arch/ia64/kernel/crash_dump.c

   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
   9 #include <linux/errno.h>
  10 #include <linux/types.h>
  11
  12 #include <asm/page.h>
  13 #include <asm/uaccess.h>
  14
  15 /**
  16  * copy_oldmem_page - copy one page from "oldmem"
  17  * @pfn: page frame number to be copied
  18  * @buf: target memory address for the copy; this can be in kernel address
  19  *      space or user address space (see @userbuf)
  20  * @csize: number of bytes to copy
  21  * @offset: offset in bytes into the page (based on pfn) to begin the copy
  22  * @userbuf: if set, @buf is in user address space, use copy_to_user(),
  23  *      otherwise @buf is in kernel address space, use memcpy().
  24  *
  25  * Copy a page from "oldmem". For this page, there is no pte mapped
  26  * in the current kernel. We stitch up a pte, similar to kmap_atomic.
  27  *
  28  * Calling copy_to_user() in atomic context is not desirable. Hence first
  29  * copying the data to a pre-allocated kernel page and then copying to user
  30  * space in non-atomic context.
  31  */
  32 ssize_t
  33 copy_oldmem_page(unsigned long pfn, char *buf,
  34                 size_t csize, unsigned long offset, int userbuf)
  35 {
  36         void  *vaddr;
  37
  38         if (!csize)
  39                 return 0;
  40         vaddr = __va(pfn<<PAGE_SHIFT);
  41         if (userbuf) {
  42                 if (copy_to_user(buf, (vaddr + offset), csize)) {
  43                         return -EFAULT;
  44                 }
  45         } else
  46                 memcpy(buf, (vaddr + offset), csize);
  47         return csize;
  48 }
  49