For ChromiumOS, we use SHA-1 to verify the integrity of the root
filesystem. The speed of the kernel sha-1 implementation has a major
impact on our boot performance.
To improve boot performance, we investigated using the heavily
optimized sha-1 implementation used in git. With the git
sha-1 implementation, we see a 11.7% improvement in boot time.
10 reboots, remove slowest/fastest.
Before:
Mean: 6.58 seconds Stdev: 0.14
After (with git sha-1, this patch):
Mean: 5.89 seconds Stdev: 0.07
The other cool thing about the git SHA-1 implementation is that
it only needs 64 bytes of stack for the workspace while the original
kernel implementation needed 320 bytes.
Signed-off-by: Mandeep Singh Baines <msb@xxxxxxxxxxxx>
CC: Ramsay Jones <ramsay@xxxxxxxxxxxxxxxxxxx>
CC: Nicolas Pitre <nico@xxxxxxx>
CC: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
CC: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
CC: David S. Miller <davem@xxxxxxxxxxxxx>
CC: linux-crypto@xxxxxxxxxxxxxxx
---
include/linux/cryptohash.h | 2 +-
lib/sha1.c | 212 ++++++++++++++++++++++++++++++++-----------
2 files changed, 159 insertions(+), 55 deletions(-)
diff --git a/include/linux/cryptohash.h b/include/linux/cryptohash.h
index ec78a4b..f945218 100644
--- a/include/linux/cryptohash.h
+++ b/include/linux/cryptohash.h
@@ -3,7 +3,7 @@
#define SHA_DIGEST_WORDS 5
#define SHA_MESSAGE_BYTES (512 /*bits*/ / 8)
-#define SHA_WORKSPACE_WORDS 80
+#define SHA_WORKSPACE_WORDS 16
void sha_init(__u32 *buf);
void sha_transform(__u32 *digest, const char *data, __u32 *W);
diff --git a/lib/sha1.c b/lib/sha1.c
index 4c45fd5..f33271d 100644
--- a/lib/sha1.c
+++ b/lib/sha1.c
@@ -1,31 +1,72 @@
/*
- * SHA transform algorithm, originally taken from code written by
- * Peter Gutmann, and placed in the public domain.
+ * SHA1 routine optimized to do word accesses rather than byte accesses,
+ * and to avoid unnecessary copies into the context array.
+ *
+ * This was based on the git SHA1 implementation.
*/
#include <linux/kernel.h>
#include <linux/module.h>
-#include <linux/cryptohash.h>
+#include <linux/bitops.h>
+#include <asm/unaligned.h>
-/* The SHA f()-functions. */
+/*
+ * If you have 32 registers or more, the compiler can (and should)
+ * try to change the array[] accesses into registers. However, on
+ * machines with less than ~25 registers, that won't really work,
+ * and at least gcc will make an unholy mess of it.
+ *
+ * So to avoid that mess which just slows things down, we force
+ * the stores to memory to actually happen (we might be better off
+ * with a 'W(t)=(val);asm("":"+m" (W(t))' there instead, as
+ * suggested by Artur Skawina - that will also make gcc unable to
+ * try to do the silly "optimize away loads" part because it won't
+ * see what the value will be).
+ *
+ * Ben Herrenschmidt reports that on PPC, the C version comes close
+ * to the optimized asm with this (ie on PPC you don't want that
+ * 'volatile', since there are lots of registers).
+ *
+ * On ARM we get the best code generation by forcing a full memory barrier
+ * between each SHA_ROUND, otherwise gcc happily get wild with spilling and
+ * the stack frame size simply explode and performance goes down the drain.
+ */
-#define f1(x,y,z) (z ^ (x & (y ^ z))) /* x ? y : z */
-#define f2(x,y,z) (x ^ y ^ z) /* XOR */
-#define f3(x,y,z) ((x & y) + (z & (x ^ y))) /* majority */
+#ifdef CONFIG_X86
+ #define setW(x, val) (*(volatile __u32 *)&W(x) = (val))
+#elif defined(CONFIG_ARM)
+ #define setW(x, val) do { W(x) = (val); __asm__("":::"memory"); } while (0)
+#else
+ #define setW(x, val) (W(x) = (val))
+#endif
-/* The SHA Mysterious Constants */
+/* This "rolls" over the 512-bit array */
+#define W(x) (array[(x)&15])
-#define K1 0x5A827999L /* Rounds 0-19: sqrt(2) * 2^30 */
-#define K2 0x6ED9EBA1L /* Rounds 20-39: sqrt(3) * 2^30 */
-#define K3 0x8F1BBCDCL /* Rounds 40-59: sqrt(5) * 2^30 */
-#define K4 0xCA62C1D6L /* Rounds 60-79: sqrt(10) * 2^30 */
+/*
+ * Where do we get the source from? The first 16 iterations get it from
+ * the input data, the next mix it from the 512-bit array.
+ */
+#define SHA_SRC(t) get_unaligned_be32((__u32 *)data + t)
+#define SHA_MIX(t) rol32(W(t+13) ^ W(t+8) ^ W(t+2) ^ W(t), 1)
+
+#define SHA_ROUND(t, input, fn, constant, A, B, C, D, E) do { \
+ __u32 TEMP = input(t); setW(t, TEMP); \
+ E += TEMP + rol32(A,5) + (fn) + (constant); \
+ B = ror32(B, 2); } while (0)
+
+#define T_0_15(t, A, B, C, D, E) SHA_ROUND(t, SHA_SRC, (((C^D)&B)^D) , 0x5a827999, A, B, C, D, E )
+#define T_16_19(t, A, B, C, D, E) SHA_ROUND(t, SHA_MIX, (((C^D)&B)^D) , 0x5a827999, A, B, C, D, E )
+#define T_20_39(t, A, B, C, D, E) SHA_ROUND(t, SHA_MIX, (B^C^D) , 0x6ed9eba1, A, B, C, D, E )
+#define T_40_59(t, A, B, C, D, E) SHA_ROUND(t, SHA_MIX, ((B&C)+(D&(B^C))) , 0x8f1bbcdc, A, B, C, D, E )
+#define T_60_79(t, A, B, C, D, E) SHA_ROUND(t, SHA_MIX, (B^C^D) , 0xca62c1d6, A, B, C, D, E )
/**
* sha_transform - single block SHA1 transform
*
* @digest: 160 bit digest to update
* @data: 512 bits of data to hash
- * @W: 80 words of workspace (see note)
+ * @array: 16 words of workspace (see note)
*
* This function generates a SHA1 digest for a single 512-bit block.
* Be warned, it does not handle padding and message digest, do not
@@ -36,47 +77,111 @@
* to clear the workspace. This is left to the caller to avoid
* unnecessary clears between chained hashing operations.
*/
-void sha_transform(__u32 *digest, const char *in, __u32 *W)
+void sha_transform(__u32 *digest, const char *data, __u32 *array)
{
- __u32 a, b, c, d, e, t, i;
-
- for (i = 0; i < 16; i++)
- W[i] = be32_to_cpu(((const __be32 *)in)[i]);
-
- for (i = 0; i < 64; i++)
- W[i+16] = rol32(W[i+13] ^ W[i+8] ^ W[i+2] ^ W[i], 1);
-
- a = digest[0];
- b = digest[1];
- c = digest[2];
- d = digest[3];
- e = digest[4];
-
- for (i = 0; i < 20; i++) {
- t = f1(b, c, d) + K1 + rol32(a, 5) + e + W[i];
- e = d; d = c; c = rol32(b, 30); b = a; a = t;
- }
-
- for (; i < 40; i ++) {
- t = f2(b, c, d) + K2 + rol32(a, 5) + e + W[i];
- e = d; d = c; c = rol32(b, 30); b = a; a = t;
- }
-
- for (; i < 60; i ++) {
- t = f3(b, c, d) + K3 + rol32(a, 5) + e + W[i];
- e = d; d = c; c = rol32(b, 30); b = a; a = t;
- }
-
- for (; i < 80; i ++) {
- t = f2(b, c, d) + K4 + rol32(a, 5) + e + W[i];
- e = d; d = c; c = rol32(b, 30); b = a; a = t;
- }
-
- digest[0] += a;
- digest[1] += b;
- digest[2] += c;
- digest[3] += d;
- digest[4] += e;
+ __u32 A, B, C, D, E;
+
+ A = digest[0];
+ B = digest[1];
+ C = digest[2];
+ D = digest[3];
+ E = digest[4];
+
+ /* Round 1 - iterations 0-16 take their input from 'data' */
+ T_0_15( 0, A, B, C, D, E);
+ T_0_15( 1, E, A, B, C, D);
+ T_0_15( 2, D, E, A, B, C);
+ T_0_15( 3, C, D, E, A, B);
+ T_0_15( 4, B, C, D, E, A);
+ T_0_15( 5, A, B, C, D, E);
+ T_0_15( 6, E, A, B, C, D);
+ T_0_15( 7, D, E, A, B, C);
+ T_0_15( 8, C, D, E, A, B);
+ T_0_15( 9, B, C, D, E, A);
+ T_0_15(10, A, B, C, D, E);
+ T_0_15(11, E, A, B, C, D);
+ T_0_15(12, D, E, A, B, C);
+ T_0_15(13, C, D, E, A, B);
+ T_0_15(14, B, C, D, E, A);
+ T_0_15(15, A, B, C, D, E);
+
+ /* Round 1 - tail. Input from 512-bit mixing array */
+ T_16_19(16, E, A, B, C, D);
+ T_16_19(17, D, E, A, B, C);
+ T_16_19(18, C, D, E, A, B);
+ T_16_19(19, B, C, D, E, A);
+
+ /* Round 2 */
+ T_20_39(20, A, B, C, D, E);
+ T_20_39(21, E, A, B, C, D);
+ T_20_39(22, D, E, A, B, C);
+ T_20_39(23, C, D, E, A, B);
+ T_20_39(24, B, C, D, E, A);
+ T_20_39(25, A, B, C, D, E);
+ T_20_39(26, E, A, B, C, D);
+ T_20_39(27, D, E, A, B, C);
+ T_20_39(28, C, D, E, A, B);
+ T_20_39(29, B, C, D, E, A);
+ T_20_39(30, A, B, C, D, E);
+ T_20_39(31, E, A, B, C, D);
+ T_20_39(32, D, E, A, B, C);
+ T_20_39(33, C, D, E, A, B);
+ T_20_39(34, B, C, D, E, A);
+ T_20_39(35, A, B, C, D, E);
+ T_20_39(36, E, A, B, C, D);
+ T_20_39(37, D, E, A, B, C);
+ T_20_39(38, C, D, E, A, B);
+ T_20_39(39, B, C, D, E, A);
+
+ /* Round 3 */
+ T_40_59(40, A, B, C, D, E);
+ T_40_59(41, E, A, B, C, D);
+ T_40_59(42, D, E, A, B, C);
+ T_40_59(43, C, D, E, A, B);
+ T_40_59(44, B, C, D, E, A);
+ T_40_59(45, A, B, C, D, E);
+ T_40_59(46, E, A, B, C, D);
+ T_40_59(47, D, E, A, B, C);
+ T_40_59(48, C, D, E, A, B);
+ T_40_59(49, B, C, D, E, A);
+ T_40_59(50, A, B, C, D, E);
+ T_40_59(51, E, A, B, C, D);
+ T_40_59(52, D, E, A, B, C);
+ T_40_59(53, C, D, E, A, B);
+ T_40_59(54, B, C, D, E, A);
+ T_40_59(55, A, B, C, D, E);
+ T_40_59(56, E, A, B, C, D);
+ T_40_59(57, D, E, A, B, C);
+ T_40_59(58, C, D, E, A, B);
+ T_40_59(59, B, C, D, E, A);
+
+ /* Round 4 */
+ T_60_79(60, A, B, C, D, E);
+ T_60_79(61, E, A, B, C, D);
+ T_60_79(62, D, E, A, B, C);
+ T_60_79(63, C, D, E, A, B);
+ T_60_79(64, B, C, D, E, A);
+ T_60_79(65, A, B, C, D, E);
+ T_60_79(66, E, A, B, C, D);
+ T_60_79(67, D, E, A, B, C);
+ T_60_79(68, C, D, E, A, B);
+ T_60_79(69, B, C, D, E, A);
+ T_60_79(70, A, B, C, D, E);
+ T_60_79(71, E, A, B, C, D);
+ T_60_79(72, D, E, A, B, C);
+ T_60_79(73, C, D, E, A, B);
+ T_60_79(74, B, C, D, E, A);
+ T_60_79(75, A, B, C, D, E);
+ T_60_79(76, E, A, B, C, D);
+ T_60_79(77, D, E, A, B, C);
+ T_60_79(78, C, D, E, A, B);
+ T_60_79(79, B, C, D, E, A);
+
+ digest[0] += A;
+ digest[1] += B;
+ digest[2] += C;
+ digest[3] += D;
+ digest[4] += E;
}
EXPORT_SYMBOL(sha_transform);
@@ -92,4 +197,3 @@ void sha_init(__u32 *buf)
buf[3] = 0x10325476;
buf[4] = 0xc3d2e1f0;
}
-
--
1.7.3.1
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