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Subject[PATCH v6 2/3] fdt: add support for rng-seed
Date
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.

Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
---
change log v5->v6:
* remove Documentation change
---
drivers/of/fdt.c | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 3d36b5afd9bd..369130dbd42c 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>
@@ -1052,6 +1053,7 @@ 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);

@@ -1086,6 +1088,14 @@ 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;
}
--
2.20.1
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