1 files changed, 67 insertions, 0 deletions
diff --git a/arch/mips/kernel/crash_dump.c b/arch/mips/kernel/crash_dump.c
new file mode 100644
index 000000000..01b2bd95b
--- /dev/null
+++ b/arch/mips/kernel/crash_dump.c
@@ -0,0 +1,67 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/highmem.h>
+#include <linux/memblock.h>
+#include <linux/crash_dump.h>
+#include <linux/uaccess.h>
+#include <linux/slab.h>
+
+static void *kdump_buf_page;
+
+/**
+ * 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.
+ *
+ * Calling copy_to_user() in atomic context is not desirable. Hence first
+ * copying the data to a pre-allocated kernel page and then copying to user
+ * space in non-atomic context.
+ */
+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 = kmap_atomic_pfn(pfn);
+
+	if (!userbuf) {
+		memcpy(buf, (vaddr + offset), csize);
+		kunmap_atomic(vaddr);
+	} else {
+		if (!kdump_buf_page) {
+			pr_warn("Kdump: Kdump buffer page not allocated\n");
+
+			return -EFAULT;
+		}
+		copy_page(kdump_buf_page, vaddr);
+		kunmap_atomic(vaddr);
+		if (copy_to_user(buf, (kdump_buf_page + offset), csize))
+			return -EFAULT;
+	}
+
+	return csize;
+}
+
+static int __init kdump_buf_page_init(void)
+{
+	int ret = 0;
+
+	kdump_buf_page = kmalloc(PAGE_SIZE, GFP_KERNEL);
+	if (!kdump_buf_page) {
+		pr_warn("Kdump: Failed to allocate kdump buffer page\n");
+		ret = -ENOMEM;
+	}
+
+	return ret;
+}
+arch_initcall(kdump_buf_page_init);