// SPDX-License-Identifier: GPL-2.0
#include <linux/crash_dump.h>
#include <linux/io.h>
#include <linux/uio.h>

ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn,
                         size_t csize, unsigned long offset)
{
        void *vaddr;

        if (!csize)
                return 0;

        vaddr = memremap(__pfn_to_phys(pfn), PAGE_SIZE, MEMREMAP_WB);
        if (!vaddr)
                return -ENOMEM;

        csize = copy_to_iter(vaddr + offset, csize, iter);

        memunmap(vaddr);

        return csize;
}