1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * kernel/crash_dump.c - Memory preserving reboot related code. 4 * 5 * Created by: Simon Horman <horms@verge.net.au> 6 * Original code moved from kernel/crash.c 7 * Original code comment copied from the i386 version of this file 8 */ 9 10 #include <linux/errno.h> 11 #include <linux/types.h> 12 #include <linux/crash_dump.h> 13 14 #include <asm/page.h> 15 #include <linux/uaccess.h> 16 17 /** 18 * copy_oldmem_page - copy one page from "oldmem" 19 * @pfn: page frame number to be copied 20 * @buf: target memory address for the copy; this can be in kernel address 21 * space or user address space (see @userbuf) 22 * @csize: number of bytes to copy 23 * @offset: offset in bytes into the page (based on pfn) to begin the copy 24 * @userbuf: if set, @buf is in user address space, use copy_to_user(), 25 * otherwise @buf is in kernel address space, use memcpy(). 26 * 27 * Copy a page from "oldmem". For this page, there is no pte mapped 28 * in the current kernel. We stitch up a pte, similar to kmap_atomic. 29 * 30 * Calling copy_to_user() in atomic context is not desirable. Hence first 31 * copying the data to a pre-allocated kernel page and then copying to user 32 * space in non-atomic context. 33 */ 34 ssize_t 35 copy_oldmem_page(unsigned long pfn, char *buf, 36 size_t csize, unsigned long offset, int userbuf) 37 { 38 void *vaddr; 39 40 if (!csize) 41 return 0; 42 vaddr = __va(pfn<<PAGE_SHIFT); 43 if (userbuf) { 44 if (copy_to_user(buf, (vaddr + offset), csize)) { 45 return -EFAULT; 46 } 47 } else 48 memcpy(buf, (vaddr + offset), csize); 49 return csize; 50 } 51 52