kernel: add a Makefile DEBUG variable and a kernel_config for debugging

Signed-off-by: David Sheets <dsheets@docker.com>

alpine/kernel/Dockerfile

@@ -2,6 +2,7 @@ FROM ubuntu:15.10
 
 ARG KERNEL_VERSION=4.4.17
 ARG ARCH=x86_64
+ARG DEBUG=0
 
 ENV KERNEL_SOURCE=https://www.kernel.org/pub/linux/kernel/v4.x/linux-${KERNEL_VERSION}.tar.xz
 
@@ -59,6 +60,11 @@ RUN git clone -b "$AUFS_BRANCH" "$AUFS_REPO" /aufs && \
 
 COPY kernel_config.x86_64 /linux/arch/x86/configs/x86_64_defconfig
 COPY kernel_config.arm /linux/arch/arm/configs/versatile_defconfig
+COPY kernel_config.debug /linux/debug_config
+
+RUN if [ $DEBUG -ne "0" ]; then \
+    cat /linux/debug_config >> /linux/arch/x86/configs/x86_64_defconfig; \
+    fi
 
 # Apply local patches
 COPY patches /patches

alpine/kernel/Makefile

@@ -1,10 +1,12 @@
 ARCH ?= x86_64
+DEBUG ?= 0
 
 all:	$(ARCH)/vmlinuz64
 
 $(ARCH)/mobykernel-build: Dockerfile kernel_config.$(ARCH)
 	mkdir -p $(ARCH) && \
-	docker build --build-arg ARCH=$(ARCH) -t mobykernel-$(ARCH):build .
+	docker build --build-arg ARCH=$(ARCH) --build-arg DEBUG=$(DEBUG) \
+		-t mobykernel-$(ARCH):build .
 	touch $@
 
 $(ARCH)/aufs-utils.tar $(ARCH)/kernel-source-info $(ARCH)/kernel-patches.tar $(ARCH)/kernel-modules.tar: $(ARCH)/mobykernel-build

alpine/kernel/kernel_config.debug

@@ -0,0 +1,25 @@
+
+
+## MOBY DEBUG OPTIONS ##
+
+CONFIG_LOCKDEP=y
+CONFIG_DEBUG_INFO=y
+CONFIG_FRAME_POINTER=y
+CONFIG_LOCKUP_DETECTOR=y
+CONFIG_DETECT_HUNG_TASK=y
+CONFIG_DEBUG_TIMEKEEPING=y
+CONFIG_DEBUG_RT_MUTEXES=y
+CONFIG_DEBUG_SPINLOCK=y
+CONFIG_DEBUG_MUTEXES=y
+CONFIG_DEBUG_WW_MUTEX_SLOWPATH=y
+CONFIG_DEBUG_LOCK_ALLOC=y
+CONFIG_PROVE_LOCKING=y
+CONFIG_LOCK_STAT=y
+CONFIG_DEBUG_ATOMIC_SLEEP=y
+CONFIG_DEBUG_LIST=y
+CONFIG_DEBUG_NOTIFIERS=y
+CONFIG_PROVE_RCU=y
+CONFIG_RCU_TRACE=y
+CONFIG_KGDB=y
+CONFIG_KGDB_SERIAL_CONSOLE=y
+CONFIG_KGDBOC=y