/* Calling copy_to_user() in atomic context is not desirable. Hence first copying the data to a pre-allocated kernel page and then copying to user space in non-atomic context.  */
ssize_t copy_oldmem_page(unsigned long pfn, char *buf, size_t csize, unsigned long offset, int userbuf)
/* Calling copy_to_user() in atomic context is not desirable. Hence first copying the data to a pre-allocated kernel page and then copying to user space in non-atomic context.  */
ssize_t copy_oldmem_page(unsigned long pfn, char *buf, size_t csize, unsigned long offset, int userbuf)
{
	void  *vaddr;
	if (!csize)
		return 0;
	if (!is_crashed_pfn_valid(pfn))
		return -EFAULT;
	vaddr = kmap_atomic_pfn(pfn, KM_PTE0);
	if (!userbuf) {
		memcpy(buf, (vaddr + offset), csize);
		kunmap_atomic(vaddr, KM_PTE0);
	} else {
		if (!kdump_buf_page) {
			printk(KERN_WARNING "Kdump: Kdump buffer page not"
				" allocated\n");
			kunmap_atomic(vaddr, KM_PTE0);
			return -EFAULT;
		}
		copy_page(kdump_buf_page, vaddr);
		kunmap_atomic(vaddr, KM_PTE0);
		if (copy_to_user(buf, (kdump_buf_page + offset), csize))
			return -EFAULT;
	}
	return csize;
}