Il 06/09/2013 13:47, Fam Zheng ha scritto:
> On Fri, 09/06 12:09, Paolo Bonzini wrote:
>> 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 <f...@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?
>>
> Because common-obj-m = $(block-obj-m), in Makefile.objs below.
>
>> Perhaps adding to mod-obj-m (better name: modules-m) can be done in
>> unnest-vars?
>
> It looks more straightforward for me to do here, and it's used very locally.
But it doesn't scale too well, does it? There's no particular reason
why all -m variables would be included in common-obj-m. In fact, block-
obj-y/block-obj-m are the only remaining case of one variable including
another. In another review I even proposed eliminating this exception.
>>> +# Generate rules for single file modules (%.so: %.o).
>>> +$(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 $(obj)/biz.o
>>
>> ?
>>
> Because I don't know how to expand foo.mo to bar.o and biz.o: I expand
> "foo.mo"
> to "bar.o biz.o" in the link command line, to skip creating to foo.mo, or
> libfoo.a, if it's to be linked static:
>
> block-obj-y += foo.mo
>
> That's for avoiding ar and ln -r.
Ah, I see now. See below for an idea (if it works).
>>> +$(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 don't understand, do you mean a "cc -shared" output can be statically linked
> into a executable?
So if I understand correctly the .mo file is never used for a
statically-linked module? So the "ar" doesn't matter as things stand
Perhaps you could just use .mo file as a placeholder that holds the
module's list of dependencies, no matter if it is shared or static:
%.mo:
$(call quiet-command,echo $(sort $^) > $@," GEN $(TARGET_DIR_$@"))
In the LINK rule include the list from all .mo files:
$(sort $(filter %.o, $1)) \
$(shell cat $(filter %.mo,$^)) \
$(filter-out %.o %.mo,$^))
And the rule for shared objects would be simply:
%.$(DSOSUF): QEMU_LDFLAGS += -shared
%.$(DSOSUF): %.mo
$(call LINK,$^)
This would remove the need for the $i-obj variables.
Paolo
