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    Subject[ 10/34] crypto: sha512 - Avoid stack bloat on i386
    2.6.32-longterm review patch.  If anyone has any objections, please let me know.

    ------------------

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

    commit 3a92d687c8015860a19213e3c102cad6b722f83c upstream.

    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.

    Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    crypto/sha512_generic.c | 68 ++++++++++++++++++++++--------------------------
    1 file changed, 32 insertions(+), 36 deletions(-)

    --- a/crypto/sha512_generic.c
    +++ b/crypto/sha512_generic.c
    @@ -89,46 +89,42 @@ sha512_transform(u64 *state, const u8 *i
    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;



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