#include <linux/config.h>#include <linux/version.h>#include <linux/init.h>#include <linux/module.h>#include <linux/fs.h>#include <linux/cdev.h>#include <linux/slab.h>#include <linux/vmalloc.h>#include <linux/mm.h>#ifdef MODVERSIONS#  include <linux/modversions.h>#endif#include <asm/io.h>/* character device structures */static dev_t mmap_dev;static struct cdev mmap_cdev;/* methods of the character device */static int mmap_open(struct inode *inode, struct file *filp);static int mmap_release(struct inode *inode, struct file *filp);static int mmap_mmap(struct file *filp, struct vm_area_struct *vma);/* the file operations, i.e. all character device methods */static struct file_operations mmap_fops = {        .open = mmap_open,        .release = mmap_release,        .mmap = mmap_mmap,        .owner = THIS_MODULE,};// internal data// length of the two memory areas#define NPAGES 16// pointer to the vmalloc'd area - alway page alignedstatic int *vmalloc_area;// pointer to the kmalloc'd area, rounded up to a page boundarystatic int *kmalloc_area;// original pointer for kmalloc'd area as returned by kmallocstatic void *kmalloc_ptr;/* character device open method */static int mmap_open(struct inode *inode, struct file *filp){        return 0;}/* character device last close method */static int mmap_release(struct inode *inode, struct file *filp){        return 0;}// helper function, mmap's the kmalloc'd area which is physically contiguousint mmap_kmem(struct file *filp, struct vm_area_struct *vma){        int ret;        long length = vma->vm_end - vma->vm_start;        /* check length - do not allow larger mappings than the number of           pages allocated */        if (length > NPAGES * PAGE_SIZE)                return -EIO;        /* map the whole physically contiguous area in one piece */        if ((ret = remap_pfn_range(vma,                                   vma->vm_start,                                   virt_to_phys((void *)kmalloc_area) >> PAGE_SHIFT,                                   length,                                   vma->vm_page_prot)) < 0) {                return ret;        }                return 0;}// helper function, mmap's the vmalloc'd area which is not physically contiguousint mmap_vmem(struct file *filp, struct vm_area_struct *vma){        int ret;        long length = vma->vm_end - vma->vm_start;        unsigned long start = vma->vm_start;        char *vmalloc_area_ptr = (char *)vmalloc_area;        unsigned long pfn;        /* check length - do not allow larger mappings than the number of           pages allocated */        if (length > NPAGES * PAGE_SIZE)                return -EIO;        /* loop over all pages, map it page individually */        while (length > 0) {                pfn = vmalloc_to_pfn(vmalloc_area_ptr);                if ((ret = remap_pfn_range(vma, start, pfn, PAGE_SIZE,                                           PAGE_SHARED)) < 0) {                        return ret;                }                start += PAGE_SIZE;                vmalloc_area_ptr += PAGE_SIZE;                length -= PAGE_SIZE;        }        return 0;}/* character device mmap method */static int mmap_mmap(struct file *filp, struct vm_area_struct *vma){        /* at offset 0 we map the vmalloc'd area */        if (vma->vm_pgoff == 0) {                return mmap_vmem(filp, vma);        }        /* at offset NPAGES we map the kmalloc'd area */        if (vma->vm_pgoff == NPAGES) {                return mmap_kmem(filp, vma);        }        /* at any other offset we return an error */        return -EIO;}/* module initialization - called at module load time */static int __init mmap_init(void){        int ret = 0;        int i;        /* allocate a memory area with kmalloc. Will be rounded up to a page boundary */        if ((kmalloc_ptr = kmalloc((NPAGES + 2) * PAGE_SIZE, GFP_KERNEL)) == NULL) {                ret = -ENOMEM;                goto out;        }        /* round it up to the page bondary */        kmalloc_area = (int *)((((unsigned long)kmalloc_ptr) + PAGE_SIZE - 1) & PAGE_MASK);        /* allocate a memory area with vmalloc. */        if ((vmalloc_area = (int *)vmalloc(NPAGES * PAGE_SIZE)) == NULL) {                ret = -ENOMEM;                goto out_kfree;        }        /* get the major number of the character device */        if ((ret = alloc_chrdev_region(&mmap_dev, 0, 1, "mmap")) < 0) {                printk(KERN_ERR "could not allocate major number for mmap\n");                goto out_vfree;        }        /* initialize the device structure and register the device with the kernel */        cdev_init(&mmap_cdev, &mmap_fops);        if ((ret = cdev_add(&mmap_cdev, mmap_dev, 1)) < 0) {                printk(KERN_ERR "could not allocate chrdev for mmap\n");                goto out_unalloc_region;        }        /* mark the pages reserved */        for (i = 0; i < NPAGES * PAGE_SIZE; i+= PAGE_SIZE) {                SetPageReserved(vmalloc_to_page((void *)(((unsigned long)vmalloc_area) + i)));                SetPageReserved(virt_to_page(((unsigned long)kmalloc_area) + i));        }        /* store a pattern in the memory - the test application will check for it */        for (i = 0; i < (NPAGES * PAGE_SIZE / sizeof(int)); i += 2) {                vmalloc_area[i] = (0xaffe << 16) + i;                vmalloc_area[i + 1] = (0xbeef << 16) + i;                kmalloc_area[i] = (0xdead << 16) + i;                kmalloc_area[i + 1] = (0xbeef << 16) + i;        }                return ret;          out_unalloc_region:        unregister_chrdev_region(mmap_dev, 1);  out_vfree:        vfree(vmalloc_area);  out_kfree:        kfree(kmalloc_ptr);  out:        return ret;}/* module unload */static void __exit mmap_exit(void){        int i;        /* remove the character deivce */        cdev_del(&mmap_cdev);        unregister_chrdev_region(mmap_dev, 1);        /* unreserve the pages */        for (i = 0; i < NPAGES * PAGE_SIZE; i+= PAGE_SIZE) {                SetPageReserved(vmalloc_to_page((void *)(((unsigned long)vmalloc_area) + i)));                SetPageReserved(virt_to_page(((unsigned long)kmalloc_area) + i));        }        /* free the memory areas */        vfree(vmalloc_area);        kfree(kmalloc_ptr);}module_init(mmap_init);module_exit(mmap_exit);MODULE_DESCRIPTION("mmap demo driver");MODULE_AUTHOR("Martin Frey <frey@scs.ch>");MODULE_LICENSE("Dual BSD/GPL");