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Record a pending exception for investigating the printk ringbuffer port after Loom rejects its speculative payload reads. Separate the state protocol model from the C access and compiler contracts without claiming that an atomic control validates ordinary C payload accesses. Keep the proposal inactive until accepted. The existing stop criteria continue to apply to production ports. Assisted-by: LLM [Codex]
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Define merging PR #24 as acceptance of the printk-specific criterion-2 amendment. Preserve the single-forwarding-call FFI restriction and state that the existing stop criterion remains tripped until acceptance. Cite the local diagnostic commit and distinguish its minimal race model from complete ringbuffer certification. Assisted-by: LLM [Codex]
Record the explicit authorization to implement printk using the scoped Loom and LKMM validation approach while PR #24 is under development. Keep certification separate from permission to investigate, and link the now-published diagnostic and validation evidence. Assisted-by: LLM [Codex]
Replace the ring buffer algorithm under CONFIG_RUST_KERNEL while retaining the C header and caller ABI. Generate layout assertions from the active C configuration, including execution-context metadata. Keep reservation and recycling decisions in Rust. Forward shared data accesses, atomics and barriers through C primitives without retaining the C algorithm behind the boundary. This is an implementation checkpoint for the printk series. Sequential differential traces, two metadata layouts, C/Rust SMP KUnit runs and three LKMM barrier projections pass. The full compiler-boundary argument, source-comment audit and unsafe classification remain under review. Assisted-by: LLM [Codex]
bherrera
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September 21, 2026 12:22
bherrera
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Keep speculative scalar reads inside C READ_ONCE helpers before descriptor validation. This avoids turning ordinary racing memcpy results into Rust scalar values while preserving the ring algorithm and C caller ABI. Test: printk ringbuffer differential harness, ten seeds and both metadata layouts. Test: SMP Rust kernel build with printk KUnit configuration. Assisted-by: LLM [Codex]
Emit the packed flags and level byte offset plus execution-context offsets from the active C layout. Use the generated values in the Rust mirror instead of deriving offsets from neighboring fields. Test: Rust main crate builds with execution-context metadata enabled. Assisted-by: LLM [Codex]
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Scope
Implement printk in the agreed order in this PR: ring buffer, nbcon, printk_safe, then printk. The ring buffer implementation is now present; the later units remain outstanding.
The user authorized the scoped LKMM/C-access investigation while this PR is developed. Acceptance of that investigation is not certification of the C/Rust boundary. The single-forwarding-call FFI restriction remains binding.
Implemented checkpoint
Validation
Published infrastructure evidence is on misttech/linux-rust branch codex/gpt-6/feature/printk-port (diagnostic 818c24e, validation 3edea95).
Not ready to merge
The compiler/FFI argument, full preservation of C comments, unsafe classification audit, cross-architecture validation, and remaining printk units are unfinished. This PR is a draft implementation checkpoint.
Kill criteria: layout not tripped; original direct-copy ordering criterion still fails, with the authorized scoped alternative under investigation; KRef unaffected.