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

[Hsin-Yi Wang]

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 <hsi...@chromium.org>
Reviewed-by: Stephen Boyd <swb...@chromium.org>
Reviewed-by: Rob Herring <r...@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