Commit 55d2eba8 authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

jump_label: Fix usage in module __init 



When the static_key is part of the module, and the module calls
static_key_inc/enable() from it's __init section *AND* has a
static_branch_*() user in that very same __init section, things go
wobbly.

If the static_key lives outside the module, jump_label_add_module()
would append this module's sites to the key and jump_label_update()
would take the static_key_linked() branch and all would be fine.

If all the sites are outside of __init, then everything will be fine
too.

However, when all is aligned just as described above,
jump_label_update() calls __jump_label_update(.init = false) and we'll
not update sites in __init text.

Fixes: 19483677 ("jump_label: Annotate entries that operate on __init code earlier")
Reported-by: default avatarDexuan Cui <decui@microsoft.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Tested-by: default avatarJessica Yu <jeyu@kernel.org>
Link: https://lkml.kernel.org/r/20201216135435.GV3092@hirez.programming.kicks-ass.net
parent 2c85ebc5

kernel/jump_label.c

+5 −3
Original line number Diff line number Diff line
@@ -793,6 +793,7 @@ int jump_label_text_reserved(void *start, void *end) 
static void jump_label_update(struct static_key *key)

{

	struct jump_entry *stop = __stop___jump_table;

	bool init = system_state < SYSTEM_RUNNING;

	struct jump_entry *entry;

#ifdef CONFIG_MODULES

	struct module *mod;
@@ -804,15 +805,16 @@ static void jump_label_update(struct static_key *key) 


	preempt_disable();

	mod = __module_address((unsigned long)key);

	if (mod)

	if (mod) {

		stop = mod->jump_entries + mod->num_jump_entries;

		init = mod->state == MODULE_STATE_COMING;

	}

	preempt_enable();

#endif

	entry = static_key_entries(key);

	/* if there are no users, entry can be NULL */

	if (entry)

		__jump_label_update(key, entry, stop,

				    system_state < SYSTEM_RUNNING);

		__jump_label_update(key, entry, stop, init);

}



#ifdef CONFIG_STATIC_KEYS_SELFTEST