1// SPDX-License-Identifier: GPL-2.0
 2/*
 3 *	Memory preserving reboot related code.
 4 *
 5 *	Created by: Hariprasad Nellitheertha (hari@in.ibm.com)
 6 *	Copyright (C) IBM Corporation, 2004. All rights reserved
 7 */
 8
 9#include <linux/slab.h>
10#include <linux/errno.h>
11#include <linux/highmem.h>
12#include <linux/crash_dump.h>
13
14#include <linux/uaccess.h>
15
16static void *kdump_buf_page;
17
18static inline bool is_crashed_pfn_valid(unsigned long pfn)
19{
20#ifndef CONFIG_X86_PAE
21	/*
22	 * non-PAE kdump kernel executed from a PAE one will crop high pte
23	 * bits and poke unwanted space counting again from address 0, we
24	 * don't want that. pte must fit into unsigned long. In fact the
25	 * test checks high 12 bits for being zero (pfn will be shifted left
26	 * by PAGE_SHIFT).
27	 */
28	return pte_pfn(pfn_pte(pfn, __pgprot(0))) == pfn;
29#else
30	return true;
31#endif
32}
33
34/**
35 * copy_oldmem_page - copy one page from "oldmem"
36 * @pfn: page frame number to be copied
37 * @buf: target memory address for the copy; this can be in kernel address
38 *	space or user address space (see @userbuf)
39 * @csize: number of bytes to copy
40 * @offset: offset in bytes into the page (based on pfn) to begin the copy
41 * @userbuf: if set, @buf is in user address space, use copy_to_user(),
42 *	otherwise @buf is in kernel address space, use memcpy().
43 *
44 * Copy a page from "oldmem". For this page, there is no pte mapped
45 * in the current kernel. We stitch up a pte, similar to kmap_atomic.
46 *
47 * Calling copy_to_user() in atomic context is not desirable. Hence first
48 * copying the data to a pre-allocated kernel page and then copying to user
49 * space in non-atomic context.
50 */
51ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
52                               size_t csize, unsigned long offset, int userbuf)
53{
54	void  *vaddr;
55
56	if (!csize)
57		return 0;
58
59	if (!is_crashed_pfn_valid(pfn))
60		return -EFAULT;
61
62	vaddr = kmap_atomic_pfn(pfn);
63
64	if (!userbuf) {
65		memcpy(buf, (vaddr + offset), csize);
66		kunmap_atomic(vaddr);
67	} else {
68		if (!kdump_buf_page) {
69			printk(KERN_WARNING "Kdump: Kdump buffer page not"
70				" allocated\n");
71			kunmap_atomic(vaddr);
72			return -EFAULT;
73		}
74		copy_page(kdump_buf_page, vaddr);
75		kunmap_atomic(vaddr);
76		if (copy_to_user(buf, (kdump_buf_page + offset), csize))
77			return -EFAULT;
78	}
79
80	return csize;
81}
82
83static int __init kdump_buf_page_init(void)
84{
85	int ret = 0;
86
87	kdump_buf_page = kmalloc(PAGE_SIZE, GFP_KERNEL);
88	if (!kdump_buf_page) {
89		printk(KERN_WARNING "Kdump: Failed to allocate kdump buffer"
90			 " page\n");
91		ret = -ENOMEM;
92	}
93
94	return ret;
95}
96arch_initcall(kdump_buf_page_init);

 1// SPDX-License-Identifier: GPL-2.0
 2/*
 3 *	Memory preserving reboot related code.
 4 *
 5 *	Created by: Hariprasad Nellitheertha (hari@in.ibm.com)
 6 *	Copyright (C) IBM Corporation, 2004. All rights reserved
 7 */
 8
 9#include <linux/slab.h>
10#include <linux/errno.h>
11#include <linux/highmem.h>
12#include <linux/crash_dump.h>
13
14#include <linux/uaccess.h>
15
 
 
16static inline bool is_crashed_pfn_valid(unsigned long pfn)
17{
18#ifndef CONFIG_X86_PAE
19	/*
20	 * non-PAE kdump kernel executed from a PAE one will crop high pte
21	 * bits and poke unwanted space counting again from address 0, we
22	 * don't want that. pte must fit into unsigned long. In fact the
23	 * test checks high 12 bits for being zero (pfn will be shifted left
24	 * by PAGE_SHIFT).
25	 */
26	return pte_pfn(pfn_pte(pfn, __pgprot(0))) == pfn;
27#else
28	return true;
29#endif
30}
31
32/**
33 * copy_oldmem_page - copy one page from "oldmem"
34 * @pfn: page frame number to be copied
35 * @buf: target memory address for the copy; this can be in kernel address
36 *	space or user address space (see @userbuf)
37 * @csize: number of bytes to copy
38 * @offset: offset in bytes into the page (based on pfn) to begin the copy
39 * @userbuf: if set, @buf is in user address space, use copy_to_user(),
40 *	otherwise @buf is in kernel address space, use memcpy().
41 *
42 * Copy a page from "oldmem". For this page, there might be no pte mapped
43 * in the current kernel.
 
 
 
 
44 */
45ssize_t copy_oldmem_page(unsigned long pfn, char *buf, size_t csize,
46			 unsigned long offset, int userbuf)
47{
48	void  *vaddr;
49
50	if (!csize)
51		return 0;
52
53	if (!is_crashed_pfn_valid(pfn))
54		return -EFAULT;
55
56	vaddr = kmap_local_pfn(pfn);
57
58	if (!userbuf) {
59		memcpy(buf, vaddr + offset, csize);
 
60	} else {
61		if (copy_to_user(buf, vaddr + offset, csize))
62			csize = -EFAULT;
 
 
 
 
 
 
 
 
63	}
64
65	kunmap_local(vaddr);
 
66
67	return csize;
 
 
 
 
 
 
 
 
 
 
 
68}