Commit e4279b59 authored by Sebastian Andrzej Siewior's avatar Sebastian Andrzej Siewior Committed by Petr Mladek
Browse files

lib/vsprintf: Remove static_branch_likely() from __ptr_to_hashval(). 



Using static_branch_likely() to signal that ptr_key has been filled is a
bit much given that it is not a fast path.

Replace static_branch_likely() with bool for condition and a memory
barrier for ptr_key.

Suggested-by: default avatarPetr Mladek <pmladek@suse.com>
Signed-off-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: default avatarPetr Mladek <pmladek@suse.com>
Signed-off-by: default avatarPetr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20220927104912.622645-2-bigeasy@linutronix.de
parent a1b02751

lib/vsprintf.c

+8 −11
Original line number Diff line number Diff line
@@ -750,12 +750,7 @@ static int __init debug_boot_weak_hash_enable(char *str) 
}

early_param("debug_boot_weak_hash", debug_boot_weak_hash_enable);



static DEFINE_STATIC_KEY_FALSE(filled_random_ptr_key);



static void enable_ptr_key_workfn(struct work_struct *work)

{

	static_branch_enable(&filled_random_ptr_key);

}

static bool filled_random_ptr_key __read_mostly;



/* Maps a pointer to a 32 bit unique identifier. */

static inline int __ptr_to_hashval(const void *ptr, unsigned long *hashval_out)
@@ -763,24 +758,26 @@ static inline int __ptr_to_hashval(const void *ptr, unsigned long *hashval_out) 
	static siphash_key_t ptr_key __read_mostly;

	unsigned long hashval;



	if (!static_branch_likely(&filled_random_ptr_key)) {

	if (!READ_ONCE(filled_random_ptr_key)) {

		static bool filled = false;

		static DEFINE_SPINLOCK(filling);

		static DECLARE_WORK(enable_ptr_key_work, enable_ptr_key_workfn);

		unsigned long flags;



		if (!system_unbound_wq || !rng_is_initialized() ||

		if (!rng_is_initialized() ||

		    !spin_trylock_irqsave(&filling, flags))

			return -EAGAIN;



		if (!filled) {

			get_random_bytes(&ptr_key, sizeof(ptr_key));

			queue_work(system_unbound_wq, &enable_ptr_key_work);

			/* Pairs with smp_rmb() before reading ptr_key. */

			smp_wmb();

			WRITE_ONCE(filled_random_ptr_key, true);

			filled = true;

		}

		spin_unlock_irqrestore(&filling, flags);

	}



	/* Pairs with smp_wmb() after writing ptr_key. */

	smp_rmb();



#ifdef CONFIG_64BIT

	hashval = (unsigned long)siphash_1u64((u64)ptr, &ptr_key);