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

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Message-Id: <20240326085037.0142d7dadc702e3b49a3251e@kernel.org>
Date: Tue, 26 Mar 2024 08:50:37 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: "Jarkko Sakkinen" <jarkko@...nel.org>
Cc: <linux-riscv@...ts.infradead.org>, "Masami Hiramatsu"
 <mhiramat@...nel.org>, "Paul Walmsley" <paul.walmsley@...ive.com>,
 "Palmer Dabbelt" <palmer@...belt.com>, "Albert Ou" <aou@...s.berkeley.edu>,
 <linux-kernel@...r.kernel.org>, "Luis Chamberlain" <mcgrof@...nel.org>,
 <linux-modules@...r.kernel.org>, "Naveen N . Rao"
 <naveen.n.rao@...ux.ibm.com>, "Anil S Keshavamurthy"
 <anil.s.keshavamurthy@...el.com>, "David S . Miller" <davem@...emloft.net>
Subject: Re: [PATCH v5 1/2] kprobes: textmem API

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