--- /dev/null
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * CIO inject interface
+ *
+ * Copyright IBM Corp. 2021
+ * Author(s): Vineeth Vijayan <vneethv@linux.ibm.com>
+ */
+
+#define KMSG_COMPONENT "cio"
+#define pr_fmt(fmt) KMSG_COMPONENT ": " 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 = vmemdup_user(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);
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