linux-kernel - [PATCH v2] init: call time_init() before rand

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Date:   Sun,  8 May 2022 02:20:18 +0200
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     linux-kernel@...r.kernel.org
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Stafford Horne <shorne@...il.com>
Subject: [PATCH v2] init: call time_init() before rand_initialize()

Currently time_init() is called after rand_initialize(), but
rand_initialize() makes use of the timer on various platforms, and
sometimes this timer needs to be initialized by time_init() first. In
order for random_get_entropy() to not return zero during early boot when
it's potentially used as an entropy source, reverse the order of these
two calls. The block doing random initialization was right before
time_init() before, so changing the order shouldn't have any complicated
effects.

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Stafford Horne <shorne@...il.com>
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
---
Changes v1->v2:
- Clarified commit message; code remains the same.

This lives in random.git and will be in linux-next for testing.

 init/main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/init/main.c b/init/main.c
index 98182c3c2c4b..e37ec99cf56d 100644
--- a/init/main.c
+++ b/init/main.c
@@ -1035,6 +1035,7 @@ asmlinkage __visible void __init __no_sanitize_address start_kernel(void)
 	softirq_init();
 	timekeeping_init();
 	kfence_init();
+	time_init();

 	/*
 	 * For best initial stack canary entropy, prepare it after:
@@ -1049,7 +1050,6 @@ asmlinkage __visible void __init __no_sanitize_address start_kernel(void)
 	add_device_randomness(command_line, strlen(command_line));
 	boot_init_stack_canary();

-	time_init();
 	perf_event_init();
 	profile_init();
 	call_function_init();
-- 
2.35.1