[PATCH] riscv: Align on L1_CACHE_BYTES when STRICT_KERNEL_RWX

[Geert Uytterhoeven]

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);
 }

Else it crashes here without any kernel output.

Feel free to fold this into your patch.

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