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 12 #include <asm/page.h> 13 #include <asm/uaccess.h> 14 15 /** 16 * copy_oldmem_page - copy one page from "oldmem" 17 * @pfn: page frame number to be copied 18 * @buf: target memory address for the copy; this can be in kernel address 19 * space or user address space (see @userbuf) 20 * @csize: number of bytes to copy 21 * @offset: offset in bytes into the page (based on pfn) to begin the copy 22 * @userbuf: if set, @buf is in user address space, use copy_to_user(), 23 * otherwise @buf is in kernel address space, use memcpy(). 24 * 25 * Copy a page from "oldmem". For this page, there is no pte mapped 26 * in the current kernel. We stitch up a pte, similar to kmap_atomic. 27 * 28 * Calling copy_to_user() in atomic context is not desirable. Hence first 29 * copying the data to a pre-allocated kernel page and then copying to user 30 * space in non-atomic context. 31 */ 32 ssize_t 33 copy_oldmem_page(unsigned long pfn, char *buf, 34 size_t csize, unsigned long offset, int userbuf) 35 { 36 void *vaddr; 37 38 if (!csize) 39 return 0; 40 vaddr = __va(pfn<<PAGE_SHIFT); 41 if (userbuf) { 42 if (copy_to_user(buf, (vaddr + offset), csize)) { 43 return -EFAULT; 44 } 45 } else 46 memcpy(buf, (vaddr + offset), csize); 47 return csize; 48 } 49 50