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
On the first real machine with a discrete card (an RTX 3060, 800x600 from
the UEFI GOP) the console was slow enough to photograph mid-scroll, and the
boot died on CPU 1's "cpu1: starting": CPU 0 spun 200M times on the console
lock while CPU 1 held it, scrolling, and called it a deadlock.
The framebuffer is device memory in the uncached 3-4 GB page of the direct
map. QEMU's stdvga is RAM underneath, so nothing showed there; on a card,
gfx_scroll_up's memmove read the whole screen back across the bus one byte
at a time, and every anti-aliased glyph read back each pixel it blended.
So the console now draws into a copy of the screen in RAM (vmap_alloc: kalloc
pages behind a page table of their own, since nothing needs it contiguous),
and gfx_flush() copies the changed rectangle onto the card through an
ioremap_wc() mapping -- PAT entry 4 set to write-combining on every CPU.
Flushes happen where drawing ends: a message, a terminal write, an echo, a
terminal switch. Scrolling moves eight bytes at a time instead of one.
/dev/fb0 reads and writes the card itself, as before. The early console's
fb_info now carries the physical address it always should have.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4
