LXR linux/arch/mips/kernel/crash

   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
   8static 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 */
  27ssize_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
  55static 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}
  67arch_initcall(kdump_buf_page_init);
  68