/*
 * Cryptographic API for the NX-842 hardware compression.
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * Copyright (C) IBM Corporation, 2011-2015
 *
 * Original Authors: Robert Jennings <rcj@linux.vnet.ibm.com>
 *                   Seth Jennings <sjenning@linux.vnet.ibm.com>
 *
 * Rewrite: Dan Streetman <ddstreet@ieee.org>
 *
 * This is an interface to the NX-842 compression hardware in PowerPC
 * processors.  Most of the complexity of this drvier is due to the fact that
 * the NX-842 compression hardware requires the input and output data buffers
 * to be specifically aligned, to be a specific multiple in length, and within
 * specific minimum and maximum lengths.  Those restrictions, provided by the
 * nx-842 driver via nx842_constraints, mean this driver must use bounce
 * buffers and headers to correct misaligned in or out buffers, and to split
 * input buffers that are too large.
 *
 * This driver will fall back to software decompression if the hardware
 * decompression fails, so this driver's decompression should never fail as
 * long as the provided compressed buffer is valid.  Any compressed buffer
 * created by this driver will have a header (except ones where the input
 * perfectly matches the constraints); so users of this driver cannot simply
 * pass a compressed buffer created by this driver over to the 842 software
 * decompression library.  Instead, users must use this driver to decompress;
 * if the hardware fails or is unavailable, the compressed buffer will be
 * parsed and the header removed, and the raw 842 buffer(s) passed to the 842
 * software decompression library.
 *
 * This does not fall back to software compression, however, since the caller
 * of this function is specifically requesting hardware compression; if the
 * hardware compression fails, the caller can fall back to software
 * compression, and the raw 842 compressed buffer that the software compressor
 * creates can be passed to this driver for hardware decompression; any
 * buffer without our specific header magic is assumed to be a raw 842 buffer
 * and passed directly to the hardware.  Note that the software compression
 * library will produce a compressed buffer that is incompatible with the
 * hardware decompressor if the original input buffer length is not a multiple
 * of 8; if such a compressed buffer is passed to this driver for
 * decompression, the hardware will reject it and this driver will then pass
 * it over to the software library for decompression.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/init.h>
#include <linux/module.h>
#include <linux/crypto.h>
#include <linux/vmalloc.h>
#include <linux/sw842.h>
#include <linux/ratelimit.h>

#include "nx-842.h"

/* The first 5 bits of this magic are 0x1f, which is an invalid 842 5-bit
 * template (see lib/842/842.h), so this magic number will never appear at
 * the start of a raw 842 compressed buffer.  That is important, as any buffer
 * passed to us without this magic is assumed to be a raw 842 compressed
 * buffer, and passed directly to the hardware to decompress.
 */
#define NX842_CRYPTO_MAGIC	(0xf842)
#define NX842_CRYPTO_GROUP_MAX	(0x20)
#define NX842_CRYPTO_HEADER_SIZE(g)				\
	(sizeof(struct nx842_crypto_header) +			\
	 sizeof(struct nx842_crypto_header_group) * (g))
#define NX842_CRYPTO_HEADER_MAX_SIZE				\
	NX842_CRYPTO_HEADER_SIZE(NX842_CRYPTO_GROUP_MAX)

/* bounce buffer size */
#define BOUNCE_BUFFER_ORDER	(2)
#define BOUNCE_BUFFER_SIZE					\
	((unsigned int)(PAGE_SIZE << BOUNCE_BUFFER_ORDER))

/* try longer on comp because we can fallback to sw decomp if hw is busy */
#define COMP_BUSY_TIMEOUT	(250) /* ms */
#define DECOMP_BUSY_TIMEOUT	(50) /* ms */

struct nx842_crypto_header_group {
	__be16 padding;			/* unused bytes at start of group */
	__be32 compressed_length;	/* compressed bytes in group */
	__be32 uncompressed_length;	/* bytes after decompression */
} __packed;

struct nx842_crypto_header {
	__be16 magic;		/* NX842_CRYPTO_MAGIC */
	__be16 ignore;		/* decompressed end bytes to ignore */
	u8 groups;		/* total groups in this header */
	struct nx842_crypto_header_group group[];
} __packed;

struct nx842_crypto_param {
	u8 *in;
	unsigned int iremain;
	u8 *out;
	unsigned int oremain;
	unsigned int ototal;
};

static int update_param(struct nx842_crypto_param *p,
			unsigned int slen, unsigned int dlen)
{
	if (p->iremain < slen)
		return -EOVERFLOW;
	if (p->oremain < dlen)
		return -ENOSPC;

	p->in += slen;
	p->iremain -= slen;
	p->out += dlen;
	p->oremain -= dlen;
	p->ototal += dlen;

	return 0;
}

struct nx842_crypto_ctx {
	u8 *wmem;
	u8 *sbounce, *dbounce;

	struct nx842_crypto_header header;
	struct nx842_crypto_header_group group[NX842_CRYPTO_GROUP_MAX];
};

static int nx842_crypto_init(struct crypto_tfm *tfm)
{
	struct nx842_crypto_ctx *ctx = crypto_tfm_ctx(tfm);

	ctx->wmem = kmalloc(nx842_workmem_size(), GFP_KERNEL);
	ctx->sbounce = (u8 *)__get_free_pages(GFP_KERNEL, BOUNCE_BUFFER_ORDER);
	ctx->dbounce = (u8 *)__get_free_pages(GFP_KERNEL, BOUNCE_BUFFER_ORDER);
	if (!ctx->wmem || !ctx->sbounce || !ctx->dbounce) {
		kfree(ctx->wmem);
		free_page((unsigned long)ctx->sbounce);
		free_page((unsigned long)ctx->dbounce);
		return -ENOMEM;
	}

	return 0;
}

static void nx842_crypto_exit(struct crypto_tfm *tfm)
{
	struct nx842_crypto_ctx *ctx = crypto_tfm_ctx(tfm);

	kfree(ctx->wmem);
	free_page((unsigned long)ctx->sbounce);
	free_page((unsigned long)ctx->dbounce);
}

static int read_constraints(struct nx842_constraints *c)
{
	int ret;

	ret = nx842_constraints(c);
	if (ret) {
		pr_err_ratelimited("could not get nx842 constraints : %d\n",
				   ret);
		return ret;
	}

	/* limit maximum, to always have enough bounce buffer to decompress */
	if (c->maximum > BOUNCE_BUFFER_SIZE) {
		c->maximum = BOUNCE_BUFFER_SIZE;
		pr_info_once("limiting nx842 maximum to %x\n", c->maximum);
	}

	return 0;
}

static int nx842_crypto_add_header(struct nx842_crypto_header *hdr, u8 *buf)
{
	int s = NX842_CRYPTO_HEADER_SIZE(hdr->groups);

	/* compress should have added space for header */
	if (s > be16_to_cpu(hdr->group[0].padding)) {
		pr_err("Internal error: no space for header\n");
		return -EINVAL;
	}

	memcpy(buf, hdr, s);

	print_hex_dump_debug("header ", DUMP_PREFIX_OFFSET, 16, 1, buf, s, 0);

	return 0;
}

static int compress(struct nx842_crypto_ctx *ctx,
		    struct nx842_crypto_param *p,
		    struct nx842_crypto_header_group *g,
		    struct nx842_constraints *c,
		    u16 *ignore,
		    unsigned int hdrsize)
{
	unsigned int slen = p->iremain, dlen = p->oremain, tmplen;
	unsigned int adj_slen = slen;
	u8 *src = p->in, *dst = p->out;
	int ret, dskip = 0;
	ktime_t timeout;

	if (p->iremain == 0)
		return -EOVERFLOW;

	if (p->oremain == 0 || hdrsize + c->minimum > dlen)
		return -ENOSPC;

	if (slen % c->multiple)
		adj_slen = round_up(slen, c->multiple);
	if (slen < c->minimum)
		adj_slen = c->minimum;
	if (slen > c->maximum)
		adj_slen = slen = c->maximum;
	if (adj_slen > slen || (u64)src % c->alignment) {
		adj_slen = min(adj_slen, BOUNCE_BUFFER_SIZE);
		slen = min(slen, BOUNCE_BUFFER_SIZE);
		if (adj_slen > slen)
			memset(ctx->sbounce + slen, 0, adj_slen - slen);
		memcpy(ctx->sbounce, src, slen);
		src = ctx->sbounce;
		slen = adj_slen;
		pr_debug("using comp sbounce buffer, len %x\n", slen);
	}

	dst += hdrsize;
	dlen -= hdrsize;

	if ((u64)dst % c->alignment) {
		dskip = (int)(PTR_ALIGN(dst, c->alignment) - dst);
		dst += dskip;
		dlen -= dskip;
	}
	if (dlen % c->multiple)
		dlen = round_down(dlen, c->multiple);
	if (dlen < c->minimum) {
nospc:
		dst = ctx->dbounce;
		dlen = min(p->oremain, BOUNCE_BUFFER_SIZE);
		dlen = round_down(dlen, c->multiple);
		dskip = 0;
		pr_debug("using comp dbounce buffer, len %x\n", dlen);
	}
	if (dlen > c->maximum)
		dlen = c->maximum;

	tmplen = dlen;
	timeout = ktime_add_ms(ktime_get(), COMP_BUSY_TIMEOUT);
	do {
		dlen = tmplen; /* reset dlen, if we're retrying */
		ret = nx842_compress(src, slen, dst, &dlen, ctx->wmem);
		/* possibly we should reduce the slen here, instead of
		 * retrying with the dbounce buffer?
		 */
		if (ret == -ENOSPC && dst != ctx->dbounce)
			goto nospc;
	} while (ret == -EBUSY && ktime_before(ktime_get(), timeout));
	if (ret)
		return ret;

	dskip += hdrsize;

	if (dst == ctx->dbounce)
		memcpy(p->out + dskip, dst, dlen);

	g->padding = cpu_to_be16(dskip);
	g->compressed_length = cpu_to_be32(dlen);
	g->uncompressed_length = cpu_to_be32(slen);

	if (p->iremain < slen) {
		*ignore = slen - p->iremain;
		slen = p->iremain;
	}

	pr_debug("compress slen %x ignore %x dlen %x padding %x\n",
		 slen, *ignore, dlen, dskip);

	return update_param(p, slen, dskip + dlen);
}

static int nx842_crypto_compress(struct crypto_tfm *tfm,
				 const u8 *src, unsigned int slen,
				 u8 *dst, unsigned int *dlen)
{
	struct nx842_crypto_ctx *ctx = crypto_tfm_ctx(tfm);
	struct nx842_crypto_header *hdr = &ctx->header;
	struct nx842_crypto_param p;
	struct nx842_constraints c;
	unsigned int groups, hdrsize, h;
	int ret, n;
	bool add_header;
	u16 ignore = 0;

	p.in = (u8 *)src;
	p.iremain = slen;
	p.out = dst;
	p.oremain = *dlen;
	p.ototal = 0;

	*dlen = 0;

	ret = read_constraints(&c);
	if (ret)
		return ret;

	groups = min_t(unsigned int, NX842_CRYPTO_GROUP_MAX,
		       DIV_ROUND_UP(p.iremain, c.maximum));
	hdrsize = NX842_CRYPTO_HEADER_SIZE(groups);

	/* skip adding header if the buffers meet all constraints */
	add_header = (p.iremain % c.multiple	||
		      p.iremain < c.minimum	||
		      p.iremain > c.maximum	||
		      (u64)p.in % c.alignment	||
		      p.oremain % c.multiple	||
		      p.oremain < c.minimum	||
		      p.oremain > c.maximum	||
		      (u64)p.out % c.alignment);

	hdr->magic = cpu_to_be16(NX842_CRYPTO_MAGIC);
	hdr->groups = 0;
	hdr->ignore = 0;

	while (p.iremain > 0) {
		n = hdr->groups++;
		if (hdr->groups > NX842_CRYPTO_GROUP_MAX)
			return -ENOSPC;

		/* header goes before first group */
		h = !n && add_header ? hdrsize : 0;

		if (ignore)
			pr_warn("interal error, ignore is set %x\n", ignore);

		ret = compress(ctx, &p, &hdr->group[n], &c, &ignore, h);
		if (ret)
			return ret;
	}

	if (!add_header && hdr->groups > 1) {
		pr_err("Internal error: No header but multiple groups\n");
		return -EINVAL;
	}

	/* ignore indicates the input stream needed to be padded */
	hdr->ignore = cpu_to_be16(ignore);
	if (ignore)
		pr_debug("marked %d bytes as ignore\n", ignore);

	if (add_header)
		ret = nx842_crypto_add_header(hdr, dst);
	if (ret)
		return ret;

	*dlen = p.ototal;

	pr_debug("compress total slen %x dlen %x\n", slen, *dlen);

	return 0;
}

static int decompress(struct nx842_crypto_ctx *ctx,
		      struct nx842_crypto_param *p,
		      struct nx842_crypto_header_group *g,
		      struct nx842_constraints *c,
		      u16 ignore,
		      bool usehw)
{
	unsigned int slen = be32_to_cpu(g->compressed_length);
	unsigned int required_len = be32_to_cpu(g->uncompressed_length);
	unsigned int dlen = p->oremain, tmplen;
	unsigned int adj_slen = slen;
	u8 *src = p->in, *dst = p->out;
	u16 padding = be16_to_cpu(g->padding);
	int ret, spadding = 0, dpadding = 0;
	ktime_t timeout;

	if (!slen || !required_len)
		return -EINVAL;

	if (p->iremain <= 0 || padding + slen > p->iremain)
		return -EOVERFLOW;

	if (p->oremain <= 0 || required_len - ignore > p->oremain)
		return -ENOSPC;

	src += padding;

	if (!usehw)
		goto usesw;

	if (slen % c->multiple)
		adj_slen = round_up(slen, c->multiple);
	if (slen < c->minimum)
		adj_slen = c->minimum;
	if (slen > c->maximum)
		goto usesw;
	if (slen < adj_slen || (u64)src % c->alignment) {
		/* we can append padding bytes because the 842 format defines
		 * an "end" template (see lib/842/842_decompress.c) and will
		 * ignore any bytes following it.
		 */
		if (slen < adj_slen)
			memset(ctx->sbounce + slen, 0, adj_slen - slen);
		memcpy(ctx->sbounce, src, slen);
		src = ctx->sbounce;
		spadding = adj_slen - slen;
		slen = adj_slen;
		pr_debug("using decomp sbounce buffer, len %x\n", slen);
	}

	if (dlen % c->multiple)
		dlen = round_down(dlen, c->multiple);
	if (dlen < required_len || (u64)dst % c->alignment) {
		dst = ctx->dbounce;
		dlen = min(required_len, BOUNCE_BUFFER_SIZE);
		pr_debug("using decomp dbounce buffer, len %x\n", dlen);
	}
	if (dlen < c->minimum)
		goto usesw;
	if (dlen > c->maximum)
		dlen = c->maximum;

	tmplen = dlen;
	timeout = ktime_add_ms(ktime_get(), DECOMP_BUSY_TIMEOUT);
	do {
		dlen = tmplen; /* reset dlen, if we're retrying */
		ret = nx842_decompress(src, slen, dst, &dlen, ctx->wmem);
	} while (ret == -EBUSY && ktime_before(ktime_get(), timeout));
	if (ret) {
usesw:
		/* reset everything, sw doesn't have constraints */
		src = p->in + padding;
		slen = be32_to_cpu(g->compressed_length);
		spadding = 0;
		dst = p->out;
		dlen = p->oremain;
		dpadding = 0;
		if (dlen < required_len) { /* have ignore bytes */
			dst = ctx->dbounce;
			dlen = BOUNCE_BUFFER_SIZE;
		}
		pr_info_ratelimited("using software 842 decompression\n");
		ret = sw842_decompress(src, slen, dst, &dlen);
	}
	if (ret)
		return ret;

	slen -= spadding;

	dlen -= ignore;
	if (ignore)
		pr_debug("ignoring last %x bytes\n", ignore);

	if (dst == ctx->dbounce)
		memcpy(p->out, dst, dlen);

	pr_debug("decompress slen %x padding %x dlen %x ignore %x\n",
		 slen, padding, dlen, ignore);

	return update_param(p, slen + padding, dlen);
}

static int nx842_crypto_decompress(struct crypto_tfm *tfm,
				   const u8 *src, unsigned int slen,
				   u8 *dst, unsigned int *dlen)
{
	struct nx842_crypto_ctx *ctx = crypto_tfm_ctx(tfm);
	struct nx842_crypto_header *hdr;
	struct nx842_crypto_param p;
	struct nx842_constraints c;
	int n, ret, hdr_len;
	u16 ignore = 0;
	bool usehw = true;

	p.in = (u8 *)src;
	p.iremain = slen;
	p.out = dst;
	p.oremain = *dlen;
	p.ototal = 0;

	*dlen = 0;

	if (read_constraints(&c))
		usehw = false;

	hdr = (struct nx842_crypto_header *)src;

	/* If it doesn't start with our header magic number, assume it's a raw
	 * 842 compressed buffer and pass it directly to the hardware driver
	 */
	if (be16_to_cpu(hdr->magic) != NX842_CRYPTO_MAGIC) {
		struct nx842_crypto_header_group g = {
			.padding =		0,
			.compressed_length =	cpu_to_be32(p.iremain),
			.uncompressed_length =	cpu_to_be32(p.oremain),
		};

		ret = decompress(ctx, &p, &g, &c, 0, usehw);
		if (ret)
			return ret;

		*dlen = p.ototal;

		return 0;
	}

	if (!hdr->groups) {
		pr_err("header has no groups\n");
		return -EINVAL;
	}
	if (hdr->groups > NX842_CRYPTO_GROUP_MAX) {
		pr_err("header has too many groups %x, max %x\n",
		       hdr->groups, NX842_CRYPTO_GROUP_MAX);
		return -EINVAL;
	}

	hdr_len = NX842_CRYPTO_HEADER_SIZE(hdr->groups);
	if (hdr_len > slen)
		return -EOVERFLOW;

	memcpy(&ctx->header, src, hdr_len);
	hdr = &ctx->header;

	for (n = 0; n < hdr->groups; n++) {
		/* ignore applies to last group */
		if (n + 1 == hdr->groups)
			ignore = be16_to_cpu(hdr->ignore);

		ret = decompress(ctx, &p, &hdr->group[n], &c, ignore, usehw);
		if (ret)
			return ret;
	}

	*dlen = p.ototal;

	pr_debug("decompress total slen %x dlen %x\n", slen, *dlen);

	return 0;
}

static struct crypto_alg alg = {
	.cra_name		= "842",
	.cra_driver_name	= "842-nx",
	.cra_priority		= 300,
	.cra_flags		= CRYPTO_ALG_TYPE_COMPRESS,
	.cra_ctxsize		= sizeof(struct nx842_crypto_ctx),
	.cra_module		= THIS_MODULE,
	.cra_init		= nx842_crypto_init,
	.cra_exit		= nx842_crypto_exit,
	.cra_u			= { .compress = {
	.coa_compress		= nx842_crypto_compress,
	.coa_decompress		= nx842_crypto_decompress } }
};

static int __init nx842_crypto_mod_init(void)
{
	return crypto_register_alg(&alg);
}
module_init(nx842_crypto_mod_init);

static void __exit nx842_crypto_mod_exit(void)
{
	crypto_unregister_alg(&alg);
}
module_exit(nx842_crypto_mod_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("IBM PowerPC Nest (NX) 842 Hardware Compression Interface");
MODULE_ALIAS_CRYPTO("842");
MODULE_ALIAS_CRYPTO("842-nx");
MODULE_AUTHOR("Dan Streetman <ddstreet@ieee.org>");