crash_dump.c 1.5 KB

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  1. /*
  2. * kernel/crash_dump.c - Memory preserving reboot related code.
  3. *
  4. * Created by: Simon Horman <horms@verge.net.au>
  5. * Original code moved from kernel/crash.c
  6. * Original code comment copied from the i386 version of this file
  7. */
  8. #include <linux/errno.h>
  9. #include <linux/types.h>
  10. #include <linux/crash_dump.h>
  11. #include <asm/page.h>
  12. #include <asm/uaccess.h>
  13. /**
  14. * copy_oldmem_page - copy one page from "oldmem"
  15. * @pfn: page frame number to be copied
  16. * @buf: target memory address for the copy; this can be in kernel address
  17. * space or user address space (see @userbuf)
  18. * @csize: number of bytes to copy
  19. * @offset: offset in bytes into the page (based on pfn) to begin the copy
  20. * @userbuf: if set, @buf is in user address space, use copy_to_user(),
  21. * otherwise @buf is in kernel address space, use memcpy().
  22. *
  23. * Copy a page from "oldmem". For this page, there is no pte mapped
  24. * in the current kernel. We stitch up a pte, similar to kmap_atomic.
  25. *
  26. * Calling copy_to_user() in atomic context is not desirable. Hence first
  27. * copying the data to a pre-allocated kernel page and then copying to user
  28. * space in non-atomic context.
  29. */
  30. ssize_t
  31. copy_oldmem_page(unsigned long pfn, char *buf,
  32. size_t csize, unsigned long offset, int userbuf)
  33. {
  34. void *vaddr;
  35. if (!csize)
  36. return 0;
  37. vaddr = __va(pfn<<PAGE_SHIFT);
  38. if (userbuf) {
  39. if (copy_to_user(buf, (vaddr + offset), csize)) {
  40. return -EFAULT;
  41. }
  42. } else
  43. memcpy(buf, (vaddr + offset), csize);
  44. return csize;
  45. }