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* Copyright IBM Corp. 2004,2010
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* Interface implementation for communication with the z/VM control program
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* Author(s): Christian Borntraeger <borntraeger@de.ibm.com>
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* z/VMs CP offers the possibility to issue commands via the diagnose code 8
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* this driver implements a character device that issues these commands and
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* returns the answer of CP.
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* The idea of this driver is based on cpint from Neale Ferguson and #CP in CMS
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/miscdevice.h>
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#include <linux/slab.h>
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#include <linux/export.h>
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#include <asm/compat.h>
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#include <asm/cpcmd.h>
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#include <asm/debug.h>
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#include <asm/uaccess.h>
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static debug_info_t *vmcp_debug;
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static int vmcp_open(struct inode *inode, struct file *file)
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struct vmcp_session *session;
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if (!capable(CAP_SYS_ADMIN))
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session = kmalloc(sizeof(*session), GFP_KERNEL);
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session->bufsize = PAGE_SIZE;
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session->response = NULL;
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session->resp_size = 0;
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mutex_init(&session->mutex);
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file->private_data = session;
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return nonseekable_open(inode, file);
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static int vmcp_release(struct inode *inode, struct file *file)
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struct vmcp_session *session;
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session = file->private_data;
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file->private_data = NULL;
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free_pages((unsigned long)session->response, get_order(session->bufsize));
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vmcp_read(struct file *file, char __user *buff, size_t count, loff_t *ppos)
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struct vmcp_session *session;
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session = file->private_data;
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if (mutex_lock_interruptible(&session->mutex))
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if (!session->response) {
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mutex_unlock(&session->mutex);
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size = min_t(size_t, session->resp_size, session->bufsize);
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ret = simple_read_from_buffer(buff, count, ppos,
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session->response, size);
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mutex_unlock(&session->mutex);
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vmcp_write(struct file *file, const char __user *buff, size_t count,
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struct vmcp_session *session;
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cmd = kmalloc(count + 1, GFP_KERNEL);
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if (copy_from_user(cmd, buff, count)) {
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session = file->private_data;
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if (mutex_lock_interruptible(&session->mutex)) {
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if (!session->response)
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session->response = (char *)__get_free_pages(GFP_KERNEL
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| __GFP_REPEAT | GFP_DMA,
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get_order(session->bufsize));
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if (!session->response) {
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mutex_unlock(&session->mutex);
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debug_text_event(vmcp_debug, 1, cmd);
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session->resp_size = cpcmd(cmd, session->response, session->bufsize,
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&session->resp_code);
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mutex_unlock(&session->mutex);
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*ppos = 0; /* reset the file pointer after a command */
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* These ioctls are available, as the semantics of the diagnose 8 call
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* does not fit very well into a Linux call. Diagnose X'08' is described in
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* CP Programming Services SC24-6084-00
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* VMCP_GETCODE: gives the CP return code back to user space
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* VMCP_SETBUF: sets the response buffer for the next write call. diagnose 8
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* expects adjacent pages in real storage and to make matters worse, we
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* dont know the size of the response. Therefore we default to PAGESIZE and
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* let userspace to change the response size, if userspace expects a bigger
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static long vmcp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
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struct vmcp_session *session;
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session = file->private_data;
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if (is_compat_task())
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argp = compat_ptr(arg);
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argp = (int __user *)arg;
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if (mutex_lock_interruptible(&session->mutex))
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temp = session->resp_code;
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mutex_unlock(&session->mutex);
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return put_user(temp, argp);
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free_pages((unsigned long)session->response,
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get_order(session->bufsize));
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session->response=NULL;
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temp = get_user(session->bufsize, argp);
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if (get_order(session->bufsize) > 8) {
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session->bufsize = PAGE_SIZE;
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mutex_unlock(&session->mutex);
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temp = session->resp_size;
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mutex_unlock(&session->mutex);
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return put_user(temp, argp);
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mutex_unlock(&session->mutex);
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static const struct file_operations vmcp_fops = {
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.owner = THIS_MODULE,
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.release = vmcp_release,
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.unlocked_ioctl = vmcp_ioctl,
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.compat_ioctl = vmcp_ioctl,
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static struct miscdevice vmcp_dev = {
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.minor = MISC_DYNAMIC_MINOR,
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static int __init vmcp_init(void)
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vmcp_debug = debug_register("vmcp", 1, 1, 240);
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ret = debug_register_view(vmcp_debug, &debug_hex_ascii_view);
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debug_unregister(vmcp_debug);
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ret = misc_register(&vmcp_dev);
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debug_unregister(vmcp_debug);
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device_initcall(vmcp_init);