lib/string_helpers: Add kstrdup_and_replace() helper

Duplicate a NULL-terminated string and replace all occurrences of
the old character with a new one. In other words, provide functionality
of kstrdup() + strreplace().

Signed-off-by: Andy Shevchenko <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Stephen Boyd <[e-mail]>

include/linux/string_helpers.h

···
 char *kstrdup_quotable_cmdline(struct task_struct *task, gfp_t gfp);
 char *kstrdup_quotable_file(struct file *file, gfp_t gfp);
 
+char *kstrdup_and_replace(const char *src, char old, char new, gfp_t gfp);
+
 char **kasprintf_strarray(gfp_t gfp, const char *prefix, size_t n);
 void kfree_strarray(char **array, size_t n);
 

lib/string_helpers.c

···
 }
 EXPORT_SYMBOL_GPL(kstrdup_quotable_file);
 
+/*
+ * Returns duplicate string in which the @old characters are replaced by @new.
+ */
+char *kstrdup_and_replace(const char *src, char old, char new, gfp_t gfp)
+{
+	char *dst;
+
+	dst = kstrdup(src, gfp);
+	if (!dst)
+		return NULL;
+
+	return strreplace(dst, old, new);
+}
+EXPORT_SYMBOL_GPL(kstrdup_and_replace);
+
 /**
  * kasprintf_strarray - allocate and fill array of sequential strings
  * @gfp: flags for the slab allocator