Re: [PATCH v5 1/2] kprobes: textmem API

Masami Hiramatsu
2024-03-25T23:50:43Z

On Tue, 26 Mar 2024 00:09:42 +0200
"Jarkko Sakkinen" <jarkko@kernel.org> wrote:

> On Mon Mar 25, 2024 at 11:55 PM EET, Jarkko Sakkinen wrote:
> > +#ifdef CONFIG_MODULES
> > if (register_module_notifier(&trace_kprobe_module_nb))
> > return -EINVAL;
> > +#endif /* CONFIG_MODULES */
>
> register_module_notifier() does have "dummy" version but what
> would I pass to it. It makes more mess than it cleans to declare
> also a "dummy" version of trace_kprobe_module_nb.

That is better than having #ifdef in the function.

>
> The callback itself has too tight module subsystem bindings so
> that they could be simply flagged with IS_DEFINED() (or correct
> if I'm mistaken, this the conclusion I've ended up with).

Please try this.

-----
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 70dc6179086e..bc98db14927f 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -2625,6 +2625,7 @@ static void remove_module_kprobe_blacklist(struct module *mod)
}
}

+#ifdef CONFIG_MODULES
/* Module notifier call back, checking kprobes on the module */
static int kprobes_module_callback(struct notifier_block *nb,
unsigned long val, void *data)
@@ -2675,6 +2676,9 @@ static int kprobes_module_callback(struct notifier_block *nb,
mutex_unlock(&kprobe_mutex);
return NOTIFY_DONE;
}
+#else
+#define kprobes_module_callback (NULL)
+#endif

static struct notifier_block kprobe_module_nb = {
.notifier_call = kprobes_module_callback,
@@ -2739,7 +2743,7 @@ static int __init init_kprobes(void)
err = arch_init_kprobes();
if (!err)
err = register_die_notifier(&kprobe_exceptions_nb);
- if (!err)
+ if (!err && IS_ENABLED(CONFIG_MODULES))
err = register_module_notifier(&kprobe_module_nb);

kprobes_initialized = (err == 0);

-----

Thank you,

--
Masami Hiramatsu (Google) <mhiramat@kernel.org>