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 <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20230804143910.15504-2-andriy.shevchenko@linux.intel.com
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

Author: andy-shev

include/linux/string_helpers.h

@@ -109,6 +109,8 @@ char *kstrdup_quotable(const char *src, gfp_t gfp);
 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

@@ -719,6 +719,21 @@ char *kstrdup_quotable_file(struct file *file, gfp_t gfp)
 }
 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