Re: [PATCH] dmaengine: Constify struct dma_descriptor_metadata_ops

On Tue, Jul 14, 2026 at 04:06:33PM +0200, Christophe JAILLET wrote:
> 'struct dma_descriptor_metadata_ops' in not modified in these drivers.
>
> Constifying these structures moves some data to a read-only section, so
> increases overall security, especially when the structure holds some
> function pointers.
>
> On a x86_64, with allmodconfig, as an example:
> Before:
> ======
>    text	   data	    bss	    dec	    hex	filename
>  120635	  21584	     64	 142283	  22bcb	drivers/dma/xilinx/xilinx_dma.o
>
> After:
> =====
>    text	   data	    bss	    dec	    hex	filename
>  120699	  21520	     64	 142283	  22bcb	drivers/dma/xilinx/xilinx_dma.o
>
> Signed-off-by: Christophe JAILLET <[email protected]>

Reviewed-by: Frank Li <[email protected]>

> ---
> Compile tested only.
> ---
>  drivers/dma/ti/k3-udma.c        | 2 +-
>  drivers/dma/xilinx/xilinx_dma.c | 2 +-
>  include/linux/dmaengine.h       | 2 +-
>  3 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/dma/ti/k3-udma.c b/drivers/dma/ti/k3-udma.c
> index 1cf158eb7bdb..fb21e0df5ab7 100644
> --- a/drivers/dma/ti/k3-udma.c
> +++ b/drivers/dma/ti/k3-udma.c
> @@ -3408,7 +3408,7 @@ static int udma_set_metadata_len(struct dma_async_tx_descriptor *desc,
>  	return 0;
>  }
>
> -static struct dma_descriptor_metadata_ops metadata_ops = {
> +static const struct dma_descriptor_metadata_ops metadata_ops = {
>  	.attach = udma_attach_metadata,
>  	.get_ptr = udma_get_metadata_ptr,
>  	.set_len = udma_set_metadata_len,
> diff --git a/drivers/dma/xilinx/xilinx_dma.c b/drivers/dma/xilinx/xilinx_dma.c
> index 98b41b8f8915..bef2b031dba1 100644
> --- a/drivers/dma/xilinx/xilinx_dma.c
> +++ b/drivers/dma/xilinx/xilinx_dma.c
> @@ -655,7 +655,7 @@ static void *xilinx_dma_get_metadata_ptr(struct dma_async_tx_descriptor *tx,
>  	return seg->hw.app;
>  }
>
> -static struct dma_descriptor_metadata_ops xilinx_dma_metadata_ops = {
> +static const struct dma_descriptor_metadata_ops xilinx_dma_metadata_ops = {
>  	.get_ptr = xilinx_dma_get_metadata_ptr,
>  };
>
> diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> index 6fe46c0c9452..fe33a20abc61 100644
> --- a/include/linux/dmaengine.h
> +++ b/include/linux/dmaengine.h
> @@ -631,7 +631,7 @@ struct dma_async_tx_descriptor {
>  	void *callback_param;
>  	struct dmaengine_unmap_data *unmap;
>  	enum dma_desc_metadata_mode desc_metadata_mode;
> -	struct dma_descriptor_metadata_ops *metadata_ops;
> +	const struct dma_descriptor_metadata_ops *metadata_ops;
>  #ifdef CONFIG_ASYNC_TX_ENABLE_CHANNEL_SWITCH
>  	struct dma_async_tx_descriptor *next;
>  	struct dma_async_tx_descriptor *parent;
> --
> 2.55.0
>