1 files changed, 15 insertions, 36 deletions

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 01b3c17ca851..b64108dd765b 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -26,6 +26,7 @@
 #include <linux/highmem.h>
 #include <linux/crash_dump.h>
 #include <linux/backing-dev.h>
+#include <linux/bootmem.h>
 
 #include <asm/uaccess.h>
 #include <asm/io.h>
@@ -278,55 +279,33 @@ static int mmap_kmem(struct file * file, struct vm_area_struct * vma)
 #ifdef CONFIG_CRASH_DUMP
 /*
  * Read memory corresponding to the old kernel.
- * If we are reading from the reserved section, which is
- * actually used by the current kernel, we just return zeroes.
- * Or if we are reading from the first 640k, we return from the
- * backed up area.
  */
-static ssize_t read_oldmem(struct file * file, char * buf,
+static ssize_t read_oldmem(struct file *file, char __user *buf,
                                 size_t count, loff_t *ppos)
 {
-        unsigned long pfn;
-        unsigned backup_start, backup_end, relocate_start;
-        size_t read=0, csize;
-
-        backup_start = CRASH_BACKUP_BASE / PAGE_SIZE;
-        backup_end = backup_start + (CRASH_BACKUP_SIZE / PAGE_SIZE);
-        relocate_start = (CRASH_BACKUP_BASE + CRASH_BACKUP_SIZE) / PAGE_SIZE;
+        unsigned long pfn, offset;
+        size_t read = 0, csize;
+        int rc = 0;
 
         while(count) {
                 pfn = *ppos / PAGE_SIZE;
+                if (pfn > saved_max_pfn)
+                        return read;
 
-                csize = (count > PAGE_SIZE) ? PAGE_SIZE : count;
-
-                /* Perform translation (see comment above) */
-                if ((pfn >= backup_start) && (pfn < backup_end)) {
-                        if (clear_user(buf, csize)) {
-                                read = -EFAULT;
-                                goto done;
-                        }
-
-                        goto copy_done;
-                } else if (pfn < (CRASH_RELOCATE_SIZE / PAGE_SIZE))
-                        pfn += relocate_start;
-
-                if (pfn > saved_max_pfn) {
-                        read = 0;
-                        goto done;
-                }
-
-                if (copy_oldmem_page(pfn, buf, csize, 1)) {
-                        read = -EFAULT;
-                        goto done;
-                }
+                offset = (unsigned long)(*ppos % PAGE_SIZE);
+                if (count > PAGE_SIZE - offset)
+                        csize = PAGE_SIZE - offset;
+                else
+                        csize = count;
 
-copy_done:
+                rc = copy_oldmem_page(pfn, buf, csize, offset, 1);
+                if (rc < 0)
+                        return rc;
                 buf += csize;
                 *ppos += csize;
                 read += csize;
                 count -= csize;
         }
-done:
         return read;
 }
 #endif