arch/mips/kernel/crash_dump.c

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