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Date:   Tue, 5 May 2020 17:15:38 -0700
From:   Atish Patra <atishp@...shpatra.org>
To:     Palmer Dabbelt <palmer@...belt.com>,
        Nick Kossifidis <mick@....forth.gr>
Cc:     Atish Patra <Atish.Patra@....com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Anup Patel <Anup.Patel@....com>,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
        Zong Li <zong.li@...ive.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        linux-riscv <linux-riscv@...ts.infradead.org>
Subject: Re: [PATCH] RISC-V: Remove unused code from STRICT_KERNEL_RWX

On Tue, May 5, 2020 at 5:03 PM Palmer Dabbelt <palmer@...belt.com> wrote:
>
> On Tue, 05 May 2020 17:00:05 PDT (-0700), atishp@...shpatra.org wrote:
> > On Tue, May 5, 2020 at 4:55 PM Palmer Dabbelt <palmer@...belt.com> wrote:
> >>
> >> On Sun, 03 May 2020 21:03:19 PDT (-0700), Atish Patra wrote:
> >> > This patch removes the unused functions set_kernel_text_rw/ro.
> >> > Currently, it is not being invoked from anywhere and no other architecture
> >> > (except arm) uses this code. Even in ARM, these functions are not invoked
> >> > from anywhere currently.
> >> >
> >> > Fixes: d27c3c90817e ("riscv: add STRICT_KERNEL_RWX support")
> >> >
> >> > Signed-off-by: Atish Patra <atish.patra@....com>
> >> > ---
> >> >  arch/riscv/mm/init.c | 16 ----------------
> >> >  1 file changed, 16 deletions(-)
> >> >
> >> > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> >> > index b55be44ff9bd..ba60a581e9b6 100644
> >> > --- a/arch/riscv/mm/init.c
> >> > +++ b/arch/riscv/mm/init.c
> >> > @@ -501,22 +501,6 @@ static inline void setup_vm_final(void)
> >> >  #endif /* CONFIG_MMU */
> >> >
> >> >  #ifdef CONFIG_STRICT_KERNEL_RWX
> >> > -void set_kernel_text_rw(void)
> >> > -{
> >> > -     unsigned long text_start = (unsigned long)_text;
> >> > -     unsigned long text_end = (unsigned long)_etext;
> >> > -
> >> > -     set_memory_rw(text_start, (text_end - text_start) >> PAGE_SHIFT);
> >> > -}
> >> > -
> >> > -void set_kernel_text_ro(void)
> >> > -{
> >> > -     unsigned long text_start = (unsigned long)_text;
> >> > -     unsigned long text_end = (unsigned long)_etext;
> >> > -
> >> > -     set_memory_ro(text_start, (text_end - text_start) >> PAGE_SHIFT);
> >> > -}
> >> > -
> >> >  void mark_rodata_ro(void)
> >> >  {
> >> >       unsigned long text_start = (unsigned long)_text;
> >>
> >> Thanks, this is on fixes.  Are you going to remove the ARM code as well?
> >>
> >
> > Yeah and also I realized that I forgot to remove the declarations from
> > the header file.
> > My bad. I will send out a v2. Please drop this one and take v2.
>
> I just fixed it up
>

Thanks. I was going over the code again and found one usage for
set_kernel_text_rw for ARM.
It is used in kexec while set_kernel_text_ro is not invoked anywhere.
I am not sure if it is required
for kexec implementation for RISC-V.

@nick: Can you please comment ?

> commit 73cb8e2a5863ccc5215660f5123db621bd57dff7
> gpg: Signature made Tue 05 May 2020 05:02:17 PM PDT
> gpg:                using RSA key 2B3C3747446843B24A943A7A2E1319F35FBB1889
> gpg:                issuer "palmer@...belt.com"
> gpg: Good signature from "Palmer Dabbelt <palmer@...belt.com>" [ultimate]
> gpg:                 aka "Palmer Dabbelt <palmerdabbelt@...gle.com>" [ultimate]
> Author: Atish Patra <atish.patra@....com>
> Date:   Sun May 3 21:03:19 2020 -0700
>
>     RISC-V: Remove unused code from STRICT_KERNEL_RWX
>
>     This patch removes the unused functions set_kernel_text_rw/ro.
>     Currently, it is not being invoked from anywhere and no other architecture
>     (except arm) uses this code. Even in ARM, these functions are not invoked
>     from anywhere currently.
>
>     Fixes: d27c3c90817e ("riscv: add STRICT_KERNEL_RWX support")
>     Signed-off-by: Atish Patra <atish.patra@....com>
>     Reviewed-by: Zong Li <zong.li@...ive.com>
>     Signed-off-by: Palmer Dabbelt <palmerdabbelt@...gle.com>
>
> diff --git a/arch/riscv/include/asm/set_memory.h b/arch/riscv/include/asm/set_memory.h
> index c38df4771c09..4c5bae7ca01c 100644
> --- a/arch/riscv/include/asm/set_memory.h
> +++ b/arch/riscv/include/asm/set_memory.h
> @@ -22,14 +22,6 @@ static inline int set_memory_x(unsigned long addr, int numpages) { return 0; }
>  static inline int set_memory_nx(unsigned long addr, int numpages) { return 0; }
>  #endif
>
> -#ifdef CONFIG_STRICT_KERNEL_RWX
> -void set_kernel_text_ro(void);
> -void set_kernel_text_rw(void);
> -#else
> -static inline void set_kernel_text_ro(void) { }
> -static inline void set_kernel_text_rw(void) { }
> -#endif
> -
>  int set_direct_map_invalid_noflush(struct page *page);
>  int set_direct_map_default_noflush(struct page *page);
>
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 5b813532db59..27a334106708 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -502,22 +502,6 @@ static inline void setup_vm_final(void)
>  #endif /* CONFIG_MMU */
>
>  #ifdef CONFIG_STRICT_KERNEL_RWX
> -void set_kernel_text_rw(void)
> -{
> -       unsigned long text_start = (unsigned long)_text;
> -       unsigned long text_end = (unsigned long)_etext;
> -
> -       set_memory_rw(text_start, (text_end - text_start) >> PAGE_SHIFT);
> -}
> -
> -void set_kernel_text_ro(void)
> -{
> -       unsigned long text_start = (unsigned long)_text;
> -       unsigned long text_end = (unsigned long)_etext;
> -
> -       set_memory_ro(text_start, (text_end - text_start) >> PAGE_SHIFT);
> -}
> -
>  void mark_rodata_ro(void)
>  {
>         unsigned long text_start = (unsigned long)_text;
>


-- 
Regards,
Atish

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