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 #include <linux/crash_dump.h>
  12
  13 #include <asm/page.h>
  14 #include <linux/uaccess.h>
  15
  16 /**
  17  * copy_oldmem_page - copy one page from "oldmem"
  18  * @pfn: page frame number to be copied
  19  * @buf: target memory address for the copy; this can be in kernel address
  20  *      space or user address space (see @userbuf)
  21  * @csize: number of bytes to copy
  22  * @offset: offset in bytes into the page (based on pfn) to begin the copy
  23  * @userbuf: if set, @buf is in user address space, use copy_to_user(),
  24  *      otherwise @buf is in kernel address space, use memcpy().
  25  *
  26  * Copy a page from "oldmem". For this page, there is no pte mapped
  27  * in the current kernel. We stitch up a pte, similar to kmap_atomic.
  28  *
  29  * Calling copy_to_user() in atomic context is not desirable. Hence first
  30  * copying the data to a pre-allocated kernel page and then copying to user
  31  * space in non-atomic context.
  32  */
  33 ssize_t
  34 copy_oldmem_page(unsigned long pfn, char *buf,
  35                 size_t csize, unsigned long offset, int userbuf)
  36 {
  37         void  *vaddr;
  38
  39         if (!csize)
  40                 return 0;
  41         vaddr = __va(pfn<<PAGE_SHIFT);
  42         if (userbuf) {
  43                 if (copy_to_user(buf, (vaddr + offset), csize)) {
  44                         return -EFAULT;
  45                 }
  46         } else
  47                 memcpy(buf, (vaddr + offset), csize);
  48         return csize;
  49 }
  50