Re: [PATCH 2/3] RISC-V: Make setup_vm() independent of GCC code model

[Anup Patel]

On Tue, Apr 9, 2019 at 10:17 PM Palmer Dabbelt <palmer@xxxxxxxxxx> wrote:
>
> On Tue, 12 Mar 2019 15:08:16 PDT (-0700), Anup Patel wrote:
> > The setup_vm() must access kernel symbols in a position independent way
> > because it will be called from head.S with MMU off.
> >
> > If we compile kernel with cmodel=medany then PC-relative addressing will
> > be used in setup_vm() to access kernel symbols so it works perfectly fine.
> >
> > Although, if we compile kernel with cmodel=medlow then either absolute
> > addressing or PC-relative addressing (based on whichever requires fewer
> > instructions) is used to access kernel symbols in setup_vm(). This can
> > break setup_vm() whenever any absolute addressing is used to access
> > kernel symbols.
> >
> > With the movement of setup_vm() from kernel/setup.c to mm/init.c, the
> > setup_vm() is now broken for cmodel=medlow but it works perfectly fine
> > for cmodel=medany.
> >
> > This patch fixes setup_vm() and makes it independent of GCC code model
> > by accessing kernel symbols relative to kernel load address instead of
> > assuming PC-relative addressing.
>
> I think we ended up with a cleaner solution as 387181dcdb6c ("RISC-V: Always
> compile mm/init.c with cmodel=medany and notrace"), but let me know if I missed
> something here.

Yes, please ignore this patch. I have dropped it in latest version of
this patch series.

Regards,
Anup