Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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 := \#