Subject: DWord alignment on ARMv7

From: [email-masked] (Marc Kleine-Budde)
Date: Fri, 4 Mar 2016 12:19:32 +0100

On 03/04/2016 12:14 PM, Ard Biesheuvel wrote:
> I wonder if we should simply apply something like the patch below
> (untested): it depends on how many 32-bit architectures implement

The "Last line effect" hit here.

> double word load instructions, but for ones that don't, the patch
> shouldn't change anything, nor should it change anything for 64-bit
> architectures.

> -------8<-----------
> diff --git a/include/linux/unaligned/access_ok.h
> b/include/linux/unaligned/access_ok.h
> index 99c1b4d20b0f..019d0b7ea6a3 100644
> --- a/include/linux/unaligned/access_ok.h
> +++ b/include/linux/unaligned/access_ok.h
> @@ -16,7 +16,11 @@ static inline u32 get_unaligned_le32(const void *p)
> 
>  static inline u64 get_unaligned_le64(const void *p)
>  {
> -       return le64_to_cpup((__le64 *)p);
> +       if (BITS_PER_LONG == 64)
> +               return le64_to_cpup((__le64 *)p);
> +       else
> +               return ((u64)le32_to_cpup((__le32 *)p)) |
> +                      ((u64)le32_to_cpup((__le32 *)p + 1) << 32);
>  }
> 
>  static inline u16 get_unaligned_be16(const void *p)
> @@ -31,7 +35,11 @@ static inline u32 get_unaligned_be32(const void *p)
> 
>  static inline u64 get_unaligned_be64(const void *p)
>  {
> -       return be64_to_cpup((__be64 *)p);
> +       if (BITS_PER_LONG == 64)
> +               return be64_to_cpup((__be64 *)p);
> +       else
> +               return ((u64)be32_to_cpup((__be32 *)p) << 32) |
> +                      ((u64)be32_to_cpup((__be32 *)p + 1));
>  }
> 
>  static inline void put_unaligned_le16(u16 val, void *p)
> @@ -46,7 +54,12 @@ static inline void put_unaligned_le32(u32 val, void *p)
> 
>  static inline void put_unaligned_le64(u64 val, void *p)
>  {
> -       *((__le64 *)p) = cpu_to_le64(val);
> +       if (BITS_PER_LONG == 64) {
> +               *((__le64 *)p) = cpu_to_le64(val);
> +       } else {
> +               *((__le32 *)p) = cpu_to_le32(val);
> +               *((__le32 *)p + 1) = cpu_to_le32(val >> 32);
> +       }
>  }
> 
>  static inline void put_unaligned_be16(u16 val, void *p)
> @@ -61,7 +74,12 @@ static inline void put_unaligned_be32(u32 val, void *p)
> 
>  static inline void put_unaligned_be64(u64 val, void *p)
>  {
> -       *((__be64 *)p) = cpu_to_be64(val);
> +       if (BITS_PER_LONG == 64) {
> +               *((__be64 *)p) = cpu_to_be64(val);
> +       } else {
> +               *((__be32 *)p) = cpu_to_le32(val >> 32);
                                          be32
> +               *((__be32 *)p + 1) = cpu_to_le32(val);
                                              be32

Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
Industrial Linux Solutions        | Phone: +49-231-2826-924     |
Vertretung West/Dortmund          | Fax:   +49-5121-206917-5555 |
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