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b2441318 | 1 | // SPDX-License-Identifier: GPL-2.0 |
45a98fc6 H |
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> | |
57cac4d1 | 12 | #include <linux/crash_dump.h> |
45a98fc6 | 13 | |
8a697d0a | 14 | #include <asm/page.h> |
7c0f6ba6 | 15 | #include <linux/uaccess.h> |
45a98fc6 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 |