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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [xen staging] xen/build: introduce if_changed and if_changed_rule
commit 4fdb4b71b152431b519345e6a8cc8738974db7e6
Author: Anthony PERARD <anthony.perard@xxxxxxxxxx>
AuthorDate: Fri Apr 24 15:01:11 2020 +0200
Commit: Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Apr 24 15:01:11 2020 +0200
xen/build: introduce if_changed and if_changed_rule
The if_changed macro from Linux, in addition to check if any files
needs an update, check if the command line has changed since the last
invocation. The latter will force a rebuild if any options to the
executable have changed.
if_changed_rule checks dependencies like if_changed, but execute
rule_$(1) instead of cmd_$(1) when a target needs to be rebuilt. A rule_
macro can call more than one cmd_ macro. One of the cmd_ macro in a
rule need to be call using a macro that record the command line, so
cmd_and_record is introduced. It is similar to cmd_and_fixup from
Linux but without a call to fixdep which we don't have yet. (We will
later replace cmd_and_record by cmd_and_fixup.)
Example of a rule_ macro:
define rule_cc_o_c
$(call cmd_and_record,cc_o_o)
$(call cmd,objcopy)
endef
This needs one of the call to use cmd_and_record, otherwise no .*.cmd
file will be created, and the target will keep been rebuilt.
In order for if_changed to works correctly, we need to load the .%.cmd
files that the macro generates, this is done by adding targets in to
the $(targets) variable. We use intermediate_targets to add %.init.o
dependency %.o to target since there aren't in obj-y.
We also add $(MAKECMDGOALS) to targets so that when running for
example `make common/memory.i`, make will load the associated .%.cmd
dependency file.
Beside the if_changed*, we import the machinery used for a "beautify
output". The important one is when running make with V=2 which help to
debug the makefiles by printing why a target is been rebuilt, via the
$(echo-why) macro.
if_changed and if_changed_rule aren't used yet.
Most of this code is copied from Linux v5.4, including the
documentation.
Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
---
.gitignore | 1 +
docs/misc/xen-makefiles/makefiles.rst | 98 +++++++++++++++++++++++++++++++
xen/Makefile | 53 ++++++++++++++++-
xen/Rules.mk | 33 ++++++++++-
xen/scripts/Kbuild.include | 107 ++++++++++++++++++++++++++++++++++
5 files changed, 290 insertions(+), 2 deletions(-)
diff --git a/.gitignore b/.gitignore
index 4ca679ddbc..bfa53723b3 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,5 @@
.hg
+.*.cmd
.*.tmp
*.orig
*~
diff --git a/docs/misc/xen-makefiles/makefiles.rst
b/docs/misc/xen-makefiles/makefiles.rst
index a86e3a612d..04bc72601c 100644
--- a/docs/misc/xen-makefiles/makefiles.rst
+++ b/docs/misc/xen-makefiles/makefiles.rst
@@ -85,3 +85,101 @@ Compilation flags
CFLAGS-y specifies options for compiling with $(CC).
AFLAGS-y specifies assembler options.
+
+
+Build system infrastructure
+===========================
+
+This chapter describe some of the macro used when building Xen.
+
+Macros
+------
+
+
+ if_changed
+ if_changed is the infrastructure used for the following commands.
+
+ Usage::
+
+ target: source(s) FORCE
+ $(call if_changed,ld/objcopy/...)
+
+ When the rule is evaluated, it is checked to see if any files
+ need an update, or the command line has changed since the last
+ invocation. The latter will force a rebuild if any options
+ to the executable have changed.
+ Any target that utilises if_changed must be listed in $(targets),
+ otherwise the command line check will fail, and the target will
+ always be built.
+ if_changed may be used in conjunction with custom commands as
+ defined in "Custom commands".
+
+ Note: It is a typical mistake to forget the FORCE prerequisite.
+ Another common pitfall is that whitespace is sometimes
+ significant; for instance, the below will fail (note the extra space
+ after the comma)::
+
+ target: source(s) FORCE
+
+ **WRONG!** $(call if_changed, ld/objcopy/...)
+
+ Note:
+ if_changed should not be used more than once per target.
+ It stores the executed command in a corresponding .cmd file
+ and multiple calls would result in overwrites and unwanted
+ results when the target is up to date and only the tests on
+ changed commands trigger execution of commands.
+
+ ld
+ Link target.
+
+ Example::
+
+ targets += setup setup.o bootsect bootsect.o
+ $(obj)/setup $(obj)/bootsect: %: %.o FORCE
+ $(call if_changed,ld)
+
+ $(targets) are assigned all potential targets, by which the build
+ system knows the targets and will:
+
+ 1) check for commandline changes
+
+ The ": %: %.o" part of the prerequisite is a shorthand that
+ frees us from listing the setup.o and bootsect.o files.
+
+ Note:
+ It is a common mistake to forget the "targets :=" assignment,
+ resulting in the target file being recompiled for no
+ obvious reason.
+
+ objcopy
+ Copy binary. Uses OBJCOPYFLAGS usually specified in
+ arch/$(ARCH)/Makefile.
+
+Custom commands
+---------------
+
+ When the build system is executing with V=0, then only
+ a shorthand of a command is normally displayed.
+ To enable this behaviour for custom commands, two variables are
+ required to be set::
+
+ quiet_cmd_<command> - what shall be echoed
+ cmd_<command> - the command to execute
+
+ Example::
+
+ # xsm/flask/Makefile
+ mkflask := policy/mkflask.sh
+ quiet_cmd_mkflask = MKFLASK $@
+ cmd_mkflask = $(CONFIG_SHELL) $(mkflask) $(AWK) include \
+ $(FLASK_H_DEPEND)
+
+ include/flask.h: $(FLASK_H_DEPEND) $(mkflask) FORCE
+ $(call if_changed,mkflask)
+
+ When updating the include/flask.h target, the line:
+
+ MKFLASK include/flask.h
+
+ will be displayed with "make V=0". (V=0 is the default)
diff --git a/xen/Makefile b/xen/Makefile
index 2a689b26a2..07f8ef8087 100644
--- a/xen/Makefile
+++ b/xen/Makefile
@@ -52,7 +52,57 @@ dist: install
ifneq ($(root-make-done),y)
# section to run before calling Rules.mk, but only once.
+
+# Beautify output
+# ---------------------------------------------------------------------------
+#
+# Normally, we echo the whole command before executing it. By making
+# that echo $($(quiet)$(cmd)), we now have the possibility to set
+# $(quiet) to choose other forms of output instead, e.g.
+#
+# quiet_cmd_cc_o_c = Compiling $(RELDIR)/$@
+# cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ $<
+#
+# If $(quiet) is empty, the whole command will be printed.
+# If it is set to "quiet_", only the short version will be printed.
+# If it is set to "silent_", nothing will be printed at all, since
+# the variable $(silent_cmd_cc_o_c) doesn't exist.
+#
+# A simple variant is to prefix commands with $(Q) - that's useful
+# for commands that shall be hidden in non-verbose mode.
#
+# $(Q)ln $@ :<
+#
+# If KBUILD_VERBOSE equals 0 then the above command will be hidden.
+# If KBUILD_VERBOSE equals 1 then the above command is displayed.
+#
+# To put more focus on warnings, be less verbose as default
+# Use 'make V=1' to see the full commands
+
+ifeq ("$(origin V)", "command line")
+ KBUILD_VERBOSE := $(V)
+endif
+ifndef KBUILD_VERBOSE
+ KBUILD_VERBOSE := 0
+endif
+
+ifeq ($(KBUILD_VERBOSE),1)
+ quiet :=
+ Q :=
+else
+ quiet := quiet_
+ Q := @
+endif
+
+# If the user is running make -s (silent mode), suppress echoing of
+# commands
+
+ifneq ($(findstring s,$(filter-out --%,$(MAKEFLAGS))),)
+ quiet := silent_
+endif
+
+export quiet Q KBUILD_VERBOSE
+
# To make sure we do not include .config for any of the *config targets
# catch them early, and hand them over to tools/kconfig/Makefile
@@ -261,7 +311,8 @@ _clean: delete-unfresh-files
$(MAKE) $(clean) arch/x86
$(MAKE) $(clean) test
$(MAKE) -f $(BASEDIR)/tools/kconfig/Makefile.kconfig ARCH=$(ARCH)
SRCARCH=$(SRCARCH) clean
- find . \( -name "*.o" -o -name ".*.d" -o -name ".*.d2" -o -name
"*.gcno" \) -exec rm -f {} \;
+ find . \( -name "*.o" -o -name ".*.d" -o -name ".*.d2" \
+ -o -name "*.gcno" -o -name ".*.cmd" \) -exec rm -f {} \;
rm -f include/asm $(TARGET) $(TARGET).gz $(TARGET).efi
$(TARGET).efi.map $(TARGET)-syms $(TARGET)-syms.map *~ core
rm -f include/asm-*/asm-offsets.h
rm -f .banner
diff --git a/xen/Rules.mk b/xen/Rules.mk
index 9d1e1ebf5e..21cac7f5f5 100644
--- a/xen/Rules.mk
+++ b/xen/Rules.mk
@@ -42,6 +42,7 @@ ALL_OBJS-y +=
$(BASEDIR)/arch/$(TARGET_ARCH)/built_in.o
ALL_OBJS-$(CONFIG_CRYPTO) += $(BASEDIR)/crypto/built_in.o
# Initialise some variables
+targets :=
CFLAGS-y :=
AFLAGS-y :=
@@ -69,6 +70,10 @@ $(foreach o,$(filter-out %/,$(obj-y) $(obj-bin-y)
$(extra-y)),$(eval $(call gend
subdir-y := $(subdir-y) $(filter %/, $(obj-y))
obj-y := $(patsubst %/, %/built_in.o, $(obj-y))
+# $(subdir-obj-y) is the list of objects in $(obj-y) which uses dir/ to
+# tell kbuild to descend
+subdir-obj-y := $(filter %/built_in.o, $(obj-y))
+
$(filter %.init.o,$(obj-y) $(obj-bin-y) $(extra-y)): CFLAGS-y +=
-DINIT_SECTIONS_ONLY
ifeq ($(CONFIG_COVERAGE),y)
@@ -123,6 +128,10 @@ else
endif
endif
+targets += built_in.o
+targets += $(filter-out $(subdir-obj-y), $(obj-y)) $(extra-y)
+targets += $(MAKECMDGOALS)
+
built_in_bin.o: $(obj-bin-y) $(extra-y)
ifeq ($(obj-bin-y),)
$(CC) $(a_flags) -c -x assembler /dev/null -o $@
@@ -131,7 +140,7 @@ else
endif
# Force execution of pattern rules (for which PHONY cannot be directly used).
-.PHONY: FORCE
+PHONY += FORCE
FORCE:
%/built_in.o: FORCE
@@ -179,4 +188,26 @@ $(filter %.init.o,$(obj-y) $(obj-bin-y) $(extra-y)):
%.init.o: %.o Makefile
%.s: %.S Makefile
$(CPP) $(filter-out -Wa$(comma)%,$(a_flags)) $< -o $@
+# Add intermediate targets:
+# When building objects with specific suffix patterns, add intermediate
+# targets that the final targets are derived from.
+intermediate_targets = $(foreach sfx, $(2), \
+ $(patsubst %$(strip $(1)),%$(sfx), \
+ $(filter %$(strip $(1)), $(targets))))
+# %.init.o <- %.o
+targets += $(call intermediate_targets, .init.o, .o)
+
-include $(DEPS_INCLUDE)
+
+# Read all saved command lines and dependencies for the $(targets) we
+# may be building above, using $(if_changed{,_dep}). As an
+# optimization, we don't need to read them if the target does not
+# exist, we will rebuild anyway in that case.
+
+existing-targets := $(wildcard $(sort $(targets)))
+
+-include $(foreach f,$(existing-targets),$(dir $(f)).$(notdir $(f)).cmd)
+
+# Declare the contents of the PHONY variable as phony. We keep that
+# information in a variable so we can use it in if_changed and friends.
+.PHONY: $(PHONY)
diff --git a/xen/scripts/Kbuild.include b/xen/scripts/Kbuild.include
index 806c68824e..e62eddc365 100644
--- a/xen/scripts/Kbuild.include
+++ b/xen/scripts/Kbuild.include
@@ -2,11 +2,30 @@
####
# kbuild: Generic definitions
+# Convenient variables
+squote := '
+empty :=
+space := $(empty) $(empty)
+space_escape := _-_SPACE_-_
+pound := \#
+
+###
+# Name of target with a '.' as filename prefix. foo/bar.o => foo/.bar.o
+dot-target = $(@D)/.$(@F)
+
###
# dependencies
DEPS = .*.d
DEPS_INCLUDE = $(addsuffix .d2, $(basename $(wildcard $(DEPS))))
+###
+# real prerequisites without phony targets
+real-prereqs = $(filter-out $(PHONY), $^)
+
+###
+# Escape single quote for use in echo statements
+escsq = $(subst $(squote),'\$(squote)',$1)
+
# as-insn: Check whether assembler supports an instruction.
# Usage: cflags-y += $(call as-insn,CC FLAGS,"insn",option-yes,option-no)
as-insn = $(if $(shell echo 'void _(void) { asm volatile ( $(2) ); }' \
@@ -32,3 +51,91 @@ cc-ifversion = $(shell [ $(CONFIG_GCC_VERSION)0 $(1) $(2)000
] && echo $(3) || e
# Usage:
# $(MAKE) $(clean) dir
clean := -f $(BASEDIR)/scripts/Makefile.clean clean -C
+
+# 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)))$(echo-why)';)
+
+# printing commands
+cmd = @set -e; $(echo-cmd) $(cmd_$(1))
+
+###
+# if_changed - execute command if any prerequisite is newer than
+# target, or command line has changed
+# if_changed_rule - as if_changed but execute rule instead
+
+ifneq ($(KBUILD_NOCMDDEP),1)
+# Check if both commands are the same including their order. Result is empty
+# string if equal. User may override this check using make KBUILD_NOCMDDEP=1
+cmd-check = $(filter-out $(subst $(space),$(space_escape),$(strip $(cmd_$@))),
\
+ $(subst $(space),$(space_escape),$(strip $(cmd_$1))))
+else
+cmd-check = $(if $(strip $(cmd_$@)),,1)
+endif
+
+# Replace >$< with >$$< to preserve $ when reloading the .cmd file
+# (needed for make)
+# Replace >#< with >$(pound)< to avoid starting a comment in the .cmd file
+# (needed for make)
+# Replace >'< with >'\''< to be able to enclose the whole string in '...'
+# (needed for the shell)
+make-cmd = $(call escsq,$(subst $(pound),$$(pound),$(subst
$$,$$$$,$(cmd_$(1)))))
+
+# Find any prerequisites that is newer than target or that does not exist.
+# PHONY targets skipped in both cases.
+any-prereq = $(filter-out $(PHONY),$?)$(filter-out $(PHONY) $(wildcard $^),$^)
+
+# Execute command if command has changed or prerequisite(s) are updated.
+if_changed = $(if $(any-prereq)$(cmd-check), \
+ $(cmd); \
+ printf '%s\n' 'cmd_$@ := $(make-cmd)' > $(dot-target).cmd, @:)
+
+# Usage: $(call if_changed_rule,foo)
+# Will check if $(cmd_foo) or any of the prerequisites changed,
+# and if so will execute $(rule_foo).
+if_changed_rule = $(if $(any-prereq)$(cmd-check),$(rule_$(1)),@:)
+
+cmd_and_record = \
+ $(cmd); \
+ printf '%s\n' 'cmd_$@ := $(make-cmd)' > $(dot-target).cmd
+
+###
+# why - tell why a target got built
+# enabled by make V=2
+# Output (listed in the order they are checked):
+# (1) - due to target is PHONY
+# (2) - due to target missing
+# (3) - due to: file1.h file2.h
+# (4) - due to command line change
+# (5) - due to missing .cmd file
+# (6) - due to target not in $(targets)
+# (1) PHONY targets are always build
+# (2) No target, so we better build it
+# (3) Prerequisite is newer than target
+# (4) The command line stored in the file named dir/.target.cmd
+# differed from actual command line. This happens when compiler
+# options changes
+# (5) No dir/.target.cmd file (used to store command line)
+# (6) No dir/.target.cmd file and target not listed in $(targets)
+# This is a good hint that there is a bug in the kbuild file
+ifeq ($(KBUILD_VERBOSE),2)
+why = \
+ $(if $(filter $@, $(PHONY)),- due to target is PHONY, \
+ $(if $(wildcard $@), \
+ $(if $(any-prereq),- due to: $(any-prereq), \
+ $(if $(cmd-check), \
+ $(if $(cmd_$@),- due to command line change, \
+ $(if $(filter $@, $(targets)), \
+ - due to missing .cmd file, \
+ - due to $(notdir $@) not in $$(targets) \
+ ) \
+ ) \
+ ) \
+ ), \
+ - due to target missing \
+ ) \
+ )
+
+echo-why = $(call escsq, $(strip $(why)))
+endif
--
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