Re: [PATCH v5 2/4] riscv: Introduce CONFIG_RELOCATABLE

[Alex Ghiti]

Hi Jerome,

Le 6/10/20 Ã 10:10 AM, Jerome Forissier a ÃcritÂ:
> On 6/7/20 9:59 AM, Alexandre Ghiti wrote:
> [...]
>
> > +config RELOCATABLE
> > +	bool
> > +	depends on MMU
> > +	help
> > +          This builds a kernel as a Position Independent Executable (PIE),
> > +          which retains all relocation metadata required to relocate the
> > +          kernel binary at runtime to a different virtual address than the
> > +          address it was linked at.
> > +          Since RISCV uses the RELA relocation format, this requires a
> > +          relocation pass at runtime even if the kernel is loaded at the
> > +          same address it was linked at.
> Is this true? I thought that the GNU linker would write the "proper"
> values by default, contrary to the LLVM linker (ld.lld) which would need
> a special flag: --apply-dynamic-relocs (by default the relocated places
> are set to zero). At least, it is my experience with Aarch64 on a
> different project. So, sorry if I'm talking nonsense here -- I have not
> looked at the details.

It seems that you're right, at least for aarch64 since they specifically 
specify the --no-apply-dynamic-relocs option. I retried to boot without 
relocating at runtime, and it fails on riscv. Can this be arch specific ?

Thanks,

Alex