Messages in this thread | | | Date | Thu, 14 Apr 2022 11:12:27 +0100 | From | "Russell King (Oracle)" <> | Subject | Re: [PATCH v4 01/11] timekeeping: add raw clock fallback for random_get_entropy() |
| |
On Wed, Apr 13, 2022 at 01:54:01PM +0200, Jason A. Donenfeld wrote: > The addition of random_get_entropy_fallback() provides access to > whichever time source has the highest frequency, which is useful for > gathering entropy on platforms without available cycle counters. It's > not necessarily as good as being able to quickly access a cycle counter > that the CPU has, but it's still something, even when it falls back to > being jiffies-based. > > In the event that a given arch does not define get_cycles(), falling > back to the get_cycles() default implementation that returns 0 is really > not the best we can do. Instead, at least calling > random_get_entropy_fallback() would be preferable, because that always > needs to return _something_, even falling back to jiffies eventually. > It's not as though random_get_entropy_fallback() is super high precision > or guaranteed to be entropic, but basically anything that's not zero all > the time is better than returning zero all the time. > > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Arnd Bergmann <arnd@arndb.de> > Cc: Theodore Ts'o <tytso@mit.edu> > Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> > --- > include/linux/timex.h | 8 ++++++++ > kernel/time/timekeeping.c | 10 ++++++++++ > 2 files changed, 18 insertions(+) > > diff --git a/include/linux/timex.h b/include/linux/timex.h > index 5745c90c8800..fbbe34226044 100644 > --- a/include/linux/timex.h > +++ b/include/linux/timex.h > @@ -62,6 +62,8 @@ > #include <linux/types.h> > #include <linux/param.h> > > +extern unsigned long random_get_entropy_fallback(void);
Hi
I'm surprised this didn't trigger checkpatch to warn. From coding-style:
6.1) Function prototypes Do not use the ``extern`` keyword with function declarations as this makes lines longer and isn't strictly necessary.
Thanks!
-- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
| |