[PATCH v8 2/3] fdt: add support for rng-seed - Hsin-Yi Wang

From: Hsin-Yi Wang <hsinyi@chromium.org>
To: linux-arm-kernel@lists.infradead.org
Cc: Mark Rutland <mark.rutland@arm.com>,
	devicetree@vger.kernel.org, Yu Zhao <yuzhao@google.com>,
	Kees Cook <keescook@chromium.org>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Stephen Boyd <swboyd@chromium.org>,
	Will Deacon <will.deacon@arm.com>,
	linux-kernel@vger.kernel.org, Mike Rapoport <rppt@linux.ibm.com>,
	Jun Yao <yaojun8558363@gmail.com>,
	Miles Chen <miles.chen@mediatek.com>,
	Rob Herring <robh+dt@kernel.org>,
	James Morse <james.morse@arm.com>,
	Hsin-Yi Wang <hsinyi@chromium.org>,
	Andrew Murray <andrew.murray@arm.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Laura Abbott <labbott@redhat.com>,
	Frank Rowand <frowand.list@gmail.com>,
	Robin Murphy <robin.murphy@arm.com>
Subject: [PATCH v8 2/3] fdt: add support for rng-seed
Date: Mon, 19 Aug 2019 15:16:04 +0800	[thread overview]
Message-ID: <20190819071602.139014-3-hsinyi@chromium.org> (raw)
In-Reply-To: <20190819071602.139014-1-hsinyi@chromium.org>

Introducing a chosen node, rng-seed, which is an entropy that can be
passed to kernel called very early to increase initial device
randomness. Bootloader should provide this entropy and the value is
read from /chosen/rng-seed in DT.

Obtain of_fdt_crc32 for CRC check after early_init_dt_scan_nodes(),
since early_init_dt_scan_chosen() would modify fdt to erase rng-seed.

Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Rob Herring <robh@kernel.org>
---
Change from v7:
obtain of_fdt_crc32 after early_init_dt_scan_nodes().
---
 drivers/of/fdt.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 9cdf14b9aaab..97a75996993c 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -24,6 +24,7 @@
 #include <linux/debugfs.h>
 #include <linux/serial_core.h>
 #include <linux/sysfs.h>
+#include <linux/random.h>
 
 #include <asm/setup.h>  /* for COMMAND_LINE_SIZE */
 #include <asm/page.h>
@@ -1044,6 +1045,7 @@ int __init early_init_dt_scan_chosen(unsigned long node, const char *uname,
 {
 	int l;
 	const char *p;
+	const void *rng_seed;
 
 	pr_debug("search \"chosen\", depth: %d, uname: %s\n", depth, uname);
 
@@ -1078,6 +1080,14 @@ int __init early_init_dt_scan_chosen(unsigned long node, const char *uname,
 
 	pr_debug("Command line is: %s\n", (char*)data);
 
+	rng_seed = of_get_flat_dt_prop(node, "rng-seed", &l);
+	if (rng_seed && l > 0) {
+		add_device_randomness(rng_seed, l);
+
+		/* try to clear seed so it won't be found. */
+		fdt_nop_property(initial_boot_params, node, "rng-seed");
+	}
+
 	/* break now */
 	return 1;
 }
@@ -1166,8 +1176,6 @@ bool __init early_init_dt_verify(void *params)
 
 	/* Setup flat device-tree pointer */
 	initial_boot_params = params;
-	of_fdt_crc32 = crc32_be(~0, initial_boot_params,
-				fdt_totalsize(initial_boot_params));
 	return true;
 }
 
@@ -1197,6 +1205,8 @@ bool __init early_init_dt_scan(void *params)
 		return false;
 
 	early_init_dt_scan_nodes();
+	of_fdt_crc32 = crc32_be(~0, initial_boot_params,
+				fdt_totalsize(initial_boot_params));
 	return true;
 }
 
-- 
2.20.1


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
