linux-kernel - Re: [PATCH v2] RISC-V: Always compile mm/init.c with cmodel=medany

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Date:   Mon, 25 Mar 2019 12:29:00 +0530
From:   Anup Patel <anup@...infault.org>
To:     Alan Kao <alankao@...estech.com>
Cc:     Anup Patel <Anup.Patel@....com>,
        Palmer Dabbelt <palmer@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Christoph Hellwig <hch@...radead.org>,
        Atish Patra <Atish.Patra@....com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>
Subject: Re: [PATCH v2] RISC-V: Always compile mm/init.c with cmodel=medany

On Mon, Mar 25, 2019 at 10:56 AM Alan Kao <alankao@...estech.com> wrote:
>
> Hi Anup,
>
> Sorry for being late to the party.  I think one more thing should
> move together with setup_vm():
>
> On Mon, Mar 25, 2019 at 03:37:38AM +0000, Anup Patel wrote:
> > The Linux RISC-V 32bit kernel is broken after we moved setup_vm() from
> > kernel/setup.c to mm/init.c because Linux RISC-V 32bit kernel by default
> > uses cmodel=medlow which results in a non-position-independent setup_vm().
> >
> > This patch fixes Linux RISC-V 32bit kernel booting by:
> > 1. Forcing cmodel=medany for mm/init.c
> > 2. Moving remaing MM-related stuff va_pa_offset, pfn_base and
> >    empty_zero_page from kernel/setup.c to mm/init.c
> >
> > Fixes: 6f1e9e946f0b ("RISC-V: Move setup_vm() to mm/init.c")
> > Suggested-by: Christoph Hellwig <hch@....de>
> > Suggested-by: Mike Rapoport <rppt@...ux.ibm.com>
> > Signed-off-by: Anup Patel <anup.patel@....com>
> > ---
> > v2: Removed CFLAGS_setup.o from kernel/Makefile and replaced SoBs
> > ---
> >  arch/riscv/kernel/Makefile | 2 --
> >  arch/riscv/kernel/setup.c  | 8 --------
> >  arch/riscv/mm/Makefile     | 2 ++
> >  arch/riscv/mm/init.c       | 9 +++++++++
> >  4 files changed, 11 insertions(+), 10 deletions(-)
> >
> > diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
> > index f13f7f276639..8b9780b6bd7f 100644
> > --- a/arch/riscv/kernel/Makefile
> > +++ b/arch/riscv/kernel/Makefile
>
> earlier in this file, there are four lines about ftrace,
>
>   5 ifdef CONFIG_FTRACE
>   6 CFLAGS_REMOVE_ftrace.o = -pg
>   7 CFLAGS_REMOVE_setup.o = -pg
>   8 endif
>
> removing "-pg" flag from setup.o was necessary for ftrace to work, since
> setup_vm() cannot process the trampoline of ftrace properly.
>
> As setup_vm() is being moved to mm/init.c, you may either mark it with a
> "notrace" attribute with its declaration, or adding corresponding CFLAGS_REMOVE*
> to mm/Makefile.

Let's handle it in same way as it was handled for kernel/setup.o

Most of the stuff is already moved to mm/init.c so no need for
"CFLAGS_REMOVE_setup.o = -pg"

I will send-out v3 with above changes and also update patch description
accordingly.

Regards,
Anup