On Wed, Sep 10, 2025 at 09:22:11PM +0100, Lorenzo Stoakes wrote:
> +static int kcov_mmap_prepare(struct vm_area_desc *desc)
> {
> int res = 0;
> - struct kcov *kcov = vma->vm_file->private_data;
> - unsigned long size, off;
> - struct page *page;
> + struct kcov *kcov = desc->file->private_data;
> + unsigned long size, nr_pages, i;
> + struct page **pages;
> unsigned long flags;
>
> spin_lock_irqsave(&kcov->lock, flags);
> size = kcov->size * sizeof(unsigned long);
> - if (kcov->area == NULL || vma->vm_pgoff != 0 ||
> - vma->vm_end - vma->vm_start != size) {
> + if (kcov->area == NULL || desc->pgoff != 0 ||
> + vma_desc_size(desc) != size) {
IMHO these range checks should be cleaned up into a helper:
/* Returns true if the VMA falls within starting_pgoff to
starting_pgoff + ROUND_DOWN(length_bytes, PAGE_SIZE))
Is careful to avoid any arithmetic overflow.
*/
vma_desc_check_range(desc, starting_pgoff=0, length_bytes=size);
> + desc->vm_flags |= VM_DONTEXPAND;
> + nr_pages = size >> PAGE_SHIFT;
> +
> + pages = mmap_action_mixedmap_pages(&desc->action, desc->start,
> + nr_pages);
> + if (!pages)
> + return -ENOMEM;
> +
> + for (i = 0; i < nr_pages; i++)
> + pages[i] = vmalloc_to_page(kcov->area + i * PAGE_SIZE);
This is not a mixed map.
All the memory comes from vmalloc_user() which makes them normal
struct pages with refcounts.
If anything the action should be called mmap_action_vmalloc_user() to
match how the memory was allocated instead of open coding something.
Jason
