cregit-Linux how code gets into the kernel

Release 4.16 lib/sha1.c

Directory: lib
// SPDX-License-Identifier: GPL-2.0
/*
 * 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/export.h>
#include <linux/bitops.h>
#include <linux/cryptohash.h>
#include <asm/unaligned.h>

/*
 * 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.
 */

#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

/* This "rolls" over the 512-bit array */

#define W(x) (array[(x)&15])

/*
 * 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
 * @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
 * confuse it with the full FIPS 180-1 digest algorithm for variable
 * length messages.
 *
 * Note: If the hash is security sensitive, the caller should be sure
 * 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 *data, __u32 *array) { __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; }

Contributors

PersonTokensPropCommitsCommitProp
Mandeep Singh Baines117389.95%133.33%
Matt Mackall13110.05%266.67%
Total1304100.00%3100.00%

EXPORT_SYMBOL(sha_transform); /** * sha_init - initialize the vectors for a SHA1 digest * @buf: vector to initialize */
void sha_init(__u32 *buf) { buf[0] = 0x67452301; buf[1] = 0xefcdab89; buf[2] = 0x98badcfe; buf[3] = 0x10325476; buf[4] = 0xc3d2e1f0; }

Contributors

PersonTokensPropCommitsCommitProp
Matt Mackall44100.00%1100.00%
Total44100.00%1100.00%

EXPORT_SYMBOL(sha_init);

Overall Contributors

PersonTokensPropCommitsCommitProp
Mandeep Singh Baines132585.54%112.50%
Matt Mackall21313.75%225.00%
Hannes Frederic Sowa50.32%112.50%
H Hartley Sweeten30.19%112.50%
Greg Kroah-Hartman10.06%112.50%
Paul Gortmaker10.06%112.50%
Robert P. J. Day10.06%112.50%
Total1549100.00%8100.00%
Directory: lib
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