1 files changed, 81 insertions, 0 deletions
diff --git a/cmd/kaslrseed.c b/cmd/kaslrseed.c
new file mode 100644
index 0000000..8a1d812
--- /dev/null
+++ b/cmd/kaslrseed.c
@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * The 'kaslrseed' command takes bytes from the hardware random number
+ * generator and uses them to set the kaslr-seed value in the chosen node.
+ *
+ * Copyright (c) 2021, Chris Morgan <macromorgan@hotmail.com>
+ */
+
+#include <common.h>
+#include <command.h>
+#include <dm.h>
+#include <hexdump.h>
+#include <malloc.h>
+#include <rng.h>
+#include <fdt_support.h>
+
+static int do_kaslr_seed(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
+{
+	size_t n = 0x8;
+	struct udevice *dev;
+	u64 *buf;
+	int nodeoffset;
+	int ret = CMD_RET_SUCCESS;
+
+	if (uclass_get_device(UCLASS_RNG, 0, &dev) || !dev) {
+		printf("No RNG device\n");
+		return CMD_RET_FAILURE;
+	}
+
+	buf = malloc(n);
+	if (!buf) {
+		printf("Out of memory\n");
+		return CMD_RET_FAILURE;
+	}
+
+	if (dm_rng_read(dev, buf, n)) {
+		printf("Reading RNG failed\n");
+		return CMD_RET_FAILURE;
+	}
+
+	if (!working_fdt) {
+		printf("No FDT memory address configured. Please configure\n"
+		       "the FDT address via \"fdt addr <address>\" command.\n"
+		       "Aborting!\n");
+		return CMD_RET_FAILURE;
+	}
+
+	ret = fdt_check_header(working_fdt);
+	if (ret < 0) {
+		printf("fdt_chosen: %s\n", fdt_strerror(ret));
+		return CMD_RET_FAILURE;
+	}
+
+	nodeoffset = fdt_find_or_add_subnode(working_fdt, 0, "chosen");
+	if (nodeoffset < 0) {
+		printf("Reading chosen node failed\n");
+		return CMD_RET_FAILURE;
+	}
+
+	ret = fdt_setprop(working_fdt, nodeoffset, "kaslr-seed", buf, sizeof(buf));
+	if (ret < 0) {
+		printf("Unable to set kaslr-seed on chosen node: %s\n", fdt_strerror(ret));
+		return CMD_RET_FAILURE;
+	}
+
+	free(buf);
+
+	return ret;
+}
+
+#ifdef CONFIG_SYS_LONGHELP
+static char kaslrseed_help_text[] =
+	"[n]\n"
+	"  - append random bytes to chosen kaslr-seed node\n";
+#endif
+
+U_BOOT_CMD(
+	kaslrseed, 1, 0, do_kaslr_seed,
+	"feed bytes from the hardware random number generator to the kaslr-seed",
+	kaslrseed_help_text
+);