Backport buildroot patch to add BR2_LINUX_KERNEL_NEEDS_HOST_PAHOLE.

This config option permits indicating the Linux kernel needs pahole to be
compiled.
Thus, host-pahole will be built before the kernel.
This is mandatory when using CONFIG_DEBUG_INFO_BTF.

Signed-off-by: Francis Laniel <flaniel@microsoft.com>

Makefile

@@ -294,6 +294,9 @@ minikube-iso-%: deploy/iso/minikube-iso/board/minikube/%/rootfs-overlay/usr/bin/
 		perl -pi -e 's@\s+source "package/sysdig/Config\.in"\n@@;' $(BUILD_DIR)/buildroot/package/Config.in; \
 		rm -r $(BUILD_DIR)/buildroot/package/sysdig; \
 		cp deploy/iso/minikube-iso/go.hash $(BUILD_DIR)/buildroot/package/go/go.hash; \
+		git --git-dir=$(BUILD_DIR)/buildroot/.git config user.email "dev@random.com"; \
+		git --git-dir=$(BUILD_DIR)/buildroot/.git config user.name "Random developer"; \
+		git --git-dir=$(BUILD_DIR)/buildroot/.git --work-tree=$(BUILD_DIR)/buildroot am ../../deploy/iso/minikube-iso/0001-linux-add-BR2_LINUX_KERNEL_NEEDS_HOST_PAHOLE.patch; \
 	fi;
 	$(MAKE) -C $(BUILD_DIR)/buildroot $(BUILDROOT_OPTIONS) O=$(BUILD_DIR)/buildroot/output-$* minikube_$*_defconfig
 	$(MAKE) -C $(BUILD_DIR)/buildroot $(BUILDROOT_OPTIONS) O=$(BUILD_DIR)/buildroot/output-$* host-python

deploy/iso/minikube-iso/0001-linux-add-BR2_LINUX_KERNEL_NEEDS_HOST_PAHOLE.patch

@@ -0,0 +1,72 @@
+From 2da2f359dba50aafef1202edda34374d99b77a14 Mon Sep 17 00:00:00 2001
+From: Francis Laniel <flaniel@linux.microsoft.com>
+Date: Wed, 22 Dec 2021 18:49:05 +0100
+Subject: [PATCH] linux: add BR2_LINUX_KERNEL_NEEDS_HOST_PAHOLE
+
+CONFIG_DEBUG_BTF_INFO relies on pahole, so kernel DWARF are converted to BTF.
+If CONFIG_DEBUG_BTF_INFO is set and BR2_LINUX_KERNEL_NEEDS_HOST_PAHOLE not,
+an error message is shown and .config is not written.
+
+Signed-off-by: Francis Laniel <flaniel@linux.microsoft.com>
+Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
+---
+ linux/Config.in | 12 ++++++++++++
+ linux/linux.mk  | 12 ++++++++++++
+ 2 files changed, 24 insertions(+)
+
+diff --git a/linux/Config.in b/linux/Config.in
+index 891e2cdcb6..582f37ba7c 100644
+--- a/linux/Config.in
++++ b/linux/Config.in
+@@ -470,6 +470,18 @@ config BR2_LINUX_KERNEL_NEEDS_HOST_LIBELF
+ 	  CONFIG_UNWINDER_ORC=y, please install libelf-dev,
+ 	  libelf-devel or elfutils-libelf-devel".
+
++config BR2_LINUX_KERNEL_NEEDS_HOST_PAHOLE
++	bool "Needs host pahole"
++	help
++	  Some Linux kernel configuration options (such as
++	  CONFIG_DEBUG_INFO_BTF) require building a host program
++	  called pahole. Enabling this option will ensure host-pahole
++	  gets built before the Linux kernel.
++
++	  Enable this option if you get a Linux kernel build failure
++	  such as "BTF: .tmp_vmlinux.btf: pahole (pahole) is not
++	  available".
++
+ # Linux extensions
+ source "linux/Config.ext.in"
+
+diff --git a/linux/linux.mk b/linux/linux.mk
+index 61fdc0c76c..dd2eebd446 100644
+--- a/linux/linux.mk
++++ b/linux/linux.mk
+@@ -114,6 +114,17 @@ ifeq ($(BR2_LINUX_KERNEL_NEEDS_HOST_LIBELF),y)
+ LINUX_DEPENDENCIES += host-elfutils host-pkgconf
+ endif
+
++ifeq ($(BR2_LINUX_KERNEL_NEEDS_HOST_PAHOLE),y)
++LINUX_DEPENDENCIES += host-pahole
++else
++define LINUX_FIXUP_CONFIG_PAHOLE_CHECK
++	if grep -q "^CONFIG_DEBUG_INFO_BTF=y" $(KCONFIG_DOT_CONFIG); then \
++		echo "To use CONFIG_DEBUG_INFO_BTF, enable host-pahole (BR2_LINUX_KERNEL_NEEDS_HOST_PAHOLE)" 1>&2; \
++		exit 1; \
++	fi
++endef
++endif
++
+ # If host-uboot-tools is selected by the user, assume it is needed to
+ # create a custom image
+ ifeq ($(BR2_PACKAGE_HOST_UBOOT_TOOLS),y)
+@@ -324,6 +335,7 @@ define LINUX_KCONFIG_FIXUP_CMDS
+ 		$(call KCONFIG_DISABLE_OPT,$(opt))
+ 	)
+ 	$(LINUX_FIXUP_CONFIG_ENDIANNESS)
++	$(LINUX_FIXUP_CONFIG_PAHOLE_CHECK)
+ 	$(if $(BR2_arm)$(BR2_armeb),
+ 		$(call KCONFIG_ENABLE_OPT,CONFIG_AEABI))
+ 	$(if $(BR2_powerpc)$(BR2_powerpc64)$(BR2_powerpc64le),
+-- 
+2.25.1
+