2 files changed, 123 insertions, 0 deletions

diff --git a/drivers/misc/sram-exec.c b/drivers/misc/sram-exec.c
new file mode 100644
index 000000000000..ac522417c462
--- /dev/null
+++ b/drivers/misc/sram-exec.c
@@ -0,0 +1,105 @@
+/*
+ * SRAM protect-exec region helper functions
+ *
+ * Copyright (C) 2017 Texas Instruments Incorporated - http://www.ti.com/
+ *	Dave Gerlach
+ *
+ * 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.
+ *
+ * This program is distributed "as is" WITHOUT ANY WARRANTY of any
+ * kind, whether express or implied; without even the implied warranty
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/device.h>
+#include <linux/genalloc.h>
+#include <linux/sram.h>
+
+#include <asm/cacheflush.h>
+
+#include "sram.h"
+
+static DEFINE_MUTEX(exec_pool_list_mutex);
+static LIST_HEAD(exec_pool_list);
+
+int sram_check_protect_exec(struct sram_dev *sram, struct sram_reserve *block,
+			    struct sram_partition *part)
+{
+	unsigned long base = (unsigned long)part->base;
+	unsigned long end = base + block->size;
+
+	if (!PAGE_ALIGNED(base) || !PAGE_ALIGNED(end)) {
+		dev_err(sram->dev,
+			"SRAM pool marked with 'protect-exec' is not page aligned and will not be created.\n");
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
+int sram_add_protect_exec(struct sram_partition *part)
+{
+	mutex_lock(&exec_pool_list_mutex);
+	list_add_tail(&part->list, &exec_pool_list);
+	mutex_unlock(&exec_pool_list_mutex);
+
+	return 0;
+}
+
+/**
+ * sram_exec_copy - copy data to a protected executable region of sram
+ *
+ * @pool: struct gen_pool retrieved that is part of this sram
+ * @dst: Destination address for the copy, that must be inside pool
+ * @src: Source address for the data to copy
+ * @size: Size of copy to perform, which starting from dst, must reside in pool
+ *
+ * This helper function allows sram driver to act as central control location
+ * of 'protect-exec' pools which are normal sram pools but are always set
+ * read-only and executable except when copying data to them, at which point
+ * they are set to read-write non-executable, to make sure no memory is
+ * writeable and executable at the same time. This region must be page-aligned
+ * and is checked during probe, otherwise page attribute manipulation would
+ * not be possible.
+ */
+int sram_exec_copy(struct gen_pool *pool, void *dst, void *src,
+		   size_t size)
+{
+	struct sram_partition *part = NULL, *p;
+	unsigned long base;
+	int pages;
+
+	mutex_lock(&exec_pool_list_mutex);
+	list_for_each_entry(p, &exec_pool_list, list) {
+		if (p->pool == pool)
+			part = p;
+	}
+	mutex_unlock(&exec_pool_list_mutex);
+
+	if (!part)
+		return -EINVAL;
+
+	if (!addr_in_gen_pool(pool, (unsigned long)dst, size))
+		return -EINVAL;
+
+	base = (unsigned long)part->base;
+	pages = PAGE_ALIGN(size) / PAGE_SIZE;
+
+	mutex_lock(&part->lock);
+
+	set_memory_nx((unsigned long)base, pages);
+	set_memory_rw((unsigned long)base, pages);
+
+	memcpy(dst, src, size);
+
+	set_memory_ro((unsigned long)base, pages);
+	set_memory_x((unsigned long)base, pages);
+
+	mutex_unlock(&part->lock);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(sram_exec_copy);
diff --git a/drivers/misc/sram.h b/drivers/misc/sram.h
index 52501a84468c..b268cd3f55bb 100644
--- a/drivers/misc/sram.h
+++ b/drivers/misc/sram.h
@@ -36,4 +36,22 @@ struct sram_reserve {
 	bool pool;
 	const char *label;
 };
+
+#ifdef CONFIG_SRAM_EXEC
+int sram_check_protect_exec(struct sram_dev *sram, struct sram_reserve *block,
+			    struct sram_partition *part);
+int sram_add_protect_exec(struct sram_partition *part);
+#else
+static inline int sram_check_protect_exec(struct sram_dev *sram,
+					  struct sram_reserve *block,
+					  struct sram_partition *part)
+{
+	return -ENODEV;
+}
+
+static inline int sram_add_protect_exec(struct sram_partition *part)
+{
+	return -ENODEV;
+}
+#endif /* CONFIG_SRAM_EXEC */
 #endif /* __SRAM_H */