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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>,
        Stafford Horne <shorne@gmail.com>,
        "Jason A. Donenfeld" <Jason@zx2c4.com>
Subject: [PATCH 4.19 134/234] init: call time_init() before rand_initialize()
Date:   Thu, 23 Jun 2022 18:43:21 +0200
Message-Id: <20220623164346.849705766@linuxfoundation.org>
In-Reply-To: <20220623164343.042598055@linuxfoundation.org>
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From: "Jason A. Donenfeld" <Jason@zx2c4.com>

commit fe222a6ca2d53c38433cba5d3be62a39099e708e upstream.

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@linux-foundation.org>
Reviewed-by: Stafford Horne <shorne@gmail.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 init/main.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/init/main.c
+++ b/init/main.c
@@ -633,11 +633,13 @@ asmlinkage __visible void __init start_k
 	hrtimers_init();
 	softirq_init();
 	timekeeping_init();
+	time_init();
 
 	/*
 	 * For best initial stack canary entropy, prepare it after:
 	 * - setup_arch() for any UEFI RNG entropy and boot cmdline access
 	 * - timekeeping_init() for ktime entropy used in rand_initialize()
+	 * - time_init() for making random_get_entropy() work on some platforms
 	 * - rand_initialize() to get any arch-specific entropy like RDRAND
 	 * - add_latent_entropy() to get any latent entropy
 	 * - adding command line entropy
@@ -647,7 +649,6 @@ asmlinkage __visible void __init start_k
 	add_device_randomness(command_line, strlen(command_line));
 	boot_init_stack_canary();
 
-	time_init();
 	perf_event_init();
 	profile_init();
 	call_function_init();