On Mon, Mar 22, 2021 at 03:50:14PM +0100, Jessica Yu wrote:
> It should be doable. If you want the exit sections to be treated the same as
> module init, the following patch should stuff any exit sections into the
> module
> init "region" (completely untested). Hence it should be freed together with
> the
> init sections and it would identify as init through within_module_init(). Let
> me know if this works for you.
That does indeed seem to DTRT from a quick scan of module.c. Very nice
tidy patch. I was afraid it'd be much worse.
Assuming it actually works; for your Changelog:
"Dynamic code patching (alternatives, jump_label and static_call) can
have sites in __exit code, even it __exit is never executed. Therefore
__exit must be present at runtime, at least for as long as __init code
is.
Additionally, for jump_label and static_call, the __exit sites must also
identify as within_module_init(), such that the infrastructure is aware
to never touch them after module init -- alternatives are only ran once
at init and hence don't have this particular constraint.
By making __exit identify as __init for UNLOAD_MODULE, the above is
satisfied."
Thanks!
> ---
>
> diff --git a/kernel/module.c b/kernel/module.c
> index 30479355ab85..1c3396a9dd8b 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -2802,7 +2802,11 @@ void * __weak module_alloc(unsigned long size)
>
> bool __weak module_init_section(const char *name)
> {
> - return strstarts(name, ".init");
> +#ifndef CONFIG_UNLOAD_MODULE
> + return strstarts(name, ".init") || module_exit_section(name);
> +#else
> + return strstarts(name, ".init")
> +#endif
> }
>
> bool __weak module_exit_section(const char *name)
> @@ -3116,11 +3120,6 @@ static int rewrite_section_headers(struct load_info
> *info, int flags)
> */
> shdr->sh_addr = (size_t)info->hdr + shdr->sh_offset;
>
> -#ifndef CONFIG_MODULE_UNLOAD
> - /* Don't load .exit sections */
> - if (module_exit_section(info->secstrings+shdr->sh_name))
> - shdr->sh_flags &= ~(unsigned long)SHF_ALLOC;
> -#endif
> }
>
> /* Track but don't keep modinfo and version sections. */
>
