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: 19483677684b ("jump_label: Annotate entries that operate on __init code earlier")
Reported-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Tested-by: Jessica Yu <jeyu@kernel.org>
Link: https://lkml.kernel.org/r/20201216135435.GV3092@hirez.programming.kicks-ass.net

diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index 015ef90..c6a39d6 100644 (file)
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -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