Re: [PATCH v2 3/3] module: Make .static_call_sites read-only after init

[Christophe Leroy <christophe.leroy@csgroup.eu>]

Le 06/03/2025 à 14:13, Petr Pavlu a écrit :
> Section .static_call_sites holds data structures that need to be sorted and
> processed only at module load time. This initial processing happens in
> static_call_add_module(), which is invoked as a callback to the
> MODULE_STATE_COMING notification from prepare_coming_module().
> 
> The section is never modified afterwards. Make it therefore read-only after
> module initialization to avoid any (non-)accidental modifications.

Maybe this suggestion is stupid, I didn't investigate the feasability 
but: why don't we group everything that is ro_after_init in a single 
section just like we do in vmlinux ? That would avoid having to add 
every new possible section in the C code.

Like we have in asm-generic/vmlinux.lds.h:

#define RO_AFTER_INIT_DATA						\
	. = ALIGN(8);							\
	__start_ro_after_init = .;					\
	*(.data..ro_after_init)						\
	JUMP_TABLE_DATA							\
	STATIC_CALL_DATA						\
	__end_ro_after_init = .;


> 
> Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
> ---
>   kernel/module/strict_rwx.c | 9 +++++++++
>   1 file changed, 9 insertions(+)
> 
> diff --git a/kernel/module/strict_rwx.c b/kernel/module/strict_rwx.c
> index fa701dad4ed1..a3fc8d603750 100644
> --- a/kernel/module/strict_rwx.c
> +++ b/kernel/module/strict_rwx.c
> @@ -120,6 +120,15 @@ static const char *const ro_after_init[] = {
>   	 * section, which are marked as such at module load time.
>   	 */
>   	"__jump_table",
> +
> +#ifdef CONFIG_HAVE_STATIC_CALL_INLINE
> +	/*
> +	 * Section .static_call_sites holds data structures that need to be
> +	 * sorted and processed at module load time but are never modified
> +	 * afterwards.
> +	 */
> +	".static_call_sites",
> +#endif
>   };
>   
>   void module_mark_ro_after_init(const Elf_Ehdr *hdr, Elf_Shdr *sechdrs,