Hi Stephan,
On 18 August 2017 at 00:22, Stephan Mueller <smueller@xxxxxxxxxx> wrote:
> Am Donnerstag, 17. August 2017, 20:25:17 CEST schrieb PrasannaKumar
> Muralidharan:
>
> Hi PrasannaKumar,
>
>> +
>> +static int jz4780_rng_generate(struct crypto_rng *tfm,
>> + const u8 *src, unsigned int slen,
>> + u8 *dst, unsigned int dlen)
>> +{
>> + struct jz4780_rng_ctx *ctx = crypto_rng_ctx(tfm);
>> + struct jz4780_rng *rng = ctx->rng;
>> + u32 data;
>> +
>> + /*
>> + * JZ4780 Programmers manual says the RNG should not run continuously
>> + * for more than 1s. So enable RNG, read data and disable it.
>> + * NOTE: No issue was observed with MIPS creator CI20 board even when
>> + * RNG ran continuously for longer periods. This is just a precaution.
>> + *
>> + * A delay is required so that the current RNG data is not bit shifted
>> + * version of previous RNG data which could happen if random data is
>> + * read continuously from this device.
>> + */
>> + jz4780_rng_writel(rng, 1, REG_RNG_CTRL);
>> + do {
>> + data = jz4780_rng_readl(rng, REG_RNG_DATA);
>> + memcpy((void *)dst, (void *)&data, 4);
>
> How do you know that dst is a multiple of 4 bytes? When dlen is only 3, you
> overflow the buffer.
You are right. I initially used hw_random framework for this driver.
But later realised that PRNG driver should use crypto framework. When
I started using crypto I reused most of the code. This was because of
porting. Will change it and send next version.
>
>> + dlen -= 4;
>> + dst += 4;
>> + udelay(20);
>> + } while (dlen >= 4);
>> +
>> + if (dlen > 0) {
>> + data = jz4780_rng_readl(rng, REG_RNG_DATA);
>> + memcpy((void *)dst, (void *)&data, dlen);
>> + }
>> + jz4780_rng_writel(rng, 0, REG_RNG_CTRL);
>> +
>> + return 0;
>> +}
>
> Ciao
> Stephan
Thanks,
PrasannaKumar
