Why do we need this page ?

Perhaps add a note about attribute((resolver)). And that for an architecture to support kernel ifuncs, in-kernel linker and toolchain must both support them.

In D20310#437745, @kib wrote:

Why do we need this page ?

I have a few motivations:

• I have explained ifuncs to several people so far and would like to be able to refer them to a man page.
• The resolver signature for userland ifuncs is FreeBSD- and architecture-dependent. IMO it is worth documenting. I know this page is for the kernel variant of the macro; I would add another page which describes the resolver signature and refers to the kernel page for the general explanation.
• My general sense is that new developers appreciate having useful man9 pages, and the definition of DEFINE_IFUNC is difficult to read. Other aspects of the implementation are not clear from the macro definition; for example, when do resolvers get called and what are they (not) permitted to do?

I understand that man9 pages impose a maintenance burden and have no wish to provide comprehensive documentation for kernel interfaces. To me, DEFINE_IFUNC is obscure enough to deserve some reference.

Perhaps add a note about attribute((resolver)). And that for an architecture to support kernel ifuncs, in-kernel linker and toolchain must both support them.

Ok.

I agree with Mark's motivation, having documentation for FreeBSD-specific kernel interfaces/defines/macros benefits new developers and downstream consumers.