Re: WARNING: [xtensa] modpost: vmlinux: section mismatch in reference: ice_adv_lnk_speed_maps+0x14 (section: .data) -> __setup_str_initcall_blacklist (section: .init.rodata)

[Przemek Kitszel <przemyslaw.kitszel@intel.com>]

On 8/24/24 08:41, Max Filippov wrote:
> Hi Przemek,
> 
> On Thu, Aug 22, 2024 at 1:23 AM Przemek Kitszel
> <przemyslaw.kitszel@intel.com> wrote:
>>> WARNING: modpost: missing MODULE_DESCRIPTION() in vmlinux.o
>>> WARNING: modpost: vmlinux: section mismatch in reference: put_page+0x78 (section: .text.unlikely) -> initcall_level_names (section: .init.data)
>>>>> WARNING: modpost: vmlinux: section mismatch in reference: ice_adv_lnk_speed_maps+0x14 (section: .data) -> __setup_str_initcall_blacklist (section: .init.rodata)
>>
>> I have spent just half of hour on that and I'm clueless.
>>
>> For reference, the driver code is:
>>          static const u32 arr_name[] __initconst = {
>>                  SOME_CONST,
>>          };
>> and core kernel has:
>>          #define __initconst __section(.init.rodata)
>>
>>
>> @Max Filippov, you have authored much of xtensa arch for kernel,
>> especially XIP support, and touched .init.rodata back then;
>> perhaps you have any idea what is going here?
> 
> I see the following:
> 
> static struct ethtool_forced_speed_map ice_adv_lnk_speed_maps[]
> __ro_after_init = {
>         ETHTOOL_FORCED_SPEED_MAP(ice_adv_lnk_speed, 100),
> 
> that array goes into the .data, but ETHTOOL_FORCED_SPEED_MAP
> expands to the following:
> 
> #define ETHTOOL_FORCED_SPEED_MAP(prefix, value)                         \
> {                                                                       \
>         .speed          = SPEED_##value,                                \
>         .cap_arr        = prefix##_##value,                             \
>         .arr_size       = ARRAY_SIZE(prefix##_##value),                 \
> }
> 
> so the first entry of that array quoted above above gets the following
> initializer:
> 
>    .cap_arr = ice_adv_lnk_speed_100,
> 
> and ice_adv_lnk_speed_100 is defined as
> 
>    static const u32 ice_adv_lnk_speed_100[] __initconst = {
> 
> so this array goes into .init.rodata.
> That's a reference from .data to .init.rodata that upsets the modpost checker.
> I see that modpost incorrectly deduces where this link points (it's
> ice_adv_lnk_speed_*, not __setup_str_initcall_blacklist).
> I also see that this link is not used after the init phase, so it's harmless.
> 

Thank you very much for the analysis :)