[PATCH v4 02/15] mm: Make empty_zero_page __ro_after_init

[Jann Horn]

On Mon, May 11, 2026 at 10:59 AM Ard Biesheuvel <ardb at kernel.org> wrote:
> I think we should simply do something along the lines of the below,
> considering that the size of a data object tends to correlate with
> its minimum alignment.
>
> I do find it rather puzzling that the compiler emits empty_zero_page
> *after* zero_page_pfn - ideally, we'd combine the below with
> -fdata-sections so that the linker sees all individual objects, but
> I suspect that would create some problems elsewhere.
>
>
> --- a/include/asm-generic/vmlinux.lds.h
> +++ b/include/asm-generic/vmlinux.lds.h
> @@ -452,7 +452,7 @@
>  #define RO_AFTER_INIT_DATA                                   \
>         . = ALIGN(8);                                         \
>         __start_ro_after_init = .;                            \
> -       *(.data..ro_after_init)                               \
> +       *(SORT_BY_ALIGNMENT(.data..ro_after_init))            \

Oh, neat, I didn't realize that's possible. That seems like a nicer
approach... (Assuming that it doesn't cause cache efficiency issues
somehow, I imagine it could be possible that source-code-adjacent
objects should also be located next to each other for cache/TLB
efficiency... but I have no concrete reason to think that, just a
thought.)