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Revision d0313e629f2690edfd269896b398048275227db0 authored by Ian Rogers on 12 August 2022, 23:09:49 UTC, committed by Arnaldo Carvalho de Melo on 13 August 2022, 18:03:09 UTC 
perf jevents: Fold strings optimization
 
If a shorter string ends a longer string then the shorter string may
reuse the longer string at an offset. For example, on x86 the event
arith.cycles_div_busy and cycles_div_busy can be folded, even though
they have difference names the strings are identical after 6
characters. cycles_div_busy can reuse the arith.cycles_div_busy string
at an offset of 6.

In pmu-events.c this looks like the following where the 'also:' lists
folded strings:

/* offset=177541 */ "arith.cycles_div_busy\000\000pipeline\000Cycles the divider is busy\000\000\000event=0x14,period=2000000,umask=0x1\000\000\000\000\000\000\000\000\000" /* also: cycles_div_busy\000\000pipeline\000Cycles the divider is busy\000\000\000event=0x14,period=2000000,umask=0x1\000\000\000\000\000\000\000\000\000 */

As jevents.py combines multiple strings for an event into a larger
string, the amount of folding is minimal as all parts of the event must
align. Other organizations can benefit more from folding, but lose space
by say recording more offsets.

Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.garry@huawei.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Will Deacon <will@kernel.org>
Cc: Xing Zhengjun <zhengjun.xing@linux.intel.com>
Cc: linux-arm-kernel@lists.infradead.org
Link: https://lore.kernel.org/r/20220812230949.683239-15-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
1 parent 9118259
Raw File
sha256_generic.c 
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Crypto API wrapper for the generic SHA256 code from lib/crypto/sha256.c
 *
 * Copyright (c) Jean-Luc Cooke <jlcooke@certainkey.com>
 * Copyright (c) Andrew McDonald <andrew@mcdonald.org.uk>
 * Copyright (c) 2002 James Morris <jmorris@intercode.com.au>
 * SHA224 Support Copyright 2007 Intel Corporation <jonathan.lynch@intel.com>
 */
#include <crypto/internal/hash.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/types.h>
#include <crypto/sha2.h>
#include <crypto/sha256_base.h>
#include <asm/byteorder.h>
#include <asm/unaligned.h>

const u8 sha224_zero_message_hash[SHA224_DIGEST_SIZE] = {
	0xd1, 0x4a, 0x02, 0x8c, 0x2a, 0x3a, 0x2b, 0xc9, 0x47,
	0x61, 0x02, 0xbb, 0x28, 0x82, 0x34, 0xc4, 0x15, 0xa2,
	0xb0, 0x1f, 0x82, 0x8e, 0xa6, 0x2a, 0xc5, 0xb3, 0xe4,
	0x2f
};
EXPORT_SYMBOL_GPL(sha224_zero_message_hash);

const u8 sha256_zero_message_hash[SHA256_DIGEST_SIZE] = {
	0xe3, 0xb0, 0xc4, 0x42, 0x98, 0xfc, 0x1c, 0x14,
	0x9a, 0xfb, 0xf4, 0xc8, 0x99, 0x6f, 0xb9, 0x24,
	0x27, 0xae, 0x41, 0xe4, 0x64, 0x9b, 0x93, 0x4c,
	0xa4, 0x95, 0x99, 0x1b, 0x78, 0x52, 0xb8, 0x55
};
EXPORT_SYMBOL_GPL(sha256_zero_message_hash);

int crypto_sha256_update(struct shash_desc *desc, const u8 *data,
			  unsigned int len)
{
	sha256_update(shash_desc_ctx(desc), data, len);
	return 0;
}
EXPORT_SYMBOL(crypto_sha256_update);

static int crypto_sha256_final(struct shash_desc *desc, u8 *out)
{
	if (crypto_shash_digestsize(desc->tfm) == SHA224_DIGEST_SIZE)
		sha224_final(shash_desc_ctx(desc), out);
	else
		sha256_final(shash_desc_ctx(desc), out);
	return 0;
}

int crypto_sha256_finup(struct shash_desc *desc, const u8 *data,
			unsigned int len, u8 *hash)
{
	sha256_update(shash_desc_ctx(desc), data, len);
	return crypto_sha256_final(desc, hash);
}
EXPORT_SYMBOL(crypto_sha256_finup);

static struct shash_alg sha256_algs[2] = { {
	.digestsize	=	SHA256_DIGEST_SIZE,
	.init		=	sha256_base_init,
	.update		=	crypto_sha256_update,
	.final		=	crypto_sha256_final,
	.finup		=	crypto_sha256_finup,
	.descsize	=	sizeof(struct sha256_state),
	.base		=	{
		.cra_name	=	"sha256",
		.cra_driver_name=	"sha256-generic",
		.cra_priority	=	100,
		.cra_blocksize	=	SHA256_BLOCK_SIZE,
		.cra_module	=	THIS_MODULE,
	}
}, {
	.digestsize	=	SHA224_DIGEST_SIZE,
	.init		=	sha224_base_init,
	.update		=	crypto_sha256_update,
	.final		=	crypto_sha256_final,
	.finup		=	crypto_sha256_finup,
	.descsize	=	sizeof(struct sha256_state),
	.base		=	{
		.cra_name	=	"sha224",
		.cra_driver_name=	"sha224-generic",
		.cra_priority	=	100,
		.cra_blocksize	=	SHA224_BLOCK_SIZE,
		.cra_module	=	THIS_MODULE,
	}
} };

static int __init sha256_generic_mod_init(void)
{
	return crypto_register_shashes(sha256_algs, ARRAY_SIZE(sha256_algs));
}

static void __exit sha256_generic_mod_fini(void)
{
	crypto_unregister_shashes(sha256_algs, ARRAY_SIZE(sha256_algs));
}

subsys_initcall(sha256_generic_mod_init);
module_exit(sha256_generic_mod_fini);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("SHA-224 and SHA-256 Secure Hash Algorithm");

MODULE_ALIAS_CRYPTO("sha224");
MODULE_ALIAS_CRYPTO("sha224-generic");
MODULE_ALIAS_CRYPTO("sha256");
MODULE_ALIAS_CRYPTO("sha256-generic");
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