linux-kernel - Re: [timekeeping] 3aeaac747d: PANIC:early

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Message-ID: <8735hnhz1q.ffs@tglx>
Date:   Fri, 06 May 2022 09:59:13 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     kernel test robot <oliver.sang@...el.com>,
        "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     0day robot <lkp@...el.com>, Arnd Bergmann <arnd@...db.de>,
        Theodore Ts'o <tytso@....edu>,
        LKML <linux-kernel@...r.kernel.org>, lkp@...ts.01.org,
        linux-crypto@...r.kernel.org, nathan@...nel.org,
        "Jason A. Donenfeld" <Jason@...c4.com>
Subject: Re: [timekeeping]  3aeaac747d: PANIC:early_exception

On Fri, May 06 2022 at 11:20, kernel test robot wrote:
> PANIC: early exception 0x0d IP 10:ffffffff812cef11 error 0 cr2 0xffff888004a3aff8
> [ 0.000000][ T0] add_device_randomness (kbuild/src/rand-3/drivers/char/random.c:1028) 
> [ 0.000000][ T0] ? dmi_walk_early (kbuild/src/rand-3/drivers/firmware/dmi_scan.c:470) 
> [ 0.000000][ T0] dmi_walk_early (kbuild/src/rand-3/drivers/firmware/dmi_scan.c:151) 
> [ 0.000000][ T0] dmi_present (kbuild/src/rand-3/drivers/firmware/dmi_scan.c:605)

Duh.

So this wants to be:

--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -2380,6 +2381,20 @@ static int timekeeping_validate_timex(co
 	return 0;
 }
 
+/**
+ * random_get_entropy_fallback - Returns the raw clock source value,
+ * used by random.c for platforms with no valid random_get_entropy().
+ */
+unsigned long random_get_entropy_fallback(void)
+{
+	struct tk_read_base *tkr = &tk_core.timekeeper.tkr_mono;
+	struct clocksource *clock = READ_ONCE(tkr->clock);
+
+	if (!timekeeping_suspended && clock)
+		return clock->read(clock);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(random_get_entropy_fallback);
 
 /**
  * do_adjtimex() - Accessor function to NTP __do_adjtimex function