[PATCH] Documentation: dt: chosen property for kaslr-seed

From: Kees Cook
Date: Fri Jul 14 2017 - 20:38:47 EST

Document then /chosen/kaslr-seed property (and its interaction with the

Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Documentation/devicetree/bindings/chosen.txt | 22 ++++++++++++++++++++--
1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/Documentation/devicetree/bindings/chosen.txt b/Documentation/devicetree/bindings/chosen.txt
index dee3f5d9df26..0cdb43b268e5 100644
--- a/Documentation/devicetree/bindings/chosen.txt
+++ b/Documentation/devicetree/bindings/chosen.txt
@@ -5,9 +5,27 @@ The chosen node does not represent a real device, but serves as a place
for passing data between firmware and the operating system, like boot
arguments. Data in the chosen node does not represent the hardware.

+The following properties are recognized:

-stdout-path property
+This property is used when booting with CONFIG_RANDOMIZE_BASE to seed
+the entropy used to randomize the kernel image base address location. It
+is parsed as a u64 value, e.g.
+/ {
+ chosen {
+ kaslr-seed = <0xfeedbeef 0xc0def00d>;
+ };
+Note that when booting through EFI when EFI_RNG_PROTOCOL is supported,
+this value will be overwritten by the EFI stub.

Device trees may specify the device to be used for boot console output
with a stdout-path property under /chosen, as described in the Devicetree

Kees Cook
Pixel Security