[PATCH] kdump: Routines for copying dump pages

This patch provides the interfaces necessary to read the dump contents,
treating it as a high memory device.

Signed off by Hariprasad Nellitheertha <hari@in.ibm.com>
Signed-off-by: Eric Biederman <ebiederm@xmission.com>
Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 50 insertions, 0 deletions

diff --git a/kernel/Makefile b/kernel/Makefile
index cfc8b0dea950..cb05cd05d237 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -28,6 +28,7 @@ obj-$(CONFIG_AUDITSYSCALL) += auditsc.o
 obj-$(CONFIG_KPROBES) += kprobes.o
 obj-$(CONFIG_SYSFS) += ksysfs.o
 obj-$(CONFIG_GENERIC_HARDIRQS) += irq/
+obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
 obj-$(CONFIG_SECCOMP) += seccomp.o
 
 ifneq ($(CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER),y)
diff --git a/kernel/crash_dump.c b/kernel/crash_dump.c
new file mode 100644
index 000000000000..5a1e6d5d203e
--- /dev/null
+++ b/kernel/crash_dump.c
@@ -0,0 +1,49 @@
+/*
+ *      kernel/crash_dump.c - Memory preserving reboot related code.
+ *
+ *      Created by: Hariprasad Nellitheertha (hari@in.ibm.com)
+ *      Copyright (C) IBM Corporation, 2004. All rights reserved
+ */
+
+#include <linux/smp_lock.h>
+#include <linux/errno.h>
+#include <linux/proc_fs.h>
+#include <linux/bootmem.h>
+#include <linux/highmem.h>
+#include <linux/crash_dump.h>
+
+#include <asm/io.h>
+#include <asm/uaccess.h>
+
+/*
+ * 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 *page, *vaddr;
+
+        if (!csize)
+                return 0;
+
+        page = kmalloc(PAGE_SIZE, GFP_KERNEL);
+        if (!page)
+                return -ENOMEM;
+
+        vaddr = kmap_atomic_pfn(pfn, KM_PTE0);
+        copy_page(page, vaddr);
+        kunmap_atomic(vaddr, KM_PTE0);
+
+        if (userbuf) {
+                if (copy_to_user(buf, (page + offset), csize)) {
+                        kfree(page);
+                        return -EFAULT;
+                }
+        } else {
+                memcpy(buf, (page + offset), csize);
+        }
+
+        kfree(page);
+        return csize;
+}