Re: [PATCH-for-6.1 1/3] hw/sd/sdcard: Document out-of-range addresses for SEND_WRITE_PROT

[Peter Maydell <peter.maydell@linaro.org>]

On Wed, 28 Jul 2021 at 19:18, Philippe Mathieu-Daudé <f4bug@amsat.org> wrote:
>
> Per the 'Physical Layer Simplified Specification Version 3.01',
> Table 4-22: 'Block Oriented Write Protection Commands'
>
>   SEND_WRITE_PROT (CMD30)
>
>   If the card provides write protection features, this command asks
>   the card to send the status of the write protection bits [1].
>
>   [1] 32 write protection bits (representing 32 write protect groups
>   starting at the specified address) [...]
>   The last (least significant) bit of the protection bits corresponds
>   to the first addressed group. If the addresses of the last groups
>   are outside the valid range, then the corresponding write protection
>   bits shall be set to 0.
>
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
>  hw/sd/sd.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/hw/sd/sd.c b/hw/sd/sd.c
> index 1f964e022b1..707dcc12a14 100644
> --- a/hw/sd/sd.c
> +++ b/hw/sd/sd.c
> @@ -822,7 +822,14 @@ static uint32_t sd_wpbits(SDState *sd, uint64_t addr)
>
>      for (i = 0; i < 32; i++, wpnum++, addr += WPGROUP_SIZE) {
>          assert(wpnum < sd->wpgrps_size);
> -        if (addr < sd->size && test_bit(wpnum, sd->wp_groups)) {
> +        if (addr >= sd->size) {
> +            /*
> +             * If the addresses of the last groups are outside the valid range,
> +             * then the corresponding write protection bits shall be set to 0.
> +             */
> +            continue;
> +        }
> +        if (test_bit(wpnum, sd->wp_groups)) {

Am I misreading it, or does this commit not actually change
the behaviour of the code ?

>              ret |= (1 << i);
>          }
>      }
> --
> 2.31.1

-- PMM