Re: [PATCH] serial: 8250: Fix section mismatch with CONFIG_MODULES=n

Re: [PATCH] serial: 8250: Fix section mismatch with CONFIG_MODULES=n

[Uwe Kleine-König]

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Hello Danish,

On Sat, Sep 26, 2026 at 11:35:06AM -0500, Danish Khateeb wrote:
> Without CONFIG_MODULES, __init_or_module means __init, so
> serial8250_pnp_exit() and serial8250_hub6_exit() end up in .init.text.
> They are also called from serial8250_exit(), which is __exit, and
> modpost warns:
> 
>   WARNING: modpost: vmlinux: section mismatch in reference: serial8250_exit+0x2a (section: .exit.text) -> serial8250_pnp_exit (section: .init.text)

Isn't that a false positive because with CONFIG_MODULES=n .exit is
discarded and so the section mismatch doesn't matter?

> The exit code never runs in such a kernel, so nothing breaks at runtime.

Ah, you found that, too.

> But a function that is called from both __init and __exit code can't
> carry either annotation, so drop it.

I thought __init_or_module was the right annotation ...

Best regards
Uwe

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Re: [PATCH] serial: 8250: Fix section mismatch with CONFIG_MODULES=n

[Danish Khateeb]

Hello Uwe,

On Sat, Sep 26, 2026 at 07:40:03PM +0200, Uwe Kleine-König wrote:
> Isn't that a false positive because with CONFIG_MODULES=n .exit is
> discarded and so the section mismatch doesn't matter?

Yes, it's harmless at runtime, but modpost still warns on every
CONFIG_MODULES=n build with SERIAL_8250_PNP (e.g. kunit.py --alltests),
and the build fails with CONFIG_SECTION_MISMATCH_WARN_ONLY=n.

> I thought __init_or_module was the right annotation ...

It is, modpost just doesn't know that. Without it the two helpers stay in
memory after boot, 16 bytes each on x86_64. The alternative is teaching
modpost to skip exit -> init references in vmlinux when CONFIG_MODULES=n.

Thanks
Danish