Re: [PATCH v4 1/5] livepatch: Fail object initialization on duplicate patched function

[Harry Hsu <x90613@gmail.com>]

On Fri, 18 Sep 2026, Miroslav Benes wrote:

> Could we also check prev_func/func->nop in the check in
> klp_init_object_loaded() and have a pass if true?

Thanks for the suggestion.

Yes, I've updated the check to skip the pair when both klp_funcs are
nops. Two nops added by klp_add_nops() for replaced aliases are
interchangeable, so an atomic replace patch that inherits nops for
__do_sys_fork and __x64_sys_fork from two previous patches now loads
fine. A non-nop func colliding with a nop (or another non-nop func)
is still rejected, since the nop would land on top of the real
replacement on ops->func_stack and silently disable it.

The incremental change on top of v4 1/5 is:

--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -894,6 +894,8 @@ static int klp_init_object_loaded(struct klp_patch *patch,
 			if (prev_func == func)
 				break;
 			if (prev_func->old_func == func->old_func) {
+				if (prev_func->nop && func->nop)
+					continue;
 				pr_err("'%s' and '%s' resolve to the same address, aliased symbols are not supported\n",
 				       prev_func->old_name, func->old_name);
 				return -EINVAL;

If this direction looks good, I'll resend the series. Petr, should I
just bundle everything into a v5, or do you have changes on your side
that I should wait for?

P.S. Sorry for the second mail. I forgot to quote the message I was
replying to in my first one.

Harry