Re: [PATCH v2 1/8] device-tree: add re-randomization helper function

[Alistair Francis]

On Wed, Oct 12, 2022 at 6:57 AM Jason A. Donenfeld <Jason@zx2c4.com> 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>

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>

Alistair

> ---
>  include/sysemu/device_tree.h |  9 +++++++++
>  softmmu/device_tree.c        | 21 +++++++++++++++++++++
>  2 files changed, 30 insertions(+)
>
> diff --git a/include/sysemu/device_tree.h b/include/sysemu/device_tree.h
> index ef060a9759..d552f324b6 100644
> --- a/include/sysemu/device_tree.h
> +++ b/include/sysemu/device_tree.h
> @@ -196,6 +196,15 @@ int qemu_fdt_setprop_sized_cells_from_array(void *fdt,
>                                                  qdt_tmp);                 \
>      })
>
> +
> +/**
> + * qemu_fdt_randomize_seeds:
> + * @fdt: device tree blob
> + *
> + * Re-randomize all "rng-seed" properties with new seeds.
> + */
> +void qemu_fdt_randomize_seeds(void *fdt);
> +
>  #define FDT_PCI_RANGE_RELOCATABLE          0x80000000
>  #define FDT_PCI_RANGE_PREFETCHABLE         0x40000000
>  #define FDT_PCI_RANGE_ALIASED              0x20000000
> diff --git a/softmmu/device_tree.c b/softmmu/device_tree.c
> index 6ca3fad285..d986c7b7b3 100644
> --- a/softmmu/device_tree.c
> +++ b/softmmu/device_tree.c
> @@ -22,6 +22,7 @@
>  #include "qemu/option.h"
>  #include "qemu/bswap.h"
>  #include "qemu/cutils.h"
> +#include "qemu/guest-random.h"
>  #include "sysemu/device_tree.h"
>  #include "hw/loader.h"
>  #include "hw/boards.h"
> @@ -643,3 +644,23 @@ out:
>      g_free(propcells);
>      return ret;
>  }
> +
> +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);
> +            if (!data || strcmp(name, "rng-seed"))
> +                continue;
> +            qemu_guest_getrandom_nofail(data, len);
> +        }
> +    }
> +}
> --
> 2.37.3
>
>