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

[Philippe Mathieu-Daudé]

On 8/2/21 2:00 PM, Peter Maydell wrote:
> 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 ?

Yes, I don't want to change the behaviour but document it
better.

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