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

[Joe Perches <joe@perches.com>]

On Mon, 2018-08-27 at 10:21 +0200, Bartosz Golaszewski wrote:
> 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().
[]
> diff --git a/mm/util.c b/mm/util.c
[]
>  /**
>   * kstrdup - allocate space for and copy an existing string
>   * @s: the string to duplicate
> @@ -78,6 +92,27 @@ const char *kstrdup_const(const char *s, gfp_t gfp)
>  }
>  EXPORT_SYMBOL(kstrdup_const);
>  
> +/**
> + * 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
> + *
> + * Function returns source string if it is in .rodata section otherwise it
> + * fallbacks to devm_kstrdup.
> + *
> + * 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);

Doesn't this lose constness and don't you get
a compiler warning here?

The kstrdup_const function returns a const char *,
why shouldn't this?