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