[uml-user] mmap fails

[P. T. <uml...@ya...>]

Hi,

  I am trying to do a mmap from the UML kernel to UML
user space. But the mmap in the user space returns
zero. Can you please tell me why ? 

Here the code :
User code:
----------
        fd = open("/dev/mymem", O_RDWR);

        if (fd < 0) {
                perror("open - failed:");
                exit (1);
        };

        kern_ptr = mmap(0, 4096, PROT_READ |          
    
           PROT_WRITE, MAP_SHARED | MAP_FIXED, fd, 0
);


UML Kernel code:
----------------

mmap_kern(struct file *file, struct vm_area_struct
*vm)
{

        int ret = -EINVAL;
        int size;

        if (vm->vm_pgoff != 0)
                goto out;

        size = vm->vm_end - vm->vm_start;
        if(size > mmapper_size) return(-EFAULT);

        if (remap_page_range(vm->vm_start, p_buf,
                           size, vm->vm_page_prot))
                goto out;
        ret = 0;
out:
         return ret;
}

mymem_module_init()
{
       major = register_chrdev(0, "mymem", &mem_ops);

        v_buf = (char *) find_iomem("my_mem_mapper",
&mmapper_size);
        if(mmapper_size == 0) {
                printk("<1> find_iomem failed \n");
                return(0);
        };

        p_buf = __pa(v_buf);

        return 0;

};


 Is there any other alternative way to memory map from
the UML kernel to the UML user space?


Regards...


		
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