arm64: kexec_file: add rng-seed support

Adding "rng-seed" to dtb. It's fine to add this property if original
fdt doesn't contain it. Since original seed will be wiped after
read, so use a default size 128 bytes here.

Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
index 5887133..81b5baa 100644 (file)
--- a/arch/arm64/kernel/machine_kexec_file.c
+++ b/arch/arm64/kernel/machine_kexec_file.c
@@ -27,6 +27,8 @@
 #define FDT_PROP_INITRD_END    "linux,initrd-end"
 #define FDT_PROP_BOOTARGS      "bootargs"
 #define FDT_PROP_KASLR_SEED    "kaslr-seed"
+#define FDT_PROP_RNG_SEED      "rng-seed"
+#define RNG_SEED_SIZE          128
 
 const struct kexec_file_ops * const kexec_file_loaders[] = {
        &kexec_image_ops,
@@ -102,6 +104,19 @@ static int setup_dtb(struct kimage *image,
                                FDT_PROP_KASLR_SEED);
        }
 
+       /* add rng-seed */
+       if (rng_is_initialized()) {
+               u8 rng_seed[RNG_SEED_SIZE];
+               get_random_bytes(rng_seed, RNG_SEED_SIZE);
+               ret = fdt_setprop(dtb, off, FDT_PROP_RNG_SEED, rng_seed,
+                               RNG_SEED_SIZE);
+               if (ret)
+                       goto out;
+       } else {
+               pr_notice("RNG is not initialised: omitting \"%s\" property\n",
+                               FDT_PROP_RNG_SEED);
+       }
+
 out:
        if (ret)
                return (ret == -FDT_ERR_NOSPACE) ? -ENOMEM : -EINVAL;
@@ -110,7 +125,8 @@ out:
 }
 
 /*
- * More space needed so that we can add initrd, bootargs and kaslr-seed.
+ * More space needed so that we can add initrd, bootargs, kaslr-seed, and
+ * rng-seed.
  */
 #define DTB_EXTRA_SPACE 0x1000