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