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debugger: D5, the network transport -- and the plan closes

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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
This commit is contained in:
Nexoniarz 2026-09-14 15:33:53 +02:00
commit bc39b73969
23 changed files with 491 additions and 293 deletions
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9
docs/plan/README.md
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@ -43,13 +43,8 @@ And the one the hybrid mechanisms were built for:
| | |
|---|---|
| ~~ldls.md~~ | **Built.** The Linux Driver Layer for SchOS: someone else's drivers, in a process, reached through `/dev/pci`. `ping` works over `8139too`. The description moved to [../architecture/ldls.md](../architecture/ldls.md). |
And one that is a tool rather than a capability:
| | |
|---|---|
| **[debugger.md](debugger.md)** | A debugger for this kernel — one that observes rather than halts, and answers in this kernel's own vocabulary. **Built**, except the network transport: symbols, a log that outlives the kernel, `/dev/dbg`, the `whose` ownership query and hardware watchpoints are all described in [../architecture/debugging.md](../architecture/debugging.md). |
| ~~ldls.md~~ | **Built.** The Linux Driver Layer for SchOS: someone else's drivers, in a process, reached through `/dev/pci`. `ping` works over `8139too` and over `e1000`. The description moved to [../architecture/ldls.md](../architecture/ldls.md). |
| ~~debugger.md~~ | **Built**, all of it, including the network transport. A debugger that observes rather than halts and answers in this kernel's own vocabulary: symbols, a log that outlives the kernel, `/dev/dbg`, `whose`, hardware watchpoints, and `schdbgd`. The description moved to [../architecture/debugging.md](../architecture/debugging.md). |
Two longer-horizon documents sit behind these: [schapi.md](schapi.md), the API
layering and the compatibility promise, and [roadmap.md](roadmap.md), which holds