docs/licensing.md section
2).
Shipped verbatim as /usr/share/usb.ids. Cached in dist/ and refreshed with
`make usb-ids`, never automatically -- the version and date are in the file's
own header, so what shipped is always knowable.
--------------------------------------------------------------------------------
Roboto Apache-2.0
--------------------------------------------------------------------------------
Copyright the Roboto Project Authors (https://github.com/googlefonts/roboto)
Shipped as /usr/share/fonts/Roboto-Regular.ttf, from ports/Roboto. Licensed
under Apache-2.0 -- the same licence as SchOS itself, so it carries no
obligation beyond this notice. Intended for the desktop, window manager and
compositor.
--------------------------------------------------------------------------------
JetBrains Mono SIL OFL 1.1
--------------------------------------------------------------------------------
Copyright 2020 The JetBrains Mono Project Authors
(https://github.com/JetBrains/JetBrainsMono)
Shipped as /usr/share/fonts/JetBrainsMono-Regular.ttf, from ports/JetBrains_Mono
(full licence text at ports/JetBrains_Mono/OFL.txt). Intended for the terminal
and TTY.
Under the SIL Open Font License 1.1 the font remains under OFL even inside this
Apache-2.0 system -- that does not reach any other part of SchOS -- and it may
not be sold on its own. Bundling it with an operating system is expressly
permitted. JetBrains Mono declares no Reserved Font Name, so a modified version
(a pre-rasterised bitmap, for instance) may keep the name.
Distinct from xv6 itself (LICENSE.MIT), which this project in turn derives from.
================================================================================
The build downloads upstream tarballs into dist/ and applies the patches in
ports/<name>/patches/. Nothing in ports/ is SchOS code; do not add first-party
work there. See docs/layout.md.
Licence questions -- what may be copied in, what may never be, and how to check
a NetBSD file's clause before using it -- are worked through in
docs/licensing.md.
fastfetch MIT
https://github.com/fastfetch-cli/fastfetch
Copyright (c) 2022 Linus Dierheimer and contributors
Built from source by ports/fastfetch and installed as /bin/fastfetch.
Unpatched: see the note at the top of that Makefile about why what it
cannot detect becomes work in the kernel rather than a patch here.
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