[PATCH v3 01/15] lib: provide kmemdup_const()

[Bartosz Golaszewski]

From: Bartosz Golaszewski <bartosz.golaszewski at linaro.org>

Provide a function similar to strdup_const() but for copying blocks of
memory that are likely to be placed in .rodata.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski at linaro.org>
---
 include/linux/string.h |  1 +
 mm/util.c              | 21 +++++++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/include/linux/string.h b/include/linux/string.h
index fdd3442c6bcbd786e177b6e87358e1065a0ffafc..1a86d61de91204563e4179938c4dfc77108e03aa 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -304,6 +304,7 @@ extern char *kstrndup(const char *s, size_t len, gfp_t gfp);
 extern void *kmemdup_noprof(const void *src, size_t len, gfp_t gfp) __realloc_size(2);
 #define kmemdup(...)	alloc_hooks(kmemdup_noprof(__VA_ARGS__))
 
+extern const void *kmemdup_const(const void *src, size_t len, gfp_t gfp);
 extern void *kvmemdup(const void *src, size_t len, gfp_t gfp) __realloc_size(2);
 extern char *kmemdup_nul(const char *s, size_t len, gfp_t gfp);
 extern void *kmemdup_array(const void *src, size_t count, size_t element_size, gfp_t gfp)
diff --git a/mm/util.c b/mm/util.c
index f814e6a59ab1d354b8cd04ebf3903626f6b23a6c..f4df9194b0c69c27ff06e6ba1d1137c559035470 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -142,6 +142,27 @@ void *kmemdup_noprof(const void *src, size_t len, gfp_t gfp)
 }
 EXPORT_SYMBOL(kmemdup_noprof);
 
+/**
+ * kmemdup_const - conditionally duplicate a region of memory
+ *
+ * @src: memory region to duplicate
+ * @len: memory region length,
+ * @gfp: GFP mask to use
+ *
+ * Return: source address if it is in .rodata or the return value of kmemdup()
+ * to which the function falls back otherwise.
+ *
+ * Note: the returned address must not be passed to kfree(), the caller must
+ * use kfree_const() instead.
+ */
+const void *kmemdup_const(const void *src, size_t len, gfp_t gfp)
+{
+	if (is_kernel_rodata((unsigned long)src))
+		return src;
+
+	return kmemdup(src, len, gfp);
+}
+
 /**
  * kmemdup_array - duplicate a given array.
  *

-- 
2.48.1