Re: [Qemu-devel] [PATCH 4/6] linux-user: Initialize aarch64 pac keys

[Richard Henderson]

On 2/1/19 7:11 AM, Peter Maydell wrote:
> On Fri, 25 Jan 2019 at 22:57, Richard Henderson
> <address@hidden> wrote:
>>
>> Initialize the keys to a non-zero value on process start.
>>
>> Signed-off-by: Richard Henderson <address@hidden>
> 
>> +static uint64_t arm_rand64(void)
>> +{
>> +    int shift = 64 - clz64(RAND_MAX);
>> +    int i, n = 64 / shift + (64 % shift != 0);
>> +    uint64_t ret = 0;
>> +
>> +    for (i = 0; i < n; i++) {
>> +        ret = (ret << shift) | rand();
>> +    }
>> +    return ret;
>> +}
> 
> I'm not a huge fan of the use of rand() here, but it's what
> we're using to initialize AT_RANDOM in linux-user, so I guess
> it's OK here. At some point we should investigate whether
> there's something better we are guaranteed to have available,
> I suppose. (Coverity gripes about use of rand().)

I considered implementing a qemu version of getentropy,
but then I saw our "-seed" option and thought perhaps
repeatability is more important for qemu.


r~