[PATCH v2 2/3] SHA256 for PPC/SPE - glue

[Markus Stockhausen]

[PATCH v2 2/3] SHA256 for PPC/SPE - glue

Glue code for crypto infrastructure. Call the assembler
code where required. Disable preemption during calculation
and enable SPE instructions in the kernel prior to the 
call. Avoid to disable preemption for too long.

Take a little care about small input data. Kick out early
for input chunks < 64 bytes and replace memset for context
cleanup with simple loop. 

v2 changes
- use MODULE_ALIAS_CRYPTO
- use memzero_explicit()
- additional aliases
- do not check for interrupt context
- priority 300, as we are assembler & CPU optimized

Signed-off-by: Markus Stockhausen <stockhausen at collogia.de>

diff --git a/arch/powerpc/crypto/sha256_spe_glue.c b/arch/powerpc/crypto/sha256_spe_glue.c
new file mode 100644
index 0000000..f4a616f
--- /dev/null
+++ b/arch/powerpc/crypto/sha256_spe_glue.c
@@ -0,0 +1,275 @@
+/*
+ * Glue code for SHA-256 implementation for SPE instructions (PPC)
+ *
+ * Based on generic implementation. The assembler module takes care 
+ * about the SPE registers so it can run from interrupt context.
+ *
+ * Copyright (c) 2015 Markus Stockhausen <stockhausen at collogia.de>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ */
+
+#include <crypto/internal/hash.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/mm.h>
+#include <linux/cryptohash.h>
+#include <linux/types.h>
+#include <crypto/sha.h>
+#include <asm/byteorder.h>
+#include <asm/switch_to.h>
+#include <linux/hardirq.h>
+
+/*
+ * MAX_BYTES defines the number of bytes that are allowed to be processed
+ * between preempt_disable() and preempt_enable(). SHA256 takes ~2,000
+ * operations per 64 bytes. e500 cores can issue two arithmetic instructions
+ * per clock cycle using one 32/64 bit unit (SU1) and one 32 bit unit (SU2).
+ * Thus 1KB of input data will need an estimated maximum of 18,000 cycles.
+ * Headroom for cache misses included. Even with the low end model clocked
+ * at 667 MHz this equals to a critical time window of less than 27us.
+ *
+ */
+#define MAX_BYTES 1024
+
+extern void ppc_spe_sha256_transform(u32 *state, const u8 *src, u32 blocks);
+
+static void spe_begin(void)
+{
+	/* We just start SPE operations and will save SPE registers later. */
+	preempt_disable();
+	enable_kernel_spe();
+}
+
+static void spe_end(void)
+{
+	/* reenable preemption */
+	preempt_enable();
+}
+
+static inline void ppc_sha256_clear_context(struct sha256_state *sctx)
+{
+	int count = sizeof(struct sha256_state) >> 2;
+	u32 *ptr = (u32 *)sctx;
+
+	/* make sure we can clear the fast way */
+	BUILD_BUG_ON(sizeof(struct sha256_state) % 4);
+	do { *ptr++ = 0; } while (--count);
+}
+
+static int ppc_spe_sha256_init(struct shash_desc *desc)
+{
+	struct sha256_state *sctx = shash_desc_ctx(desc);
+
+	sctx->state[0] = SHA256_H0;
+	sctx->state[1] = SHA256_H1;
+	sctx->state[2] = SHA256_H2;
+	sctx->state[3] = SHA256_H3;
+	sctx->state[4] = SHA256_H4;
+	sctx->state[5] = SHA256_H5;
+	sctx->state[6] = SHA256_H6;
+	sctx->state[7] = SHA256_H7;
+	sctx->count = 0;
+
+	return 0;
+}
+
+static int ppc_spe_sha224_init(struct shash_desc *desc)
+{
+	struct sha256_state *sctx = shash_desc_ctx(desc);
+
+	sctx->state[0] = SHA224_H0;
+	sctx->state[1] = SHA224_H1;
+	sctx->state[2] = SHA224_H2;
+	sctx->state[3] = SHA224_H3;
+	sctx->state[4] = SHA224_H4;
+	sctx->state[5] = SHA224_H5;
+	sctx->state[6] = SHA224_H6;
+	sctx->state[7] = SHA224_H7;
+	sctx->count = 0;
+
+	return 0;
+}
+
+static int ppc_spe_sha256_update(struct shash_desc *desc, const u8 *data,
+			unsigned int len)
+{
+	struct sha256_state *sctx = shash_desc_ctx(desc);
+	const unsigned int offset = sctx->count & 0x3f;
+	const unsigned int avail = 64 - offset;
+	unsigned int bytes;
+	const u8 *src = data;
+
+	if (avail > len) {
+		sctx->count += len;
+		memcpy((char *)sctx->buf + offset, src, len);
+		return 0;
+	}
+
+	sctx->count += len;
+
+	if (offset) {
+		memcpy((char *)sctx->buf + offset, src, avail);
+
+		spe_begin();
+		ppc_spe_sha256_transform(sctx->state, (const u8 *)sctx->buf, 1);
+		spe_end();
+
+		len -= avail;
+		src += avail;
+	}
+
+	while (len > 63) {
+		/* cut input data into smaller blocks */
+		bytes = (len > MAX_BYTES) ? MAX_BYTES : len;
+		bytes = bytes & ~0x3f;
+
+		spe_begin();
+		ppc_spe_sha256_transform(sctx->state, src, bytes >> 6);
+		spe_end();
+
+		src += bytes;
+		len -= bytes;
+	};
+
+	memcpy((char *)sctx->buf, src, len);
+	return 0;
+}
+
+static int ppc_spe_sha256_final(struct shash_desc *desc, u8 *out)
+{
+	struct sha256_state *sctx = shash_desc_ctx(desc);
+	const unsigned int offset = sctx->count & 0x3f;
+	char *p = (char *)sctx->buf + offset;
+	int padlen;
+	__be64 *pbits = (__be64 *)(((char *)&sctx->buf) + 56);
+	__be32 *dst = (__be32 *)out;
+
+	padlen = 55 - offset;
+	*p++ = 0x80;
+
+	spe_begin();
+
+	if (padlen < 0) {
+		memset(p, 0x00, padlen + sizeof (u64));
+		ppc_spe_sha256_transform(sctx->state, sctx->buf, 1);
+		p = (char *)sctx->buf;
+		padlen = 56;
+	}
+
+	memset(p, 0, padlen);
+	*pbits = cpu_to_be64(sctx->count << 3);
+	ppc_spe_sha256_transform(sctx->state, sctx->buf, 1);
+
+	spe_end();
+
+	dst[0] = cpu_to_be32(sctx->state[0]);
+	dst[1] = cpu_to_be32(sctx->state[1]);
+	dst[2] = cpu_to_be32(sctx->state[2]);
+	dst[3] = cpu_to_be32(sctx->state[3]);
+	dst[4] = cpu_to_be32(sctx->state[4]);
+	dst[5] = cpu_to_be32(sctx->state[5]);
+	dst[6] = cpu_to_be32(sctx->state[6]);
+	dst[7] = cpu_to_be32(sctx->state[7]);
+
+	ppc_sha256_clear_context(sctx);
+	return 0;
+}
+
+static int ppc_spe_sha224_final(struct shash_desc *desc, u8 *out)
+{
+	u32 D[SHA256_DIGEST_SIZE >> 2];
+	__be32 *dst = (__be32 *)out;
+
+	ppc_spe_sha256_final(desc, (u8 *)D);
+
+	/* avoid bytewise memcpy */
+	dst[0] = D[0];
+	dst[1] = D[1];
+	dst[2] = D[2];
+	dst[3] = D[3];
+	dst[4] = D[4];
+	dst[5] = D[5];
+	dst[6] = D[6];
+
+	/* clear sensitive data */
+	memzero_explicit(D, SHA256_DIGEST_SIZE);
+	return 0;
+}
+
+static int ppc_spe_sha256_export(struct shash_desc *desc, void *out)
+{
+	struct sha256_state *sctx = shash_desc_ctx(desc);
+
+	memcpy(out, sctx, sizeof(*sctx));
+	return 0;
+}
+
+static int ppc_spe_sha256_import(struct shash_desc *desc, const void *in)
+{
+	struct sha256_state *sctx = shash_desc_ctx(desc);
+
+	memcpy(sctx, in, sizeof(*sctx));
+	return 0;
+}
+
+static struct shash_alg algs[2] = { {
+	.digestsize	=	SHA256_DIGEST_SIZE,
+	.init		=	ppc_spe_sha256_init,
+	.update		=	ppc_spe_sha256_update,
+	.final		=	ppc_spe_sha256_final,
+	.export		=	ppc_spe_sha256_export,
+	.import		=	ppc_spe_sha256_import,
+	.descsize	=	sizeof(struct sha256_state),
+	.statesize	=	sizeof(struct sha256_state),
+	.base		=	{
+		.cra_name	=	"sha256",
+		.cra_driver_name=	"sha256-ppc-spe",
+		.cra_priority	=	300,
+		.cra_flags	=	CRYPTO_ALG_TYPE_SHASH,
+		.cra_blocksize	=	SHA256_BLOCK_SIZE,
+		.cra_module	=	THIS_MODULE,
+	}
+}, {
+	.digestsize	=	SHA224_DIGEST_SIZE,
+	.init		=	ppc_spe_sha224_init,
+	.update		=	ppc_spe_sha256_update,
+	.final		=	ppc_spe_sha224_final,
+	.export		=	ppc_spe_sha256_export,
+	.import		=	ppc_spe_sha256_import,
+	.descsize	=	sizeof(struct sha256_state),
+	.statesize	=	sizeof(struct sha256_state),
+	.base		=	{
+		.cra_name	=	"sha224",
+		.cra_driver_name=	"sha224-ppc-spe",
+		.cra_priority	=	300,
+		.cra_flags	=	CRYPTO_ALG_TYPE_SHASH,
+		.cra_blocksize	=	SHA224_BLOCK_SIZE,
+		.cra_module	=	THIS_MODULE,
+	}
+} };
+
+static int __init ppc_spe_sha256_mod_init(void)
+{
+	return crypto_register_shashes(algs, ARRAY_SIZE(algs));
+}
+
+static void __exit ppc_spe_sha256_mod_fini(void)
+{
+	crypto_unregister_shashes(algs, ARRAY_SIZE(algs));
+}
+
+module_init(ppc_spe_sha256_mod_init);
+module_exit(ppc_spe_sha256_mod_fini);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("SHA-224 and SHA-256 Secure Hash Algorithm, SPE optimized");
+
+MODULE_ALIAS_CRYPTO("sha224");
+MODULE_ALIAS_CRYPTO("sha224-ppc-spe");
+MODULE_ALIAS_CRYPTO("sha256");
+MODULE_ALIAS_CRYPTO("sha256-ppc-spe");
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