From 6d7f5424b67e29bccea95708a835d0709294fa7d Mon Sep 17 00:00:00 2001
From: Jose Quaresma <jose.quaresma@foundries.io>
Date: Mon, 26 Sep 2022 11:56:13 +0000
Subject: [PATCH] [WIP] base: linux-lmp: build the kernel with clang

- Tested only on v90 main-next

Signed-off-by: Jose Quaresma <jose.quaresma@foundries.io>
---
 .../recipes-kernel/linux/linux-lmp-clang.inc  | 25 +++++++++++++++++++
 .../recipes-kernel/linux/linux-lmp.inc        |  2 ++
 2 files changed, 27 insertions(+)
 create mode 100644 meta-lmp-base/recipes-kernel/linux/linux-lmp-clang.inc

diff --git a/meta-lmp-base/recipes-kernel/linux/linux-lmp-clang.inc b/meta-lmp-base/recipes-kernel/linux/linux-lmp-clang.inc
new file mode 100644
index 0000000000..6f68d28372
--- /dev/null
+++ b/meta-lmp-base/recipes-kernel/linux/linux-lmp-clang.inc
@@ -0,0 +1,25 @@
+# https://github.com/kraj/meta-clang#kernel-build-with-clang
+
+TOOLCHAIN:forcevariable = "clang"
+
+DEPENDS:append:toolchain-clang = " clang-cross-${TARGET_ARCH}"
+KERNEL_CC:toolchain-clang = "${CCACHE}clang ${HOST_CC_KERNEL_ARCH} ${DEBUG_PREFIX_MAP} -fdebug-prefix-map=${STAGING_KERNEL_DIR}=${KERNEL_SRC_PATH}"
+KERNEL_LD:toolchain-clang = "${CCACHE}ld.lld"
+KERNEL_AR:toolchain-clang = "${CCACHE}llvm-ar"
+
+# FIXME: hacks
+do_kernel_configcheck[noexec] = "1"
+
+# error: taking address of packed member 'xxx' of class or structure 'yyy' may result in an unaligned pointer value [-Werror,-Waddress-of-packed-member]
+# because kernel don't use CFLAGS we need to pass it over EXTRA_OEMAKE
+EXTRA_OEMAKE += 'CFLAGS="-Wno-address-of-packed-member"'
+
+# explicitly enable LLVM
+# https://docs.kernel.org/kbuild/llvm.html
+KERNEL_EXTRA_ARGS += "LLVM=1"
+
+# verbose build
+#KERNEL_EXTRA_ARGS += "V=1"
+
+# disable pararel make
+#PARALLEL_MAKE = "-j1"
diff --git a/meta-lmp-base/recipes-kernel/linux/linux-lmp.inc b/meta-lmp-base/recipes-kernel/linux/linux-lmp.inc
index 080bcc5de2..93a164e924 100644
--- a/meta-lmp-base/recipes-kernel/linux/linux-lmp.inc
+++ b/meta-lmp-base/recipes-kernel/linux/linux-lmp.inc
@@ -26,3 +26,5 @@ do_deploy:append() {
     cp -a ${B}/.config ${DEPLOYDIR}/${KERNEL_CONFIG_NAME}
     ln -sf ${KERNEL_CONFIG_NAME} ${DEPLOYDIR}/${KERNEL_CONFIG_LINK_NAME}
 }
+
+require linux-lmp-clang.inc