Re: [RFC PATCH 6/9] memory: apple: Add apple-mcc driver to manage MCC perf in Apple SoCs

[Hector Martin]

On 14/10/2021 17.04, Krzysztof Kozlowski wrote:
> > It is; only modules with a GPL-compatible MODULE_LICENSE get to use
> > symbols exported via EXPORT_SYMBOL_GPL.
>
> Although there might be such correlation but it's not a rule. You can
> have a GPL module exporting symbols without GPL requirement
> (EXPORT_SYMBOLS). You can have a GPL+MIT module exporting symbols as
> GPL. Obviously you cannot have a non-GPL module, as we do not accept
> these and there is no such choice.

What I mean is that modules can only import GPL symbols if they 
themselves are GPL compatible. What I didn't know is that "Dual MIT/GPL" 
is a valid string for MODULE_LICENSE to qualify as such.

> > See kernel/module.c for the symbol lookup logic and
> > include/linux/license.h for the logic to check the string (seems like
> > "Dual MIT/GPL" is explicitly whitelisted there).
>
> Not related to export symbol. It is used for determining the tainted
> kernel via other licenses.

Not just that; that module taint is used as a filter so that 
non-GPL-compatible modules are technically prevented from resolving 
EXPORT_SYMBOL_GPL symbols.

> > Of course, this is a futile effort, as ~every time I see a proprietary
> > module in some embedded device, it either falsely declares itself to be
> > GPL, or they have a shim module that re-exports GPL symbols as non-GPL.
>
> This is being removed soon (or already).

? Good luck getting proprietary embedded vendors to start following 
licenses... :)

--
Hector Martin (marcan@xxxxxxxxx)
Public Key: https://mrcn.st/pub