[PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone

[Benjamin Herrenschmidt]

On Tue, 2020-07-21 at 16:48 -0700, Palmer Dabbelt wrote:
> > Why ? Branch distance limits ? You can't use trampolines ?
> 
> Nothing fundamental, it's just that we don't have a large code model in the C
> compiler.  As a result all the global symbols are resolved as 32-bit
> PC-relative accesses.  We could fix this with a fast large code model, but then
> the kernel would need to relax global symbol references in modules and we don't
> even do that for the simple code models we have now.  FWIW, some of the
> proposed large code models are essentially just split-PLT/GOT and therefor
> don't require relaxation, but at that point we're essentially PIC until we
> have more that 2GiB of kernel text -- and even then, we keep all the
> performance issues.

My memory might be out of date but I *think* we do it on powerpc
without going to a large code model, but just having the in-kernel
linker insert trampolines.

Cheers,
Ben.