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 int __init parse_savemaxmem(char *p)
   8 {
   9         if (p)
  10                 saved_max_pfn = (memparse(p, &p) >> PAGE_SHIFT) - 1;
  11
  12         return 1;
  13 }
  14 __setup("savemaxmem=", parse_savemaxmem);
  15
  16
  17 static void *kdump_buf_page;
  18
  19 /**
  20  * copy_oldmem_page - copy one page from "oldmem"
  21  * @pfn: page frame number to be copied
  22  * @buf: target memory address for the copy; this can be in kernel address
  23  *      space or user address space (see @userbuf)
  24  * @csize: number of bytes to copy
  25  * @offset: offset in bytes into the page (based on pfn) to begin the copy
  26  * @userbuf: if set, @buf is in user address space, use copy_to_user(),
  27  *      otherwise @buf is in kernel address space, use memcpy().
  28  *
  29  * Copy a page from "oldmem". For this page, there is no pte mapped
  30  * in the current kernel.
  31  *
  32  * Calling copy_to_user() in atomic context is not desirable. Hence first
  33  * copying the data to a pre-allocated kernel page and then copying to user
  34  * space in non-atomic context.
  35  */
  36 ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
  37                          size_t csize, unsigned long offset, int userbuf)
  38 {
  39         void  *vaddr;
  40
  41         if (!csize)
  42                 return 0;
  43
  44         vaddr = kmap_atomic_pfn(pfn);
  45
  46         if (!userbuf) {
  47                 memcpy(buf, (vaddr + offset), csize);
  48                 kunmap_atomic(vaddr);
  49         } else {
  50                 if (!kdump_buf_page) {
  51                         pr_warning("Kdump: Kdump buffer page not allocated\n");
  52
  53                         return -EFAULT;
  54                 }
  55                 copy_page(kdump_buf_page, vaddr);
  56                 kunmap_atomic(vaddr);
  57                 if (copy_to_user(buf, (kdump_buf_page + offset), csize))
  58                         return -EFAULT;
  59         }
  60
  61         return csize;
  62 }
  63
  64 static int __init kdump_buf_page_init(void)
  65 {
  66         int ret = 0;
  67
  68         kdump_buf_page = kmalloc(PAGE_SIZE, GFP_KERNEL);
  69         if (!kdump_buf_page) {
  70                 pr_warning("Kdump: Failed to allocate kdump buffer page\n");
  71                 ret = -ENOMEM;
  72         }
  73
  74         return ret;
  75 }
  76 arch_initcall(kdump_buf_page_init);