/*
 * AMD Cryptographic Coprocessor (CCP) crypto API support
 *
 * Copyright (C) 2013 Advanced Micro Devices, Inc.
 *
 * Author: Tom Lendacky <thomas.lendacky@amd.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/ccp.h>
#include <linux/scatterlist.h>
#include <crypto/internal/hash.h>

#include "ccp-crypto.h"

MODULE_AUTHOR("Tom Lendacky <thomas.lendacky@amd.com>");
MODULE_LICENSE("GPL");
MODULE_VERSION("1.0.0");
MODULE_DESCRIPTION("AMD Cryptographic Coprocessor crypto API support");

static unsigned int aes_disable;
module_param(aes_disable, uint, 0444);
MODULE_PARM_DESC(aes_disable, "Disable use of AES - any non-zero value");

static unsigned int sha_disable;
module_param(sha_disable, uint, 0444);
MODULE_PARM_DESC(sha_disable, "Disable use of SHA - any non-zero value");

/* List heads for the supported algorithms */
static LIST_HEAD(hash_algs);
static LIST_HEAD(cipher_algs);

/* For any tfm, requests for that tfm must be returned on the order
 * received.  With multiple queues available, the CCP can process more
 * than one cmd at a time.  Therefore we must maintain a cmd list to insure
 * the proper ordering of requests on a given tfm.
 */
struct ccp_crypto_queue {
        struct list_head cmds;
        struct list_head *backlog;
        unsigned int cmd_count;
};

#define CCP_CRYPTO_MAX_QLEN     100

static struct ccp_crypto_queue req_queue;
static spinlock_t req_queue_lock;

struct ccp_crypto_cmd {
        struct list_head entry;

        struct ccp_cmd *cmd;

        /* Save the crypto_tfm and crypto_async_request addresses
         * separately to avoid any reference to a possibly invalid
         * crypto_async_request structure after invoking the request
         * callback
         */
        struct crypto_async_request *req;
        struct crypto_tfm *tfm;

        /* Used for held command processing to determine state */
        int ret;
};

struct ccp_crypto_cpu {
        struct work_struct work;
        struct completion completion;
        struct ccp_crypto_cmd *crypto_cmd;
        int err;
};

static inline bool ccp_crypto_success(int err)
{
        if (err && (err != -EINPROGRESS) && (err != -EBUSY))
                return false;

        return true;
}

static struct ccp_crypto_cmd *ccp_crypto_cmd_complete(
        struct ccp_crypto_cmd *crypto_cmd, struct ccp_crypto_cmd **backlog)
{
        struct ccp_crypto_cmd *held = NULL, *tmp;
        unsigned long flags;

        *backlog = NULL;

        spin_lock_irqsave(&req_queue_lock, flags);

        /* Held cmds will be after the current cmd in the queue so start
         * searching for a cmd with a matching tfm for submission.
         */
        tmp = crypto_cmd;
        list_for_each_entry_continue(tmp, &req_queue.cmds, entry) {
                if (crypto_cmd->tfm != tmp->tfm)
                        continue;
                held = tmp;
                break;
        }

        /* Process the backlog:
         *   Because cmds can be executed from any point in the cmd list
         *   special precautions have to be taken when handling the backlog.
         */
        if (req_queue.backlog != &req_queue.cmds) {
                /* Skip over this cmd if it is the next backlog cmd */
                if (req_queue.backlog == &crypto_cmd->entry)
                        req_queue.backlog = crypto_cmd->entry.next;

                *backlog = container_of(req_queue.backlog,
                                        struct ccp_crypto_cmd, entry);
                req_queue.backlog = req_queue.backlog->next;

                /* Skip over this cmd if it is now the next backlog cmd */
                if (req_queue.backlog == &crypto_cmd->entry)
                        req_queue.backlog = crypto_cmd->entry.next;
        }

        /* Remove the cmd entry from the list of cmds */
        req_queue.cmd_count--;
        list_del(&crypto_cmd->entry);

        spin_unlock_irqrestore(&req_queue_lock, flags);

        return held;
}

static void ccp_crypto_complete(void *data, int err)
{
        struct ccp_crypto_cmd *crypto_cmd = data;
        struct ccp_crypto_cmd *held, *next, *backlog;
        struct crypto_async_request *req = crypto_cmd->req;
        struct ccp_ctx *ctx = crypto_tfm_ctx(req->tfm);
        int ret;

        if (err == -EINPROGRESS) {
                /* Only propagate the -EINPROGRESS if necessary */
                if (crypto_cmd->ret == -EBUSY) {
                        crypto_cmd->ret = -EINPROGRESS;
                        req->complete(req, -EINPROGRESS);
                }

                return;
        }

        /* Operation has completed - update the queue before invoking
         * the completion callbacks and retrieve the next cmd (cmd with
         * a matching tfm) that can be submitted to the CCP.
         */
        held = ccp_crypto_cmd_complete(crypto_cmd, &backlog);
        if (backlog) {
                backlog->ret = -EINPROGRESS;
                backlog->req->complete(backlog->req, -EINPROGRESS);
        }

        /* Transition the state from -EBUSY to -EINPROGRESS first */
        if (crypto_cmd->ret == -EBUSY)
                req->complete(req, -EINPROGRESS);

        /* Completion callbacks */
        ret = err;
        if (ctx->complete)
                ret = ctx->complete(req, ret);
        req->complete(req, ret);

        /* Submit the next cmd */
        while (held) {
                /* Since we have already queued the cmd, we must indicate that
                 * we can backlog so as not to "lose" this request.
                 */
                held->cmd->flags |= CCP_CMD_MAY_BACKLOG;
                ret = ccp_enqueue_cmd(held->cmd);
                if (ccp_crypto_success(ret))
                        break;

                /* Error occurred, report it and get the next entry */
                ctx = crypto_tfm_ctx(held->req->tfm);
                if (ctx->complete)
                        ret = ctx->complete(held->req, ret);
                held->req->complete(held->req, ret);

                next = ccp_crypto_cmd_complete(held, &backlog);
                if (backlog) {
                        backlog->ret = -EINPROGRESS;
                        backlog->req->complete(backlog->req, -EINPROGRESS);
                }

                kfree(held);
                held = next;
        }

        kfree(crypto_cmd);
}

static int ccp_crypto_enqueue_cmd(struct ccp_crypto_cmd *crypto_cmd)
{
        struct ccp_crypto_cmd *active = NULL, *tmp;
        unsigned long flags;
        bool free_cmd = true;
        int ret;

        spin_lock_irqsave(&req_queue_lock, flags);

        /* Check if the cmd can/should be queued */
        if (req_queue.cmd_count >= CCP_CRYPTO_MAX_QLEN) {
                ret = -EBUSY;
                if (!(crypto_cmd->cmd->flags & CCP_CMD_MAY_BACKLOG))
                        goto e_lock;
        }

        /* Look for an entry with the same tfm.  If there is a cmd
         * with the same tfm in the list then the current cmd cannot
         * be submitted to the CCP yet.
         */
        list_for_each_entry(tmp, &req_queue.cmds, entry) {
                if (crypto_cmd->tfm != tmp->tfm)
                        continue;
                active = tmp;
                break;
        }

        ret = -EINPROGRESS;
        if (!active) {
                ret = ccp_enqueue_cmd(crypto_cmd->cmd);
                if (!ccp_crypto_success(ret))
                        goto e_lock;    /* Error, don't queue it */
                if ((ret == -EBUSY) &&
                    !(crypto_cmd->cmd->flags & CCP_CMD_MAY_BACKLOG))
                        goto e_lock;    /* Not backlogging, don't queue it */
        }

        if (req_queue.cmd_count >= CCP_CRYPTO_MAX_QLEN) {
                ret = -EBUSY;
                if (req_queue.backlog == &req_queue.cmds)
                        req_queue.backlog = &crypto_cmd->entry;
        }
        crypto_cmd->ret = ret;

        req_queue.cmd_count++;
        list_add_tail(&crypto_cmd->entry, &req_queue.cmds);

        free_cmd = false;

e_lock:
        spin_unlock_irqrestore(&req_queue_lock, flags);

        if (free_cmd)
                kfree(crypto_cmd);

        return ret;
}

/**
 * ccp_crypto_enqueue_request - queue an crypto async request for processing
 *                              by the CCP
 *
 * @req: crypto_async_request struct to be processed
 * @cmd: ccp_cmd struct to be sent to the CCP
 */
int ccp_crypto_enqueue_request(struct crypto_async_request *req,
                               struct ccp_cmd *cmd)
{
        struct ccp_crypto_cmd *crypto_cmd;
        gfp_t gfp;

        gfp = req->flags & CRYPTO_TFM_REQ_MAY_SLEEP ? GFP_KERNEL : GFP_ATOMIC;

        crypto_cmd = kzalloc(sizeof(*crypto_cmd), gfp);
        if (!crypto_cmd)
                return -ENOMEM;

        /* The tfm pointer must be saved and not referenced from the
         * crypto_async_request (req) pointer because it is used after
         * completion callback for the request and the req pointer
         * might not be valid anymore.
         */
        crypto_cmd->cmd = cmd;
        crypto_cmd->req = req;
        crypto_cmd->tfm = req->tfm;

        cmd->callback = ccp_crypto_complete;
        cmd->data = crypto_cmd;

        if (req->flags & CRYPTO_TFM_REQ_MAY_BACKLOG)
                cmd->flags |= CCP_CMD_MAY_BACKLOG;
        else
                cmd->flags &= ~CCP_CMD_MAY_BACKLOG;

        return ccp_crypto_enqueue_cmd(crypto_cmd);
}

struct scatterlist *ccp_crypto_sg_table_add(struct sg_table *table,
                                            struct scatterlist *sg_add)
{
        struct scatterlist *sg, *sg_last = NULL;

        for (sg = table->sgl; sg; sg = sg_next(sg))
                if (!sg_page(sg))
                        break;
        if (WARN_ON(!sg))
                return NULL;

        for (; sg && sg_add; sg = sg_next(sg), sg_add = sg_next(sg_add)) {
                sg_set_page(sg, sg_page(sg_add), sg_add->length,
                            sg_add->offset);
                sg_last = sg;
        }
        if (WARN_ON(sg_add))
                return NULL;

        return sg_last;
}

static int ccp_register_algs(void)
{
        int ret;

        if (!aes_disable) {
                ret = ccp_register_aes_algs(&cipher_algs);
                if (ret)
                        return ret;

                ret = ccp_register_aes_cmac_algs(&hash_algs);
                if (ret)
                        return ret;

                ret = ccp_register_aes_xts_algs(&cipher_algs);
                if (ret)
                        return ret;
        }

        if (!sha_disable) {
                ret = ccp_register_sha_algs(&hash_algs);
                if (ret)
                        return ret;
        }

        return 0;
}

static void ccp_unregister_algs(void)
{
        struct ccp_crypto_ahash_alg *ahash_alg, *ahash_tmp;
        struct ccp_crypto_ablkcipher_alg *ablk_alg, *ablk_tmp;

        list_for_each_entry_safe(ahash_alg, ahash_tmp, &hash_algs, entry) {
                crypto_unregister_ahash(&ahash_alg->alg);
                list_del(&ahash_alg->entry);
                kfree(ahash_alg);
        }

        list_for_each_entry_safe(ablk_alg, ablk_tmp, &cipher_algs, entry) {
                crypto_unregister_alg(&ablk_alg->alg);
                list_del(&ablk_alg->entry);
                kfree(ablk_alg);
        }
}

static int ccp_crypto_init(void)
{
        int ret;

        ret = ccp_present();
        if (ret)
                return ret;

        spin_lock_init(&req_queue_lock);
        INIT_LIST_HEAD(&req_queue.cmds);
        req_queue.backlog = &req_queue.cmds;
        req_queue.cmd_count = 0;

        ret = ccp_register_algs();
        if (ret)
                ccp_unregister_algs();

        return ret;
}

static void ccp_crypto_exit(void)
{
        ccp_unregister_algs();
}

module_init(ccp_crypto_init);
module_exit(ccp_crypto_exit);