arm: re-randomize rng-seed on reboot

When the system reboots, the rng-seed that the FDT has should be
re-randomized, so that the new boot gets a new seed. Since the FDT is in
the ROM region at this point, we add a hook right after the ROM has been
added, so that we have a pointer to that copy of the FDT.

Cc: Peter Maydell <peter.maydell@linaro.org>
Cc: qemu-arm@nongnu.org
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Message-id: 20221025004327.568476-5-Jason@zx2c4.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/arm/boot.c

@@ -683,6 +683,8 @@ int arm_load_dtb(hwaddr addr, const struct arm_boot_info *binfo,
      * the DTB is copied again upon reset, even if addr points into RAM.
      */
     rom_add_blob_fixed_as("dtb", fdt, size, addr, as);
+    qemu_register_reset_nosnapshotload(qemu_fdt_randomize_seeds,
+                                       rom_ptr_for_as(as, addr, size));
 
     g_free(fdt);