devcoredump: add scatterlist support

Add scatterlist support (dev_coredumpsg) to allow drivers to avoid
vmalloc() like dev_coredumpm(), while also avoiding the module
reference that the latter function requires.

This internally uses dev_coredumpm() with function inside the
devcoredump module, requiring removing the const
(which touches the driver using it.)

Signed-off-by: Aviya Erenfeld <[e-mail]>
Signed-off-by: Johannes Berg <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/base/devcoredump.c

···
  * GPL LICENSE SUMMARY
  *
  * Copyright(c) 2014 Intel Mobile Communications GmbH
+ * Copyright(c) 2015 Intel Deutschland GmbH
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of version 2 of the GNU General Public License as
···
 
 struct devcd_entry {
 	struct device devcd_dev;
-	const void *data;
+	void *data;
 	size_t datalen;
 	struct module *owner;
 	ssize_t (*read)(char *buffer, loff_t offset, size_t count,
-			const void *data, size_t datalen);
-	void (*free)(const void *data);
+			void *data, size_t datalen);
+	void (*free)(void *data);
 	struct delayed_work del_wk;
 	struct device *failing_dev;
 };
···
 };
 
 static ssize_t devcd_readv(char *buffer, loff_t offset, size_t count,
-			   const void *data, size_t datalen)
+			   void *data, size_t datalen)
 {
 	if (offset > datalen)
 		return -EINVAL;
···
 	return count;
 }
 
+static void devcd_freev(void *data)
+{
+	vfree(data);
+}
+
 /**
  * dev_coredumpv - create device coredump with vmalloc data
  * @dev: the struct device for the crashed device
···
  * This function takes ownership of the vmalloc'ed data and will free
  * it when it is no longer used. See dev_coredumpm() for more information.
  */
-void dev_coredumpv(struct device *dev, const void *data, size_t datalen,
+void dev_coredumpv(struct device *dev, void *data, size_t datalen,
 		   gfp_t gfp)
 {
-	dev_coredumpm(dev, NULL, data, datalen, gfp, devcd_readv, vfree);
+	dev_coredumpm(dev, NULL, data, datalen, gfp, devcd_readv, devcd_freev);
 }
 EXPORT_SYMBOL_GPL(dev_coredumpv);
 
···
 	struct devcd_entry *devcd = dev_to_devcd(dev);
 
 	return devcd->failing_dev == failing;
+}
+
+/**
+ * devcd_free_sgtable - free all the memory of the given scatterlist table
+ * (i.e. both pages and scatterlist instances)
+ * NOTE: if two tables allocated with devcd_alloc_sgtable and then chained
+ * using the sg_chain function then that function should be called only once
+ * on the chained table
+ * @table: pointer to sg_table to free
+ */
+static void devcd_free_sgtable(void *data)
+{
+	_devcd_free_sgtable(data);
+}
+
+/**
+ * devcd_read_from_table - copy data from sg_table to a given buffer
+ * and return the number of bytes read
+ * @buffer: the buffer to copy the data to it
+ * @buf_len: the length of the buffer
+ * @data: the scatterlist table to copy from
+ * @offset: start copy from @offset@ bytes from the head of the data
+ *	in the given scatterlist
+ * @data_len: the length of the data in the sg_table
+ */
+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);
 }
 
 /**
···
  * function will be called to free the data.
  */
 void dev_coredumpm(struct device *dev, struct module *owner,
-		   const void *data, size_t datalen, gfp_t gfp,
+		   void *data, size_t datalen, gfp_t gfp,
 		   ssize_t (*read)(char *buffer, loff_t offset, size_t count,
-				   const void *data, size_t datalen),
-		   void (*free)(const void *data))
+				   void *data, size_t datalen),
+		   void (*free)(void *data))
 {
 	static atomic_t devcd_count = ATOMIC_INIT(0);
 	struct devcd_entry *devcd;
···
 	free(data);
 }
 EXPORT_SYMBOL_GPL(dev_coredumpm);
+
+/**
+ * dev_coredumpmsg - create device coredump that uses scatterlist as data
+ * parameter
+ * @dev: the struct device for the crashed device
+ * @table: the dump data
+ * @datalen: length of the data
+ * @gfp: allocation flags
+ *
+ * Creates a new device coredump for the given device. If a previous one hasn't
+ * been read yet, the new coredump is discarded. The data lifetime is determined
+ * by the device coredump framework and when it is no longer needed
+ * it will free the data.
+ */
+void dev_coredumpsg(struct device *dev, struct scatterlist *table,
+		    size_t datalen, gfp_t gfp)
+{
+	dev_coredumpm(dev, NULL, table, datalen, gfp, devcd_read_from_sgtable,
+		      devcd_free_sgtable);
+}
+EXPORT_SYMBOL_GPL(dev_coredumpsg);
 
 static int __init devcoredump_init(void)
 {

drivers/net/wireless/intel/iwlwifi/mvm/fw-dbg.c

···
 #include "iwl-csr.h"
 
 static ssize_t iwl_mvm_read_coredump(char *buffer, loff_t offset, size_t count,
-				     const void *data, size_t datalen)
+				     void *data, size_t datalen)
 {
 	const struct iwl_mvm_dump_ptrs *dump_ptrs = data;
 	ssize_t bytes_read;
···
 	return bytes_read + bytes_read_trans;
 }
 
-static void iwl_mvm_free_coredump(const void *data)
+static void iwl_mvm_free_coredump(void *data)
 {
 	const struct iwl_mvm_dump_ptrs *fw_error_dump = data;
 

include/linux/devcoredump.h

···
+/*
+ * This file is provided under the GPLv2 license.
+ *
+ * GPL LICENSE SUMMARY
+ *
+ * Copyright(c) 2015 Intel Deutschland GmbH
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * The full GNU General Public License is included in this distribution
+ * in the file called COPYING.
+ */
 #ifndef __DEVCOREDUMP_H
 #define __DEVCOREDUMP_H
 
···
 #include <linux/module.h>
 #include <linux/vmalloc.h>
 
+#include <linux/scatterlist.h>
+#include <linux/slab.h>
+
+/*
+ * _devcd_free_sgtable - free all the memory of the given scatterlist table
+ * (i.e. both pages and scatterlist instances)
+ * NOTE: if two tables allocated and chained using the sg_chain function then
+ * this function should be called only once on the first table
+ * @table: pointer to sg_table to free
+ */
+static inline void _devcd_free_sgtable(struct scatterlist *table)
+{
+	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);
+}
+
+
 #ifdef CONFIG_DEV_COREDUMP
-void dev_coredumpv(struct device *dev, const void *data, size_t datalen,
+void dev_coredumpv(struct device *dev, void *data, size_t datalen,
 		   gfp_t gfp);
 
 void dev_coredumpm(struct device *dev, struct module *owner,
-		   const void *data, size_t datalen, gfp_t gfp,
+		   void *data, size_t datalen, gfp_t gfp,
 		   ssize_t (*read)(char *buffer, loff_t offset, size_t count,
-				   const void *data, size_t datalen),
-		   void (*free)(const void *data));
+				   void *data, size_t datalen),
+		   void (*free)(void *data));
+
+void dev_coredumpsg(struct device *dev, struct scatterlist *table,
+		    size_t datalen, gfp_t gfp);
 #else
-static inline void dev_coredumpv(struct device *dev, const void *data,
+static inline void dev_coredumpv(struct device *dev, void *data,
 				 size_t datalen, gfp_t gfp)
 {
 	vfree(data);
···
 
 static inline void
 dev_coredumpm(struct device *dev, struct module *owner,
-	      const void *data, size_t datalen, gfp_t gfp,
+	      void *data, size_t datalen, gfp_t gfp,
 	      ssize_t (*read)(char *buffer, loff_t offset, size_t count,
-			      const void *data, size_t datalen),
-	      void (*free)(const void *data))
+			      void *data, size_t datalen),
+	      void (*free)(void *data))
 {
 	free(data);
+}
+
+static inline void dev_coredumpsg(struct device *dev, struct scatterlist *table,
+				  size_t datalen, gfp_t gfp)
+{
+	_devcd_free_sgtable(table);
 }
 #endif /* CONFIG_DEV_COREDUMP */