Stephan von Krawczynski wrote:
you may have already heard about it or not (several times in the past),
non-kernel devices run into a symbol export problem as soon as something is
only exported GPL from the kernel.
Currently there is a discussion regarding zfs using this call chain:
vdev_bio_associate_blkg (zfs) -> blkg_tryget (kernel) -> percpu_ref_tryget
(kernel) -> rcu_read_unlock (kernel) -> __rcu_read_unlock (kernel)
where __rcu_read_[lock|unlock] is a GPL symbol now used by (not GPL exported)
That this popped up (again) made me think a bit more general about the issue.
And I do wonder if this rather ideologic problem is on the right track
currently. Because what the kernel tries to do with the export GPL symbol
stuff is to prevent any other licensed software from _using_ it in _runtime_.
It does not try to prevent use/copy of the source code inside another non-gpl
And I do think that this is not the intention of GPL. If it were, then 100% of
all mobile phones on this planet are illegal. All of them use GPL software
from non-gpl software, be it kernel modules or apps - and I see no difference
in the two. The constructed difference between kernel mode software and
user-space software is pure ideology. Because during runtime everything is
Which means if you fopen() a file in user-space it of course uses GPL symbols
down in the chain somewhere. The contents of the opened file are not
If you/we follow the current completely ideology-driven GPL strategy then I am
all for completely giving up this whole project. In real world you simply
cannot use such a piece of software. The success of linux during the last
years (i.e. decade) is not based on the pure GPL strategy, but on the
successful interaction between linux and non-GPL software.
Just think of the billions of smartphones all using a non-gpl firmware
(underneath, and there is no GPL version at all), the kernel (with non-gpl
modules) and apps (quite some of which are non-gpl).
This is only one prominent example, but there are lots of others.
In the end it all sums up to one simple question:
Can one _use_ GPL software during runtime as a base for own projects of any
license type or not? We are not talking about _copying_ gpl code, we are
talking about runtime use.
If runtime use is generally allowed, then the export gpl symbol stuff inside
the kernel code is nonsense. Because to use the kernel you must be allowed to
call it, no matter from where.