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
   6 static int __init parse_savemaxmem(char *p)
   7 {
   8         if (p)
   9                 saved_max_pfn = (memparse(p, &p) >> PAGE_SHIFT) - 1;
  10
  11         return 1;
  12 }
  13 __setup("savemaxmem=", parse_savemaxmem);
  14
  15
  16 static void *kdump_buf_page;
  17
  18 /**
  19  * copy_oldmem_page - copy one page from "oldmem"
  20  * @pfn: page frame number to be copied
  21  * @buf: target memory address for the copy; this can be in kernel address
  22  *      space or user address space (see @userbuf)
  23  * @csize: number of bytes to copy
  24  * @offset: offset in bytes into the page (based on pfn) to begin the copy
  25  * @userbuf: if set, @buf is in user address space, use copy_to_user(),
  26  *      otherwise @buf is in kernel address space, use memcpy().
  27  *
  28  * Copy a page from "oldmem". For this page, there is no pte mapped
  29  * in the current kernel.
  30  *
  31  * Calling copy_to_user() in atomic context is not desirable. Hence first
  32  * copying the data to a pre-allocated kernel page and then copying to user
  33  * space in non-atomic context.
  34  */
  35 ssize_t 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
  43         vaddr = kmap_atomic_pfn(pfn);
  44
  45         if (!userbuf) {
  46                 memcpy(buf, (vaddr + offset), csize);
  47                 kunmap_atomic(vaddr);
  48         } else {
  49                 if (!kdump_buf_page) {
  50                         pr_warning("Kdump: Kdump buffer page not allocated\n");
  51
  52                         return -EFAULT;
  53                 }
  54                 copy_page(kdump_buf_page, vaddr);
  55                 kunmap_atomic(vaddr);
  56                 if (copy_to_user(buf, (kdump_buf_page + offset), csize))
  57                         return -EFAULT;
  58         }
  59
  60         return csize;
  61 }
  62
  63 static int __init kdump_buf_page_init(void)
  64 {
  65         int ret = 0;
  66
  67         kdump_buf_page = kmalloc(PAGE_SIZE, GFP_KERNEL);
  68         if (!kdump_buf_page) {
  69                 pr_warning("Kdump: Failed to allocate kdump buffer page\n");
  70                 ret = -ENOMEM;
  71         }
  72
  73         return ret;
  74 }
  75 arch_initcall(kdump_buf_page_init);