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From:   Daniel Wagner <wagi@monom.org>
To:     LKML <linux-kernel@vger.kernel.org>,
        linux-rt-users <linux-rt-users@vger.kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Carsten Emde <C.Emde@osadl.org>,
        John Kacur <jkacur@redhat.com>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        Tom Zanussi <tom.zanussi@linux.intel.com>,
        Clark Williams <williams@redhat.com>,
        Pavel Machek <pavel@denx.de>
Cc:     Daniel Wagner <dwagner@suse.de>
Subject: [PATCH RT 2/9] random: Bring back the local_locks
Date:   Mon, 24 Oct 2022 12:44:18 +0200
Message-Id: <20221024104425.16423-3-wagi@monom.org>
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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

v4.19.255-rt114-rc1 stable review patch.
If anyone has any objections, please let me know.

-----------


As part of the backports the random code lost its local_lock_t type and
the whole operation became a local_irq_{disable|enable}() simply because
the older kernel did not provide those primitives.

RT as of v4.9 has a slightly different variant of local_locks.
Replace the local_irq_*() operations with matching local_lock_irq*()
operations which were there as part of commit
   77760fd7f7ae3 ("random: remove batched entropy locking")

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/all/20220819092446.980320-2-bigeasy@linutronix.de/
Signed-off-by: Daniel Wagner <dwagner@suse.de>
---
 drivers/char/random.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 2be38780a7f7..0fd0462054bd 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -53,6 +53,7 @@
 #include <linux/uaccess.h>
 #include <linux/siphash.h>
 #include <linux/uio.h>
+#include <linux/locallock.h>
 #include <crypto/chacha20.h>
 #include <crypto/blake2s.h>
 #include <asm/processor.h>
@@ -229,10 +230,12 @@ static struct {
 struct crng {
 	u8 key[CHACHA20_KEY_SIZE];
 	unsigned long generation;
+	struct local_irq_lock lock;
 };
 
 static DEFINE_PER_CPU(struct crng, crngs) = {
-	.generation = ULONG_MAX
+	.generation = ULONG_MAX,
+	.lock.lock = __SPIN_LOCK_UNLOCKED(crngs.lock.lock),
 };
 
 /* Used by crng_reseed() and crng_make_state() to extract a new seed from the input pool. */
@@ -362,7 +365,7 @@ static void crng_make_state(u32 chacha_state[CHACHA20_BLOCK_SIZE / sizeof(u32)],
 	if (unlikely(crng_has_old_seed()))
 		crng_reseed();
 
-	local_irq_save(flags);
+	local_lock_irqsave(crngs.lock, flags);
 	crng = raw_cpu_ptr(&crngs);
 
 	/*
@@ -387,7 +390,7 @@ static void crng_make_state(u32 chacha_state[CHACHA20_BLOCK_SIZE / sizeof(u32)],
 	 * should wind up here immediately.
 	 */
 	crng_fast_key_erasure(crng->key, chacha_state, random_data, random_data_len);
-	local_irq_restore(flags);
+	local_unlock_irqrestore(crngs.lock, flags);
 }
 
 static void _get_random_bytes(void *buf, size_t len)
@@ -505,11 +508,13 @@ struct batch_ ##type {								\
 	 * formula of (integer_blocks + 0.5) * CHACHA20_BLOCK_SIZE.		\
 	 */									\
 	type entropy[CHACHA20_BLOCK_SIZE * 3 / (2 * sizeof(type))];		\
+	struct local_irq_lock lock;						\
 	unsigned long generation;						\
 	unsigned int position;							\
 };										\
 										\
 static DEFINE_PER_CPU(struct batch_ ##type, batched_entropy_ ##type) = {	\
+	.lock.lock = __SPIN_LOCK_UNLOCKED(batched_entropy_ ##type.lock.lock),	\
 	.position = UINT_MAX							\
 };										\
 										\
@@ -527,7 +532,7 @@ type get_random_ ##type(void)							\
 		return ret;							\
 	}									\
 										\
-	local_irq_save(flags);		\
+	local_lock_irqsave(batched_entropy_ ##type.lock, flags);		\
 	batch = raw_cpu_ptr(&batched_entropy_##type);				\
 										\
 	next_gen = READ_ONCE(base_crng.generation);				\
@@ -541,7 +546,7 @@ type get_random_ ##type(void)							\
 	ret = batch->entropy[batch->position];					\
 	batch->entropy[batch->position] = 0;					\
 	++batch->position;							\
-	local_irq_restore(flags);		\
+	local_unlock_irqrestore(batched_entropy_ ##type.lock, flags);		\
 	return ret;								\
 }										\
 EXPORT_SYMBOL(get_random_ ##type);
-- 
2.38.0