sha256.h

 1/* SPDX-License-Identifier: GPL-2.0-or-later */
 2/*
 3 * SHA-256 Secure Hash Algorithm, SPE optimized
 4 *
 5 * Based on generic implementation. The assembler module takes care
 6 * about the SPE registers so it can run from interrupt context.
 7 *
 8 * Copyright (c) 2015 Markus Stockhausen <stockhausen@collogia.de>
 9 */
10
11#include <asm/switch_to.h>
12#include <linux/preempt.h>
13
14/*
15 * MAX_BYTES defines the number of bytes that are allowed to be processed
16 * between preempt_disable() and preempt_enable(). SHA256 takes ~2,000
17 * operations per 64 bytes. e500 cores can issue two arithmetic instructions
18 * per clock cycle using one 32/64 bit unit (SU1) and one 32 bit unit (SU2).
19 * Thus 1KB of input data will need an estimated maximum of 18,000 cycles.
20 * Headroom for cache misses included. Even with the low end model clocked
21 * at 667 MHz this equals to a critical time window of less than 27us.
22 *
23 */
24#define MAX_BYTES 1024
25
26extern void ppc_spe_sha256_transform(struct sha256_block_state *state,
27				     const u8 *src, u32 blocks);
28
29static void spe_begin(void)
30{
31	/* We just start SPE operations and will save SPE registers later. */
32	preempt_disable();
33	enable_kernel_spe();
34}
35
36static void spe_end(void)
37{
38	disable_kernel_spe();
39	/* reenable preemption */
40	preempt_enable();
41}
42
43static void sha256_blocks(struct sha256_block_state *state,
44			  const u8 *data, size_t nblocks)
45{
46	do {
47		/* cut input data into smaller blocks */
48		u32 unit = min_t(size_t, nblocks,
49				 MAX_BYTES / SHA256_BLOCK_SIZE);
50
51		spe_begin();
52		ppc_spe_sha256_transform(state, data, unit);
53		spe_end();
54
55		data += unit * SHA256_BLOCK_SIZE;
56		nblocks -= unit;
57	} while (nblocks);
58}