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mem.c

/*
 *  linux/drivers/char/mem.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  Added devfs support. 
 *    Jan-11-1998, C. Scott Ananian <cananian@alumni.princeton.edu>
 *  Shared /dev/zero mmaping support, Feb 2000, Kanoj Sarcar <kanoj@sgi.com>
 */

#include <linux/mm.h>
#include <linux/miscdevice.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/mman.h>
#include <linux/random.h>
#include <linux/init.h>
#include <linux/raw.h>
#include <linux/tty.h>
#include <linux/capability.h>
#include <linux/ptrace.h>
#include <linux/device.h>
#include <linux/highmem.h>
#include <linux/crash_dump.h>
#include <linux/backing-dev.h>
#include <linux/bootmem.h>
#include <linux/splice.h>
#include <linux/pfn.h>

#include <asm/uaccess.h>
#include <asm/io.h>

#ifdef CONFIG_IA64
# include <linux/efi.h>
#endif

/*
 * Architectures vary in how they handle caching for addresses
 * outside of main memory.
 *
 */
static inline int uncached_access(struct file *file, unsigned long addr)
{
#if defined(__i386__) && !defined(__arch_um__)
      /*
       * On the PPro and successors, the MTRRs are used to set
       * memory types for physical addresses outside main memory,
       * so blindly setting PCD or PWT on those pages is wrong.
       * For Pentiums and earlier, the surround logic should disable
       * caching for the high addresses through the KEN pin, but
       * we maintain the tradition of paranoia in this code.
       */
      if (file->f_flags & O_SYNC)
            return 1;
      return !( test_bit(X86_FEATURE_MTRR, boot_cpu_data.x86_capability) ||
              test_bit(X86_FEATURE_K6_MTRR, boot_cpu_data.x86_capability) ||
              test_bit(X86_FEATURE_CYRIX_ARR, boot_cpu_data.x86_capability) ||
              test_bit(X86_FEATURE_CENTAUR_MCR, boot_cpu_data.x86_capability) )
        && addr >= __pa(high_memory);
#elif defined(__x86_64__) && !defined(__arch_um__)
      /* 
       * This is broken because it can generate memory type aliases,
       * which can cause cache corruptions
       * But it is only available for root and we have to be bug-to-bug
       * compatible with i386.
       */
      if (file->f_flags & O_SYNC)
            return 1;
      /* same behaviour as i386. PAT always set to cached and MTRRs control the
         caching behaviour. 
         Hopefully a full PAT implementation will fix that soon. */        
      return 0;
#elif defined(CONFIG_IA64)
      /*
       * On ia64, we ignore O_SYNC because we cannot tolerate memory attribute aliases.
       */
      return !(efi_mem_attributes(addr) & EFI_MEMORY_WB);
#elif defined(CONFIG_MIPS)
      {
            extern int __uncached_access(struct file *file,
                                   unsigned long addr);

            return __uncached_access(file, addr);
      }
#else
      /*
       * Accessing memory above the top the kernel knows about or through a file pointer
       * that was marked O_SYNC will be done non-cached.
       */
      if (file->f_flags & O_SYNC)
            return 1;
      return addr >= __pa(high_memory);
#endif
}

#ifndef ARCH_HAS_VALID_PHYS_ADDR_RANGE
static inline int valid_phys_addr_range(unsigned long addr, size_t count)
{
      if (addr + count > __pa(high_memory))
            return 0;

      return 1;
}

static inline int valid_mmap_phys_addr_range(unsigned long pfn, size_t size)
{
      return 1;
}
#endif

/*
 * This funcion reads the *physical* memory. The f_pos points directly to the 
 * memory location. 
 */
static ssize_t read_mem(struct file * file, char __user * buf,
                  size_t count, loff_t *ppos)
{
      unsigned long p = *ppos;
      ssize_t read, sz;
      char *ptr;

      if (!valid_phys_addr_range(p, count))
            return -EFAULT;
      read = 0;
#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
      /* we don't have page 0 mapped on sparc and m68k.. */
      if (p < PAGE_SIZE) {
            sz = PAGE_SIZE - p;
            if (sz > count) 
                  sz = count; 
            if (sz > 0) {
                  if (clear_user(buf, sz))
                        return -EFAULT;
                  buf += sz; 
                  p += sz; 
                  count -= sz; 
                  read += sz; 
            }
      }
#endif

      while (count > 0) {
            /*
             * Handle first page in case it's not aligned
             */
            if (-p & (PAGE_SIZE - 1))
                  sz = -p & (PAGE_SIZE - 1);
            else
                  sz = PAGE_SIZE;

            sz = min_t(unsigned long, sz, count);

            /*
             * On ia64 if a page has been mapped somewhere as
             * uncached, then it must also be accessed uncached
             * by the kernel or data corruption may occur
             */
            ptr = xlate_dev_mem_ptr(p);

            if (copy_to_user(buf, ptr, sz))
                  return -EFAULT;
            buf += sz;
            p += sz;
            count -= sz;
            read += sz;
      }

      *ppos += read;
      return read;
}

static ssize_t write_mem(struct file * file, const char __user * buf, 
                   size_t count, loff_t *ppos)
{
      unsigned long p = *ppos;
      ssize_t written, sz;
      unsigned long copied;
      void *ptr;

      if (!valid_phys_addr_range(p, count))
            return -EFAULT;

      written = 0;

#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
      /* we don't have page 0 mapped on sparc and m68k.. */
      if (p < PAGE_SIZE) {
            unsigned long sz = PAGE_SIZE - p;
            if (sz > count)
                  sz = count;
            /* Hmm. Do something? */
            buf += sz;
            p += sz;
            count -= sz;
            written += sz;
      }
#endif

      while (count > 0) {
            /*
             * Handle first page in case it's not aligned
             */
            if (-p & (PAGE_SIZE - 1))
                  sz = -p & (PAGE_SIZE - 1);
            else
                  sz = PAGE_SIZE;

            sz = min_t(unsigned long, sz, count);

            /*
             * On ia64 if a page has been mapped somewhere as
             * uncached, then it must also be accessed uncached
             * by the kernel or data corruption may occur
             */
            ptr = xlate_dev_mem_ptr(p);

            copied = copy_from_user(ptr, buf, sz);
            if (copied) {
                  written += sz - copied;
                  if (written)
                        break;
                  return -EFAULT;
            }
            buf += sz;
            p += sz;
            count -= sz;
            written += sz;
      }

      *ppos += written;
      return written;
}

#ifndef __HAVE_PHYS_MEM_ACCESS_PROT
static pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
                             unsigned long size, pgprot_t vma_prot)
{
#ifdef pgprot_noncached
      unsigned long offset = pfn << PAGE_SHIFT;

      if (uncached_access(file, offset))
            return pgprot_noncached(vma_prot);
#endif
      return vma_prot;
}
#endif

#ifndef CONFIG_MMU
static unsigned long get_unmapped_area_mem(struct file *file,
                                 unsigned long addr,
                                 unsigned long len,
                                 unsigned long pgoff,
                                 unsigned long flags)
{
      if (!valid_mmap_phys_addr_range(pgoff, len))
            return (unsigned long) -EINVAL;
      return pgoff << PAGE_SHIFT;
}

/* can't do an in-place private mapping if there's no MMU */
static inline int private_mapping_ok(struct vm_area_struct *vma)
{
      return vma->vm_flags & VM_MAYSHARE;
}
#else
#define get_unmapped_area_mem NULL

static inline int private_mapping_ok(struct vm_area_struct *vma)
{
      return 1;
}
#endif

static int mmap_mem(struct file * file, struct vm_area_struct * vma)
{
      size_t size = vma->vm_end - vma->vm_start;

      if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size))
            return -EINVAL;

      if (!private_mapping_ok(vma))
            return -ENOSYS;

      vma->vm_page_prot = phys_mem_access_prot(file, vma->vm_pgoff,
                                     size,
                                     vma->vm_page_prot);

      /* Remap-pfn-range will mark the range VM_IO and VM_RESERVED */
      if (remap_pfn_range(vma,
                      vma->vm_start,
                      vma->vm_pgoff,
                      size,
                      vma->vm_page_prot))
            return -EAGAIN;
      return 0;
}

static int mmap_kmem(struct file * file, struct vm_area_struct * vma)
{
      unsigned long pfn;

      /* Turn a kernel-virtual address into a physical page frame */
      pfn = __pa((u64)vma->vm_pgoff << PAGE_SHIFT) >> PAGE_SHIFT;

      /*
       * RED-PEN: on some architectures there is more mapped memory
       * than available in mem_map which pfn_valid checks
       * for. Perhaps should add a new macro here.
       *
       * RED-PEN: vmalloc is not supported right now.
       */
      if (!pfn_valid(pfn))
            return -EIO;

      vma->vm_pgoff = pfn;
      return mmap_mem(file, vma);
}

#ifdef CONFIG_CRASH_DUMP
/*
 * Read memory corresponding to the old kernel.
 */
static ssize_t read_oldmem(struct file *file, char __user *buf,
                        size_t count, loff_t *ppos)
{
      unsigned long pfn, offset;
      size_t read = 0, csize;
      int rc = 0;

      while (count) {
            pfn = *ppos / PAGE_SIZE;
            if (pfn > saved_max_pfn)
                  return read;

            offset = (unsigned long)(*ppos % PAGE_SIZE);
            if (count > PAGE_SIZE - offset)
                  csize = PAGE_SIZE - offset;
            else
                  csize = count;

            rc = copy_oldmem_page(pfn, buf, csize, offset, 1);
            if (rc < 0)
                  return rc;
            buf += csize;
            *ppos += csize;
            read += csize;
            count -= csize;
      }
      return read;
}
#endif

extern long vread(char *buf, char *addr, unsigned long count);
extern long vwrite(char *buf, char *addr, unsigned long count);

/*
 * This function reads the *virtual* memory as seen by the kernel.
 */
static ssize_t read_kmem(struct file *file, char __user *buf, 
                   size_t count, loff_t *ppos)
{
      unsigned long p = *ppos;
      ssize_t low_count, read, sz;
      char * kbuf; /* k-addr because vread() takes vmlist_lock rwlock */

      read = 0;
      if (p < (unsigned long) high_memory) {
            low_count = count;
            if (count > (unsigned long) high_memory - p)
                  low_count = (unsigned long) high_memory - p;

#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
            /* we don't have page 0 mapped on sparc and m68k.. */
            if (p < PAGE_SIZE && low_count > 0) {
                  size_t tmp = PAGE_SIZE - p;
                  if (tmp > low_count) tmp = low_count;
                  if (clear_user(buf, tmp))
                        return -EFAULT;
                  buf += tmp;
                  p += tmp;
                  read += tmp;
                  low_count -= tmp;
                  count -= tmp;
            }
#endif
            while (low_count > 0) {
                  /*
                   * Handle first page in case it's not aligned
                   */
                  if (-p & (PAGE_SIZE - 1))
                        sz = -p & (PAGE_SIZE - 1);
                  else
                        sz = PAGE_SIZE;

                  sz = min_t(unsigned long, sz, low_count);

                  /*
                   * On ia64 if a page has been mapped somewhere as
                   * uncached, then it must also be accessed uncached
                   * by the kernel or data corruption may occur
                   */
                  kbuf = xlate_dev_kmem_ptr((char *)p);

                  if (copy_to_user(buf, kbuf, sz))
                        return -EFAULT;
                  buf += sz;
                  p += sz;
                  read += sz;
                  low_count -= sz;
                  count -= sz;
            }
      }

      if (count > 0) {
            kbuf = (char *)__get_free_page(GFP_KERNEL);
            if (!kbuf)
                  return -ENOMEM;
            while (count > 0) {
                  int len = count;

                  if (len > PAGE_SIZE)
                        len = PAGE_SIZE;
                  len = vread(kbuf, (char *)p, len);
                  if (!len)
                        break;
                  if (copy_to_user(buf, kbuf, len)) {
                        free_page((unsigned long)kbuf);
                        return -EFAULT;
                  }
                  count -= len;
                  buf += len;
                  read += len;
                  p += len;
            }
            free_page((unsigned long)kbuf);
      }
      *ppos = p;
      return read;
}


static inline ssize_t
do_write_kmem(void *p, unsigned long realp, const char __user * buf,
            size_t count, loff_t *ppos)
{
      ssize_t written, sz;
      unsigned long copied;

      written = 0;
#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
      /* we don't have page 0 mapped on sparc and m68k.. */
      if (realp < PAGE_SIZE) {
            unsigned long sz = PAGE_SIZE - realp;
            if (sz > count)
                  sz = count;
            /* Hmm. Do something? */
            buf += sz;
            p += sz;
            realp += sz;
            count -= sz;
            written += sz;
      }
#endif

      while (count > 0) {
            char *ptr;
            /*
             * Handle first page in case it's not aligned
             */
            if (-realp & (PAGE_SIZE - 1))
                  sz = -realp & (PAGE_SIZE - 1);
            else
                  sz = PAGE_SIZE;

            sz = min_t(unsigned long, sz, count);

            /*
             * On ia64 if a page has been mapped somewhere as
             * uncached, then it must also be accessed uncached
             * by the kernel or data corruption may occur
             */
            ptr = xlate_dev_kmem_ptr(p);

            copied = copy_from_user(ptr, buf, sz);
            if (copied) {
                  written += sz - copied;
                  if (written)
                        break;
                  return -EFAULT;
            }
            buf += sz;
            p += sz;
            realp += sz;
            count -= sz;
            written += sz;
      }

      *ppos += written;
      return written;
}


/*
 * This function writes to the *virtual* memory as seen by the kernel.
 */
static ssize_t write_kmem(struct file * file, const char __user * buf, 
                    size_t count, loff_t *ppos)
{
      unsigned long p = *ppos;
      ssize_t wrote = 0;
      ssize_t virtr = 0;
      ssize_t written;
      char * kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */

      if (p < (unsigned long) high_memory) {

            wrote = count;
            if (count > (unsigned long) high_memory - p)
                  wrote = (unsigned long) high_memory - p;

            written = do_write_kmem((void*)p, p, buf, wrote, ppos);
            if (written != wrote)
                  return written;
            wrote = written;
            p += wrote;
            buf += wrote;
            count -= wrote;
      }

      if (count > 0) {
            kbuf = (char *)__get_free_page(GFP_KERNEL);
            if (!kbuf)
                  return wrote ? wrote : -ENOMEM;
            while (count > 0) {
                  int len = count;

                  if (len > PAGE_SIZE)
                        len = PAGE_SIZE;
                  if (len) {
                        written = copy_from_user(kbuf, buf, len);
                        if (written) {
                              if (wrote + virtr)
                                    break;
                              free_page((unsigned long)kbuf);
                              return -EFAULT;
                        }
                  }
                  len = vwrite(kbuf, (char *)p, len);
                  count -= len;
                  buf += len;
                  virtr += len;
                  p += len;
            }
            free_page((unsigned long)kbuf);
      }

      *ppos = p;
      return virtr + wrote;
}

#ifdef CONFIG_DEVPORT
static ssize_t read_port(struct file * file, char __user * buf,
                   size_t count, loff_t *ppos)
{
      unsigned long i = *ppos;
      char __user *tmp = buf;

      if (!access_ok(VERIFY_WRITE, buf, count))
            return -EFAULT; 
      while (count-- > 0 && i < 65536) {
            if (__put_user(inb(i),tmp) < 0) 
                  return -EFAULT;  
            i++;
            tmp++;
      }
      *ppos = i;
      return tmp-buf;
}

static ssize_t write_port(struct file * file, const char __user * buf,
                    size_t count, loff_t *ppos)
{
      unsigned long i = *ppos;
      const char __user * tmp = buf;

      if (!access_ok(VERIFY_READ,buf,count))
            return -EFAULT;
      while (count-- > 0 && i < 65536) {
            char c;
            if (__get_user(c, tmp)) {
                  if (tmp > buf)
                        break;
                  return -EFAULT; 
            }
            outb(c,i);
            i++;
            tmp++;
      }
      *ppos = i;
      return tmp-buf;
}
#endif

static ssize_t read_null(struct file * file, char __user * buf,
                   size_t count, loff_t *ppos)
{
      return 0;
}

static ssize_t write_null(struct file * file, const char __user * buf,
                    size_t count, loff_t *ppos)
{
      return count;
}

static int pipe_to_null(struct pipe_inode_info *info, struct pipe_buffer *buf,
                  struct splice_desc *sd)
{
      return sd->len;
}

static ssize_t splice_write_null(struct pipe_inode_info *pipe,struct file *out,
                         loff_t *ppos, size_t len, unsigned int flags)
{
      return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_null);
}

static ssize_t read_zero(struct file * file, char __user * buf, 
                   size_t count, loff_t *ppos)
{
      size_t written;

      if (!count)
            return 0;

      if (!access_ok(VERIFY_WRITE, buf, count))
            return -EFAULT;

      written = 0;
      while (count) {
            unsigned long unwritten;
            size_t chunk = count;

            if (chunk > PAGE_SIZE)
                  chunk = PAGE_SIZE;      /* Just for latency reasons */
            unwritten = clear_user(buf, chunk);
            written += chunk - unwritten;
            if (unwritten)
                  break;
            buf += chunk;
            count -= chunk;
            cond_resched();
      }
      return written ? written : -EFAULT;
}

static int mmap_zero(struct file * file, struct vm_area_struct * vma)
{
#ifndef CONFIG_MMU
      return -ENOSYS;
#endif
      if (vma->vm_flags & VM_SHARED)
            return shmem_zero_setup(vma);
      return 0;
}

static ssize_t write_full(struct file * file, const char __user * buf,
                    size_t count, loff_t *ppos)
{
      return -ENOSPC;
}

/*
 * Special lseek() function for /dev/null and /dev/zero.  Most notably, you
 * can fopen() both devices with "a" now.  This was previously impossible.
 * -- SRB.
 */

static loff_t null_lseek(struct file * file, loff_t offset, int orig)
{
      return file->f_pos = 0;
}

/*
 * The memory devices use the full 32/64 bits of the offset, and so we cannot
 * check against negative addresses: they are ok. The return value is weird,
 * though, in that case (0).
 *
 * also note that seeking relative to the "end of file" isn't supported:
 * it has no meaning, so it returns -EINVAL.
 */
static loff_t memory_lseek(struct file * file, loff_t offset, int orig)
{
      loff_t ret;

      mutex_lock(&file->f_path.dentry->d_inode->i_mutex);
      switch (orig) {
            case 0:
                  file->f_pos = offset;
                  ret = file->f_pos;
                  force_successful_syscall_return();
                  break;
            case 1:
                  file->f_pos += offset;
                  ret = file->f_pos;
                  force_successful_syscall_return();
                  break;
            default:
                  ret = -EINVAL;
      }
      mutex_unlock(&file->f_path.dentry->d_inode->i_mutex);
      return ret;
}

static int open_port(struct inode * inode, struct file * filp)
{
      return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
}

#define zero_lseek      null_lseek
#define full_lseek      null_lseek
#define write_zero      write_null
#define read_full       read_zero
#define open_mem  open_port
#define open_kmem open_mem
#define open_oldmem     open_mem

static const struct file_operations mem_fops = {
      .llseek           = memory_lseek,
      .read       = read_mem,
      .write            = write_mem,
      .mmap       = mmap_mem,
      .open       = open_mem,
      .get_unmapped_area = get_unmapped_area_mem,
};

static const struct file_operations kmem_fops = {
      .llseek           = memory_lseek,
      .read       = read_kmem,
      .write            = write_kmem,
      .mmap       = mmap_kmem,
      .open       = open_kmem,
      .get_unmapped_area = get_unmapped_area_mem,
};

static const struct file_operations null_fops = {
      .llseek           = null_lseek,
      .read       = read_null,
      .write            = write_null,
      .splice_write     = splice_write_null,
};

#ifdef CONFIG_DEVPORT
static const struct file_operations port_fops = {
      .llseek           = memory_lseek,
      .read       = read_port,
      .write            = write_port,
      .open       = open_port,
};
#endif

static const struct file_operations zero_fops = {
      .llseek           = zero_lseek,
      .read       = read_zero,
      .write            = write_zero,
      .mmap       = mmap_zero,
};

/*
 * capabilities for /dev/zero
 * - permits private mappings, "copies" are taken of the source of zeros
 */
static struct backing_dev_info zero_bdi = {
      .capabilities     = BDI_CAP_MAP_COPY,
};

static const struct file_operations full_fops = {
      .llseek           = full_lseek,
      .read       = read_full,
      .write            = write_full,
};

#ifdef CONFIG_CRASH_DUMP
static const struct file_operations oldmem_fops = {
      .read = read_oldmem,
      .open = open_oldmem,
};
#endif

static ssize_t kmsg_write(struct file * file, const char __user * buf,
                    size_t count, loff_t *ppos)
{
      char *tmp;
      ssize_t ret;

      tmp = kmalloc(count + 1, GFP_KERNEL);
      if (tmp == NULL)
            return -ENOMEM;
      ret = -EFAULT;
      if (!copy_from_user(tmp, buf, count)) {
            tmp[count] = 0;
            ret = printk("%s", tmp);
            if (ret > count)
                  /* printk can add a prefix */
                  ret = count;
      }
      kfree(tmp);
      return ret;
}

static const struct file_operations kmsg_fops = {
      .write =    kmsg_write,
};

static int memory_open(struct inode * inode, struct file * filp)
{
      switch (iminor(inode)) {
            case 1:
                  filp->f_op = &mem_fops;
                  filp->f_mapping->backing_dev_info =
                        &directly_mappable_cdev_bdi;
                  break;
            case 2:
                  filp->f_op = &kmem_fops;
                  filp->f_mapping->backing_dev_info =
                        &directly_mappable_cdev_bdi;
                  break;
            case 3:
                  filp->f_op = &null_fops;
                  break;
#ifdef CONFIG_DEVPORT
            case 4:
                  filp->f_op = &port_fops;
                  break;
#endif
            case 5:
                  filp->f_mapping->backing_dev_info = &zero_bdi;
                  filp->f_op = &zero_fops;
                  break;
            case 7:
                  filp->f_op = &full_fops;
                  break;
            case 8:
                  filp->f_op = &random_fops;
                  break;
            case 9:
                  filp->f_op = &urandom_fops;
                  break;
            case 11:
                  filp->f_op = &kmsg_fops;
                  break;
#ifdef CONFIG_CRASH_DUMP
            case 12:
                  filp->f_op = &oldmem_fops;
                  break;
#endif
            default:
                  return -ENXIO;
      }
      if (filp->f_op && filp->f_op->open)
            return filp->f_op->open(inode,filp);
      return 0;
}

static const struct file_operations memory_fops = {
      .open       = memory_open,    /* just a selector for the real open */
};

static const struct {
      unsigned int            minor;
      char              *name;
      umode_t                 mode;
      const struct file_operations  *fops;
} devlist[] = { /* list of minor devices */
      {1, "mem",     S_IRUSR | S_IWUSR | S_IRGRP, &mem_fops},
      {2, "kmem",    S_IRUSR | S_IWUSR | S_IRGRP, &kmem_fops},
      {3, "null",    S_IRUGO | S_IWUGO,           &null_fops},
#ifdef CONFIG_DEVPORT
      {4, "port",    S_IRUSR | S_IWUSR | S_IRGRP, &port_fops},
#endif
      {5, "zero",    S_IRUGO | S_IWUGO,           &zero_fops},
      {7, "full",    S_IRUGO | S_IWUGO,           &full_fops},
      {8, "random",  S_IRUGO | S_IWUSR,           &random_fops},
      {9, "urandom", S_IRUGO | S_IWUSR,           &urandom_fops},
      {11,"kmsg",    S_IRUGO | S_IWUSR,           &kmsg_fops},
#ifdef CONFIG_CRASH_DUMP
      {12,"oldmem",    S_IRUSR | S_IWUSR | S_IRGRP, &oldmem_fops},
#endif
};

static struct class *mem_class;

static int __init chr_dev_init(void)
{
      int i;
      int err;

      err = bdi_init(&zero_bdi);
      if (err)
            return err;

      if (register_chrdev(MEM_MAJOR,"mem",&memory_fops))
            printk("unable to get major %d for memory devs\n", MEM_MAJOR);

      mem_class = class_create(THIS_MODULE, "mem");
      for (i = 0; i < ARRAY_SIZE(devlist); i++)
            device_create(mem_class, NULL,
                        MKDEV(MEM_MAJOR, devlist[i].minor),
                        devlist[i].name);

      return 0;
}

fs_initcall(chr_dev_init);

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