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