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 /* Stores the physical address of elf header of crash image. */ 17 unsigned long long elfcorehdr_addr = ELFCORE_ADDR_MAX; 18 19 /** 20 * copy_oldmem_page - copy one page from "oldmem" 21 * @pfn: page frame number to be copied 22 * @buf: target memory address for the copy; this can be in kernel address 23 * space or user address space (see @userbuf) 24 * @csize: number of bytes to copy 25 * @offset: offset in bytes into the page (based on pfn) to begin the copy 26 * @userbuf: if set, @buf is in user address space, use copy_to_user(), 27 * otherwise @buf is in kernel address space, use memcpy(). 28 * 29 * Copy a page from "oldmem". For this page, there is no pte mapped 30 * in the current kernel. We stitch up a pte, similar to kmap_atomic. 31 * 32 * Calling copy_to_user() in atomic context is not desirable. Hence first 33 * copying the data to a pre-allocated kernel page and then copying to user 34 * space in non-atomic context. 35 */ 36 ssize_t 37 copy_oldmem_page(unsigned long pfn, char *buf, 38 size_t csize, unsigned long offset, int userbuf) 39 { 40 void *vaddr; 41 42 if (!csize) 43 return 0; 44 vaddr = __va(pfn<<PAGE_SHIFT); 45 if (userbuf) { 46 if (copy_to_user(buf, (vaddr + offset), csize)) { 47 return -EFAULT; 48 } 49 } else 50 memcpy(buf, (vaddr + offset), csize); 51 return csize; 52 } 53 54