From ec8549e611465558bdf1bb5e9d308f39e5e248cd Mon Sep 17 00:00:00 2001
From: Hauke Mehrtens <hauke@hauke-m.de>
Date: Sun, 17 Sep 2017 14:41:48 +0200
Subject: backport dev_coredumpm() function

This is copied from a more recent backports version to add the
dev_coredumpm() function when the internal core devdump is not used.
---
 compat/Makefile                |  1 +
 compat/backport-4.7.c          | 82 ++++++++++++++++++++++++++++++++++++++++++
 include/linux/bp-devcoredump.h | 32 +++++++++++++++++
 include/linux/devcoredump.h    |  1 +
 4 files changed, 116 insertions(+)
 create mode 100644 compat/backport-4.7.c
 create mode 100644 include/linux/bp-devcoredump.h

--- a/compat/Makefile
+++ b/compat/Makefile
@@ -32,6 +32,7 @@ compat-$(CPTCFG_KERNEL_4_3) += backport-
 compat-$(CPTCFG_KERNEL_4_4) += backport-4.4.o
 compat-$(CPTCFG_KERNEL_4_5) += backport-4.5.o
 compat-$(CPTCFG_KERNEL_4_6) += backport-4.6.o
+compat-$(CPTCFG_KERNEL_4_6) += backport-4.7.o
 
 compat-$(CPTCFG_BPAUTO_BUILD_CRYPTO_CCM) += crypto-ccm.o
 compat-$(CPTCFG_BPAUTO_CRYPTO_SKCIPHER) += crypto-skcipher.o
--- /dev/null
+++ b/compat/backport-4.7.c
@@ -0,0 +1,82 @@
+/*
+ * Copyright(c) 2016 Hauke Mehrtens <hauke@hauke-m.de>
+ *
+ * Backport functionality introduced in Linux 4.7.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/export.h>
+#include <linux/list.h>
+#include <linux/rcupdate.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/skbuff.h>
+#include <net/netlink.h>
+
+/*
+ * Below 3.18 or if the kernel has devcoredump disabled, we copied the
+ * entire devcoredump, so no need to define these functions.
+ */
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,18,0) && \
+	!defined(CPTCFG_BPAUTO_BUILD_WANT_DEV_COREDUMP)
+#include <linux/devcoredump.h>
+#include <linux/scatterlist.h>
+
+static void devcd_free_sgtable(void *data)
+{
+	struct scatterlist *table = data;
+	int i;
+	struct page *page;
+	struct scatterlist *iter;
+	struct scatterlist *delete_iter;
+
+	/* free pages */
+	iter = table;
+	for_each_sg(table, iter, sg_nents(table), i) {
+		page = sg_page(iter);
+		if (page)
+			__free_page(page);
+	}
+
+	/* then free all chained tables */
+	iter = table;
+	delete_iter = table;	/* always points on a head of a table */
+	while (!sg_is_last(iter)) {
+		iter++;
+		if (sg_is_chain(iter)) {
+			iter = sg_chain_ptr(iter);
+			kfree(delete_iter);
+			delete_iter = iter;
+		}
+	}
+
+	/* free the last table */
+	kfree(delete_iter);
+}
+
+static ssize_t devcd_read_from_sgtable(char *buffer, loff_t offset,
+				       size_t buf_len, void *data,
+				       size_t data_len)
+{
+	struct scatterlist *table = data;
+
+	if (offset > data_len)
+		return -EINVAL;
+
+	if (offset + buf_len > data_len)
+		buf_len = data_len - offset;
+	return sg_pcopy_to_buffer(table, sg_nents(table), buffer, buf_len,
+				  offset);
+}
+
+void dev_coredumpsg(struct device *dev, struct scatterlist *table,
+		    size_t datalen, gfp_t gfp)
+{
+	dev_coredumpm(dev, THIS_MODULE, table, datalen, gfp,
+		      devcd_read_from_sgtable, devcd_free_sgtable);
+}
+EXPORT_SYMBOL_GPL(dev_coredumpsg);
+#endif /* >= 3.18.0 */
--- /dev/null
+++ b/include/linux/bp-devcoredump.h
@@ -0,0 +1,32 @@
+#ifndef __BACKPORT_LINUX_DEVCOREDUMP_H
+#define __BACKPORT_LINUX_DEVCOREDUMP_H
+#include <linux/version.h>
+#include <linux/scatterlist.h>
+
+/* We only need to add our wrapper inside the range from 3.18 until
+ * 4.6, outside that we can let our BPAUTO mechanism handle it.
+ */
+#if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,18,0)  &&	\
+     LINUX_VERSION_CODE < KERNEL_VERSION(4,7,0))
+static inline
+void backport_dev_coredumpm(struct device *dev, struct module *owner,
+			    void *data, size_t datalen, gfp_t gfp,
+			    ssize_t (*read_fn)(char *buffer, loff_t offset,
+					    size_t count, void *data,
+					    size_t datalen),
+			    void (*free_fn)(void *data))
+{
+	return dev_coredumpm(dev, owner, (const void *)data, datalen, gfp,
+			     (void *)read_fn, (void *)free_fn);
+}
+
+#define dev_coredumpm LINUX_BACKPORT(dev_coredumpm)
+
+#define dev_coredumpsg LINUX_BACKPORT(dev_coredumpsg)
+void dev_coredumpsg(struct device *dev, struct scatterlist *table,
+		    size_t datalen, gfp_t gfp);
+
+#endif /* (LINUX_VERSION_IS_GEQ(3,18,0) &&	\
+	   LINUX_VERSION_IS_LESS(4,7,0)) */
+
+#endif /* __BACKPORT_LINUX_DEVCOREDUMP_H */
--- a/include/linux/devcoredump.h
+++ b/include/linux/devcoredump.h
@@ -1,6 +1,7 @@
 /* Automatically created during backport process */
 #ifndef CPTCFG_BPAUTO_BUILD_WANT_DEV_COREDUMP
 #include_next <linux/devcoredump.h>
+#include <linux/bp-devcoredump.h>
 #else
 #undef dev_coredumpv
 #define dev_coredumpv LINUX_BACKPORT(dev_coredumpv)