tools build: Add new build support

Adding new build framework into 'tools/build' to be used by tools.

There's no change for actual building at this point, it comes in the
next patches.

The idea and more details are explained in the
'tools/build/Documentation/Build.txt' file.

I adopted everything from the kernel build system, with some changes to
allow for multiple binaries build definitions.

While the kernel's build output is single image (forget modules) we need
to be able to build several binaries/libraries.

The basic idea is that sser provides 'Build' files with objects
definitions like:

perf-y += a.o
perf-y += b.o
libperf-y += c.o
libperf-y += d.o

and the build framework outputs files:

perf-in.o # a.o, b.o compiled in
libperf-in.o # c.o, d.o compiled in

Signed-off-by: Jiri Olsa <[e-mail]>
Tested-by: Sukadev Bhattiprolu <[e-mail]>
Tested-by: Will Deacon <[e-mail]>
Cc: Alexis Berlemont <[e-mail]>
Cc: Borislav Petkov <[e-mail]>
Cc: Corey Ashford <[e-mail]>
Cc: David Ahern <[e-mail]>
Cc: Frederic Weisbecker <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Paul Mackerras <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Stephane Eranian <[e-mail]>
Link: http://lkml.kernel.org/n/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/build/Build.include

···
+###
+# build: Generic definitions
+#
+#  Lots of this code have been borrowed or heavily inspired from parts
+#  of kbuild code, which is not credited, but mostly developed by:
+#
+#  Copyright (C) Sam Ravnborg <[e-mail]>, 2015
+#  Copyright (C) Linus Torvalds <[e-mail]>, 2015
+#
+
+###
+# Convenient variables
+comma   := ,
+squote  := '
+
+###
+# Name of target with a '.' as filename prefix. foo/bar.o => foo/.bar.o
+dot-target = $(dir $@).$(notdir $@)
+
+###
+# filename of target with directory and extension stripped
+basetarget = $(basename $(notdir $@))
+
+###
+# The temporary file to save gcc -MD generated dependencies must not
+# contain a comma
+depfile = $(subst $(comma),_,$(dot-target).d)
+
+###
+# Check if both arguments has same arguments. Result is empty string if equal.
+arg-check = $(strip $(filter-out $(cmd_$(1)), $(cmd_$@)) \
+                    $(filter-out $(cmd_$@),   $(cmd_$(1))) )
+
+###
+# Escape single quote for use in echo statements
+escsq = $(subst $(squote),'\$(squote)',$1)
+
+# Echo command
+# Short version is used, if $(quiet) equals `quiet_', otherwise full one.
+echo-cmd = $(if $($(quiet)cmd_$(1)),\
+           echo '  $(call escsq,$($(quiet)cmd_$(1)))';)
+
+###
+# Replace >$< with >$$< to preserve $ when reloading the .cmd file
+# (needed for make)
+# Replace >#< with >\#< to avoid starting a comment in the .cmd file
+# (needed for make)
+# Replace >'< with >'\''< to be able to enclose the whole string in '...'
+# (needed for the shell)
+make-cmd = $(call escsq,$(subst \#,\\\#,$(subst $$,$$$$,$(cmd_$(1)))))
+
+###
+# Find any prerequisites that is newer than target or that does not exist.
+# PHONY targets skipped in both cases.
+any-prereq = $(filter-out $(PHONY),$?) $(filter-out $(PHONY) $(wildcard $^),$^)
+
+###
+# if_changed_dep  - execute command if any prerequisite is newer than
+#                   target, or command line has changed and update
+#                   dependencies in the cmd file
+if_changed_dep = $(if $(strip $(any-prereq) $(arg-check)),         \
+	@set -e;                                                   \
+	$(echo-cmd) $(cmd_$(1));                                   \
+	cat $(depfile) > $(dot-target).cmd;                        \
+	printf '%s\n' 'cmd_$@ := $(make-cmd)' >> $(dot-target).cmd)
+
+# if_changed      - execute command if any prerequisite is newer than
+#                   target, or command line has changed
+if_changed = $(if $(strip $(any-prereq) $(arg-check)),             \
+	@set -e;                                                   \
+	$(echo-cmd) $(cmd_$(1));                                   \
+	printf '%s\n' 'cmd_$@ := $(make-cmd)' > $(dot-target).cmd)
+
+###
+# C flags to be used in rule definitions, includes:
+# - depfile generation
+# - global $(CFLAGS)
+# - per target C flags
+# - per object C flags
+# - BUILD_STR macro to allow '-D"$(variable)"' constructs
+c_flags = -Wp,-MD,$(depfile),-MT,$@ $(CFLAGS) -D"BUILD_STR(s)=\#s" $(CFLAGS_$(basetarget).o) $(CFLAGS_$(obj))

tools/build/Documentation/Build.txt

···
+Build Framework
+===============
+
+The perf build framework was adopted from the kernel build system, hence the
+idea and the way how objects are built is the same.
+
+Basically the user provides set of 'Build' files that list objects and
+directories to nest for specific target to be build.
+
+Unlike the kernel we don't have a single build object 'obj-y' list that where
+we setup source objects, but we support more. This allows one 'Build' file to
+carry a sources list for multiple build objects.
+
+a) Build framework makefiles
+----------------------------
+
+The build framework consists of 2 Makefiles:
+
+  Build.include
+  Makefile.build
+
+While the 'Build.include' file contains just some generic definitions, the
+'Makefile.build' file is the makefile used from the outside. It's
+interface/usage is following:
+
+  $ make -f tools/build/Makefile srctree=$(KSRC) dir=$(DIR) obj=$(OBJECT)
+
+where:
+
+  KSRC   - is the path to kernel sources
+  DIR    - is the path to the project to be built
+  OBJECT - is the name of the build object
+
+When succefully finished the $(DIR) directory contains the final object file
+called $(OBJECT)-in.o:
+
+  $ ls $(DIR)/$(OBJECT)-in.o
+
+which includes all compiled sources described in 'Build' makefiles.
+
+a) Build makefiles
+------------------
+
+The user supplies 'Build' makefiles that contains a objects list, and connects
+the build to nested directories.
+
+Assume we have the following project structure:
+
+  ex/a.c
+    /b.c
+    /c.c
+    /d.c
+    /arch/e.c
+    /arch/f.c
+
+Out of which you build the 'ex' binary ' and the 'libex.a' library:
+
+  'ex'      - consists of 'a.o', 'b.o' and libex.a
+  'libex.a' - consists of 'c.o', 'd.o', 'e.o' and 'f.o'
+
+The build framework does not create the 'ex' and 'libex.a' binaries for you, it
+only prepares proper objects to be compiled and grouped together.
+
+To follow the above example, the user provides following 'Build' files:
+
+  ex/Build:
+    ex-y += a.o
+    ex-y += b.o
+
+    libex-y += c.o
+    libex-y += d.o
+    libex-y += arch/
+
+  ex/arch/Build:
+    libex-y += e.o
+    libex-y += f.o
+
+and runs:
+
+  $ make -f tools/build/Makefile.build dir=. obj=ex
+  $ make -f tools/build/Makefile.build dir=. obj=libex
+
+which creates the following objects:
+
+  ex/ex-in.o
+  ex/libex-in.o
+
+that contain request objects names in Build files.
+
+It's only a matter of 2 single commands to create the final binaries:
+
+  $ ar  rcs libex.a libex-in.o
+  $ gcc -o ex ex-in.o libex.a
+
+You can check the 'ex' example in 'tools/build/tests/ex' for more details.
+
+b) Rules
+--------
+
+The build framework provides standard compilation rules to handle .S and .c
+compilation.
+
+It's possible to include special rule if needed (like we do for flex or bison
+code generation).
+
+c) CFLAGS
+---------
+
+It's possible to alter the standard object C flags in the following way:
+
+  CFLAGS_perf.o += '...' - alters CFLAGS for perf.o object
+  CFLAGS_gtk += '...'    - alters CFLAGS for gtk build object
+
+This C flags changes has the scope of the Build makefile they are defined in.
+
+
+d) Dependencies
+---------------
+
+For each built object file 'a.o' the '.a.cmd' is created and holds:
+
+  - Command line used to built that object
+    (for each object)
+
+  - Dependency rules generated by 'gcc -Wp,-MD,...'
+    (for compiled object)
+
+All existing '.cmd' files are included in the Build process to follow properly
+the dependencies and trigger a rebuild when necessary.
+
+
+e) Single rules
+---------------
+
+It's possible to build single object file by choice, like:
+
+  $ make util/map.o    # objects
+  $ make util/map.i    # preprocessor
+  $ make util/map.s    # assembly

tools/build/Makefile.build

···
+###
+# Main build makefile.
+#
+#  Lots of this code have been borrowed or heavily inspired from parts
+#  of kbuild code, which is not credited, but mostly developed by:
+#
+#  Copyright (C) Sam Ravnborg <[e-mail]>, 2015
+#  Copyright (C) Linus Torvalds <[e-mail]>, 2015
+#
+
+PHONY := __build
+__build:
+
+ifeq ($(V),1)
+  quiet =
+else
+  quiet=quiet_
+endif
+
+build-dir := $(srctree)/tools/build
+
+# Generic definitions
+include $(build-dir)/Build.include
+
+# Init all relevant variables used in build files so
+# 1) they have correct type
+# 2) they do not inherit any value from the environment
+subdir-y     :=
+obj-y        :=
+subdir-y     :=
+subdir-obj-y :=
+
+# Build definitions
+build-file := $(dir)/Build
+include $(build-file)
+
+# Compile command
+quiet_cmd_cc_o_c = CC       $@
+      cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ $<
+
+# Link agregate command
+# If there's nothing to link, create empty $@ object.
+quiet_cmd_ld_multi = LD       $@
+      cmd_ld_multi = $(if $(strip $(obj-y)),\
+		       $(LD) -r -o $@ $(obj-y),rm -f $@; $(AR) rcs $@)
+
+# Build rules
+$(OUTPUT)%.o: %.c FORCE
+	$(call if_changed_dep,cc_o_c)
+
+$(OUTPUT)%.o: %.S FORCE
+	$(call if_changed_dep,cc_o_c)
+
+# Gather build data:
+#   obj-y        - list of build objects
+#   subdir-y     - list of directories to nest
+#   subdir-obj-y - list of directories objects 'dir/$(obj)-in.o'
+obj-y        := $($(obj)-y)
+subdir-y     := $(patsubst %/,%,$(filter %/, $(obj-y)))
+obj-y        := $(patsubst %/, %/$(obj)-in.o, $(obj-y))
+subdir-obj-y := $(filter %/$(obj)-in.o, $(obj-y))
+
+# '$(OUTPUT)/dir' prefix to all objects
+prefix       := $(subst ./,,$(OUTPUT)$(dir)/)
+obj-y        := $(addprefix $(prefix),$(obj-y))
+subdir-obj-y := $(addprefix $(prefix),$(subdir-obj-y))
+
+# Final '$(obj)-in.o' object
+in-target := $(prefix)$(obj)-in.o
+
+PHONY += $(subdir-y)
+
+$(subdir-y):
+	@$(MAKE) -f $(build-dir)/Makefile.build dir=$(dir)/$@ obj=$(obj)
+
+$(sort $(subdir-obj-y)): $(subdir-y) ;
+
+$(in-target): $(obj-y) FORCE
+	$(call rule_mkdir)
+	$(call if_changed,ld_multi)
+
+__build: $(in-target)
+	@:
+
+PHONY += FORCE
+FORCE:
+
+# Include all cmd files to get all the dependency rules
+# for all objects included
+targets   := $(wildcard $(sort $(obj-y) $(in-target)))
+cmd_files := $(wildcard $(foreach f,$(targets),$(dir $(f)).$(notdir $(f)).cmd))
+
+ifneq ($(cmd_files),)
+  include $(cmd_files)
+endif
+
+.PHONY: $(PHONY)

tools/build/tests/ex/Build

···
+ex-y += ex.o
+ex-y += a.o
+ex-y += b.o
+ex-y += empty/
+
+libex-y += c.o
+libex-y += d.o
+libex-y += arch/

tools/build/tests/ex/Makefile

···
+export srctree := ../../../..
+export CC      := gcc
+export LD      := ld
+export AR      := ar
+
+build := -f $(srctree)/tools/build/Makefile.build dir=. obj
+ex: ex-in.o libex-in.o
+	gcc -o $@ $^
+
+ex.%: FORCE
+	make -f $(srctree)/tools/build/Makefile.build dir=. $@
+
+ex-in.o: FORCE
+	make $(build)=ex
+
+libex-in.o: FORCE
+	make $(build)=libex
+
+clean:
+	find . -name '*.o' -delete -o -name '\.*.cmd' -delete -o -name '\.*.d' -delete
+	rm -f ex ex.i ex.s
+
+.PHONY: FORCE

tools/build/tests/ex/a.c

···
+
+int a(void)
+{
+	return 0;
+}

tools/build/tests/ex/arch/Build

···
+libex-y += e.o
+libex-y += f.o

tools/build/tests/ex/arch/e.c

···
+
+int e(void)
+{
+	return 0;
+}

tools/build/tests/ex/arch/f.c

···
+
+int f(void)
+{
+	return 0;
+}

tools/build/tests/ex/b.c

···
+
+int b(void)
+{
+	return 0;
+}

tools/build/tests/ex/c.c

···
+
+int c(void)
+{
+	return 0;
+}

tools/build/tests/ex/d.c

···
+
+int d(void)
+{
+	return 0;
+}

tools/build/tests/ex/ex.c

···
+
+int a(void);
+int b(void);
+int c(void);
+int d(void);
+int e(void);
+int f(void);
+
+int main(void)
+{
+	a();
+	b();
+	c();
+	d();
+	e();
+	f();
+
+	return 0;
+}

tools/build/tests/run.sh

···
+#!/bin/sh
+
+function test_ex {
+	make -C ex V=1 clean > ex.out 2>&1
+	make -C ex V=1 >> ex.out 2>&1
+
+	if [ ! -x ./ex/ex ]; then
+	  echo FAILED
+	  exit -1
+	fi
+
+	make -C ex V=1 clean > /dev/null 2>&1
+	rm -f ex.out
+}
+
+function test_ex_suffix {
+	make -C ex V=1 clean > ex.out 2>&1
+
+	# use -rR to disable make's builtin rules
+	make -rR -C ex V=1 ex.o >> ex.out 2>&1
+	make -rR -C ex V=1 ex.i >> ex.out 2>&1
+	make -rR -C ex V=1 ex.s >> ex.out 2>&1
+
+	if [ -x ./ex/ex ]; then
+	  echo FAILED
+	  exit -1
+	fi
+
+	if [ ! -f ./ex/ex.o -o ! -f ./ex/ex.i -o ! -f ./ex/ex.s ]; then
+	  echo FAILED
+	  exit -1
+	fi
+
+	make -C ex V=1 clean > /dev/null 2>&1
+	rm -f ex.out
+}
+echo -n Testing..
+
+test_ex
+test_ex_suffix
+
+echo OK

tools/perf/MANIFEST

···
 tools/perf
 tools/scripts
+tools/build
 tools/lib/traceevent
 tools/lib/api
 tools/lib/symbol/kallsyms.c