arch/mips/kernel/crash_dump.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/highmem.h>
   3 #include <linux/memblock.h>
   4 #include <linux/crash_dump.h>
   5 #include <linux/uaccess.h>
   6 #include <linux/slab.h>
   7
   8 static void *kdump_buf_page;
   9
  10 /**
  11  * copy_oldmem_page - copy one page from "oldmem"
  12  * @pfn: page frame number to be copied
  13  * @buf: target memory address for the copy; this can be in kernel address
  14  *      space or user address space (see @userbuf)
  15  * @csize: number of bytes to copy
  16  * @offset: offset in bytes into the page (based on pfn) to begin the copy
  17  * @userbuf: if set, @buf is in user address space, use copy_to_user(),
  18  *      otherwise @buf is in kernel address space, use memcpy().
  19  *
  20  * Copy a page from "oldmem". For this page, there is no pte mapped
  21  * in the current kernel.
  22  *
  23  * Calling copy_to_user() in atomic context is not desirable. Hence first
  24  * copying the data to a pre-allocated kernel page and then copying to user
  25  * space in non-atomic context.
  26  */
  27 ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
  28                          size_t csize, unsigned long offset, int userbuf)
  29 {
  30         void  *vaddr;
  31
  32         if (!csize)
  33                 return 0;
  34
  35         vaddr = kmap_atomic_pfn(pfn);
  36
  37         if (!userbuf) {
  38                 memcpy(buf, (vaddr + offset), csize);
  39                 kunmap_atomic(vaddr);
  40         } else {
  41                 if (!kdump_buf_page) {
  42                         pr_warn("Kdump: Kdump buffer page not allocated\n");
  43
  44                         return -EFAULT;
  45                 }
  46                 copy_page(kdump_buf_page, vaddr);
  47                 kunmap_atomic(vaddr);
  48                 if (copy_to_user(buf, (kdump_buf_page + offset), csize))
  49                         return -EFAULT;
  50         }
  51
  52         return csize;
  53 }
  54
  55 static int __init kdump_buf_page_init(void)
  56 {
  57         int ret = 0;
  58
  59         kdump_buf_page = kmalloc(PAGE_SIZE, GFP_KERNEL);
  60         if (!kdump_buf_page) {
  61                 pr_warn("Kdump: Failed to allocate kdump buffer page\n");
  62                 ret = -ENOMEM;
  63         }
  64
  65         return ret;
  66 }
  67 arch_initcall(kdump_buf_page_init);