random: clean up interrupt entropy accounting for archs w/o cycle counters (840f9507) · Commits · 戴 / test

drivers/char/random.c

+23 −19

Original line number	Diff line number	Diff line
		@@ -548,9 +548,9 @@ static void mix_pool_bytes(struct entropy_store r, const void in,
		struct fast_pool {
		__u32 pool[4];
		unsigned long last;
		unsigned short count;
		unsigned char count;
		unsigned char notimer_count;
		unsigned char rotate;
		unsigned char last_timer_intr;
		};

		/*
		@@ -850,15 +850,23 @@ void add_interrupt_randomness(int irq, int irq_flags)
		input[3] = ip >> 32;

		fast_mix(fast_pool, input);
		if ((irq_flags & __IRQF_TIMER) == 0)
		fast_pool->notimer_count++;

		if ((fast_pool->count & 63) && !time_after(now, fast_pool->last + HZ))
		if (cycles) {
		if ((fast_pool->count < 64) &&
		!time_after(now, fast_pool->last + HZ))
		return;
		} else {
		/* CPU does not have a cycle counting register :-( */
		if (fast_pool->count < 64)
		return;
		}

		r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
		if (!spin_trylock(&r->lock)) {
		fast_pool->count--;
		if (!spin_trylock(&r->lock))
		return;
		}

		fast_pool->last = now;
		__mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool));

		@@ -874,19 +882,15 @@ void add_interrupt_randomness(int irq, int irq_flags)
		spin_unlock(&r->lock);

		/*
		* If we don't have a valid cycle counter, and we see
		* back-to-back timer interrupts, then skip giving credit for
		* any entropy, otherwise credit 1 bit.
		* If we have a valid cycle counter or if the majority of
		* interrupts collected were non-timer interrupts, then give
		* an entropy credit of 1 bit. Yes, this is being very
		* conservative.
		*/
		if (cycles \|\| (fast_pool->notimer_count >= 32))
		credit++;
		if (cycles == 0) {
		if (irq_flags & __IRQF_TIMER) {
		if (fast_pool->last_timer_intr)
		credit--;
		fast_pool->last_timer_intr = 1;
		} else
		fast_pool->last_timer_intr = 0;
		}

		fast_pool->count = fast_pool->notimer_count = 0;

		credit_entropy_bits(r, credit);
		}

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