From 280812bec8d2885ef259aa7a9130393a7281f55e Mon Sep 17 00:00:00 2001
From: Elliot Berman <eberman@codeaurora.org>
Date: Fri, 24 Jul 2020 18:12:48 -0700
Subject: [PATCH] ANDROID: kbuild: Add support for installing out-of-tree
 kernel headers

Add support for installing out-of-tree kernel headers. The
"headers_install" target was copied to the external module compilation
section (lines 1245:1270), and the src/obj variables were tweaked to
include $(KBUILD_EXTMODULE).

Bug: 162332589
Change-Id: I2e2c7598612bea94267e6a9bc6d0793da53915ac
Signed-off-by: Elliot Berman <eberman@codeaurora.org>
---
 Documentation/kbuild/modules.rst | 16 ++++++++
 Makefile                         | 64 ++++++++++++++++++--------------
 2 files changed, 53 insertions(+), 27 deletions(-)

diff --git a/Documentation/kbuild/modules.rst b/Documentation/kbuild/modules.rst
index 85ccc878895e..d4b3e0c1d9fb 100644
--- a/Documentation/kbuild/modules.rst
+++ b/Documentation/kbuild/modules.rst
@@ -21,6 +21,7 @@ This document describes how to build an out-of-tree kernel module.
 	   --- 4.1 Kernel Includes
 	   --- 4.2 Single Subdirectory
 	   --- 4.3 Several Subdirectories
+	   --- 4.4 UAPI Headers Installation
 	=== 5. Module Installation
 	   --- 5.1 INSTALL_MOD_PATH
 	   --- 5.2 INSTALL_MOD_DIR
@@ -131,6 +132,10 @@ executed to make module versioning work.
 		/lib/modules/<kernel_release>/extra/, but a prefix may
 		be added with INSTALL_MOD_PATH (discussed in section 5).
 
+	headers_install
+		Export headers in a format suitable for userspace. The default
+		location is $PWD/usr. INSTALL_HDR_PATH can change this path.
+
 	clean
 		Remove all generated files in the module directory only.
 
@@ -406,6 +411,17 @@ according to the following rule:
 	pointing to the directory where the currently executing kbuild
 	file is located.
 
+4.4 UAPI Headers Installation
+-----------------------------
+
+	External modules may export headers to userspace in a similar
+	fashion to the in-tree counterpart drivers. kbuild supports
+	running headers_install target in an out-of-tree. The location
+	where kbuild searches for headers is $(M)/include/uapi and
+	$(M)/arch/$(SRCARCH)/include/uapi.
+
+	See also Documentation/kbuild/headers_install.rst.
+
 
 5. Module Installation
 ======================
diff --git a/Makefile b/Makefile
index 8e13dda19c87..effb910aa8ef 100644
--- a/Makefile
+++ b/Makefile
@@ -1073,6 +1073,41 @@ PHONY += prepare0
 export MODORDER := $(extmod-prefix)modules.order
 export MODULES_NSDEPS := $(extmod-prefix)modules.nsdeps
 
+# ---------------------------------------------------------------------------
+# Kernel headers
+
+PHONY += headers
+
+#Default location for installed headers
+ifeq ($(KBUILD_EXTMOD),)
+PHONY += archheaders archscripts
+hdr-inst := -f $(srctree)/scripts/Makefile.headersinst obj
+headers: $(version_h) scripts_unifdef uapi-asm-generic archheaders archscripts
+else
+hdr-prefix = $(KBUILD_EXTMOD)/
+hdr-inst := -f $(srctree)/scripts/Makefile.headersinst dst=$(KBUILD_EXTMOD)/usr/include objtree=$(objtree)/$(KBUILD_EXTMOD) obj
+endif
+
+export INSTALL_HDR_PATH = $(objtree)/$(hdr-prefix)usr
+
+quiet_cmd_headers_install = INSTALL $(INSTALL_HDR_PATH)/include
+      cmd_headers_install = \
+	mkdir -p $(INSTALL_HDR_PATH); \
+	rsync -mrl --include='*/' --include='*\.h' --exclude='*' \
+	usr/include $(INSTALL_HDR_PATH)
+
+PHONY += headers_install
+headers_install: headers
+	$(call cmd,headers_install)
+
+headers:
+ifeq ($(KBUILD_EXTMOD),)
+	$(if $(wildcard $(srctree)/arch/$(SRCARCH)/include/uapi/asm/Kbuild),, \
+	  $(error Headers not exportable for the $(SRCARCH) architecture))
+endif
+	$(Q)$(MAKE) $(hdr-inst)=$(hdr-prefix)include/uapi
+	$(Q)$(MAKE) $(hdr-inst)=$(hdr-prefix)arch/$(SRCARCH)/include/uapi
+
 ifeq ($(KBUILD_EXTMOD),)
 core-y		+= kernel/ certs/ mm/ fs/ ipc/ security/ crypto/ block/
 
@@ -1242,33 +1277,6 @@ headerdep:
 	$(Q)find $(srctree)/include/ -name '*.h' | xargs --max-args 1 \
 	$(srctree)/scripts/headerdep.pl -I$(srctree)/include
 
-# ---------------------------------------------------------------------------
-# Kernel headers
-
-#Default location for installed headers
-export INSTALL_HDR_PATH = $(objtree)/usr
-
-quiet_cmd_headers_install = INSTALL $(INSTALL_HDR_PATH)/include
-      cmd_headers_install = \
-	mkdir -p $(INSTALL_HDR_PATH); \
-	rsync -mrl --include='*/' --include='*\.h' --exclude='*' \
-	usr/include $(INSTALL_HDR_PATH)
-
-PHONY += headers_install
-headers_install: headers
-	$(call cmd,headers_install)
-
-PHONY += archheaders archscripts
-
-hdr-inst := -f $(srctree)/scripts/Makefile.headersinst obj
-
-PHONY += headers
-headers: $(version_h) scripts_unifdef uapi-asm-generic archheaders archscripts
-	$(if $(wildcard $(srctree)/arch/$(SRCARCH)/include/uapi/asm/Kbuild),, \
-	  $(error Headers not exportable for the $(SRCARCH) architecture))
-	$(Q)$(MAKE) $(hdr-inst)=include/uapi
-	$(Q)$(MAKE) $(hdr-inst)=arch/$(SRCARCH)/include/uapi
-
 # Deprecated. It is no-op now.
 PHONY += headers_check
 headers_check:
@@ -1701,6 +1709,8 @@ help:
 	@echo  ''
 	@echo  '  modules         - default target, build the module(s)'
 	@echo  '  modules_install - install the module'
+	@echo  '  headers_install - Install sanitised kernel headers to INSTALL_HDR_PATH'
+	@echo  '                    (default: $(abspath $(INSTALL_HDR_PATH)))'
 	@echo  '  clean           - remove generated files in module directory only'
 	@echo  ''