1 #include <linux/highmem.h>
2 #include <linux/bootmem.h>
3 #include <linux/crash_dump.h>
4 #include <asm/uaccess.h>
5 #include <linux/slab.h>
6
parse_savemaxmem(char * p)7 static int __init parse_savemaxmem(char *p)
8 {
9 if (p)
10 saved_max_pfn = (memparse(p, &p) >> PAGE_SHIFT) - 1;
11
12 return 1;
13 }
14 __setup("savemaxmem=", parse_savemaxmem);
15
16
17 static void *kdump_buf_page;
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.
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 */
copy_oldmem_page(unsigned long pfn,char * buf,size_t csize,unsigned long offset,int userbuf)36 ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
37 size_t csize, unsigned long offset, int userbuf)
38 {
39 void *vaddr;
40
41 if (!csize)
42 return 0;
43
44 vaddr = kmap_atomic_pfn(pfn);
45
46 if (!userbuf) {
47 memcpy(buf, (vaddr + offset), csize);
48 kunmap_atomic(vaddr);
49 } else {
50 if (!kdump_buf_page) {
51 pr_warning("Kdump: Kdump buffer page not allocated\n");
52
53 return -EFAULT;
54 }
55 copy_page(kdump_buf_page, vaddr);
56 kunmap_atomic(vaddr);
57 if (copy_to_user(buf, (kdump_buf_page + offset), csize))
58 return -EFAULT;
59 }
60
61 return csize;
62 }
63
kdump_buf_page_init(void)64 static int __init kdump_buf_page_init(void)
65 {
66 int ret = 0;
67
68 kdump_buf_page = kmalloc(PAGE_SIZE, GFP_KERNEL);
69 if (!kdump_buf_page) {
70 pr_warning("Kdump: Failed to allocate kdump buffer page\n");
71 ret = -ENOMEM;
72 }
73
74 return ret;
75 }
76 arch_initcall(kdump_buf_page_init);
77