Re: [PATCH] Narrow Linux symbol CRCs to 32 bits

[Dodji Seketeli <dodji@seketeli.org>]

Hello Giuliano,

Giuliano Procida <gprocida@google.com> a écrit:

> Self-reply.
>
> On Thu, 27 Oct 2022 at 15:09, Giuliano Procida <gprocida@google.com> wrote:
>>
>> MODVERSIONS CRCs are 32-bit hashes of strings representing C type
>> elements or typed symbols. The hash is calculated using a 32-bit CRC,
>> hence the name. The kernel module loading code (implicitly) truncates
>> any provided CRC value to 32 bits before comparing it with anything.
>>
>> When support was added to libabigail, values up to 64 bits wide were
>> supported.
>
> True so far.
>
>> Recently, Linux kernel builds have now started generating
>> ELF CRC symbols with 64-bit values (where the low 32 bits are the
>> CRC). Together this has resulted in incorrect CRCs in ABIs.
>
> The actual problem is a change to how CRCs are emitted in kernel objects.
> I think the change 7b4537199a4a8480b8c3ba37a2d44765ce76cd9b was
> responsible.
>
>> This change resolves the problem by narrowing libabigail's concept of
>> Linux CRC to 32 bits. No tests are affected.
>
> The representation change is fine. The problem with bad CRCs is still
> there.

The changes look good to me.  Do you want me to apply it right now, or
do you prefer to send a subsequent patch that addresses the new way how
CRCs are emitted in kernel object?

I am fine with either way. 

[...]

Cheers,

-- 
		Dodji