1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/highmem.h>
3 #include <linux/crash_dump.h>
4
5 /**
6 * copy_oldmem_page - copy one page from "oldmem"
7 * @pfn: page frame number to be copied
8 * @buf: target memory address for the copy; this can be in kernel address
9 * space or user address space (see @userbuf)
10 * @csize: number of bytes to copy
11 * @offset: offset in bytes into the page (based on pfn) to begin the copy
12 * @userbuf: if set, @buf is in user address space, use copy_to_user(),
13 * otherwise @buf is in kernel address space, use memcpy().
14 *
15 * Copy a page from "oldmem". For this page, there is no pte mapped
16 * in the current kernel.
17 */
copy_oldmem_page(unsigned long pfn,char * buf,size_t csize,unsigned long offset,int userbuf)18 ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
19 size_t csize, unsigned long offset, int userbuf)
20 {
21 void *vaddr;
22
23 if (!csize)
24 return 0;
25
26 vaddr = kmap_local_pfn(pfn);
27
28 if (!userbuf) {
29 memcpy(buf, vaddr + offset, csize);
30 } else {
31 if (copy_to_user(buf, vaddr + offset, csize))
32 csize = -EFAULT;
33 }
34
35 kunmap_local(vaddr);
36
37 return csize;
38 }
39