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
schdbgd ships Disabled, and its manifest explains why: a debugger that can read
the process table should not run on a machine whose owner never asked for one.
That default is right and has one bad consequence -- **the machines that most
need debugging are the ones you cannot get a shell on to enable it.** A laptop
with no serial port that stops before it can draw has nowhere to say why, and
`schinitd enable` needs a prompt that does not exist.
So `make DEBUG=1` adds a sixth entry to the F8 menu. Picking it toggles;
booting carries the choice through SCHBOOT_DEBUG_FLAG; the kernel publishes
/proc/bootdebug; schinitd starts the one job that flag may un-disable, with
the manifest's Args now naming 0.0.0.0 -- a debugger reachable only from the
machine being debugged is no use when that machine is the one that will not
talk to you.
Four decisions, since this is a network-reachable debugger:
compiled out, not hidden A release build cannot set the flag because the
code that would set it is not in the binary. A
menu item that is present and refuses is an
invitation to make it not refuse.
consent at the machine Somebody standing at the keyboard during boot is
the strongest consent this system can ask for and
the weakest one that is any use on hardware that
will not boot.
one job, named in schinitd Not a manifest key like EnableIfDebug: the general
version of "the boot menu starts things that ship
off" is worse than the specific one, and this way
what the flag can start is one readable line.
the kernel only publishes Nothing in the kernel behaves differently, so a
debug kernel and a release kernel are the same
kernel and a bug cannot be the flag's fault.
/proc/bootdebug is its own file rather than a second line in /proc/bootmode,
because bootmode's whole promise is that reading it is a string compare and
not a parser.
**Also: `tone` stopped lying.** On a machine with no sound card it reported
"the device will not take 16-bit samples", which sends you looking at the
format code instead of at the empty PCI slot -- /dev/dsp exists whether or not
hardware is behind it, and the ioctl is where the absence shows up. ENODEV is
now told apart from a format refusal.
Verified end to end: F8 -> item 6 -> boot -> schinitd says it is starting
schdbgd -> a client outside the VM connected to the forwarded port and ran
`dma`, getting the real arena dump back. The release build has no such entry
in the binary at all, and boots clean.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
schdbgd bridges TCP to the debugger, which is the one way in that does not
need you to be sitting at the machine. It is a bridge and nothing else: a line
in becomes a line written to /dev/dbgro and the answer comes back, so `nc` is a
complete client and there is no clever client to be broken on the day you need
this.
# schdbgd &
schdbgd: debugger on port 4444, loopback only
$ nc 127.0.0.1 4444
dma
arena 0xffff80003da41000-0xffff80003ea41000 16384 KB total, ...
A kernel debugger plus a TCP socket is a remote root hole, so three things were
decided rather than discovered:
- It does not start by itself. schdbgd.job ships Disabled. SchOS has no
kernel command line, so the boot flag the plan asked for is the job
manifest, which is the same thing in this system's own idiom.
- It binds loopback; -a names an address and says so in a paragraph.
- It cannot reach a view that changes state, enforced in the kernel.
That last one is /dev/dbgro: /dev/dbg on minor 1. The minor is the one piece of
per-open state a character device already sees, so which node you opened is the
permission -- nothing to latch, nothing to remember between the write and the
read, no way across. Which views are refused comes from dbg_register_rw() on
the registration itself, because a central list of dangerous views goes stale
in the direction where a new view is quietly treated as safe. Today that is
`watch <addr>`; `watch` with no argument is still the listing and still
answered.
Also: socket() now accepts IPPROTO_TCP with SOCK_STREAM and IPPROTO_UDP with
SOCK_DGRAM. They name the default rather than departing from it, and toybox's
nc writes them out -- so TCP was "Protocol not supported" on a system whose
whole network is TCP.
docs/plan/debugger.md retires into docs/architecture/debugging.md; 16 files
repointed. Every plan in docs/plan/ that was open is now closed, so the next
thing is Gate 0 itself: the survey, with the instrument built.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VQ7Qx8E1q1M1bbCq8QLHS2
