1 /*
2 * Routines for doing kexec-based kdump
3 *
4 * Copyright (C) 2017 Linaro Limited
5 * Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 */
11
12 #include <linux/crash_dump.h>
13 #include <linux/errno.h>
14 #include <linux/io.h>
15 #include <linux/memblock.h>
16 #include <linux/uaccess.h>
17 #include <asm/memory.h>
18
19 /**
20 * copy_oldmem_page() - copy one page from old kernel memory
21 * @pfn: page frame number to be copied
22 * @buf: buffer where the copied page is placed
23 * @csize: number of bytes to copy
24 * @offset: offset in bytes into the page
25 * @userbuf: if set, @buf is in a user address space
26 *
27 * This function copies one page from old kernel memory into buffer pointed by
28 * @buf. If @buf is in userspace, set @userbuf to %1. Returns number of bytes
29 * copied or negative error in case of failure.
30 */
copy_oldmem_page(unsigned long pfn,char * buf,size_t csize,unsigned long offset,int userbuf)31 ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
32 size_t csize, unsigned long offset,
33 int userbuf)
34 {
35 void *vaddr;
36
37 if (!csize)
38 return 0;
39
40 vaddr = memremap(__pfn_to_phys(pfn), PAGE_SIZE, MEMREMAP_WB);
41 if (!vaddr)
42 return -ENOMEM;
43
44 if (userbuf) {
45 if (copy_to_user((char __user *)buf, vaddr + offset, csize)) {
46 memunmap(vaddr);
47 return -EFAULT;
48 }
49 } else {
50 memcpy(buf, vaddr + offset, csize);
51 }
52
53 memunmap(vaddr);
54
55 return csize;
56 }
57
58 /**
59 * elfcorehdr_read - read from ELF core header
60 * @buf: buffer where the data is placed
61 * @csize: number of bytes to read
62 * @ppos: address in the memory
63 *
64 * This function reads @count bytes from elf core header which exists
65 * on crash dump kernel's memory.
66 */
elfcorehdr_read(char * buf,size_t count,u64 * ppos)67 ssize_t elfcorehdr_read(char *buf, size_t count, u64 *ppos)
68 {
69 memcpy(buf, phys_to_virt((phys_addr_t)*ppos), count);
70 return count;
71 }
72
