0.3.5 — the forwarder for an optional interface must not demand it - #8
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`openkal.random` is optional, and clause 6.1 expresses an implementation
that does not provide it as the absence of a link-time definition. This
dispatcher is linked into every program, so a strong reference to
`kal_random_fill` turned that absence into a failure for programs that
never ask for a random byte:
ld.lld: error: undefined symbol: kal_random_fill
>>> referenced by okm_syscall.c:409
>>> obj/…/okm_syscall.o:(__okm_syscall)
measured on a bare-metal program over openkal-opensbi, which provides
eight interfaces and not this one. A whole class of programs — every
freestanding one — could not link because one optional interface was
referenced unconditionally.
⚠️ THE WEAK REFERENCE IS NOT THE RUN-TIME REFUSAL CLAUSE 6.1 FORBIDS.
That clause governs an implementation of openkal: one shall not offer an
interface whose operations report a lack of support while running. This
is on the other side of the layer — the file implements Linux's system
call ABI, where `ENOSYS` is that ABI's answer for a call the kernel does
not have, and musl's own `getrandom` is written against that answer.
Both the idiom and the convention were already here and neither was
reached for: `okm_phdr.c` declares `__ehdr_start` weak, and this file's
opening comment says calls that can be told they do not exist return
`-ENOSYS`.
Proved by removing it again rather than by reasoning:
weak examples/same-source --target riscv64-none-elf → text 2490664
strong the same build → the error above
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A strong reference to
kal_random_fillin the syscall dispatcher made an optional interface mandatory: every freestanding program failed to link, whether or not it wanted a random byte.The weak reference is on the other side of the layer from clause 6.1 — this file implements Linux's syscall ABI, where
ENOSYSis the defined answer for a call the kernel does not have.Proved by removing it again: strong → the link error, weak → text 2490664.