// SPDX-License-Identifier: GPL-2.0
/*
 *   CIO inject interface
 *
 *    Copyright IBM Corp. 2021
 *    Author(s): Vineeth Vijayan <vneethv@linux.ibm.com>
 */

#define pr_fmt(fmt) "cio: " fmt

#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/mm.h>
#include <linux/debugfs.h>
#include <asm/chpid.h>

#include "cio_inject.h"
#include "cio_debug.h"

static DEFINE_SPINLOCK(crw_inject_lock);
DEFINE_STATIC_KEY_FALSE(cio_inject_enabled);
static struct crw *crw_inject_data;

/**
 * crw_inject : Initiate the artificial CRW inject
 * @crw: The data which needs to be injected as new CRW.
 *
 * The CRW handler is called, which will use the provided artificial
 * data instead of the CRW from the underlying hardware.
 *
 * Return: 0 on success
 */
static int crw_inject(struct crw *crw)
{
        int rc = 0;
        struct crw *copy;
        unsigned long flags;

        copy = kmemdup(crw, sizeof(*crw), GFP_KERNEL);
        if (!copy)
                return -ENOMEM;

        spin_lock_irqsave(&crw_inject_lock, flags);
        if (crw_inject_data) {
                kfree(copy);
                rc = -EBUSY;
        } else {
                crw_inject_data = copy;
        }
        spin_unlock_irqrestore(&crw_inject_lock, flags);

        if (!rc)
                crw_handle_channel_report();

        return rc;
}

/**
 * stcrw_get_injected: Copy the artificial CRW data to CRW struct.
 * @crw: The target CRW pointer.
 *
 * Retrieve an injected CRW data. Return 0 on success, 1 if no
 * injected-CRW is available. The function reproduces the return
 * code of the actual STCRW function.
 */
int stcrw_get_injected(struct crw *crw)
{
        int rc = 1;
        unsigned long flags;

        spin_lock_irqsave(&crw_inject_lock, flags);
        if (crw_inject_data) {
                memcpy(crw, crw_inject_data, sizeof(*crw));
                kfree(crw_inject_data);
                crw_inject_data = NULL;
                rc = 0;
        }
        spin_unlock_irqrestore(&crw_inject_lock, flags);

        return rc;
}

/* The debugfs write handler for crw_inject nodes operation */
static ssize_t crw_inject_write(struct file *file, const char __user *buf,
                                size_t lbuf, loff_t *ppos)
{
        u32 slct, oflw, chn, rsc, anc, erc, rsid;
        struct crw crw;
        char *buffer;
        int rc;

        if (!static_branch_likely(&cio_inject_enabled)) {
                pr_warn("CIO inject is not enabled - ignoring CRW inject\n");
                return -EINVAL;
        }

        buffer = memdup_user_nul(buf, lbuf);
        if (IS_ERR(buffer))
                return -ENOMEM;

        rc = sscanf(buffer, "%x %x %x %x %x %x %x", &slct, &oflw, &chn, &rsc, &anc,
                    &erc, &rsid);

        kvfree(buffer);
        if (rc != 7) {
                pr_warn("crw_inject: Invalid format (need <solicited> <overflow> <chaining> <rsc> <ancillary> <erc> <rsid>)\n");
                return -EINVAL;
        }

        memset(&crw, 0, sizeof(crw));
        crw.slct = slct;
        crw.oflw = oflw;
        crw.chn = chn;
        crw.rsc = rsc;
        crw.anc = anc;
        crw.erc = erc;
        crw.rsid = rsid;

        rc = crw_inject(&crw);
        if (rc)
                return rc;

        return lbuf;
}

/* Debugfs write handler for inject_enable node*/
static ssize_t enable_inject_write(struct file *file, const char __user *buf,
                                   size_t lbuf, loff_t *ppos)
{
        unsigned long en = 0;
        int rc;

        rc = kstrtoul_from_user(buf, lbuf, 10, &en);
        if (rc)
                return rc;

        switch (en) {
        case 0:
                static_branch_disable(&cio_inject_enabled);
                break;
        case 1:
                static_branch_enable(&cio_inject_enabled);
                break;
        }

        return lbuf;
}

static const struct file_operations crw_fops = {
        .owner = THIS_MODULE,
        .write = crw_inject_write,
};

static const struct file_operations cio_en_fops = {
        .owner = THIS_MODULE,
        .write = enable_inject_write,
};

static int __init cio_inject_init(void)
{
        /* enable_inject node enables the static branching */
        debugfs_create_file("enable_inject", 0200, cio_debugfs_dir,
                            NULL, &cio_en_fops);

        debugfs_create_file("crw_inject", 0200, cio_debugfs_dir,
                            NULL, &crw_fops);
        return 0;
}

device_initcall(cio_inject_init);