| 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 | |