| Message ID | 20220419111650.1582274-11-Jason@zx2c4.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | archs/random: fallback to best raw ktime when no cycle counter | expand |
On Tue, Apr 19, 2022 at 4:18 AM Jason A. Donenfeld <Jason@zx2c4.com> wrote: > > In the event that random_get_entropy() can't access a cycle counter or > similar, falling back to returning 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. > > This is accomplished by just including the asm-generic code like on > other architectures, which means we can get rid of the empty stub > function here. > > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Arnd Bergmann <arnd@arndb.de> > Cc: Max Filippov <jcmvbkbc@gmail.com> > Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> > --- > arch/xtensa/include/asm/timex.h | 6 ++---- > 1 file changed, 2 insertions(+), 4 deletions(-) Acked-by: Max Filippov <jcmvbkbc@gmail.com>
diff --git a/arch/xtensa/include/asm/timex.h b/arch/xtensa/include/asm/timex.h index 233ec75e60c6..3f2462f2d027 100644 --- a/arch/xtensa/include/asm/timex.h +++ b/arch/xtensa/include/asm/timex.h @@ -29,10 +29,6 @@ extern unsigned long ccount_freq; -typedef unsigned long long cycles_t; - -#define get_cycles() (0) - void local_timer_setup(unsigned cpu); /* @@ -59,4 +55,6 @@ static inline void set_linux_timer (unsigned long ccompare) xtensa_set_sr(ccompare, SREG_CCOMPARE + LINUX_TIMER); } +#include <asm-generic/timex.h> + #endif /* _XTENSA_TIMEX_H */
In the event that random_get_entropy() can't access a cycle counter or similar, falling back to returning 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. This is accomplished by just including the asm-generic code like on other architectures, which means we can get rid of the empty stub function here. Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Max Filippov <jcmvbkbc@gmail.com> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> --- arch/xtensa/include/asm/timex.h | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)