xref: /openbmc/linux/arch/arm64/kernel/crash_dump.c (revision 3dc4b6fb)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Routines for doing kexec-based kdump
4  *
5  * Copyright (C) 2017 Linaro Limited
6  * Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
7  */
8 
9 #include <linux/crash_dump.h>
10 #include <linux/errno.h>
11 #include <linux/io.h>
12 #include <linux/memblock.h>
13 #include <linux/uaccess.h>
14 #include <asm/memory.h>
15 
16 /**
17  * copy_oldmem_page() - copy one page from old kernel memory
18  * @pfn: page frame number to be copied
19  * @buf: buffer where the copied page is placed
20  * @csize: number of bytes to copy
21  * @offset: offset in bytes into the page
22  * @userbuf: if set, @buf is in a user address space
23  *
24  * This function copies one page from old kernel memory into buffer pointed by
25  * @buf. If @buf is in userspace, set @userbuf to %1. Returns number of bytes
26  * copied or negative error in case of failure.
27  */
28 ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
29 			 size_t csize, unsigned long offset,
30 			 int userbuf)
31 {
32 	void *vaddr;
33 
34 	if (!csize)
35 		return 0;
36 
37 	vaddr = memremap(__pfn_to_phys(pfn), PAGE_SIZE, MEMREMAP_WB);
38 	if (!vaddr)
39 		return -ENOMEM;
40 
41 	if (userbuf) {
42 		if (copy_to_user((char __user *)buf, vaddr + offset, csize)) {
43 			memunmap(vaddr);
44 			return -EFAULT;
45 		}
46 	} else {
47 		memcpy(buf, vaddr + offset, csize);
48 	}
49 
50 	memunmap(vaddr);
51 
52 	return csize;
53 }
54 
55 /**
56  * elfcorehdr_read - read from ELF core header
57  * @buf: buffer where the data is placed
58  * @count: number of bytes to read
59  * @ppos: address in the memory
60  *
61  * This function reads @count bytes from elf core header which exists
62  * on crash dump kernel's memory.
63  */
64 ssize_t elfcorehdr_read(char *buf, size_t count, u64 *ppos)
65 {
66 	memcpy(buf, phys_to_virt((phys_addr_t)*ppos), count);
67 	return count;
68 }
69