| Filename | Latest commit message | Latest commit date |
|---|---|---|
7a7c7611e0
docs/plan/ldls.md milestone L1. Every undefined symbol resolves to a
trampoline -- twenty generated bytes that load the symbol's index and jump to
a shared thunk, which saves the argument registers and reports the call. Then
init_module is simply called.
$ ldls-run 8139too.ko
module 8139too
license GPL
wants 94 symbols
calling init_module at 0x416fc020
1 _printk(0x416fb6c0, 0, 0)
| 8139too: 8139too Fast Ethernet driver 0.9.28
2 __pci_register_driver(0x416fb400, 0x416fff80, 0x416fbdbb)
init_module returned 0 after 2 stub call(s)
That second line is the driver's own banner, printed through a _printk that
is ours, from a string in the module's own .rodata that a relocation put
there. There is no stronger evidence that a load worked than the loaded thing
speaking.
Stubs return zero rather than stopping, which departs from what the milestone
originally said and does so deliberately: stopping at the first call tells you
one name, carrying on tells you the sequence, and the sequence is the thing a
symbol table cannot give you. A driver that then dereferences the zero faults,
and that is a result too -- it says how far it got before it needed the kernel
to have really done something.
The first run failed on neither of those. It failed on a relocation:
ldls-run: relocate: a signed 32-bit relocation does not fit
A module is compiled -mcmodel=kernel, so the compiler emits R_X86_64_32S for
anything it believes lives in the top 2 GB, and an ordinary mmap at 0x7f...
has nowhere to put it. Linux gives modules a region within 2 GB of the kernel
text; the harness uses MAP_32BIT to reach the same window from the other end.
On SchOS this costs nothing -- a process's mmap area starts at 0x40000000 and
is already inside it -- but it is a real constraint on where the host may load
a module, and a loader that did not check its own arithmetic would have found
it much later and much more confusingly.
Swept over 500 stock modules: 449 ran init to completion, 22 faulted on a
stub's zero, 29 have no init_module, and zero hit a loader error.
Recorded honestly in "what it will not do": running init is not working. Every
symbol is a stub, so what has been shown is that drivers ask for things in a
readable order, not that anything answers. Also recorded: every undefined
symbol in a module is NOTYPE, so the stubs cannot tell jiffies from
pci_iomap and both get a trampoline -- BTF distinguishes VAR from FUNC and
that is where the fix belongs rather than in a guess.
make ldls-check is 23 checks now, five of them L1's, all against
ldls/test/refmod.c which is ours and now has an init_module of its own.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VQ7Qx8E1q1M1bbCq8QLHS2
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| .. | ||
| architecture | ||
| branding | ||
| guides | ||
| history | ||
| plan | ||
| Website | ||
| licensing.md | ||
| README.md | ||
SchOS documentation
Four kinds of document, kept in four directories, because they answer four different questions and go stale at four different rates.
| architecture/ | What SchOS is | Present tense. Describes what is built and working. |
| plan/ | What SchOS will be | Future tense. Everything here is unbuilt. |
| guides/ | How to work on it | Imperative. Build it, test it, add to it. |
| history/ | Why it is the way it is | Past tense. Bugs whose cause is not visible from the fix. |
Plus two that belong to no category and apply to everything: licensing.md — read it before copying anyone else's code in — and branding/, which holds the marks and the rules for using them.
The rule that keeps this from rotting
When something is finished, it moves from
plan/toarchitecture/and is rewritten as a description of the thing rather than a record of building it.
A completed item is not a ticked checkbox. A ticked checkbox says the work happened; it does not say what the work produced, and six months later the checkbox is the only thing left and it explains nothing.
So finishing a piece of work has three steps, and the third is not optional:
- The code works and is tested.
- The plan entry is deleted.
- A description exists in
architecture/written for somebody who was not there — what it does, what shape it has, what it costs, and what it still does not do.
This is not bookkeeping. The tree has already proved it necessary: the network stack was finished, verified end to end, and for a month afterwards the only description of it anywhere was a checkbox in a roadmap, four levels of indentation deep, written in the past tense of somebody arguing for the work rather than explaining the result.
The "what it does not do" section is the one that pays. Every description in
architecture/ ends with one. A document that only lists a subsystem's
strengths is marketing, and the reader who most needs the document is the one
about to trip over a limitation nobody wrote down.
Start here
New to the tree → architecture/README.md, the system layer by layer, then guides/layout.md for where the files are.
Trying to build it → guides/building.md.
Wondering what happens next → plan/1.0.md, which is the finish line and the register of everything half-built. Then plan/README.md for the order.
About to start something new → the register, first. Nothing new starts while it has rows in it, and a row leaves only by being finished or deleted.
Something is broken and it feels familiar → history/. There is a good chance it is in there.
architecture/ — what SchOS is
| README | The system, layer by layer. Read first. |
| boot.md | Firmware to the first userspace process. |
| kernel.md | SchIFT: memory, processes, scheduling, traps, signals, SMP. |
| syscalls.md | The call table, and the Linux personality that lets real software run. |
| filesystem.md | The VFS, the buffer cache, procfs, mounts. |
| schfs.md | SchFS: the copy-on-write root filesystem. |
| devices.md | The device model, driver binding, the class vtables. |
| usb.md | xHCI, the USB core, and the class drivers. |
| graphics.md | Framebuffer, text rendering, console, and the crash screen. |
| terminals.md | The six virtual terminals, and how one is switched to. |
| networking.md | Drivers, lwIP, sockets — Unix and INET. |
| init.md | schinit, PID 1 as a role, and the job manifests. |
plan/ — what SchOS will be
| README | The three current decisions and the order they happen in. |
| 1.0.md | The finish line, and the freeze. What 1.0 contains, what is deferred, and the register of every half-built thing in the tree. |
| foundations.md | The kernel work everything else is blocked on. |
| wayland.md | The GUI stack, and what gets deleted to make room. |
| hybrid.md | Moving drivers out of the kernel. |
| schapi.md | The long-term API layering, and the compatibility promise. |
| roadmap.md | Everything else still open. |
guides/ — how to work on it
| building.md | Prerequisites and the build, per host. |
| testing.md | The harnesses, and what each one actually proves. |
| layout.md | Repository map, and how to add a program or a port. |
| adding-a-driver.md | Writing one, binding it, publishing its class vtable. |
branding/ — the marks
| README | Shift the logo, Guru the icon, SchCotie the mascot: what each is for, the colour rule, and why a raster is committed next to its SVG. |
history/ — why it is the way it is
| README | What belongs in here and what does not. |
| kernel.md | Bugs whose cause was nowhere near their symptom. |
| schfs.md | The filesystem's own, from the same period as its design. |
| moving-to-linux.md | The Windows-to-Fedora move, kept for the parts that recur. |
Writing one of these
Four conventions, all of them observable in the existing files:
State the cost. Every design choice gave something up. A document that does not say what is a document that will be argued with later by somebody who only sees the downside.
Prefer the measured number to the remembered one. "500 of 3565 files carry the advertising clause" is worth more than "some do", and it was worth the minute it took to count.
Write down the bug that shaped it. Half the non-obvious code in this tree is non-obvious because something failed once. If a design is strange, the strangeness is load-bearing and the reader deserves to know why before changing it.
No dates in headings. A date in a heading turns a description into a
changelog, and the description is the thing with a long life. Dates belong in
history/, where they mean something.