[PATCH 1/2] devres: provide devm_kstrdup_const()

[Bartosz Golaszewski <brgl@xxxxxxxx>]

Provide a resource managed version of kstrdup_const(). This variant
internally calls devm_kstrdup() on pointers that are outside of
.rodata section. Also provide a corresponding version of devm_kfree().

Signed-off-by: Bartosz Golaszewski <brgl@xxxxxxxx>
---
 include/linux/device.h |  2 ++
 mm/util.c              | 35 +++++++++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+)

diff --git a/include/linux/device.h b/include/linux/device.h
index 8f882549edee..f8f5982d26b2 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -693,7 +693,9 @@ 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, void *p);
+extern void devm_kfree_const(struct device *dev, void *p);
 extern char *devm_kstrdup(struct device *dev, const char *s, gfp_t gfp) __malloc;
+extern 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);
 
diff --git a/mm/util.c b/mm/util.c
index d2890a407332..6d1f41b5775e 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -39,6 +39,20 @@ void kfree_const(const void *x)
 }
 EXPORT_SYMBOL(kfree_const);
 
+/**
+ * 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, void *p)
+{
+	if (!is_kernel_rodata((unsigned long)p))
+		devm_kfree(dev, p);
+}
+EXPORT_SYMBOL(devm_kfree_const);
+
 /**
  * kstrdup - allocate space for and copy an existing string
  * @s: the string to duplicate
@@ -78,6 +92,27 @@ const char *kstrdup_const(const char *s, gfp_t gfp)
 }
 EXPORT_SYMBOL(kstrdup_const);
 
+/**
+ * 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
+ *
+ * Function returns source string if it is in .rodata section otherwise it
+ * fallbacks to devm_kstrdup.
+ *
+ * Strings allocated by devm_kstrdup_const will be automatically freed when
+ * the associated device is detached.
+ */
+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);
+
 /**
  * kstrndup - allocate space for and copy an existing string
  * @s: the string to duplicate
-- 
2.18.0