Regenerate DTB if QEMU_BIN changes

Author: gsingh93

Makefile

@@ -409,6 +409,11 @@ TRUSTY_KERNEL_IMAGE := $(TRUSTY_OUT)/linux-build/arch/arm64/boot/Image
 
 QEMU_BRANCH := stable-7.2
 
+ifeq ($(TRUSTY),1)
+  # Trusty needs to use its own build of QEMU which has some custom patches
+  QEMU_BIN ?= $(TRUSTY_OUT)/qemu-build/aarch64-softmmu/qemu-system-aarch64
+endif
+
 ATF_DIR := $(TRUSTY_OUT)/atf/qemu/debug
 ATF_BL1 := $(ATF_DIR)/bl1.bin
 ATF_BL33 := $(ATF_DIR)/bl33.bin
@@ -496,13 +501,21 @@ ANDROID_DTB := $(OUT_DIR)/android.dtb
 QEMU_DTB := $(OUT_DIR)/qemu.dtb
 QEMU_DTS := $(OUT_DIR)/qemu.dts
 
+# We use DUMPING_DTB to avoid infinite recursion
+DUMPING_DTB := 0
+
+# We depend on QEMU_BIN because it's best if we generate this every time (as it
+# the DTB can change if run with a different version QEMU and we want to make
+# sure it exactly matches the DTB for the current QEMU binary being used)
 .PHONY: android-dtb
 android-dtb $(ANDROID_DTB):
 ifneq ($(ARCH),arm64)
     $(error android-dtb is only supported from arm64)
 endif
 
-	QEMU_EXTRA_ARGS="-M dumpdtb=$(QEMU_DTB)" $(MAKE) run
+# DUMPING_DTB=1 prevents infinite recursion. It must be set as a `make` argument,
+# not an environment variable
+	QEMU_EXTRA_ARGS="-M dumpdtb=$(QEMU_DTB)" $(MAKE) run DUMPING_DTB=1
 	$(DTC) -I dtb -O dts $(QEMU_DTB) > $(QEMU_DTS)
 	cat $(QEMU_DTS) $(ATF_DIR)/firmware.android.dts > $(ANDROID_DTS)
 	$(DTC) -I dts -O dtb $(ANDROID_DTS) > $(ANDROID_DTB)
@@ -572,7 +585,12 @@ ifeq ($(ANDROID_USERSPACE),1)
     -device virtio-blk,drive=vdc -drive file=$(USERDATA_IMG),index=2,if=none,id=vdc,format=raw \
     -device virtio-net,netdev=adbnet0 -netdev user,id=adbnet0,hostfwd=tcp::5554-:5554,hostfwd=tcp::5555-:5555
   QEMU_KERNEL_CMDLINE += root=$(ROOT) $(RW) kvm-arm.mode=protected earlyprintk androidboot.hardware=qemu_trusty trusty-log.log_ratelimit_interval=0 trusty-log.log_to_dmesg=always
+
+# Don't add the DTB as an argument if we're in the process of dumping it
+ifneq ($(DUMPING_DTB),1)
   QEMU_ARGS += -dtb $(ANDROID_DTB)
+endif
+
 else ifneq ($(INITRD),)
   ifeq ($(INITRD),1)
     INITRD := $(CPIO_FILE)
@@ -605,13 +623,7 @@ else ifeq ($(ARCH),i386)
   QEMU_BIN ?= qemu-system-i386
   QEMU_KERNEL_CMDLINE += console=ttyS0
 else
-  ifeq ($(TRUSTY),1)
-    # Trusty needs to use its own build of QEMU which has some custom patches
-    QEMU_BIN ?= $(TRUSTY_OUT)/qemu-build/aarch64-softmmu/qemu-system-aarch64
-  else
-    QEMU_BIN ?= qemu-system-aarch64
-  endif
-
+  QEMU_BIN ?= qemu-system-aarch64
   QEMU_KERNEL_CMDLINE += console=ttyAMA0
 
   ifeq ($(TRUSTY),1)
@@ -652,8 +664,15 @@ ifeq ($(TRUSTY),1)
 endif
 
 ifeq ($(ANDROID_USERSPACE),1)
-  # We need this device tree blob to mount /vendor
-  RUN_DEPS += $(ANDROID_DTB)
+  # We need a device tree blob to mount /vendor. If DUMPING_DTB is set, that
+  # means we're already in the process of dumping the DTB and shouldn't add it
+  # as a run dependency, otherwise we'll run into infinite recursion
+  ifneq ($(DUMPING_DTB),1)
+    # Add `android-dtb` instead of ANDROID_DTB so that this target is forced to
+    # be run every time (to prevent accidentally using a DTB generated from a
+    # different QEMU binary)
+    RUN_DEPS += android-dtb
+  endif
 endif
 
 # Make sure the modules directory exists, even if it's empty. Otherwise mount
@@ -663,16 +682,23 @@ $(LINUX_MODULES_INSTALL_PATH)/lib/modules:
 
 .PHONY: run
 run: $(RUN_DEPS) | $(SHARED_DIR) $(LINUX_MODULES_INSTALL_PATH)/lib/modules
+ifneq ($(DUMPING_DTB), 1)
 	@echo "$(GREEN)Running QEMU, press 'ctrl-a x' to quit $(NC)"
+endif
+
 ifeq ($(GDB),1)
+
+ifneq ($(DUMPING_DTB),1)
 	@echo "$(ARCH) $(ACK) $(TRUSTY) $(TRUSTY_TARGET)" > $(OUT_DIR)/.gdb
 	@echo "$(GREEN)Waiting for GDB, attach with \`scripts/gdb.sh\` $(NC)"
 
 ifdef TERMINAL_CMD
 	$(TERMINAL_CMD) $(SCRIPT_DIR)/gdb.sh
 endif
 
-endif
+endif # DUMPING_DTB
+endif # GDB
+
 	@echo ''
 	cd $(RUN_DIR) && $(QEMU_BIN) $(QEMU_ARGS)