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Message-ID: <20120203033450.GA17668@gondor.apana.org.au>
Date: Fri, 3 Feb 2012 14:34:50 +1100
From: Herbert Xu <herbert@...dor.apana.org.au>
To: Alexey Dobriyan <adobriyan@...il.com>
Cc: David Laight <David.Laight@...lab.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
linux-crypto@...r.kernel.org, netdev@...r.kernel.org,
ken@...elabs.ch, Steffen Klassert <steffen.klassert@...unet.com>,
security@...nel.org, Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [PATCH 4/3] sha512: reduce stack usage even on i386
On Mon, Jan 30, 2012 at 01:10:48PM +0200, Alexey Dobriyan wrote:
>
> For some reason it doesn't. :-( I've also tried full barriers.
OK, I don't think it worked in the sha1 case either, as on my
i386 here lib/sha1.c ends up using nearly 500 bytes of stack
space.
It appears that the crux of the issue here is the use of 64-bit
ops. gcc just doesn't like that at all on i386 and ends up
putting every other intermediate result on the stack in its own
unique place.
While you de-unrolling patch does reduce the stack use, it also
incurs a speed penalty of around 15%, and that's on top of the
4% we've already added by getting rid of per_cpu.
However, this patch seems to work for me, and reduces the stack
usage to a level about the same as lib/sha1.c + crypto/sha1_generic.c
without adding any new overhead.
So let me know if you have any better ideas.
diff --git a/crypto/sha512_generic.c b/crypto/sha512_generic.c
index 3edebfd..f04af93 100644
--- 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;
Thanks!
--
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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