random: simplify add_ptr logic (993ba211) · Commits · 戴 / test

drivers/char/random.c

+10 −11

Original line number	Diff line number	Diff line
		@@ -454,7 +454,7 @@ static void __add_entropy_words(struct entropy_store r, const __u32 in,
		static __u32 const twist_table[8] = {
		0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
		0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
		unsigned long i, add_ptr, tap1, tap2, tap3, tap4, tap5;
		unsigned long i, j, tap1, tap2, tap3, tap4, tap5;
		int input_rotate;
		int wordmask = r->poolinfo->poolwords - 1;
		__u32 w;
		@@ -469,19 +469,21 @@ static void __add_entropy_words(struct entropy_store r, const __u32 in,

		spin_lock_irqsave(&r->lock, flags);
		input_rotate = r->input_rotate;
		add_ptr = r->add_ptr;
		i = r->add_ptr;

		while (nwords--) {
		w = rol32(*in++, input_rotate & 31);
		i = add_ptr = (add_ptr - 1) & wordmask;
		i = (i - 1) & wordmask;

		/* XOR in the various taps */
		w ^= r->pool[i];
		w ^= r->pool[(i + tap1) & wordmask];
		w ^= r->pool[(i + tap2) & wordmask];
		w ^= r->pool[(i + tap3) & wordmask];
		w ^= r->pool[(i + tap4) & wordmask];
		w ^= r->pool[(i + tap5) & wordmask];
		w ^= r->pool[i];

		/* Mix the result back in with a twist */
		r->pool[i] = (w >> 3) ^ twist_table[w & 7];

		/*
		@@ -494,14 +496,11 @@ static void __add_entropy_words(struct entropy_store r, const __u32 in,
		}

		r->input_rotate = input_rotate;
		r->add_ptr = add_ptr;
		r->add_ptr = i;

		if (out) {
		for (i = 0; i < 16; i++) {
		out[i] = r->pool[add_ptr];
		add_ptr = (add_ptr - 1) & wordmask;
		}
		}
		if (out)
		for (j = 0; j < 16; j++)
		out[j] = r->pool[(i - j) & wordmask];

		spin_unlock_irqrestore(&r->lock, flags);
		}