[U-Boot] [PATCH] fdt_support: fix unaligned u64 accesses in fdt_fixup_memory_banks

[Simon Glass]

+Tom

Hi Rob,

On 15 October 2014 03:21, Rob Herring <robherring2 at gmail.com> wrote:
> From: Rob Herring <robh at kernel.org>
>
> Commit f18295d3837c282f (fdt_support: fix an endian bug of
> fdt_fixup_memory_banks) changed fdt_fixup_memory_banks cell writing from a
> byte at a time to casting the buffer pointer to a 64-bit pointer. This can
> result in unaligned accesses when there is a mixture of cell sizes of 1
> and 2.

Should that be 739a01ed8e0?

>
> Cc: Masahiro Yamada <yamada.m at jp.panasonic.com>
> Signed-off-by: Rob Herring <robh at kernel.org>
> ---
>  common/fdt_support.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/common/fdt_support.c b/common/fdt_support.c
> index 3f64156..9c41f3a 100644
> --- a/common/fdt_support.c
> +++ b/common/fdt_support.c
> @@ -388,19 +388,22 @@ static int fdt_pack_reg(const void *fdt, void *buf, uint64_t *address,
>         int i;
>         int address_len = get_cells_len(fdt, "#address-cells");
>         int size_len = get_cells_len(fdt, "#size-cells");
> +       u64 cell;
>         char *p = buf;
>
>         for (i = 0; i < n; i++) {
>                 if (address_len == 8)
> -                       *(fdt64_t *)p = cpu_to_fdt64(address[i]);
> +                       cell = cpu_to_fdt64(address[i]);
>                 else
> -                       *(fdt32_t *)p = cpu_to_fdt32(address[i]);
> +                       cell = cpu_to_fdt32(address[i]);
> +               memcpy(p, &cell, address_len);
>                 p += address_len;
>
>                 if (size_len == 8)
> -                       *(fdt64_t *)p = cpu_to_fdt64(size[i]);
> +                       cell = cpu_to_fdt64(size[i]);
>                 else
> -                       *(fdt32_t *)p = cpu_to_fdt32(size[i]);
> +                       cell = cpu_to_fdt32(size[i]);
> +               memcpy(p, &cell, size_len);

What will this do with 32-bit values? Aren't use assuming that the
first 32-bit word of 'cell' will contain the least significant 32
bits? Is that always true? I'm not quite sure.

Also I really thing this needs a test. It's a pretty simple function
so a unit test would be easy to write.

>                 p += size_len;
>         }

Regards,
Simon