Claude review: gpu: nova-core: export Rust symbols for dependent modules

[Claude Code Review Bot <claude-review@example.com>]

Patch Review

**Verdict: Functional workaround, a few observations.**

The approach — using `nm` to find Rust text symbols (prefixed `_R`) and wrapping them with `EXPORT_SYMBOL_GPL` — is pragmatic:

```makefile
rust_exports = \
	$(NM) -p --defined-only $(1) | \
	awk '$$2 == "T" && $$3 ~ /^_R/ { \
		printf "extern void %s(void); EXPORT_SYMBOL_GPL(%s);\n", $$3, $$3 \
	}'
```

Observations:

1. **Over-export risk**: This exports *every* `_R`-prefixed global text symbol in `nova_core.o`. Rust's v0 mangling means that includes all `pub` functions that weren't inlined or elided, including potentially internal helpers, trait impls, drop glue, etc. that consumers shouldn't rely on. The comment should acknowledge this blanket export is intentional and that narrowing it is a future improvement. For a temporary workaround this is acceptable, but if this persists it could create an unstable ABI surface.

2. **Symbol type filter**: Only `T` (global text) symbols are exported. This misses `D`/`B` (global data/BSS) symbols which could also be needed if `nova-core` exposes `pub static` items. For the current POC this works, but worth noting.

3. The `nova_core_exports.c` file is clean and minimal — just includes `<linux/export.h>` and the generated header. The `extern void` declarations for non-void functions are technically wrong C, but for the purpose of `EXPORT_SYMBOL_GPL` it only needs the symbol name, not the actual prototype. This is fine.

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