linux-kernel - [PATCH] random: inform about bootloader-provided randomness

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Message-ID: <20191005113632.GA74715@light.dominikbrodowski.net>
Date:   Sat, 5 Oct 2019 13:36:32 +0200
From:   Dominik Brodowski <linux@...inikbrodowski.net>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Rob Herring <robh@...nel.org>, Theodore Ts'o <tytso@....edu>,
        Will Deacon <will@...nel.org>
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH] random: inform about bootloader-provided randomness

Inform how many bits of randomness were provided by the bootloader,
and whether we trust that input.

Signed-off-by: Dominik Brodowski <linux@...inikbrodowski.net>
Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc: Hsin-Yi Wang <hsinyi@...omium.org>
Cc: Stephen Boyd <swboyd@...omium.org>
Cc: Rob Herring <robh@...nel.org>
Cc: Theodore Ts'o <tytso@....edu>
Cc: Will Deacon <will@...nel.org>

diff --git a/drivers/char/random.c b/drivers/char/random.c
index de434feb873a..673375e05c0d 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -2515,6 +2515,10 @@ EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);
  */
 void add_bootloader_randomness(const void *buf, unsigned int size)
 {
+	pr_notice("random: adding %u bits of %sbootloader-provided randomness",
+		size * 8,
+		IS_ENABLED(CONFIG_RANDOM_TRUST_BOOTLOADER) ? "trusted " : "");
+
 	if (IS_ENABLED(CONFIG_RANDOM_TRUST_BOOTLOADER))
 		add_hwgenerator_randomness(buf, size, size * 8);
 	else