Re: L4Linux and mmap

On Wed Aug 03, 2011 at 16:17:04 +0400, Vasily Sartakov wrote:

I try to use a mmap for communicate userspace application and other servers via kernel character driver. and its doesn't work. but, of course its work in native linux. my mmap call return no error, but when i try acces to memmory via returned pointer, i got seg fault

Here is driver source and example program, based on mmap example: any of vmalloc or kalloc got seg fault:

mmap ok, vaddr = 40034000 Segmentation fault

Which memory access is it? I do not see corresponding printf.

    /* 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;
    }

virt_to_phys is probably not a good choice. On native, __pa and virt_to_phys indeed do the same but on L4Linux virt_to_phys does what the name says and __pa does what you probably want here. And shouldn't kmalloc memory be always contiguous?

Adam