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

From: Przemek Kitszel
Date: Mon Aug 26 2024 - 04:53:41 EST


On 8/24/24 08:41, Max Filippov wrote:
Hi Przemek,

On Thu, Aug 22, 2024 at 1:23 AM Przemek Kitszel
<przemyslaw.kitszel@xxxxxxxxx> 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 :)