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

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Date:   Fri, 14 Jul 2017 17:38:36 -0700
From:   Kees Cook <keescook@...omium.org>
To:     linux-kernel@...r.kernel.org
Cc:     devicetree@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Matt Redfearn <matt.redfearn@...tec.com>
Subject: [PATCH] Documentation: dt: chosen property for kaslr-seed

Document then /chosen/kaslr-seed property (and its interaction with the
EFI_RNG_PROTOCOL API).

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 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
---------------------
+
+kaslr-seed
+-----------
+
+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.
+
+stdout-path
+-----------
 
 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
-- 
2.7.4


-- 
Kees Cook
Pixel Security