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: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/crypto/sha512_generic.c b/crypto/sha512_generic.c
index 3edebfd..f04af93 100644 (file)
--- a/crypto/sha512_generic.c
+++ b/crypto/sha512_generic.c
@@ -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);
-       }
-       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);
+       /* 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);
+                               }
+                       }
+               }
+
+               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;