From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hsin-Yi Wang Subject: [PATCH v5 2/3] fdt: add support for rng-seed Date: Mon, 27 May 2019 12:33:35 +0800 Message-ID: <20190527043336.112854-2-hsinyi@chromium.org> References: <20190527043336.112854-1-hsinyi@chromium.org> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20190527043336.112854-1-hsinyi@chromium.org> Sender: linux-kernel-owner@vger.kernel.org To: linux-arm-kernel@lists.infradead.org Cc: Rob Herring , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Frank Rowand , Catalin Marinas , Will Deacon , Andrew Morton , Mike Rapoport , Ard Biesheuvel , Miles Chen , Hsin-Yi Wang , James Morse , Andrew Murray , Mark Rutland , Jun Yao , Yu Zhao , Robin Murphy , Laura Abbott , Stephen Boyd , Kees Cook , Nicolas Boichat List-Id: devicetree@vger.kernel.org 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 --- change log v4->v5: * use fdt_nop_property() since property might not be wiped entirely if following entries are smaller than property length. --- Documentation/devicetree/bindings/chosen.txt | 14 ++++++++++++++ drivers/of/fdt.c | 10 ++++++++++ 2 files changed, 24 insertions(+) diff --git a/Documentation/devicetree/bindings/chosen.txt b/Documentation/devicetree/bindings/chosen.txt index 45e79172a646..678e81bc4383 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 serves 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..9d63330582bb 100644 --- a/drivers/of/fdt.c +++ b/drivers/of/fdt.c @@ -24,6 +24,7 @@ #include #include #include +#include #include /* for COMMAND_LINE_SIZE */ #include @@ -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 +1115,14 @@ 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