[PATCH v3 3/4] devres: provide devm_kstrdup_const()

From: Bartosz Golaszewski
Date: Mon Sep 24 2018 - 06:12:23 EST


Provide a resource managed version of kstrdup_const(). This variant
internally calls devm_kstrdup() on pointers that are outside of
.rodata section and returns the string as is otherwise.

Also provide a corresponding version of devm_kfree().

Signed-off-by: Bartosz Golaszewski <brgl@xxxxxxxx>
Reviewed-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
---
drivers/base/devres.c | 38 ++++++++++++++++++++++++++++++++++++++
include/linux/device.h | 3 +++
2 files changed, 41 insertions(+)

diff --git a/drivers/base/devres.c b/drivers/base/devres.c
index 438c91a43508..48185d57bc5b 100644
--- a/drivers/base/devres.c
+++ b/drivers/base/devres.c
@@ -11,6 +11,8 @@
#include <linux/slab.h>
#include <linux/percpu.h>

+#include <asm/sections.h>
+
#include "base.h"

struct devres_node {
@@ -822,6 +824,28 @@ char *devm_kstrdup(struct device *dev, const char *s, gfp_t gfp)
}
EXPORT_SYMBOL_GPL(devm_kstrdup);

+/**
+ * devm_kstrdup_const - resource managed conditional string duplication
+ * @dev: device for which to duplicate the string
+ * @s: the string to duplicate
+ * @gfp: the GFP mask used in the kmalloc() call when allocating memory
+ *
+ * Strings allocated by devm_kstrdup_const will be automatically freed when
+ * the associated device is detached.
+ *
+ * RETURNS:
+ * Source string if it is in .rodata section otherwise it falls back to
+ * devm_kstrdup.
+ */
+const char *devm_kstrdup_const(struct device *dev, const char *s, gfp_t gfp)
+{
+ if (is_kernel_rodata((unsigned long)s))
+ return s;
+
+ return devm_kstrdup(dev, s, gfp);
+}
+EXPORT_SYMBOL(devm_kstrdup_const);
+
/**
* devm_kvasprintf - Allocate resource managed space and format a string
* into that.
@@ -895,6 +919,20 @@ void devm_kfree(struct device *dev, const void *p)
}
EXPORT_SYMBOL_GPL(devm_kfree);

+/**
+ * devm_kfree_const - Resource managed conditional kfree
+ * @dev: device this memory belongs to
+ * @p: memory to free
+ *
+ * Function calls devm_kfree only if @p is not in .rodata section.
+ */
+void devm_kfree_const(struct device *dev, const void *p)
+{
+ if (!is_kernel_rodata((unsigned long)p))
+ devm_kfree(dev, p);
+}
+EXPORT_SYMBOL(devm_kfree_const);
+
/**
* devm_kmemdup - Resource-managed kmemdup
* @dev: Device this memory belongs to
diff --git a/include/linux/device.h b/include/linux/device.h
index 33f7cb271fbb..79ccc6eb0975 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -693,7 +693,10 @@ static inline void *devm_kcalloc(struct device *dev,
return devm_kmalloc_array(dev, n, size, flags | __GFP_ZERO);
}
extern void devm_kfree(struct device *dev, const void *p);
+extern void devm_kfree_const(struct device *dev, const void *p);
extern char *devm_kstrdup(struct device *dev, const char *s, gfp_t gfp) __malloc;
+extern const char *devm_kstrdup_const(struct device *dev,
+ const char *s, gfp_t gfp);
extern void *devm_kmemdup(struct device *dev, const void *src, size_t len,
gfp_t gfp);

--
2.18.0