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

On Mon, Aug 27, 2018 at 04:28:55PM +0200, Bartosz Golaszewski wrote:

2018-08-27 12:33 GMT+02:00 Mike Rapoport [off-list ref]:

quoted

On Mon, Aug 27, 2018 at 10:21:00AM +0200, Bartosz Golaszewski wrote:

quoted

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 <redacted>
---
 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

[ ... ]

quoted

quoted

+ * 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);
+

The devm_ variants seem to belong to drivers/base/devres.c rather than
mm/util.c

Not all devm_ variants live in drivers/base/devres.c, many subsystems
implement them locally. In this case we need to choose between
exporting is_kernel_rodata() and putting devm_kstrdup_const() in
mm/util.c. I chose the latter, since it's cleaner.

I rather think that moving is_kernel_rodata() to
include/asm-generic/sections.h and having devm_kstrdup_const() next to
devm_kstrdup() would be cleaner.
 

Bart

-- 
Sincerely yours,
Mike.