Re: [PATCH v2] livepatch: Match old_sympos 0 and 1 in klp_find_func()

[Petr Mladek <pmladek@suse.com>]

On Mon 2025-10-13 10:30:19, Song Liu wrote:
> When there is only one function of the same name, old_sympos of 0 and 1
> are logically identical. Match them in klp_find_func().
> 
> This is to avoid a corner case with different toolchain behavior.
> 
> In this specific issue, issue two versions of kpatch-build were used to

  s/issue, issue/issue/

> build livepatch for the same kernel. One assigns old_sympos == 0 for
> unique local functions, the other assigns old_sympos == 1 for unique
> local functions. Both versions work fine by themselves. (PS: This
> behavior change was introduced in a downstream version of kpatch-build.
> This change does not exist in upstream kpatch-build.)
> 
> However, during livepatch upgrade (with the replace flag set) from a
> patch built with one version of kpatch-build to the same fix built with
> the other version of kpatch-build, livepatching fails with errors like:
> 
> --- a/kernel/livepatch/core.c
> +++ b/kernel/livepatch/core.c
> @@ -88,8 +88,14 @@ static struct klp_func *klp_find_func(struct klp_object *obj,
>  	struct klp_func *func;
>  
>  	klp_for_each_func(obj, func) {
> +		/*
> +		 * Besides identical old_sympos, also condiser old_sympos

As Josh already pointed out:

   s/condiser/consider/

> +		 * of 0 and 1 are identical.
> +		 */
>  		if ((strcmp(old_func->old_name, func->old_name) == 0) &&
> -		    (old_func->old_sympos == func->old_sympos)) {
> +		    ((old_func->old_sympos == func->old_sympos) ||
> +		     (old_func->old_sympos == 0 && func->old_sympos == 1) ||
> +		     (old_func->old_sympos == 1 && func->old_sympos == 0))) {
>  			return func;
>  		}
>  	}

With the two above fixes:

Reviewed-by: Petr Mladek <pmladek@suse.com>
Tested-by: Petr Mladek <pmladek@suse.com>

I have fixed both problems when committing.

And the patch has been committed into livepatching.git,
branch for-6.19/trivial.

Best Regards,
Petr