1 files changed, 53 insertions, 0 deletions

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index e3085b22a365..42187381506b 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -23,7 +23,10 @@
 #include <linux/devfs_fs_kernel.h>
 #include <linux/ptrace.h>
 #include <linux/device.h>
+#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>
@@ -273,6 +276,40 @@ static int mmap_kmem(struct file * file, struct vm_area_struct * vma)
         return mmap_mem(file, vma);
 }
 
+#ifdef CONFIG_CRASH_DUMP
+/*
+ * Read memory corresponding to the old kernel.
+ */
+static ssize_t read_oldmem(struct file *file, char __user *buf,
+                                size_t count, loff_t *ppos)
+{
+        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;
+
+                offset = (unsigned long)(*ppos % PAGE_SIZE);
+                if (count > PAGE_SIZE - offset)
+                        csize = PAGE_SIZE - offset;
+                else
+                        csize = count;
+
+                rc = copy_oldmem_page(pfn, buf, csize, offset, 1);
+                if (rc < 0)
+                        return rc;
+                buf += csize;
+                *ppos += csize;
+                read += csize;
+                count -= csize;
+        }
+        return read;
+}
+#endif
+
 extern long vread(char *buf, char *addr, unsigned long count);
 extern long vwrite(char *buf, char *addr, unsigned long count);
 
@@ -721,6 +758,7 @@ static int open_port(struct inode * inode, struct file * filp)
 #define read_full       read_zero
 #define open_mem        open_port
 #define open_kmem       open_mem
+#define open_oldmem     open_mem
 
 static struct file_operations mem_fops = {
         .llseek         = memory_lseek,
@@ -770,6 +808,13 @@ static struct file_operations full_fops = {
         .write          = write_full,
 };
 
+#ifdef CONFIG_CRASH_DUMP
+static struct file_operations oldmem_fops = {
+        .read   = read_oldmem,
+        .open   = open_oldmem,
+};
+#endif
+
 static ssize_t kmsg_write(struct file * file, const char __user * buf,
                           size_t count, loff_t *ppos)
 {
@@ -825,6 +870,11 @@ static int memory_open(struct inode * inode, struct file * filp)
                 case 11:
                         filp->f_op = &kmsg_fops;
                         break;
+#ifdef CONFIG_CRASH_DUMP
+                case 12:
+                        filp->f_op = &oldmem_fops;
+                        break;
+#endif
                 default:
                         return -ENXIO;
         }
@@ -854,6 +904,9 @@ static const struct {
         {8, "random",  S_IRUGO | S_IWUSR,           &random_fops},
         {9, "urandom", S_IRUGO | S_IWUSR,           &urandom_fops},
         {11,"kmsg",    S_IRUGO | S_IWUSR,           &kmsg_fops},
+#ifdef CONFIG_CRASH_DUMP
+        {12,"oldmem",    S_IRUSR | S_IWUSR | S_IRGRP, &oldmem_fops},
+#endif
 };
 
 static struct class *mem_class;