1 files changed, 36 insertions, 0 deletions

diff --git a/arch/powerpc/kernel/crash_dump.c b/arch/powerpc/kernel/crash_dump.c
index 5337ab759780..87effa3f21a7 100644
--- a/arch/powerpc/kernel/crash_dump.c
+++ b/arch/powerpc/kernel/crash_dump.c
@@ -16,6 +16,7 @@
 #include <asm/kdump.h>
 #include <asm/lmb.h>
 #include <asm/firmware.h>
+#include <asm/uaccess.h>
 
 #ifdef DEBUG
 #include <asm/udbg.h>
@@ -71,3 +72,38 @@ static int __init parse_savemaxmem(char *p)
         return 0;
 }
 __setup("savemaxmem=", parse_savemaxmem);
+
+/*
+ * copy_oldmem_page - copy one page from "oldmem"
+ * @pfn: page frame number to be copied
+ * @buf: target memory address for the copy; this can be in kernel address
+ *      space or user address space (see @userbuf)
+ * @csize: number of bytes to copy
+ * @offset: offset in bytes into the page (based on pfn) to begin the copy
+ * @userbuf: if set, @buf is in user address space, use copy_to_user(),
+ *      otherwise @buf is in kernel address space, use memcpy().
+ *
+ * Copy a page from "oldmem". For this page, there is no pte mapped
+ * in the current kernel. We stitch up a pte, similar to kmap_atomic.
+ */
+ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
+                        size_t csize, unsigned long offset, int userbuf)
+{
+        void  *vaddr;
+
+        if (!csize)
+                return 0;
+
+        vaddr = __ioremap(pfn << PAGE_SHIFT, PAGE_SIZE, 0);
+
+        if (userbuf) {
+                if (copy_to_user((char __user *)buf, (vaddr + offset), csize)) {
+                        iounmap(vaddr);
+                        return -EFAULT;
+                }
+        } else
+                memcpy(buf, (vaddr + offset), csize);
+
+        iounmap(vaddr);
+        return csize;
+}