Re: [RESEND PATCH v6 3/4] devres: provide devm_kstrdup_const()

[Greg Kroah-Hartman]

On Sun, Oct 14, 2018 at 05:20:09PM +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 and returns the string as is otherwise.
> 
> Make devm_kfree() check if the passed pointer doesn't point to .rodata
> and if so - don't actually destroy the resource.
> 
> Signed-off-by: Bartosz Golaszewski <brgl@xxxxxxxx>
> Reviewed-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
> Acked-by: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
> Acked-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
> Reviewed-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> ---
>  drivers/base/devres.c  | 31 +++++++++++++++++++++++++++++++
>  include/linux/device.h |  2 ++
>  2 files changed, 33 insertions(+)
> 
> diff --git a/drivers/base/devres.c b/drivers/base/devres.c
> index 438c91a43508..00c70f0fcdcd 100644
> --- a/drivers/base/devres.c
> +++ b/drivers/base/devres.c
> @@ -11,6 +11,8 @@
>  #include <linux/slab.h>
>  #include <linux/percpu.h>
>  
> +#include <asm/sections.h>
> +
>  #include "base.h"
>  
>  struct devres_node {
> @@ -822,6 +824,28 @@ char *devm_kstrdup(struct device *dev, const char *s, gfp_t gfp)
>  }
>  EXPORT_SYMBOL_GPL(devm_kstrdup);
>  
> +/**
> + * 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
> + *
> + * Strings allocated by devm_kstrdup_const will be automatically freed when
> + * the associated device is detached.
> + *
> + * RETURNS:
> + * Source string if it is in .rodata section otherwise it falls back to
> + * devm_kstrdup.
> + */
> +const 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);

This should be EXPORT_SYMBOL_GPL() to match the rest of the file.  I'll
go fix that up when I apply it.

thanks,

greg k-h