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 */ 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