Hi,
first of let me know why you are allocating space for the new vma, as
find_vma will return a pointer to the existing vma and in that case you'll create a
memory leak there, as you will lose the track for the allocated vma in case if one
vma is returned by find_vma() ;-)
I think to spilt a vma you can use the functionality explained in
madvise_fixup_start(), madvise_fixup_end or madvise_fixup_middle() functions
defined in mm/filemap.c... go through them, I think it'll solve your problem.
Thanks.
Sumit Sharma.
On Thu, 16 Sep 2004 Naren wrote :
>Hi,
>I am trying to write a system call that splits a VMA into two halves. The problem
is that, as I am using do_mmap() system call, it is only creating one area and that
too at a different address than the old one.
>
>The code:
>(*addr is passed as some arbitrary address that falls in any VMA)
>
>struct mm_struct *mm = current->mm;
>struct vm_area_struct *vma;
>unsigned long ret, ret2, old_length,length, start_add, end_add, second_add;
>
>
> if (flag == 0) {
> vma = (struct vm_area_struct *) kmalloc(sizeof(struct
vm_area_struct));
> vma = find_vma(mm, *addr);
> if (vma == NULL){
> return ENOMEM;
> }
> old_length = (vma->vm_end - vma->vm_start);
> length = old_length/2;
> start_add = PAGE_ALIGN(vma->vm_start);
> end_add = PAGE_ALIGN(vma->vm_end);
> second_add = PAGE_ALIGN(start_add + length);
> ret = do_mremap(start_add, old_length, length, NULL, NULL);
> ret2 = do_mmap(NULL, second_add, length, PROT_READ,
MAP_EXECUTABLE, 0);
>
> }
>
>
>Is there anything that i m doing wrong over here ..
>
>Thanks and Regards,
>Narinder
>
