crash_dump.c 1.3 KB

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  1. // SPDX-License-Identifier: GPL-2.0
  2. /*
  3. * crash_dump.c - 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. #include <linux/errno.h>
  9. #include <linux/crash_dump.h>
  10. #include <linux/io.h>
  11. #include <linux/uaccess.h>
  12. /**
  13. * copy_oldmem_page - copy one page from "oldmem"
  14. * @pfn: page frame number to be copied
  15. * @buf: target memory address for the copy; this can be in kernel address
  16. * space or user address space (see @userbuf)
  17. * @csize: number of bytes to copy
  18. * @offset: offset in bytes into the page (based on pfn) to begin the copy
  19. * @userbuf: if set, @buf is in user address space, use copy_to_user(),
  20. * otherwise @buf is in kernel address space, use memcpy().
  21. *
  22. * Copy a page from "oldmem". For this page, there is no pte mapped
  23. * in the current kernel. We stitch up a pte, similar to kmap_atomic.
  24. */
  25. ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
  26. size_t csize, unsigned long offset, int userbuf)
  27. {
  28. void *vaddr;
  29. if (!csize)
  30. return 0;
  31. vaddr = ioremap(pfn << PAGE_SHIFT, PAGE_SIZE);
  32. if (userbuf) {
  33. if (copy_to_user(buf, (vaddr + offset), csize)) {
  34. iounmap(vaddr);
  35. return -EFAULT;
  36. }
  37. } else
  38. memcpy(buf, (vaddr + offset), csize);
  39. iounmap(vaddr);
  40. return csize;
  41. }