1 files changed, 47 insertions, 0 deletions
diff --git a/arch/x86/kernel/crash_dump_32.c b/arch/x86/kernel/crash_dump_32.c
new file mode 100644
index 000000000..5f4ae5476
--- /dev/null
+++ b/arch/x86/kernel/crash_dump_32.c
@@ -0,0 +1,47 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *	Memory preserving reboot related code.
+ *
+ *	Created by: Hariprasad Nellitheertha (hari@in.ibm.com)
+ *	Copyright (C) IBM Corporation, 2004. All rights reserved
+ */
+
+#include <linux/slab.h>
+#include <linux/errno.h>
+#include <linux/highmem.h>
+#include <linux/crash_dump.h>
+#include <linux/uio.h>
+
+static inline bool is_crashed_pfn_valid(unsigned long pfn)
+{
+#ifndef CONFIG_X86_PAE
+	/*
+	 * non-PAE kdump kernel executed from a PAE one will crop high pte
+	 * bits and poke unwanted space counting again from address 0, we
+	 * don't want that. pte must fit into unsigned long. In fact the
+	 * test checks high 12 bits for being zero (pfn will be shifted left
+	 * by PAGE_SHIFT).
+	 */
+	return pte_pfn(pfn_pte(pfn, __pgprot(0))) == pfn;
+#else
+	return true;
+#endif
+}
+
+ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn, size_t csize,
+			 unsigned long offset)
+{
+	void  *vaddr;
+
+	if (!csize)
+		return 0;
+
+	if (!is_crashed_pfn_valid(pfn))
+		return -EFAULT;
+
+	vaddr = kmap_local_pfn(pfn);
+	csize = copy_to_iter(vaddr + offset, csize, iter);
+	kunmap_local(vaddr);
+
+	return csize;
+}