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Starting with Rust 1.89.0 (expected 2025-08-07), the Rust compiler fails
to build the `rusttest` target due to undefined references such as:
kernel...-cgu.0:(.text....+0x116): undefined reference to
`rust_helper_kunit_get_current_test'
Moreover, tooling like `modpost` gets confused:
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/gpu/drm/nova/nova.o
ERROR: modpost: missing MODULE_LICENSE() in drivers/gpu/nova-core/nova_core.o
The reason behind both issues is that the Rust compiler will now [1]
treat `#[used]` as `#[used(linker)]` instead of `#[used(compiler)]`
for our targets. This means that the retain section flag (`R`,
`SHF_GNU_RETAIN`) will be used and that they will be marked as `unique`
too, with different IDs. In turn, that means we end up with undefined
references that did not get discarded in `rusttest` and that multiple
`.modinfo` sections are generated, which confuse tooling like `modpost`
because they only expect one.
Thus start using `#[used(compiler)]` to keep the previous behavior
and to be explicit about what we want. Sadly, it is an unstable feature
(`used_with_arg`) [2] -- we will talk to upstream Rust about it. The good
news is that it has been available for a long time (Rust >= 1.60) [3].
The changes should also be fine for previous Rust versions, since they
behave the same way as before [4].
Alternatively, we could use `#[no_mangle]` or `#[export_name = ...]`
since those still behave like `#[used(compiler)]`, but of course it is
not really what we want to express, and it requires other changes to
avoid symbol conflicts.
Cc: David Wood <david@davidtw.co>
Cc: Wesley Wiser <wwiser@gmail.com>
Cc: stable@vger.kernel.org # Needed in 6.12.y and later (Rust is pinned in older LTSs).
Link: https://github.com/rust-lang/rust/pull/140872 [1]
Link: https://github.com/rust-lang/rust/issues/93798 [2]
Link: https://github.com/rust-lang/rust/pull/91504 [3]
Link: https://godbolt.org/z/sxzWTMfzW [4]
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Björn Roy Baron <bjorn3_gh@protonmail.com>
Link: https://lore.kernel.org/r/20250712160103.1244945-3-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
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| .. | ||
| alloc | ||
| block | ||
| drm | ||
| fs | ||
| list | ||
| mm | ||
| net | ||
| sync | ||
| time | ||
| .gitignore | ||
| alloc.rs | ||
| auxiliary.rs | ||
| block.rs | ||
| build_assert.rs | ||
| clk.rs | ||
| configfs.rs | ||
| cpu.rs | ||
| cpufreq.rs | ||
| cpumask.rs | ||
| cred.rs | ||
| device_id.rs | ||
| device.rs | ||
| devres.rs | ||
| dma.rs | ||
| driver.rs | ||
| error.rs | ||
| faux.rs | ||
| firmware.rs | ||
| fs.rs | ||
| generated_arch_static_branch_asm.rs.S | ||
| init.rs | ||
| io.rs | ||
| ioctl.rs | ||
| jump_label.rs | ||
| kunit.rs | ||
| lib.rs | ||
| list.rs | ||
| miscdevice.rs | ||
| mm.rs | ||
| net.rs | ||
| of.rs | ||
| opp.rs | ||
| page.rs | ||
| pci.rs | ||
| pid_namespace.rs | ||
| platform.rs | ||
| prelude.rs | ||
| print.rs | ||
| rbtree.rs | ||
| revocable.rs | ||
| security.rs | ||
| seq_file.rs | ||
| sizes.rs | ||
| static_assert.rs | ||
| std_vendor.rs | ||
| str.rs | ||
| sync.rs | ||
| task.rs | ||
| time.rs | ||
| tracepoint.rs | ||
| transmute.rs | ||
| types.rs | ||
| uaccess.rs | ||
| workqueue.rs | ||
| xarray.rs | ||