Add the rt linux 4.1.3-rt3 as base
[kvmfornfv.git] / kernel / drivers / char / mem.c
diff --git a/kernel/drivers/char/mem.c b/kernel/drivers/char/mem.c
new file mode 100644 (file)
index 0000000..6b1721f
--- /dev/null
@@ -0,0 +1,872 @@
+/*
+ *  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 mmapping 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/backing-dev.h>
+#include <linux/splice.h>
+#include <linux/pfn.h>
+#include <linux/export.h>
+#include <linux/io.h>
+#include <linux/uio.h>
+
+#include <linux/uaccess.h>
+
+#ifdef CONFIG_IA64
+# include <linux/efi.h>
+#endif
+
+#define DEVPORT_MINOR  4
+
+static inline unsigned long size_inside_page(unsigned long start,
+                                            unsigned long size)
+{
+       unsigned long sz;
+
+       sz = PAGE_SIZE - (start & (PAGE_SIZE - 1));
+
+       return min(sz, size);
+}
+
+#ifndef ARCH_HAS_VALID_PHYS_ADDR_RANGE
+static inline int valid_phys_addr_range(phys_addr_t addr, size_t count)
+{
+       return addr + count <= __pa(high_memory);
+}
+
+static inline int valid_mmap_phys_addr_range(unsigned long pfn, size_t size)
+{
+       return 1;
+}
+#endif
+
+#ifdef CONFIG_STRICT_DEVMEM
+static inline int range_is_allowed(unsigned long pfn, unsigned long size)
+{
+       u64 from = ((u64)pfn) << PAGE_SHIFT;
+       u64 to = from + size;
+       u64 cursor = from;
+
+       while (cursor < to) {
+               if (!devmem_is_allowed(pfn)) {
+                       printk(KERN_INFO
+               "Program %s tried to access /dev/mem between %Lx->%Lx.\n",
+                               current->comm, from, to);
+                       return 0;
+               }
+               cursor += PAGE_SIZE;
+               pfn++;
+       }
+       return 1;
+}
+#else
+static inline int range_is_allowed(unsigned long pfn, unsigned long size)
+{
+       return 1;
+}
+#endif
+
+#ifndef unxlate_dev_mem_ptr
+#define unxlate_dev_mem_ptr unxlate_dev_mem_ptr
+void __weak unxlate_dev_mem_ptr(phys_addr_t phys, void *addr)
+{
+}
+#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)
+{
+       phys_addr_t p = *ppos;
+       ssize_t read, sz;
+       void *ptr;
+
+       if (p != *ppos)
+               return 0;
+
+       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 = size_inside_page(p, count);
+               if (sz > 0) {
+                       if (clear_user(buf, sz))
+                               return -EFAULT;
+                       buf += sz;
+                       p += sz;
+                       count -= sz;
+                       read += sz;
+               }
+       }
+#endif
+
+       while (count > 0) {
+               unsigned long remaining;
+
+               sz = size_inside_page(p, count);
+
+               if (!range_is_allowed(p >> PAGE_SHIFT, count))
+                       return -EPERM;
+
+               /*
+                * 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 (!ptr)
+                       return -EFAULT;
+
+               remaining = copy_to_user(buf, ptr, sz);
+               unxlate_dev_mem_ptr(p, ptr);
+               if (remaining)
+                       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)
+{
+       phys_addr_t p = *ppos;
+       ssize_t written, sz;
+       unsigned long copied;
+       void *ptr;
+
+       if (p != *ppos)
+               return -EFBIG;
+
+       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) {
+               sz = size_inside_page(p, count);
+               /* Hmm. Do something? */
+               buf += sz;
+               p += sz;
+               count -= sz;
+               written += sz;
+       }
+#endif
+
+       while (count > 0) {
+               sz = size_inside_page(p, count);
+
+               if (!range_is_allowed(p >> PAGE_SHIFT, sz))
+                       return -EPERM;
+
+               /*
+                * 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 (!ptr) {
+                       if (written)
+                               break;
+                       return -EFAULT;
+               }
+
+               copied = copy_from_user(ptr, buf, sz);
+               unxlate_dev_mem_ptr(p, ptr);
+               if (copied) {
+                       written += sz - copied;
+                       if (written)
+                               break;
+                       return -EFAULT;
+               }
+
+               buf += sz;
+               p += sz;
+               count -= sz;
+               written += sz;
+       }
+
+       *ppos += written;
+       return written;
+}
+
+int __weak phys_mem_access_prot_allowed(struct file *file,
+       unsigned long pfn, unsigned long size, pgprot_t *vma_prot)
+{
+       return 1;
+}
+
+#ifndef __HAVE_PHYS_MEM_ACCESS_PROT
+
+/*
+ * Architectures vary in how they handle caching for addresses
+ * outside of main memory.
+ *
+ */
+#ifdef pgprot_noncached
+static int uncached_access(struct file *file, phys_addr_t addr)
+{
+#if defined(CONFIG_IA64)
+       /*
+        * On ia64, we ignore O_DSYNC 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_DSYNC will be done non-cached.
+        */
+       if (file->f_flags & O_DSYNC)
+               return 1;
+       return addr >= __pa(high_memory);
+#endif
+}
+#endif
+
+static pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
+                                    unsigned long size, pgprot_t vma_prot)
+{
+#ifdef pgprot_noncached
+       phys_addr_t 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;
+}
+
+/* permit direct mmap, for read, write or exec */
+static unsigned memory_mmap_capabilities(struct file *file)
+{
+       return NOMMU_MAP_DIRECT |
+               NOMMU_MAP_READ | NOMMU_MAP_WRITE | NOMMU_MAP_EXEC;
+}
+
+static unsigned zero_mmap_capabilities(struct file *file)
+{
+       return NOMMU_MAP_COPY;
+}
+
+/* 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
+
+static inline int private_mapping_ok(struct vm_area_struct *vma)
+{
+       return 1;
+}
+#endif
+
+static const struct vm_operations_struct mmap_mem_ops = {
+#ifdef CONFIG_HAVE_IOREMAP_PROT
+       .access = generic_access_phys
+#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;
+
+       if (!range_is_allowed(vma->vm_pgoff, size))
+               return -EPERM;
+
+       if (!phys_mem_access_prot_allowed(file, vma->vm_pgoff, size,
+                                               &vma->vm_page_prot))
+               return -EINVAL;
+
+       vma->vm_page_prot = phys_mem_access_prot(file, vma->vm_pgoff,
+                                                size,
+                                                vma->vm_page_prot);
+
+       vma->vm_ops = &mmap_mem_ops;
+
+       /* Remap-pfn-range will mark the range VM_IO */
+       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);
+}
+
+/*
+ * 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 */
+       int err = 0;
+
+       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) {
+                       sz = size_inside_page(p, low_count);
+                       if (clear_user(buf, sz))
+                               return -EFAULT;
+                       buf += sz;
+                       p += sz;
+                       read += sz;
+                       low_count -= sz;
+                       count -= sz;
+               }
+#endif
+               while (low_count > 0) {
+                       sz = size_inside_page(p, 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((void *)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) {
+                       sz = size_inside_page(p, count);
+                       if (!is_vmalloc_or_module_addr((void *)p)) {
+                               err = -ENXIO;
+                               break;
+                       }
+                       sz = vread(kbuf, (char *)p, sz);
+                       if (!sz)
+                               break;
+                       if (copy_to_user(buf, kbuf, sz)) {
+                               err = -EFAULT;
+                               break;
+                       }
+                       count -= sz;
+                       buf += sz;
+                       read += sz;
+                       p += sz;
+               }
+               free_page((unsigned long)kbuf);
+       }
+       *ppos = p;
+       return read ? read : err;
+}
+
+
+static ssize_t do_write_kmem(unsigned long p, 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 (p < PAGE_SIZE) {
+               sz = size_inside_page(p, count);
+               /* Hmm. Do something? */
+               buf += sz;
+               p += sz;
+               count -= sz;
+               written += sz;
+       }
+#endif
+
+       while (count > 0) {
+               void *ptr;
+
+               sz = size_inside_page(p, 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((void *)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;
+}
+
+/*
+ * 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;
+       char *kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */
+       int err = 0;
+
+       if (p < (unsigned long) high_memory) {
+               unsigned long to_write = min_t(unsigned long, count,
+                                              (unsigned long)high_memory - p);
+               wrote = do_write_kmem(p, buf, to_write, ppos);
+               if (wrote != to_write)
+                       return wrote;
+               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) {
+                       unsigned long sz = size_inside_page(p, count);
+                       unsigned long n;
+
+                       if (!is_vmalloc_or_module_addr((void *)p)) {
+                               err = -ENXIO;
+                               break;
+                       }
+                       n = copy_from_user(kbuf, buf, sz);
+                       if (n) {
+                               err = -EFAULT;
+                               break;
+                       }
+                       vwrite(kbuf, (char *)p, sz);
+                       count -= sz;
+                       buf += sz;
+                       virtr += sz;
+                       p += sz;
+               }
+               free_page((unsigned long)kbuf);
+       }
+
+       *ppos = p;
+       return virtr + wrote ? : err;
+}
+
+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;
+}
+
+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 ssize_t read_iter_null(struct kiocb *iocb, struct iov_iter *to)
+{
+       return 0;
+}
+
+static ssize_t write_iter_null(struct kiocb *iocb, struct iov_iter *from)
+{
+       size_t count = iov_iter_count(from);
+       iov_iter_advance(from, count);
+       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_iter_zero(struct kiocb *iocb, struct iov_iter *iter)
+{
+       size_t written = 0;
+
+       while (iov_iter_count(iter)) {
+               size_t chunk = iov_iter_count(iter), n;
+
+               if (chunk > PAGE_SIZE)
+                       chunk = PAGE_SIZE;      /* Just for latency reasons */
+               n = iov_iter_zero(chunk, iter);
+               if (!n && iov_iter_count(iter))
+                       return written ? written : -EFAULT;
+               written += n;
+               if (signal_pending(current))
+                       return written ? written : -ERESTARTSYS;
+               cond_resched();
+       }
+       return written;
+}
+
+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_inode(file)->i_mutex);
+       switch (orig) {
+       case SEEK_CUR:
+               offset += file->f_pos;
+       case SEEK_SET:
+               /* to avoid userland mistaking f_pos=-9 as -EBADF=-9 */
+               if (IS_ERR_VALUE((unsigned long long)offset)) {
+                       ret = -EOVERFLOW;
+                       break;
+               }
+               file->f_pos = offset;
+               ret = file->f_pos;
+               force_successful_syscall_return();
+               break;
+       default:
+               ret = -EINVAL;
+       }
+       mutex_unlock(&file_inode(file)->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 write_iter_zero        write_iter_null
+#define open_mem       open_port
+#define open_kmem      open_mem
+
+static const struct file_operations __maybe_unused mem_fops = {
+       .llseek         = memory_lseek,
+       .read           = read_mem,
+       .write          = write_mem,
+       .mmap           = mmap_mem,
+       .open           = open_mem,
+#ifndef CONFIG_MMU
+       .get_unmapped_area = get_unmapped_area_mem,
+       .mmap_capabilities = memory_mmap_capabilities,
+#endif
+};
+
+static const struct file_operations __maybe_unused kmem_fops = {
+       .llseek         = memory_lseek,
+       .read           = read_kmem,
+       .write          = write_kmem,
+       .mmap           = mmap_kmem,
+       .open           = open_kmem,
+#ifndef CONFIG_MMU
+       .get_unmapped_area = get_unmapped_area_mem,
+       .mmap_capabilities = memory_mmap_capabilities,
+#endif
+};
+
+static const struct file_operations null_fops = {
+       .llseek         = null_lseek,
+       .read           = read_null,
+       .write          = write_null,
+       .read_iter      = read_iter_null,
+       .write_iter     = write_iter_null,
+       .splice_write   = splice_write_null,
+};
+
+static const struct file_operations __maybe_unused port_fops = {
+       .llseek         = memory_lseek,
+       .read           = read_port,
+       .write          = write_port,
+       .open           = open_port,
+};
+
+static const struct file_operations zero_fops = {
+       .llseek         = zero_lseek,
+       .write          = write_zero,
+       .read_iter      = read_iter_zero,
+       .write_iter     = write_iter_zero,
+       .mmap           = mmap_zero,
+#ifndef CONFIG_MMU
+       .mmap_capabilities = zero_mmap_capabilities,
+#endif
+};
+
+static const struct file_operations full_fops = {
+       .llseek         = full_lseek,
+       .read_iter      = read_iter_zero,
+       .write          = write_full,
+};
+
+static const struct memdev {
+       const char *name;
+       umode_t mode;
+       const struct file_operations *fops;
+       fmode_t fmode;
+} devlist[] = {
+#ifdef CONFIG_DEVMEM
+        [1] = { "mem", 0, &mem_fops, FMODE_UNSIGNED_OFFSET },
+#endif
+#ifdef CONFIG_DEVKMEM
+        [2] = { "kmem", 0, &kmem_fops, FMODE_UNSIGNED_OFFSET },
+#endif
+        [3] = { "null", 0666, &null_fops, 0 },
+#ifdef CONFIG_DEVPORT
+        [4] = { "port", 0, &port_fops, 0 },
+#endif
+        [5] = { "zero", 0666, &zero_fops, 0 },
+        [7] = { "full", 0666, &full_fops, 0 },
+        [8] = { "random", 0666, &random_fops, 0 },
+        [9] = { "urandom", 0666, &urandom_fops, 0 },
+#ifdef CONFIG_PRINTK
+       [11] = { "kmsg", 0644, &kmsg_fops, 0 },
+#endif
+};
+
+static int memory_open(struct inode *inode, struct file *filp)
+{
+       int minor;
+       const struct memdev *dev;
+
+       minor = iminor(inode);
+       if (minor >= ARRAY_SIZE(devlist))
+               return -ENXIO;
+
+       dev = &devlist[minor];
+       if (!dev->fops)
+               return -ENXIO;
+
+       filp->f_op = dev->fops;
+       filp->f_mode |= dev->fmode;
+
+       if (dev->fops->open)
+               return dev->fops->open(inode, filp);
+
+       return 0;
+}
+
+static const struct file_operations memory_fops = {
+       .open = memory_open,
+       .llseek = noop_llseek,
+};
+
+static char *mem_devnode(struct device *dev, umode_t *mode)
+{
+       if (mode && devlist[MINOR(dev->devt)].mode)
+               *mode = devlist[MINOR(dev->devt)].mode;
+       return NULL;
+}
+
+static struct class *mem_class;
+
+static int __init chr_dev_init(void)
+{
+       int minor;
+
+       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");
+       if (IS_ERR(mem_class))
+               return PTR_ERR(mem_class);
+
+       mem_class->devnode = mem_devnode;
+       for (minor = 1; minor < ARRAY_SIZE(devlist); minor++) {
+               if (!devlist[minor].name)
+                       continue;
+
+               /*
+                * Create /dev/port?
+                */
+               if ((minor == DEVPORT_MINOR) && !arch_has_dev_port())
+                       continue;
+
+               device_create(mem_class, NULL, MKDEV(MEM_MAJOR, minor),
+                             NULL, devlist[minor].name);
+       }
+
+       return tty_init();
+}
+
+fs_initcall(chr_dev_init);