Re: [PATCH net-next] net: enetc: use get/put_unaligned() for mac address handling

[Heiner Kallweit <hkallweit1@gmail.com>]

On 04.06.2021 14:30, Michael Walle wrote:
> The supplied buffer for the MAC address might not be aligned. Thus
> doing a 32bit (or 16bit) access could be on an unaligned address. For
> now, enetc is only used on aarch64 which can do unaligned accesses, thus
> there is no error. In any case, be correct and use the get/put_unaligned()
> helpers.
> 
> Signed-off-by: Michael Walle <michael@walle.cc>
> ---
>  drivers/net/ethernet/freescale/enetc/enetc_pf.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/freescale/enetc/enetc_pf.c b/drivers/net/ethernet/freescale/enetc/enetc_pf.c
> index 31274325159a..a96d2acb5e11 100644
> --- a/drivers/net/ethernet/freescale/enetc/enetc_pf.c
> +++ b/drivers/net/ethernet/freescale/enetc/enetc_pf.c
> @@ -1,6 +1,7 @@
>  // SPDX-License-Identifier: (GPL-2.0+ OR BSD-3-Clause)
>  /* Copyright 2017-2019 NXP */
>  
> +#include <asm/unaligned.h>
>  #include <linux/mdio.h>
>  #include <linux/module.h>
>  #include <linux/fsl/enetc_mdio.h>
> @@ -17,15 +18,15 @@ static void enetc_pf_get_primary_mac_addr(struct enetc_hw *hw, int si, u8 *addr)
>  	u32 upper = __raw_readl(hw->port + ENETC_PSIPMAR0(si));
>  	u16 lower = __raw_readw(hw->port + ENETC_PSIPMAR1(si));
>  
> -	*(u32 *)addr = upper;
> -	*(u16 *)(addr + 4) = lower;
> +	put_unaligned(upper, (u32 *)addr);
> +	put_unaligned(lower, (u16 *)(addr + 4));

I think you want to write little endian, therefore on a BE platform
this code may be wrong. Better use put_unaligned_le32?
By using these versions of the unaligned helpers you could also
remove the pointer cast.

>  }
>  
>  static void enetc_pf_set_primary_mac_addr(struct enetc_hw *hw, int si,
>  					  const u8 *addr)
>  {
> -	u32 upper = *(const u32 *)addr;
> -	u16 lower = *(const u16 *)(addr + 4);
> +	u32 upper = get_unaligned((const u32 *)addr);
> +	u16 lower = get_unaligned((const u16 *)(addr + 4));
>  
>  	__raw_writel(upper, hw->port + ENETC_PSIPMAR0(si));
>  	__raw_writew(lower, hw->port + ENETC_PSIPMAR1(si));
>