On Sun, May 12, 2019 at 7:39 PM Hsin-Yi Wang hsinyi@chromium.org wrote:
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
change log: v1->v2:
- call function in early_init_dt_scan_chosen
- will add doc to devicetree-org/dt-schema on github if this is accepted
Documentation/devicetree/bindings/chosen.txt | 14 ++++++++++++++ drivers/of/fdt.c | 11 +++++++++++ 2 files changed, 25 insertions(+)
diff --git a/Documentation/devicetree/bindings/chosen.txt b/Documentation/devicetree/bindings/chosen.txt index 45e79172a646..fef5c82672dc 100644 --- a/Documentation/devicetree/bindings/chosen.txt +++ b/Documentation/devicetree/bindings/chosen.txt @@ -28,6 +28,20 @@ mode) when EFI_RNG_PROTOCOL is supported, it will be overwritten by the Linux EFI stub (which will populate the property itself, using EFI_RNG_PROTOCOL).
+rng-seed +-----------
+This property served as an entropy to add device randomness. It is parsed +as a byte array, e.g.
+/ {
chosen {rng-seed = <0x31 0x95 0x1b 0x3c 0xc9 0xfa 0xb3 ...>;};+};
+This random value should be provided by bootloader.
stdout-path
diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c index de893c9616a1..96ea5eba9dd5 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> @@ -1079,6 +1080,7 @@ 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);@@ -1113,6 +1115,15 @@ 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)return 1;
This only works if this hunk stays at the end of the function. I'd invert the if and move the next 2 functions under it.
/* try to clear seed so it won't be found. */fdt_nop_property(initial_boot_params, node, "rng-seed");
I'd just delete the property.
Also, what about kexec? Don't you need to add a new seed?
add_device_randomness(rng_seed, l);/* break now */ return 1;}
2.20.1