arch/arm64/kernel/crash_dump.c

   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 }