Re: [PATCH 1/2] modpost: don't add warnings for LTO-generated symbols

[Arnd Bergmann]

On Mon, Feb 5, 2018 at 4:50 PM, Andi Kleen <ak@xxxxxxxxxxxxxxx> wrote:
> On Mon, Feb 05, 2018 at 04:12:52PM +0100, Arnd Bergmann wrote:
>> WARNING: vmlinux.o(.data+0x12e0): Section mismatch in reference from the variable pfkey_net_ops.lto_priv.2992 to the function .init.text:pfkey_net_init.lto_priv.2977()
>> The variable pfkey_net_ops.lto_priv.2992 references
>> the function __init pfkey_net_init.lto_priv.2977()
>> If the reference is valid then annotate the
>> variable with __init* or __refdata (see linux/init.h) or name the variable:
>> *_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console
>
> A better fix would be to ensure modpost always runs on already LD_FINALed
> objects, so it never sees LTO.
>
> Otherwise you would need to teach modpost about the LTO symbol table
> and some other magic. I did that once, but it turned out to be very
> ugly.

I'm not sure I understand what that means. Do you mean that with LD_FINAL,
those symbol references are completely eliminated so we don't need to worry
about them any more?

I got about a dozen section mismatch errors with LTO in cases where the
calling function gets a specialized version of a structure, and my oneline
patch above addresses them all.

        Arnd