1# SPDX-License-Identifier: GPL-2.0 2ifneq ($(O),) 3ifeq ($(origin O), command line) 4 $(if $(shell cd $(PWD); test -d $(O) || echo $(O)),$(error O=$(O) does not exist),) 5 ABSOLUTE_O := $(shell cd $(PWD); cd $(O) ; pwd) 6 OUTPUT := $(ABSOLUTE_O)/$(if $(subdir),$(subdir)/) 7 COMMAND_O := O=$(ABSOLUTE_O) 8ifeq ($(objtree),) 9 objtree := $(O) 10endif 11endif 12endif 13 14# check that the output directory actually exists 15ifneq ($(OUTPUT),) 16OUTDIR := $(shell cd $(OUTPUT) && pwd) 17$(if $(OUTDIR),, $(error output directory "$(OUTPUT)" does not exist)) 18endif 19 20# 21# Include saner warnings here, which can catch bugs: 22# 23EXTRA_WARNINGS := -Wbad-function-cast 24EXTRA_WARNINGS += -Wdeclaration-after-statement 25EXTRA_WARNINGS += -Wformat-security 26EXTRA_WARNINGS += -Wformat-y2k 27EXTRA_WARNINGS += -Winit-self 28EXTRA_WARNINGS += -Wmissing-declarations 29EXTRA_WARNINGS += -Wmissing-prototypes 30EXTRA_WARNINGS += -Wnested-externs 31EXTRA_WARNINGS += -Wno-system-headers 32EXTRA_WARNINGS += -Wold-style-definition 33EXTRA_WARNINGS += -Wpacked 34EXTRA_WARNINGS += -Wredundant-decls 35EXTRA_WARNINGS += -Wstrict-prototypes 36EXTRA_WARNINGS += -Wswitch-default 37EXTRA_WARNINGS += -Wswitch-enum 38EXTRA_WARNINGS += -Wundef 39EXTRA_WARNINGS += -Wwrite-strings 40EXTRA_WARNINGS += -Wformat 41EXTRA_WARNINGS += -Wno-type-limits 42 43# Makefiles suck: This macro sets a default value of $(2) for the 44# variable named by $(1), unless the variable has been set by 45# environment or command line. This is necessary for CC and AR 46# because make sets default values, so the simpler ?= approach 47# won't work as expected. 48define allow-override 49 $(if $(or $(findstring environment,$(origin $(1))),\ 50 $(findstring command line,$(origin $(1)))),,\ 51 $(eval $(1) = $(2))) 52endef 53 54ifneq ($(LLVM),) 55ifneq ($(filter %/,$(LLVM)),) 56LLVM_PREFIX := $(LLVM) 57else ifneq ($(filter -%,$(LLVM)),) 58LLVM_SUFFIX := $(LLVM) 59else ifneq ($(LLVM),1) 60$(error Invalid value for LLVM, see Documentation/kbuild/llvm.rst) 61endif 62 63$(call allow-override,CC,$(LLVM_PREFIX)clang$(LLVM_SUFFIX)) 64$(call allow-override,AR,$(LLVM_PREFIX)llvm-ar$(LLVM_SUFFIX)) 65$(call allow-override,LD,$(LLVM_PREFIX)ld.lld$(LLVM_SUFFIX)) 66$(call allow-override,CXX,$(LLVM_PREFIX)clang++$(LLVM_SUFFIX)) 67$(call allow-override,STRIP,$(LLVM_PREFIX)llvm-strip$(LLVM_SUFFIX)) 68else 69# Allow setting various cross-compile vars or setting CROSS_COMPILE as a prefix. 70$(call allow-override,CC,$(CROSS_COMPILE)gcc) 71$(call allow-override,AR,$(CROSS_COMPILE)ar) 72$(call allow-override,LD,$(CROSS_COMPILE)ld) 73$(call allow-override,CXX,$(CROSS_COMPILE)g++) 74$(call allow-override,STRIP,$(CROSS_COMPILE)strip) 75endif 76 77CC_NO_CLANG := $(shell $(CC) -dM -E -x c /dev/null | grep -Fq "__clang__"; echo $$?) 78 79ifneq ($(LLVM),) 80HOSTAR ?= $(LLVM_PREFIX)llvm-ar$(LLVM_SUFFIX) 81HOSTCC ?= $(LLVM_PREFIX)clang$(LLVM_SUFFIX) 82HOSTLD ?= $(LLVM_PREFIX)ld.lld$(LLVM_SUFFIX) 83else 84HOSTAR ?= ar 85HOSTCC ?= gcc 86HOSTLD ?= ld 87endif 88 89# Some tools require Clang, LLC and/or LLVM utils 90CLANG ?= clang 91LLC ?= llc 92LLVM_CONFIG ?= llvm-config 93LLVM_OBJCOPY ?= llvm-objcopy 94LLVM_STRIP ?= llvm-strip 95 96# Some tools require bpftool 97SYSTEM_BPFTOOL ?= bpftool 98 99RUSTC ?= rustc 100 101ifeq ($(CC_NO_CLANG), 1) 102EXTRA_WARNINGS += -Wstrict-aliasing=3 103 104else ifneq ($(CROSS_COMPILE),) 105# Allow userspace to override CLANG_CROSS_FLAGS to specify their own 106# sysroots and flags or to avoid the GCC call in pure Clang builds. 107ifeq ($(CLANG_CROSS_FLAGS),) 108CLANG_TARGET := $(notdir $(CROSS_COMPILE:%-=%)) 109CLANG_TARGET := $(subst s390-linux,s390x-linux,$(CLANG_TARGET)) 110CLANG_CROSS_FLAGS := --target=$(CLANG_TARGET) 111GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)gcc 2>/dev/null)) 112ifneq ($(GCC_TOOLCHAIN_DIR),) 113CLANG_CROSS_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE)) 114CLANG_CROSS_FLAGS += --sysroot=$(shell $(CROSS_COMPILE)gcc -print-sysroot) 115CLANG_CROSS_FLAGS += --gcc-toolchain=$(realpath $(GCC_TOOLCHAIN_DIR)/..) 116endif # GCC_TOOLCHAIN_DIR 117endif # CLANG_CROSS_FLAGS 118CFLAGS += $(CLANG_CROSS_FLAGS) 119AFLAGS += $(CLANG_CROSS_FLAGS) 120else 121CLANG_CROSS_FLAGS := 122endif # CROSS_COMPILE 123 124# Hack to avoid type-punned warnings on old systems such as RHEL5: 125# We should be changing CFLAGS and checking gcc version, but this 126# will do for now and keep the above -Wstrict-aliasing=3 in place 127# in newer systems. 128# Needed for the __raw_cmpxchg in tools/arch/x86/include/asm/cmpxchg.h 129# 130# See https://lore.kernel.org/lkml/9a8748490611281710g78402fbeh8ff7fcc162dbcbca@mail.gmail.com/ 131# and https://gcc.gnu.org/gcc-4.8/changes.html, 132# that takes into account Linus's comments (search for Wshadow) for the reasoning about 133# -Wshadow not being interesting before gcc 4.8. 134 135ifneq ($(filter 3.%,$(MAKE_VERSION)),) # make-3 136EXTRA_WARNINGS += -fno-strict-aliasing 137EXTRA_WARNINGS += -Wno-shadow 138else 139EXTRA_WARNINGS += -Wshadow 140endif 141 142ifneq ($(findstring $(MAKEFLAGS), w),w) 143PRINT_DIR = --no-print-directory 144else 145NO_SUBDIR = : 146endif 147 148# Beautify output 149# --------------------------------------------------------------------------- 150# 151# Most of build commands in Kbuild start with "cmd_". You can optionally define 152# "quiet_cmd_*". If defined, the short log is printed. Otherwise, no log from 153# that command is printed by default. 154# 155# e.g.) 156# quiet_cmd_depmod = DEPMOD $(MODLIB) 157# cmd_depmod = $(srctree)/scripts/depmod.sh $(DEPMOD) $(KERNELRELEASE) 158# 159# A simple variant is to prefix commands with $(Q) - that's useful 160# for commands that shall be hidden in non-verbose mode. 161# 162# $(Q)$(MAKE) $(build)=scripts/basic 163# 164# To put more focus on warnings, be less verbose as default 165# Use 'make V=1' to see the full commands 166 167ifeq ($(V),1) 168 quiet = 169 Q = 170else 171 quiet = quiet_ 172 Q = @ 173endif 174 175# If the user is running make -s (silent mode), suppress echoing of commands 176# make-4.0 (and later) keep single letter options in the 1st word of MAKEFLAGS. 177ifeq ($(filter 3.%,$(MAKE_VERSION)),) 178short-opts := $(firstword -$(MAKEFLAGS)) 179else 180short-opts := $(filter-out --%,$(MAKEFLAGS)) 181endif 182 183ifneq ($(findstring s,$(short-opts)),) 184 silent=1 185 quiet=silent_ 186endif 187 188export quiet Q 189 190# 191# Define a callable command for descending to a new directory 192# 193# Call by doing: $(call descend,directory[,target]) 194# 195descend = \ 196 +mkdir -p $(OUTPUT)$(1) && \ 197 $(MAKE) $(COMMAND_O) subdir=$(if $(subdir),$(subdir)/$(1),$(1)) $(PRINT_DIR) -C $(1) $(2) 198 199QUIET_SUBDIR0 = +$(MAKE) $(COMMAND_O) -C # space to separate -C and subdir 200QUIET_SUBDIR1 = 201 202ifneq ($(silent),1) 203 ifneq ($(V),1) 204 QUIET_CC = @echo ' CC '$@; 205 QUIET_CC_FPIC = @echo ' CC FPIC '$@; 206 QUIET_CLANG = @echo ' CLANG '$@; 207 QUIET_AR = @echo ' AR '$@; 208 QUIET_LINK = @echo ' LINK '$@; 209 QUIET_MKDIR = @echo ' MKDIR '$@; 210 QUIET_GEN = @echo ' GEN '$@; 211 QUIET_SUBDIR0 = +@subdir= 212 QUIET_SUBDIR1 = ;$(NO_SUBDIR) \ 213 echo ' SUBDIR '$$subdir; \ 214 $(MAKE) $(PRINT_DIR) -C $$subdir 215 QUIET_FLEX = @echo ' FLEX '$@; 216 QUIET_BISON = @echo ' BISON '$@; 217 QUIET_GENSKEL = @echo ' GENSKEL '$@; 218 219 descend = \ 220 +@echo ' DESCEND '$(1); \ 221 mkdir -p $(OUTPUT)$(1) && \ 222 $(MAKE) $(COMMAND_O) subdir=$(if $(subdir),$(subdir)/$(1),$(1)) $(PRINT_DIR) -C $(1) $(2) 223 224 QUIET_CLEAN = @printf ' CLEAN %s\n' $1; 225 QUIET_INSTALL = @printf ' INSTALL %s\n' $1; 226 QUIET_UNINST = @printf ' UNINST %s\n' $1; 227 endif 228endif 229 230pound := \# 231