arch/ia64/kernel/crash_dump.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *      kernel/crash_dump.c - Memory preserving reboot related code.
   4  *
   5  *      Created by: Simon Horman <horms@verge.net.au>
   6  *      Original code moved from kernel/crash.c
   7  *      Original code comment copied from the i386 version of this file
   8  */
   9
  10 #include <linux/errno.h>
  11 #include <linux/types.h>
  12 #include <linux/crash_dump.h>
  13
  14 #include <asm/page.h>
  15 #include <linux/uaccess.h>
  16
  17 /**
  18  * copy_oldmem_page - copy one page from "oldmem"
  19  * @pfn: page frame number to be copied
  20  * @buf: target memory address for the copy; this can be in kernel address
  21  *      space or user address space (see @userbuf)
  22  * @csize: number of bytes to copy
  23  * @offset: offset in bytes into the page (based on pfn) to begin the copy
  24  * @userbuf: if set, @buf is in user address space, use copy_to_user(),
  25  *      otherwise @buf is in kernel address space, use memcpy().
  26  *
  27  * Copy a page from "oldmem". For this page, there is no pte mapped
  28  * in the current kernel. We stitch up a pte, similar to kmap_atomic.
  29  *
  30  * Calling copy_to_user() in atomic context is not desirable. Hence first
  31  * copying the data to a pre-allocated kernel page and then copying to user
  32  * space in non-atomic context.
  33  */
  34 ssize_t
  35 copy_oldmem_page(unsigned long pfn, char *buf,
  36                 size_t csize, unsigned long offset, int userbuf)
  37 {
  38         void  *vaddr;
  39
  40         if (!csize)
  41                 return 0;
  42         vaddr = __va(pfn<<PAGE_SHIFT);
  43         if (userbuf) {
  44                 if (copy_to_user(buf, (vaddr + offset), csize)) {
  45                         return -EFAULT;
  46                 }
  47         } else
  48                 memcpy(buf, (vaddr + offset), csize);
  49         return csize;
  50 }
  51