Commit 3a92d687 authored by Herbert Xu's avatar Herbert Xu
Browse files

crypto: sha512 - Avoid stack bloat on i386 



Unfortunately in reducing W from 80 to 16 we ended up unrolling
the loop twice.  As gcc has issues dealing with 64-bit ops on
i386 this means that we end up using even more stack space (>1K).

This patch solves the W reduction by moving LOAD_OP/BLEND_OP
into the loop itself, thus avoiding the need to duplicate it.

While the stack space still isn't great (>0.5K) it is at least
in the same ball park as the amount of stack used for our C sha1
implementation.

Note that this patch basically reverts to the original code so
the diff looks bigger than it really is.

Cc: stable@vger.kernel.org
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent 58d7d18b

crypto/sha512_generic.c

+32 −36
Original line number Diff line number Diff line
@@ -89,46 +89,42 @@ sha512_transform(u64 *state, const u8 *input) 
	int i;

	u64 W[16];



	/* load the input */

        for (i = 0; i < 16; i++)

                LOAD_OP(i, W, input);



	/* load the state into our registers */

	a=state[0];   b=state[1];   c=state[2];   d=state[3];

	e=state[4];   f=state[5];   g=state[6];   h=state[7];



#define SHA512_0_15(i, a, b, c, d, e, f, g, h)			\

	t1 = h + e1(e) + Ch(e, f, g) + sha512_K[i] + W[i];	\

	t2 = e0(a) + Maj(a, b, c);				\

	d += t1;						\

	h = t1 + t2



#define SHA512_16_79(i, a, b, c, d, e, f, g, h)			\

	BLEND_OP(i, W);						\

	t1 = h + e1(e) + Ch(e, f, g) + sha512_K[i] + W[(i)&15];	\

	t2 = e0(a) + Maj(a, b, c);				\

	d += t1;						\

	h = t1 + t2



	for (i = 0; i < 16; i += 8) {

		SHA512_0_15(i, a, b, c, d, e, f, g, h);

		SHA512_0_15(i + 1, h, a, b, c, d, e, f, g);

		SHA512_0_15(i + 2, g, h, a, b, c, d, e, f);

		SHA512_0_15(i + 3, f, g, h, a, b, c, d, e);

		SHA512_0_15(i + 4, e, f, g, h, a, b, c, d);

		SHA512_0_15(i + 5, d, e, f, g, h, a, b, c);

		SHA512_0_15(i + 6, c, d, e, f, g, h, a, b);

		SHA512_0_15(i + 7, b, c, d, e, f, g, h, a);

	/* now iterate */

	for (i=0; i<80; i+=8) {

		if (!(i & 8)) {

			int j;



			if (i < 16) {

				/* load the input */

				for (j = 0; j < 16; j++)

					LOAD_OP(i + j, W, input);

			} else {

				for (j = 0; j < 16; j++) {

					BLEND_OP(i + j, W);

				}

			}

	for (i = 16; i < 80; i += 8) {

		SHA512_16_79(i, a, b, c, d, e, f, g, h);

		SHA512_16_79(i + 1, h, a, b, c, d, e, f, g);

		SHA512_16_79(i + 2, g, h, a, b, c, d, e, f);

		SHA512_16_79(i + 3, f, g, h, a, b, c, d, e);

		SHA512_16_79(i + 4, e, f, g, h, a, b, c, d);

		SHA512_16_79(i + 5, d, e, f, g, h, a, b, c);

		SHA512_16_79(i + 6, c, d, e, f, g, h, a, b);

		SHA512_16_79(i + 7, b, c, d, e, f, g, h, a);

		}



		t1 = h + e1(e) + Ch(e,f,g) + sha512_K[i  ] + W[(i & 15)];

		t2 = e0(a) + Maj(a,b,c);    d+=t1;    h=t1+t2;

		t1 = g + e1(d) + Ch(d,e,f) + sha512_K[i+1] + W[(i & 15) + 1];

		t2 = e0(h) + Maj(h,a,b);    c+=t1;    g=t1+t2;

		t1 = f + e1(c) + Ch(c,d,e) + sha512_K[i+2] + W[(i & 15) + 2];

		t2 = e0(g) + Maj(g,h,a);    b+=t1;    f=t1+t2;

		t1 = e + e1(b) + Ch(b,c,d) + sha512_K[i+3] + W[(i & 15) + 3];

		t2 = e0(f) + Maj(f,g,h);    a+=t1;    e=t1+t2;

		t1 = d + e1(a) + Ch(a,b,c) + sha512_K[i+4] + W[(i & 15) + 4];

		t2 = e0(e) + Maj(e,f,g);    h+=t1;    d=t1+t2;

		t1 = c + e1(h) + Ch(h,a,b) + sha512_K[i+5] + W[(i & 15) + 5];

		t2 = e0(d) + Maj(d,e,f);    g+=t1;    c=t1+t2;

		t1 = b + e1(g) + Ch(g,h,a) + sha512_K[i+6] + W[(i & 15) + 6];

		t2 = e0(c) + Maj(c,d,e);    f+=t1;    b=t1+t2;

		t1 = a + e1(f) + Ch(f,g,h) + sha512_K[i+7] + W[(i & 15) + 7];

		t2 = e0(b) + Maj(b,c,d);    e+=t1;    a=t1+t2;

	}



	state[0] += a; state[1] += b; state[2] += c; state[3] += d;

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