arch/x86/kernel/crash_dump_64.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *      Memory preserving reboot related code.
   4  *
   5  *      Created by: Hariprasad Nellitheertha (hari@in.ibm.com)
   6  *      Copyright (C) IBM Corporation, 2004. All rights reserved
   7  */
   8
   9 #include <linux/errno.h>
  10 #include <linux/crash_dump.h>
  11 #include <linux/uaccess.h>
  12 #include <linux/io.h>
  13
  14 static ssize_t __copy_oldmem_page(unsigned long pfn, char *buf, size_t csize,
  15                                   unsigned long offset, int userbuf,
  16                                   bool encrypted)
  17 {
  18         void  *vaddr;
  19
  20         if (!csize)
  21                 return 0;
  22
  23         if (encrypted)
  24                 vaddr = (__force void *)ioremap_encrypted(pfn << PAGE_SHIFT, PAGE_SIZE);
  25         else
  26                 vaddr = (__force void *)ioremap_cache(pfn << PAGE_SHIFT, PAGE_SIZE);
  27
  28         if (!vaddr)
  29                 return -ENOMEM;
  30
  31         if (userbuf) {
  32                 if (copy_to_user((void __user *)buf, vaddr + offset, csize)) {
  33                         iounmap((void __iomem *)vaddr);
  34                         return -EFAULT;
  35                 }
  36         } else
  37                 memcpy(buf, vaddr + offset, csize);
  38
  39         set_iounmap_nonlazy();
  40         iounmap((void __iomem *)vaddr);
  41         return csize;
  42 }
  43
  44 /**
  45  * copy_oldmem_page - copy one page of memory
  46  * @pfn: page frame number to be copied
  47  * @buf: target memory address for the copy; this can be in kernel address
  48  *      space or user address space (see @userbuf)
  49  * @csize: number of bytes to copy
  50  * @offset: offset in bytes into the page (based on pfn) to begin the copy
  51  * @userbuf: if set, @buf is in user address space, use copy_to_user(),
  52  *      otherwise @buf is in kernel address space, use memcpy().
  53  *
  54  * Copy a page from the old kernel's memory. For this page, there is no pte
  55  * mapped in the current kernel. We stitch up a pte, similar to kmap_atomic.
  56  */
  57 ssize_t copy_oldmem_page(unsigned long pfn, char *buf, size_t csize,
  58                          unsigned long offset, int userbuf)
  59 {
  60         return __copy_oldmem_page(pfn, buf, csize, offset, userbuf, false);
  61 }
  62
  63 /**
  64  * copy_oldmem_page_encrypted - same as copy_oldmem_page() above but ioremap the
  65  * memory with the encryption mask set to accommodate kdump on SME-enabled
  66  * machines.
  67  */
  68 ssize_t copy_oldmem_page_encrypted(unsigned long pfn, char *buf, size_t csize,
  69                                    unsigned long offset, int userbuf)
  70 {
  71         return __copy_oldmem_page(pfn, buf, csize, offset, userbuf, true);
  72 }
  73
  74 ssize_t elfcorehdr_read(char *buf, size_t count, u64 *ppos)
  75 {
  76         return read_from_oldmem(buf, count, ppos, 0, sev_active());
  77 }