Re: [PATCH v4 02/11] device-tree: add re-randomization helper function

[Jason A. Donenfeld]

On Tue, Oct 25, 2022 at 3:30 PM Philippe Mathieu-Daudé
<philmd@linaro.org> wrote:
>
> On 25/10/22 02:43, Jason A. Donenfeld wrote:
> > When the system reboots, the rng-seed that the FDT has should be
> > re-randomized, so that the new boot gets a new seed. Several
> > architectures require this functionality, so export a function for
> > injecting a new seed into the given FDT.
> >
> > Cc: Alistair Francis <alistair.francis@wdc.com>
> > Cc: David Gibson <david@gibson.dropbear.id.au>
> > Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
> > ---
> >   include/sysemu/device_tree.h |  9 +++++++++
> >   softmmu/device_tree.c        | 21 +++++++++++++++++++++
> >   2 files changed, 30 insertions(+)
>
> > +void qemu_fdt_randomize_seeds(void *fdt)
> > +{
> > +    int noffset, poffset, len;
> > +    const char *name;
> > +    uint8_t *data;
> > +
> > +    for (noffset = fdt_next_node(fdt, 0, NULL);
> > +         noffset >= 0;
> > +         noffset = fdt_next_node(fdt, noffset, NULL)) {
> > +        for (poffset = fdt_first_property_offset(fdt, noffset);
> > +             poffset >= 0;
> > +             poffset = fdt_next_property_offset(fdt, poffset)) {
> > +            data = (uint8_t *)fdt_getprop_by_offset(fdt, poffset, &name, 
> > &len);
>
> Is this non-const cast is safe?

This is how the libfdt/fdt_rw.c helpers of libfdt do it, so I think so.

Jason