[PATCH] riscv: Align on L1_CACHE_BYTES when STRICT_KERNEL_RWX

[Atish Patra]

On Fri, Jan 8, 2021 at 8:37 AM Geert Uytterhoeven <geert at linux-m68k.org> wrote:
>
> Hi Sebastien,
>
> On Mon, Nov 16, 2020 at 1:59 PM Sebastien Van Cauwenberghe
> <svancau at gmail.com> wrote:
> > From 5690c2f91d87a007babb13e2d2c9c45d1ff68b7a Mon Sep 17 00:00:00 2001
> > From: Sebastien Van Cauwenberghe <svancau at gmail.com>
> > Date: Mon, 16 Nov 2020 13:37:32 +0100
> > Subject: [PATCH] riscv: Align on L1_CACHE_BYTES when STRICT_KERNEL_RWX is
> >  disabled
> >
> > Allows the sections to be aligned on smaller boundaries and
> > therefore results in a smaller kernel image size.
> >
> > Signed-off-by: Sebastien Van Cauwenberghe <svancau at gmail.com>
>
> Thanks for your patch!
>
> > --- a/arch/riscv/include/asm/set_memory.h
> > +++ b/arch/riscv/include/asm/set_memory.h
> > @@ -27,14 +27,14 @@ int set_direct_map_default_noflush(struct page *page);
> >
> >  #endif /* __ASSEMBLY__ */
> >
> > -#ifdef CONFIG_ARCH_HAS_STRICT_KERNEL_RWX
> > +#ifdef CONFIG_STRICT_KERNEL_RWX
> >  #ifdef CONFIG_64BIT
> >  #define SECTION_ALIGN (1 << 21)
> >  #else
> >  #define SECTION_ALIGN (1 << 22)
> >  #endif
> > -#else /* !CONFIG_ARCH_HAS_STRICT_KERNEL_RWX */
> > +#else /* !CONFIG_STRICT_KERNEL_RWX */
> >  #define SECTION_ALIGN L1_CACHE_BYTES
> > -#endif /* CONFIG_ARCH_HAS_STRICT_KERNEL_RWX */
> > +#endif /* CONFIG_STRICT_KERNEL_RWX */
> >
> >  #endif /* _ASM_RISCV_SET_MEMORY_H */
>
> Since commit 19a00869028f4a28 ("RISC-V: Protect all kernel sections
> including init early"), you also need (whitespace-damaged-gmail-patch):
>
> --- a/arch/riscv/kernel/setup.c
> +++ b/arch/riscv/kernel/setup.c
> @@ -293,6 +293,8 @@ void free_initmem(void)
>         unsigned long init_begin = (unsigned long)__init_begin;
>         unsigned long init_end = (unsigned long)__init_end;
>
> -       set_memory_rw_nx(init_begin, (init_end - init_begin) >> PAGE_SHIFT);
> +       if (IS_ENABLED(CONFIG_STRICT_KERNEL_RWX))
> +               set_memory_rw_nx(init_begin,
> +                                (init_end - init_begin) >> PAGE_SHIFT);
>         free_initmem_default(POISON_FREE_INITMEM);
>  }
>

Thanks for the fix. I guess you need to disable
CONFIG_STRICT_KERNEL_RWX explicitly
to notice this issue.

> Else it crashes here without any kernel output.
>
> Feel free to fold this into your patch.
>

IMO, this can be a separate patch with Fixes tag.

> Gr{oetje,eeting}s,
>
>                         Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds
>
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-- 
Regards,
Atish