Re: [PATCH] hw/arm/virt: Add DT property /secure-chosen/kaslr-seed

[Peter Maydell]

On Fri, 17 Apr 2020 at 13:01, Pavel Dovgalyuk <address@hidden> wrote:
>
>
> On 17.04.2020 13:18, Peter Maydell wrote:
> > On Fri, 10 Apr 2020 at 18:02, Jerome Forissier <address@hidden> wrote:
> >> This commit generates a random seed to be used by the secure OS for
> >> ASLR when the machine is secure. The seed is a 64-bit random value
> >> exported via the DT in /secure-chosen/kaslr-seed. This interface is
> >> used by OP-TEE [1].
> >>
> >> [1] https://github.com/OP-TEE/optee_os/commit/ef262691fe0e
> > The kernel devicetree documentation documents this as a generic
> > property of /chosen -- should we be providing a /chosen/kaslr-seed
> > too ?
> >
> >> Signed-off-by: Jerome Forissier <address@hidden>
> >> ---
> >> +static void create_secure_kaslr_seed(VirtMachineState *vms)
> >> +{
> >> +    Error *err = NULL;
> >> +    uint64_t seed;
> >> +
> >> +    if (qcrypto_random_bytes(&seed, sizeof(seed), &err)) {
> >> +        error_free(err);
> >> +        return;
> >> +    }
> > Since this is exposed to the guest I'm wondering if we should
> > use qemu_guest_getrandom() (which lets you make the randomness
> > deterministic for the benefit of record-and-replay). But I'm
> > not sure if that function is usable before the guest has even
> > started running. Pavel, could you answer that?
>
> Yes, usage of deterministic functions is possible before machine is running,
>
> because replay_configure is executed before machine initialization.

Great, thanks. Sonuds like we should use qemu_guest_getrandom() then.

-- PMM