linux-kernel - [PATCH v4 3/4] devres: provide devm_kstrdup

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Date:   Tue, 25 Sep 2018 14:46:28 +0200
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Jassi Brar <jassisinghbrar@...il.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Arnd Bergmann <arnd@...db.de>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Rob Herring <robh@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Arend van Spriel <aspriel@...il.com>,
        Robin Murphy <robin.murphy@....com>,
        Vivek Gautam <vivek.gautam@...eaurora.org>,
        Joe Perches <joe@...ches.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Roman Gushchin <guro@...com>, Michal Hocko <mhocko@...e.com>,
        Huang Ying <ying.huang@...el.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     linux-kernel@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-mm@...ck.org,
        Bartosz Golaszewski <brgl@...ev.pl>
Subject: [PATCH v4 3/4] devres: provide devm_kstrdup_const()

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@...ev.pl>
Reviewed-by: Bjorn Andersson <bjorn.andersson@...aro.org>
Acked-by: Mike Rapoport <rppt@...ux.vnet.ibm.com>
---
 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