Re: [Qemu-devel] [RFC PATCH v2 3/6] Makefile: introduce common-obj-m and block-obj-m for DSO

[Paolo Bonzini <pbonzini@redhat.com>]

Il 06/09/2013 09:28, Fam Zheng ha scritto:
> Add necessary rules and flags for shared object generation.
> $(common-obj-m) will include $(block-obj-m), like $(common-obj-y) does
> for $(block-obj-y). The new rules introduced here are:
> 
> 0) For all %.so compiling:
> 
>     QEMU_CFLAGS += -shared -fPIC
> 
> 1) %.o in $(common-obj-m) is compiled to %.o, with "QEMU_CFLAGS +=
> -shared -fPIC". Then linked to %.so.
> 
> 2) %.mo in $(common-obj-m) is the placeholder for %.so for pattern
> matching in Makefile. It's linked to "-shared" with all its dependencies
> (multiple *.o) as input. Which means the list of depended objects must
> be ruled out in each sub-Makefile.objs with an variable:
> 
>     $(obj)/foo.mo-obj := $(addprefix $(obj)/,bar.o baz.o qux.o)
> 
> Notice that $(obj)/ is required for both target and dependency in the
> rule. DSO suffix (.so) is configure variable (.dll for Windows).

Some kinks to iron, but this is really well-architected.  You took all
the best parts of mjt's patches and fixed almost all the ugly ones.  Kudos!

> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
>  Makefile      | 32 +++++++++++++++++++++++++++++---
>  Makefile.objs | 14 +++++++++++++-
>  configure     |  3 +++
>  rules.mak     | 10 ++++++++++
>  4 files changed, 55 insertions(+), 4 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index 806946e..cf47ea9 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -56,7 +56,7 @@ Makefile: ;
>  configure: ;
>  
>  .PHONY: all clean cscope distclean dvi html info install install-doc \
> -	pdf recurse-all speed test dist
> +	pdf recurse-all speed test dist modules
>  
>  $(call set-vpath, $(SRC_PATH))
>  
> @@ -121,7 +121,30 @@ ifeq ($(CONFIG_SMARTCARD_NSS),y)
>  include $(SRC_PATH)/libcacard/Makefile
>  endif
>  
> -all: $(DOCS) $(TOOLS) $(HELPERS-y) recurse-all
> +all: $(DOCS) $(TOOLS) $(HELPERS-y) recurse-all modules
> +
> +mod-obj-m = $(patsubst %.o,%$(DSOSUF),$(filter %.o,$(common-obj-m))) \
> +            $(patsubst %.mo,%$(DSOSUF),$(filter %.mo,$(common-obj-m)))


Why common-obj-m only, what about block-obj-m?

Perhaps adding to mod-obj-m (better name: modules-m) can be done in
unnest-vars?

> +# Generate rules for single file modules (%.so: %.o).
> +$(foreach o,$(filter %.o,$(common-obj-m)),$(eval \
> +	$(patsubst %.o,%.so,$o): $o ))

If you subst %.o to %.mo, you can use the same set of rules for both cases.

> +# For multi file modules, dependencies should be listed explicitly in
> +# Makefile.objs as
> +#     $(obj)/foo.mo-obj := $(obj)/bar.o $(obj)/biz.o

Why not

$(obj)/foo.mo: $(obj)/bar.o $(obj)/biz.o

?

> +$(foreach o,$(filter %.mo,$(mod-obj-m)),$(eval \
> +	$o: $($o-obj)))
> +
> +%.mo:
> +	$(if $(BUILD_DYNAMIC), \
> +		$(call quiet-command,$(CC) $(sort $^) -shared -o $@,"  LD[M] $(TARGET_DIR)$@"), \
> +		$(call quiet-command,$(AR) rcs $@ $(sort $^),"  AR    $(TARGET_DIR)$@"))

I think we can always build modules dynamically.  If the
module/no-module configure option decides whether an object moves
between *-obj-y and *-obj-m, statically-linked modules will just go on
the linker command line with no need for $(AR) or
--whole-archive/--no-whole-archive.

I'm missing where is the .so built (or I guess it can just be
hard-linked?) from the .mo file.

IIRC -shared is not portable to Darwin.  Darwin has separate file
formats for dynamic libraries (.dylib) and loadable modules (.so), so it
needs "-bundle" instad.  All this screams "just use libtool"...

> +
> +
> +modules: $(mod-obj-m)
> +modules: BUILD_DYNAMIC = 1
> +modules: QEMU_CFLAGS += -shared -fPIC

-shared is not needed here, only -fPIC.  Again, libtool would abstract
this nicely.  But it's fine if you prefer to have v3 still without
libtool and only working on ELF systems.

In fact, you probably don't need a special modules target.  You can just
add $(mod-obj-m) to "all".

>  
>  config-host.h: config-host.h-timestamp
>  config-host.h-timestamp: config-host.mak
> @@ -155,7 +178,7 @@ subdir-dtc:dtc/libfdt dtc/tests
>  dtc/%:
>  	mkdir -p $@
>  
> -$(SUBDIR_RULES): libqemuutil.a libqemustub.a $(common-obj-y)
> +$(SUBDIR_RULES): libqemuutil.a libqemustub.a $(common-obj-y) $(common-obj-m)
>  
>  ROMSUBDIR_RULES=$(patsubst %,romsubdir-%, $(ROMS))
>  romsubdir-%:
> @@ -235,6 +258,9 @@ clean:
>  	rm -f qemu-options.def
>  	find . -name '*.[oda]' -type f -exec rm -f {} +
>  	find . -name '*.l[oa]' -type f -exec rm -f {} +
> +	find . -name '*'$(DSOSUF) -type f -exec rm -f {} +
> +	find . -name '*.mo' -type f -exec rm -f {} +
> +
>  	rm -f $(TOOLS) $(HELPERS-y) qemu-ga TAGS cscope.* *.pod *~ */*~
>  	rm -Rf .libs
>  	rm -f qemu-img-cmds.h
> diff --git a/Makefile.objs b/Makefile.objs
> index f46a4cd..8984a20 100644
> --- a/Makefile.objs
> +++ b/Makefile.objs
> @@ -19,6 +19,8 @@ block-obj-y += qemu-coroutine.o qemu-coroutine-lock.o qemu-coroutine-io.o
>  block-obj-y += qemu-coroutine-sleep.o
>  block-obj-y += coroutine-$(CONFIG_COROUTINE_BACKEND).o
>  
> +block-obj-m = block/
> +
>  ifeq ($(CONFIG_VIRTIO)$(CONFIG_VIRTFS)$(CONFIG_PCI),yyy)
>  # Lots of the fsdev/9pcode is pulled in by vl.c via qemu_fsdev_add.
>  # only pull in the actual virtio-9p device if we also enabled virtio.
> @@ -83,6 +85,9 @@ common-obj-$(CONFIG_SMARTCARD_NSS) += $(libcacard-y)
>  
>  common-obj-y += qmp-marshal.o
>  common-obj-y += qmp.o hmp.o
> +
> +common-obj-m = $(block-obj-m)
> +
>  endif
>  
>  ######################################################################
> @@ -121,5 +126,12 @@ nested-vars += \
>  	util-obj-y \
>  	qga-obj-y \
>  	block-obj-y \
> -	common-obj-y
> +	block-obj-m \
> +	common-obj-y \
> +	common-obj-m
> +
>  dummy := $(call unnest-vars)
> +
> +# static linked mods are expanded to .o list
> +dummy := $(call expand-mod-obj,common-obj-y)
> +dummy := $(call expand-mod-obj,block-obj-y)
> diff --git a/configure b/configure
> index af6b048..75abb87 100755
> --- a/configure
> +++ b/configure
> @@ -190,6 +190,7 @@ mingw32="no"
>  gcov="no"
>  gcov_tool="gcov"
>  EXESUF=""
> +DSOSUF=".so"
>  prefix="/usr/local"
>  mandir="\${prefix}/share/man"
>  datadir="\${prefix}/share"
> @@ -584,6 +585,7 @@ fi
>  
>  if test "$mingw32" = "yes" ; then
>    EXESUF=".exe"
> +  DSOSUF=".dll"
>    QEMU_CFLAGS="-DWIN32_LEAN_AND_MEAN -DWINVER=0x501 $QEMU_CFLAGS"
>    # enable C99/POSIX format strings (needs mingw32-runtime 3.15 or later)
>    QEMU_CFLAGS="-D__USE_MINGW_ANSI_STDIO=1 $QEMU_CFLAGS"
> @@ -4175,6 +4177,7 @@ echo "LIBTOOLFLAGS=$LIBTOOLFLAGS" >> $config_host_mak
>  echo "LIBS+=$LIBS" >> $config_host_mak
>  echo "LIBS_TOOLS+=$libs_tools" >> $config_host_mak
>  echo "EXESUF=$EXESUF" >> $config_host_mak
> +echo "DSOSUF=$DSOSUF" >> $config_host_mak
>  echo "LIBS_QGA+=$libs_qga" >> $config_host_mak
>  echo "POD2MAN=$POD2MAN" >> $config_host_mak
>  echo "TRANSLATE_OPT_CFLAGS=$TRANSLATE_OPT_CFLAGS" >> $config_host_mak
> diff --git a/rules.mak b/rules.mak
> index e581d55..0a39499 100644
> --- a/rules.mak
> +++ b/rules.mak
> @@ -58,6 +58,10 @@ endif
>  %.o: %.dtrace
>  	$(call quiet-command,dtrace -o $@ -G -s $<, "  GEN   $(TARGET_DIR)$@")
>  
> +%$(DSOSUF): QEMU_CLFAGS += -shared -fPIC
> +%$(DSOSUF): %.o
> +	$(call quiet-command,$(LD) $< -o $@ -shared,"  LD[M] $(TARGET_DIR)$@")
> +

As mentioned above, I think these four lines are not needed and you can
always go through the "modules" or $(mod-obj-m) targets.  In fact,
CLFAGS sounds dubious. :)

Paolo

>  %$(EXESUF): %.o
>  	$(call LINK,$^)
>  
> @@ -145,3 +149,9 @@ $(shell mkdir -p $(sort $(foreach var,$(nested-vars),$(dir $($(var))))))
>  $(foreach var,$(nested-vars), $(eval \
>    -include $(addsuffix *.d, $(sort $(dir $($(var)))))))
>  endef
> +
> +define expand-mod-obj
> +$(eval pref = $(if $(obj-base),$(obj-base)/,))
> +$(eval t = $(foreach o,$($1),$(if $($(pref)$o-obj),$($(pref)$o-obj),$o)))
> +$(eval $1 = $t)
> +endef
>