LXR linux/drivers/char/crash.c

   1/*
   2 *  linux/drivers/char/crash.c
   3 *
   4 *  Copyright (C) 2004  Dave Anderson <anderson@redhat.com>
   5 *  Copyright (C) 2004  Red Hat, Inc.
   6 */
   7
   8/******************************************************************************
   9 *
  10 *   This program is free software; you can redistribute it and/or modify
  11 *   it under the terms of the GNU General Public License as published by
  12 *   the Free Software Foundation; either version 2, or (at your option)
  13 *   any later version.
  14 *
  15 *   This program is distributed in the hope that it will be useful,
  16 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 *   GNU General Public License for more details.
  19 *
  20 *   You should have received a copy of the GNU General Public License
  21 *   along with this program; if not, write to the Free Software
  22 *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  23 *
  24 *****************************************************************************/
  25
  26#include <linux/module.h>
  27#include <linux/types.h>
  28#include <linux/miscdevice.h>
  29#include <linux/init.h>
  30#include <asm/io.h>
  31#include <asm/uaccess.h>
  32#include <asm/types.h>
  33#include <asm/crash-driver.h>
  34
  35#define CRASH_VERSION   "1.1"
  36
  37/*
  38 *  These are the file operation functions that allow crash utility
  39 *  access to physical memory.
  40 */
  41
  42static loff_t 
  43crash_llseek(struct file * file, loff_t offset, int orig)
  44{
  45        switch (orig) {
  46        case 0:
  47                file->f_pos = offset;
  48                return file->f_pos;
  49        case 1:
  50                file->f_pos += offset;
  51                return file->f_pos;
  52        default:
  53                return -EINVAL;
  54        }
  55}
  56
  57/*
  58 *  Determine the page address for an address offset value, 
  59 *  get a virtual address for it, and copy it out.
  60 *  Accesses must fit within a page.
  61 */
  62static ssize_t
  63crash_read(struct file *file, char *buf, size_t count, loff_t *poff)
  64{
  65        void *vaddr;
  66        struct page *page;
  67        u64 offset;
  68        ssize_t read;
  69
  70        offset = *poff;
  71        if (offset >> PAGE_SHIFT != (offset+count-1) >> PAGE_SHIFT) 
  72                return -EINVAL;
  73
  74        vaddr = map_virtual(offset, &page);
  75        if (!vaddr)
  76                return -EFAULT;
  77
  78        if (copy_to_user(buf, vaddr, count)) {
  79                unmap_virtual(page);
  80                return -EFAULT;
  81        }
  82        unmap_virtual(page);
  83
  84        read = count;
  85        *poff += read;
  86        return read;
  87}
  88
  89static int 
  90crash_open(struct inode * inode, struct file * filp)
  91{
  92        return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
  93}
  94
  95static struct file_operations crash_fops = {
  96        .owner = THIS_MODULE,
  97        .llseek = crash_llseek,
  98        .read = crash_read,
  99        .open = crash_open,
 100};
 101
 102static struct miscdevice crash_dev = {
 103        MISC_DYNAMIC_MINOR,
 104        "crash",
 105        &crash_fops
 106};
 107
 108static int __init
 109crash_init(void)
 110{
 111        int ret;
 112
 113        ret = misc_register(&crash_dev);
 114        if (ret) {
 115                printk(KERN_ERR 
 116                    "crash memory driver: cannot misc_register (MISC_DYNAMIC_MINOR)\n");
 117                goto out;
 118        }
 119        
 120        ret = 0;
 121        printk(KERN_INFO "crash memory driver: version %s\n", CRASH_VERSION);
 122out:
 123        return ret;
 124}
 125
 126static void __exit
 127crash_cleanup_module(void)
 128{
 129        misc_deregister(&crash_dev);
 130}
 131
 132module_init(crash_init);
 133module_exit(crash_cleanup_module);
 134
 135MODULE_LICENSE("GPL");
 136