Commit 1b2439db authored by Arjan van de Ven's avatar Arjan van de Ven Committed by Ingo Molnar
Browse files

debug: add notifier chain debugging 



during some development we suspected a case where we left something
in a notifier chain that was from a module that was unloaded already...
and that sort of thing is rather hard to track down.

This patch adds a very simple sanity check (which isn't all that
expensive) to make sure the notifier we're about to call is
actually from either the kernel itself of from a still-loaded
module, avoiding a hard-to-chase-down crash.

Signed-off-by: default avatarArjan van de Ven <arjan@linux.intel.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent b09c3e3f

kernel/notifier.c

+16 −0
Original line number Diff line number Diff line
@@ -21,6 +21,10 @@ BLOCKING_NOTIFIER_HEAD(reboot_notifier_list); 
static int notifier_chain_register(struct notifier_block **nl,

		struct notifier_block *n)

{

	if (!kernel_text_address((unsigned long)n->notifier_call)) {

		WARN(1, "Invalid notifier registered!");

		return 0;

	}

	while ((*nl) != NULL) {

		if (n->priority > (*nl)->priority)

			break;
@@ -34,6 +38,10 @@ static int notifier_chain_register(struct notifier_block **nl, 
static int notifier_chain_cond_register(struct notifier_block **nl,

		struct notifier_block *n)

{

	if (!kernel_text_address((unsigned long)n->notifier_call)) {

		WARN(1, "Invalid notifier registered!");

		return 0;

	}

	while ((*nl) != NULL) {

		if ((*nl) == n)

			return 0;
@@ -82,6 +90,14 @@ static int __kprobes notifier_call_chain(struct notifier_block **nl, 


	while (nb && nr_to_call) {

		next_nb = rcu_dereference(nb->next);



#ifdef CONFIG_DEBUG_NOTIFIERS

		if (!kernel_text_address((unsigned long)nb->notifier_call)) {

			WARN(1, "Invalid notifier called!");

			nb = next_nb;

			continue;

		}

#endif

		ret = nb->notifier_call(nb, val, v);



		if (nr_calls)

lib/Kconfig.debug

+10 −0
Original line number Diff line number Diff line
@@ -536,6 +536,16 @@ config DEBUG_SG 


	  If unsure, say N.



config DEBUG_NOTIFIERS

	bool "Debug notifier call chains"

	depends on DEBUG_KERNEL

	help

	  Enable this to turn on sanity checking for notifier call chains.

	  This is most useful for kernel developers to make sure that

	  modules properly unregister themselves from notifier chains.

	  This is a relatively cheap check but if you care about maximum

	  performance, say N.



config FRAME_POINTER

	bool "Compile the kernel with frame pointers"

	depends on DEBUG_KERNEL && \

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