Re: [PATCH] xen: unexport __init-annotated xen_xlate_map_ballooned_pages()

[Oleksandr <olekstysh@xxxxxxxxx>]

On 06.06.22 07:59, Masahiro Yamada wrote:

Hello

> EXPORT_SYMBOL and __init is a bad combination because the .init.text
> section is freed up after the initialization. Hence, modules cannot
> use symbols annotated __init. The access to a freed symbol may end up
> with kernel panic.
>
> modpost used to detect it, but it has been broken for a decade.
>
> Recently, I fixed modpost so it started to warn it again, then this
> showed up in linux-next builds.
>
> There are two ways to fix it:
>
>    - Remove __init
>    - Remove EXPORT_SYMBOL
>
> I chose the latter for this case because none of the in-tree call-sites
> (arch/arm/xen/enlighten.c, arch/x86/xen/grant-table.c) is compiled as
> modular.
Good description.


> Fixes: 243848fc018c ("xen/grant-table: Move xlated_setup_gnttab_pages to common 
> place")
> Reported-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
> Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
I think the patch is correct.

Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>

> ---
>
>   drivers/xen/xlate_mmu.c | 1 -
>   1 file changed, 1 deletion(-)
>
> diff --git a/drivers/xen/xlate_mmu.c b/drivers/xen/xlate_mmu.c
> index 34742c6e189e..f17c4c03db30 100644
> --- a/drivers/xen/xlate_mmu.c
> +++ b/drivers/xen/xlate_mmu.c
> @@ -261,7 +261,6 @@ int __init xen_xlate_map_ballooned_pages(xen_pfn_t **gfns, 
> void **virt,
>   
>   	return 0;
>   }
> -EXPORT_SYMBOL_GPL(xen_xlate_map_ballooned_pages);
>   
>   struct remap_pfn {
>         struct mm_struct *mm;
--
Regards,

Oleksandr Tyshchenko