Re: [PATCH 1/2] module: get symbol crc back to unsigned

[Masahiro Yamada]

On Sun, Dec 29, 2024 at 12:46 AM Masahiro Yamada <masahiroy@xxxxxxxxxx> wrote:
>
> Commit 71810db27c1c ("modversions: treat symbol CRCs as 32 bit
> quantities") changed the CRC fields to s32 because the __kcrctab and
> __kcrctab_gpl sections contained relative references to the actual
> CRC values stored in the .rodata section when CONFIG_MODULE_REL_CRCS=y.
>
> Commit 7b4537199a4a ("kbuild: link symbol CRCs at final link, removing
> CONFIG_MODULE_REL_CRCS") removed this complexity. Now, the __kcrctab
> and __kcrctab_gpl sections directly contain the CRC values in all cases.
>
> The genksyms tool outputs unsigned 32-bit CRC values, so u32 is preferred
> over s32.
>
> No functional changes are intended.
>
> Regardless of this change, the CRC value is assigned to the u32 variable,
> 'crcval' before the comparison, as seen in kernel/module/version.c:
>
>     crcval = *crc;


[Just in case for confused reviewers]

It was previously mandatory (but now optional) in order to avoid sign
extension because the following line previously compared 'unsigned long'
and 's32':

    if (versions[i].crc == crcval)
            return 1;

versions[i].crc is still 'unsigned long' for backward compatibility.










-- 
Best Regards
Masahiro Yamada