[RFC PATCH 2/4] scripts/Makefile.lib: Embed capsule public key in platform's dtb

[Sughosh Ganu]

The EFI capsule authentication logic in u-boot expects the public key
in the form of an EFI Signature List(ESL) to be provided as part of
the platform's dtb. Currently, the embedding of the ESL file into the
dtb needs to be done manually.

Add a target for generating a dtsi file which contains the signature
node with the ESL file included as a property under the signature
node. Include the dtsi file in the dtb. This brings the embedding of
the ESL in the dtb into the U-Boot build flow.

The path to the ESL file is specified through the
CONFIG_EFI_CAPSULE_ESL_FILE symbol.

Signed-off-by: Sughosh Ganu <sughosh.ganu at linaro.org>
---
 lib/efi_loader/Kconfig             |  9 +++++++++
 lib/efi_loader/capsule_esl.dtsi.in | 11 +++++++++++
 scripts/Makefile.lib               | 17 +++++++++++++++++
 3 files changed, 37 insertions(+)
 create mode 100644 lib/efi_loader/capsule_esl.dtsi.in

diff --git a/lib/efi_loader/Kconfig b/lib/efi_loader/Kconfig
index 9989e3f384..f40a62a0ba 100644
--- a/lib/efi_loader/Kconfig
+++ b/lib/efi_loader/Kconfig
@@ -272,6 +272,15 @@ config EFI_CAPSULE_MAX
 	  Select the max capsule index value used for capsule report
 	  variables. This value is used to create CapsuleMax variable.
 
+config EFI_CAPSULE_ESL_FILE
+	string "Path to the EFI Signature List File"
+	default ""
+	depends on EFI_CAPSULE_AUTHENTICATE
+	help
+	  Provides the path to the EFI Signature List file which will
+	  be embedded in the platform's device tree and used for
+	  capsule authentication at the time of capsule update.
+
 config EFI_DEVICE_PATH_TO_TEXT
 	bool "Device path to text protocol"
 	default y
diff --git a/lib/efi_loader/capsule_esl.dtsi.in b/lib/efi_loader/capsule_esl.dtsi.in
new file mode 100644
index 0000000000..61a9f2b25e
--- /dev/null
+++ b/lib/efi_loader/capsule_esl.dtsi.in
@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: GPL-2.0+
+/**
+ * Devicetree file with the public key EFI Signature List(ESL)
+ * node. This file is used to generate the dtsi file to be
+ * included into the DTB.
+*/
+/ {
+	signature {
+		capsule-key = /incbin/("ESL_BIN_FILE");
+	};
+};
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index f41b16781d..cf4eef0b05 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -334,8 +334,25 @@ cmd_dtc = mkdir -p $(dir ${dtc-tmp}) ; \
 		; \
 	sed "s:$(pre-tmp):$(<):" $(depfile).pre.tmp $(depfile).dtc.tmp > $(depfile)
 
+ifdef CONFIG_EFI_CAPSULE_AUTHENTICATE
+quiet_cmd_capsule_esl_gen = CAPSULE_ESL_GEN $@
+cmd_capsule_esl_gen = \
+	$(shell sed "s:ESL_BIN_FILE:$(capsule_esl_path):" $(capsule_esl_input_file) > $@)
+
+$(obj)/.capsule_esl.dtsi:
+	$(call cmd_capsule_esl_gen)
+
+capsule_esl_input_file=$(srctree)/lib/efi_loader/capsule_esl.dtsi.in
+capsule_esl_dtsi = .capsule_esl.dtsi
+capsule_esl_path=$(abspath $(srctree)/$(subst $(quote),,$(CONFIG_EFI_CAPSULE_ESL_FILE)))
+include_files += $(capsule_esl_dtsi)
+
+$(obj)/%.dtb: $(src)/%.dts $(DTC) $(obj)/.capsule_esl.dtsi FORCE
+	$(call if_changed_dep,dtc)
+else
 $(obj)/%.dtb: $(src)/%.dts $(DTC) FORCE
 	$(call if_changed_dep,dtc)
+endif
 
 pre-tmp = $(subst $(comma),_,$(dot-target).pre.tmp)
 dtc-tmp = $(subst $(comma),_,$(dot-target).dts.tmp)
-- 
2.34.1